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Publication Date: 2025
Journal of Membrane Science (18733123) 713
This study investigates the effects of various porous supports and the presence of additional gases in the feed on hydrogen permeation using an unsupported Pd82–Ag15–Y3 membrane. The pore sizes and thicknesses of metallic supports varied from 1 to 270 μm and 50–3000 μm, respectively. The membrane was unsupported, synthesized by cold-rolling, and characterized by a thickness of 38 μm. The tests were performed at 400 °C with pressures ranging from 1.4 to 3 bar. Results showed that the unsupported Pd82–Ag15–Y3 membrane reached 12 % and 267 % higher hydrogen permeation than the supported membrane by 1 μm pore size and 50 μm thick woven mesh, and 1 μm pore size and 3 mm thick of porous stainless steel (PSS), respectively. The unsupported Pd82–Ag15–Y3 membrane showed one of the highest hydrogen permeability in the literature (7.5 × 10−8 mol m−1 s−1.Pa−0.5 at 400 °C). However, the presence of porous supports used to enhance the mechanical stability of the membrane negatively affected the hydrogen permeation due to mass transfer limitation. In addition, the presence of supports induced an unreal ‘n’ value for the Pd-based membrane, where the ‘n’ value is the exponent of the driving force in the equation of hydrogen transport, varying between 0.5 and 1. In particular, for the unsupported membrane, the ‘n’ value was 0.6, but it increased to 0.7 and 0.8 when supports with 1 μm pore size and 50 μm thick and 5 μm and 80 μm thick were utilized. Binary hydrogen permeation tests were also performed in the presence of N2, CH4, CO2, and CO at 400 °C by using unsupported and supported membranes to investigate the reduction in hydrogen permeation flux due to the effect of the supports plus the effect of the presence of other gas. The results revealed that CO had the highest inhibition effect for all the unsupported and supported membranes tested due to competitive adsorption on the surface. No superficial adsorption on the membrane was observed for N2, CH4, and CO2 during permeation, and they inhibited hydrogen permeation mainly due to depletion, dilution, and concentration polarization. The PSS_1–3000 indicated the lowest hydrogen permeation between the gas mixture and the porous support, whereas the presence of 40 % of the binary gas mixture had lower hydrogen permeation than porous support except for the PSS. © 2024 Elsevier B.V.
Publication Date: 2025
Colloids and Surfaces A: Physicochemical and Engineering Aspects (18734359) 725
The development of epoxy adhesives with superior adhesion properties has long been a critical requirement in the high-tech applications. In this study, two metal organic frameworks (MOFs), MIL-101(Cr) (MIL, Matérial Institut Lavoisier) and NH2-MIL-101(Cr), were used to enhance the adhesion characteristics. These MOFs, were characterized by different analytical techniques, and subsequently integrated into high-temperature epoxy adhesives to improve their mechanical and thermal properties as well as adhesion strength. Notably, the addition of 0.3 parts per hundred resin (phr) of MIL-101(Cr) to the epoxy matrix resulted in an impressive ∼100 % increase in tensile strength and a remarkable 24 % enhancement in lap shear strength. Furthermore, the incorporation of the amine-functionalized NH2-MIL-101(Cr) into the epoxy matrix led to even more significant improvements in mechanical strength. The addition of just 0.3 phr of NH2-MIL-101(Cr) gave rise in a striking ∼150 % increment in tensile strength compared to the pristine epoxy adhesives, while lap shear strength experienced a substantial 50 % growth. The thermal stability of the epoxy adhesive was notably enhanced in the presence of the MOFs. Differential scanning calorimetry (DSC) analysis indicated an increase in the curing enthalpy upon the incorporation of both MIL-101(Cr) and NH2-MIL-101(Cr) into the epoxy matrices. The use of amine-functionalized MOFs significantly improved the thermal and mechanical properties of the epoxy adhesives, paving the way for the development of innovative epoxy formulations. © 2025
Kaveh, A. ,
Moini jazani, O. ,
Asghari, S. ,
Mirmohammadi, S.M. ,
Ghaderi, H. ,
Taghavi, M.R. Publication Date: 2025
Journal of Reinforced Plastics and Composites (07316844)
The enhancement of epoxy composites has emerged as a captivating area of research in recent years, particularly in addressing the critical challenge of filler debonding within the epoxy matrix. This study explores the use of chemically oxidized carbon fibers (CFs) as a reinforcing agent to significantly improve the thermal and mechanical properties of epoxy composites. The oxidation process increases the surface functional groups on CFs, facilitating better interaction during curing. Our findings reveal a remarkable 32% increase in tensile strength and a 28% increase in modulus strength when comparing molded composites of pristine and oxidized CFs. Furthermore, interlaminar shear strength analysis demonstrates a striking 92% improvement in adhesion properties, rising from 30.4 MPa for pristine CFs to 58.3 MPa for oxidized CFs. Thermal gravimetric analysis indicates a substantial enhancement in thermal stability for the epoxy/oxidized CFs composite. Notably, the fracture mode transitions from adhesive failure in pristine CFs to cohesive failure in the oxidized variants. This paper presents a straightforward and effective strategy for modifying CFs, paving the way for the development of advanced composites with superior thermal and mechanical properties. © The Author(s) 2025
Publication Date: 2025
BioNanoScience (21911630) 15(1)
Carbon dots (CDs) are nanoparticles (NPs) used in cancer treatment for medical imaging and drug delivery. This research examines the characteristics of carbon quantum dots (CQDs) that make them suitable for medical purposes. CQDs, consisting of carbon atoms with unique properties, are less than 10 nm in size and possess biocompatibility and energy release capabilities. Recent advancements in utilizing CQDs for bioimaging and therapy, including light-based treatments and antibacterial therapies, are discussed. The study also emphasizes the importance of monitoring, self-transformation, and future advancements in biological applications to obtain regulatory approval for clinical use, such as from the FDA. The research provides a detailed analysis of CQDs’ biomedical applications, highlighting their dispersibility, compatibility, and photoluminescent properties for applications such as drug delivery, biosensing, and controlled release. Various synthetic methods for different types of CQDs, including modified versions, are explored, along with investigations into pharmacokinetics, toxicity profiles, and implications in clinical and biological settings. Overall, this study offers a comprehensive understanding of CQDs’ synthesis, modification, pharmacokinetics, toxicity, polymer composite, and future research directions for bioimaging applications. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.
Publication Date: 2025
Chemical Engineering Journal (13858947) 523
This study examines hydrogen gas production from biogas dry reforming in a Pd/YSZ membrane reactor (MR) packed with a Ni-based catalyst. The MR performance was investigated in terms of hydrogen permeation, methane and carbon dioxide conversion, hydrogen recovery, and hydrogen yield with a temperature range of 500–600 °C and pressures between 1 and 5 bar. At 600 °C, the Pd/YSZ membrane demonstrated a hydrogen permeance of 1.8 × 10−6 mol·m−2·s−1·Pa−1 and an apparent activation energy of 11.9 kJ/mol. Increasing the temperature from 500 °C to 550 °C at 5 bar resulted in CH4 and CO2 conversions increasing by 26 % and 6 %, respectively, while hydrogen recovery and yield improved by 6 % and 24 %. Our results showed higher CH4 conversion than other membrane reactors and conventional reactors under the same operating conditions. Experimental results indicate that methane decomposition occurs simultaneously with biogas reforming, contributing significantly to coke formation, particularly at elevated temperatures. Introducing small amounts of oxygen into the feed effectively reduced carbon deposition from 1.0 g to 0.65 g at 550 °C and 5 bar by oxidizing deposited carbon. However, this also led to a reduction in CO2 conversion from 22 % to 6 %, due to the consumption of CO2 during carbon oxidation reactions. Importantly, the addition of O2 did not negatively impact membrane and catalyst activity, and hydrogen recovery and yield remained stable. Additionally, steam regeneration was shown to effectively remove carbon deposits from both the catalyst and membrane, while simultaneously generating hydrogen via gas–solid reactions. So far, no research study has evaluated the effect of steam for coke removal on Pd-based membrane reactors. The MR exhibited stable hydrogen permeation flux and maintained complete selectivity over 800 h of continuous operation. Up to now, no Pd-based membrane has been resisted for this period under dry reforming reaction. Thus, Pd-YSZ MR demonstrates strong long-term operational stability and viability for low-carbon hydrogen production from renewable biogas. © 2025 Elsevier B.V.
Joseph, T.M. ,
Azat, S. ,
Kianfar, E. ,
Joshy, K.S. ,
Moini jazani, O. ,
Esmaeili, A. ,
Ahmadi, Z. ,
Haponiuk, J. ,
Thomas, S. Publication Date: 2025
Reviews in Chemical Engineering (01678299) 41(3)pp. 269-308
Epoxy foam/aerogel materials (EP-AGs) have potential in the aerospace, construction, and energy industries, allowing the development of lightweight high-performance products for a wide range of applications. Research interest in developing EP-AGs is increasing as it has the potential to create greener and more sustainable materials for making various products. Several commercial applications of EP-AGs and techniques for creating, processing, and drying them have already been reported. The introduction of EP-AGs into value-added materials is one of the most promising options but suffers from a lack of knowledge about the relationships between microstructure and properties. The current obstacles to their use in the industrial sector and for applications and challenges related to factory scale-up are also taken into account. EP-AGs are hindered by critical gaps in applicational and processing complexity, such as scaling up from laboratory to large-scale production, optimizing synthesis and processing techniques, and developing standardized testing protocols. The review focuses on the processing complexities and further difficulties associated with EP-AGs to improve casting burdens, cost-effectiveness, and accessibility in various applications. This review also examines the challenges in synthesizing EP-AGs used to make special materials, their practices, and the technological barriers one would face. © 2025 the author(s), published by De Gruyter, Berlin/Boston.
Publication Date: 2025
Polymer Composites (02728397) 46(9)pp. 7858-7881
Epoxy resins (EP), as significant thermosetting macromolecules, are widely used in various engineering applications due to their wide range of properties. However, the poor control over curing process of EP, limits their manufacturing process. Here, a SiO2-nanoscale ionic materials (SiO2-NIMs)/EP nanocomposite was prepared. The Friedman, Kissinger, Ozawa, Málek, and Friedman autocatalytic models were used to determine kinetic parameters and reaction models, which demonstrates that the SiO2-NIMs improve the curing characteristics of EP through an exclusive mechanism. The solvent role of SiO2-NIMs decreased viscosity and increased reactant mobility, leading to increased curing reactivity. The multi-function groups in the corona-canopy make multiple hydrogen bonding and proton transfer interactions in EP resin, leading to the autocatalytic curing mechanism and effectiveness of treatments. The frequency factor of EP increased by 9% with the addition of SiO2-NIMs. The differential scanning calorimetry tests revealed that SiO2-NIMs decreased Tonset and Tpeak compared to EP. The non-isothermal rheometric mechanical spectrometery (RMS) test indicated that SiO2-NIMs decreased the Tgel of EP resin from 75 to 71°C and increased the initial storage modulus by 90.9%. This study introduces SiO2-NIMs as significant fillers to enhance control over the process conditions and curing kinetic of EP resin for advanced applications such as aerospace and satellite industries. Highlights: Introducing new catalyst based on 3D-dynamic networks strategy of SiO2-NIMs. The SiO2-NIMs show great potential in improving curing characteristics of EP. The SiO2-NIMs increase the frequency factor of EP by 9%. The RMS test indicated SiO2-NIMs increased initial storage modulus by 90.9%. The Fourier transform infrared spectroscopy analysis indicated that SiO2-NIMs accelerate curing process of EP. © 2025 Society of Plastics Engineers.
Publication Date: 2025
Polymer Composites (02728397)
This study addresses the effect of the morphology and surface chemistry of Ti3C2Tx MXene nanoparticles (NPs) on the mechanical properties, adhesion, and thermal stability of the epoxy-based adhesives using a combination of experimental and molecular dynamics (MD) simulation techniques. The results reveal that the incorporation of 0.5 phr (3-aminopropyl) triethoxysilane (APTES)-functionalized MXene enhances the tensile strength, modulus, toughness, lap shear strength, and initial degradation temperature (TIDT) by 14.08%, 32.19%, 50.81%, 56.13%, and 14.40%, respectively, compared to the neat adhesive. The results show that the adhesives reinforced by the functionalized NPs exhibit the best performance in comparison with those reinforced by blank single-layer or multilayer NPs. The MD simulation results indicate that the blank single-layer and multilayer MXene NPs increase the flexibility and diffusivity of the epoxy chains and also demonstrate that using single-layer MXene leads to a higher modulus compared to using multilayer MXene, which confirms the experimental trends. © 2025 Society of Plastics Engineers.
Publication Date: 2025
Journal of Inorganic and Organometallic Polymers and Materials (15741443)
This research examines the use of molybdenum disulfide (MoS2) nanosheets in drug delivery and cancer treatment, highlighting their unique characteristics, including anisotropy, mechanical strength, and biocompatibility. It discusses various synthesis techniques, surface modifications, and diverse drug delivery systems that incorporate MoS2, underscoring its notable absorbance in the near-infrared spectrum and its magnetic properties, which enhance its efficacy in photothermal therapy and biosensing. Despite the increasing interest in MoS2 for biomedical applications, challenges remain in its functionalization, particularly when compared to graphene, due to its more complex structure. This review emphasizes the necessity for environmentally friendly synthesis methods, scalable production techniques, and the incorporation of targeting ligands to improve the therapeutic effectiveness and biocompatibility of MoS2 nanoparticles. Furthermore, it highlights crucial research areas that explore biosafety, long-term effects, metabolic pathways, and the clinical potential of MoS2 in bioimaging and photothermal therapy (PTT). Ultimately, it is essential for researchers to collaborate to advance the clinical application of MoS2 in nanomedicine and to develop innovative therapeutic strategies. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.
Publication Date: 2025
Scientific Reports (20452322) 15(1)
Epoxy adhesives are widely used as structural adhesives distinguished by a significant degree of cross-linking, resulting in their brittle characteristics. Some specialized applications require improved thermal stability and adhesive strength. The incorporation of zinc oxide nanoparticles into a core–shell rubber (CSR) structure composed of poly(butyl acrylate-allyl methacrylate) core and poly(methyl methacrylate-glycidyl methacrylate) shell will enhance the adhesion, toughness, and thermal stability of epoxy adhesives. We synthesized CSR particles using a two-stage emulsion polymerization method, characterizing them through Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and differential scanning calorimetry (DSC) analyses. We synthesized epoxy adhesives with different CSR particles ratios (1.25, 2.5, and 3.75 phr) and zinc oxide nanoparticles (1, 2, and 5 phr) using mechanical stirring and ultrasonication (a two-step mixing process) to enhance dispersion. We cured the epoxy adhesive samples for 7 days for tensile tests and 2 days for lap shear tests at room temperature. We employed the tensile and lap shear tests to assess the mechanical properties of the samples. The samples underwent thermogravimetric analysis (TGA) to assess their thermal stability. We assessed the fracture surface of the optimum samples using field-emission scanning electron microscopy (FESEM). We utilized design-of-experiments (DOE) and artificial neural network (ANN) approaches to model the mechanical properties. The outcomes of FTIR, SEM, TEM and DCS analyses validated the successful synthesis of CSR particles. The tensile test findings on the dumbbell-shaped samples show a 51%, 30%, and 218% enhancement in tensile strength, modulus, and toughness for the samples containing 2.5 phr CSR particles and 2 phr zinc oxide nanoparticles, respectively. Furthermore, the lap shear tests revealed that the addition of 3.75 phr CSR particles and 5 phr zinc oxide nanoparticles increased the shear strength to 19.5 MPa. This is 127% higher than the pure epoxy. The TGA data indicated that both additions improved the thermal stability of the pure epoxy. Additionally, the predictions of shear strength, toughness, tensile modulus, and tensile strength by DOE and ANN were very close to the experimental results (R2adj > 0.95 for DOE and MREave < 3.2 for ANN). © The Author(s) 2025.
Publication Date: 2025
ChemCatChem (18673880) 17(3)
The modern world's major challenges, such as global warming, air pollution, and increasing energy demands, escalate the importance of sustainable development and transition toward renewables using innovative and environmentally friendly solutions, such as intensifying chemical processes, to reduce carbon footprints effectively. Aiming to enhance the process toward negative carbon emissions, this perspective explores the intensified membrane reactors for reducing the energy intensity of converting biogas into methanol, a versatile chemical feedstock, and renewable liquid fuel. Syngas and methanol synthesis processes, catalysts, and membranes were explored, and novel reactor designs were proposed. Introduction of selective membranes into the catalytic reaction zone to combine synthesis separation steps could enhance the system efficiency and intensify the process by recycling energy and materials, besides reducing costs and required energy for the separation process: the continuous harnessing of products shifts reactions toward desired species while recycling energy and materials enhances the process efficiency, and separating water from methanol reduces the required energy and costs of extra processes for methanol separation. The successful implementation of this technology holds significant promise for sustainable developments in producing chemicals and renewable fuel from renewable biogas and reducing methane and carbon dioxide emissions toward achieving carbon-negative technologies. © 2024 The Author(s). ChemCatChem published by Wiley-VCH GmbH.
Publication Date: 2024
Polymer Composites (02728397) 45(8)pp. 7689-7700
Epoxy film adhesives are typically used in different industries. However, these adhesives suffer from brittleness, low flexibility, and thermal stability problems. In this research, phenolic resin (Novolac) and poly (butyl acrylate-block-styrene) were used in the formulation of epoxy film adhesive (Diglycidyl ether bisphenol A) to increase thermal stability and adhesion strength and as the toughening agent, respectively. Alumina nanoparticles were also employed to enhance the mechanical properties. The influence of block copolymer and alumina nano particles was also assessed on the mechanical and thermal properties of epoxy-based film adhesives. The investigation of the mechanical properties of dumbbell-shaped samples and adhesion strength of the Al-Al bonded joints were evaluated by tensile, lap shear, and T-peel tests. The thermal stability of the optimal samples was assessed by thermogravimetry analysis (TGA). SEM analysis was also utilized to study the toughening mechanism. Tensile test of the dumbbell-shaped samples indicated that the incorporation of 2.5 phr block copolymer and 2 phr alumina nanoparticles enhanced the toughness to 250%. The shear and peel strengths of this sample also exhibited 51% and 76% increase, respectively, showing a remarkable synergistic effect. On the other hand, TGA results revealed that the incorporation of block copolymer improved the thermal stability of the adhesive matrix. The copresence of these two materials also showed a considerable synergistic effect on the thermal stability. The SEM results were also in line with the results of mechanical tests as the crack deviation, crack pinning, and debonding were the most important mechanisms of toughening. Highlights: A new platform was developed for designing epoxy films adhesives with high mechanical, adhesion, and thermal properties. The hybrid of butyl acrylate block styrene copolymer, phenolic resin, and alumina nanoparticles showed synergistic effects on the lap shear and T-peel strength. The greatest improvement in toughness was related to the epoxy adhesive containing 2.5 phr block copolymer and 2 phr alumina nanoparticles. Analysis of the fracture surface showed that by using hybrid of nanoparticles and block copolymers in the epoxy film adhesive formulation, the cohesive failure occurred. The use of hybrid additives in film adhesive formulations enlightened manufacture of adhesives for future studies on adhesive formulations. © 2024 Society of Plastics Engineers.
Publication Date: 2024
Polymers for Advanced Technologies (10427147) 35(1)
In this study, MIL-101 (Cr) and NH2-MIL-101 (Cr) nanoparticles were synthesized by hydrothermal method. Butyl acrylate-styrene copolymer was used along with these nanoparticles to improve the mechanical properties of epoxy adhesive. The results of the Fourier Transform Infrared (FTIR) and X-ray diffraction (XRD) test showed that the synthesis and functionalization of the metal organic framework (MOFs) were successful. The mechanical properties and adhesion features in the lap joint bonding of aluminum foil to the aluminum foil of modified epoxy adhesives were investigated by tensile and lap shear tests. The results of the tensile test showed that by adding 0.3 wt% of NH2-MIL-101 (Cr) and 2.5 wt% of poly(butyl acrylate-block-styrene) to epoxy adhesive, the tensile strength, modulus and toughness of dumbbell samples were increased up to 34.46%, 31.74% and 58.53%, respectively. Furthermore, based on the lap shear test results, by adding 0.3 wt% NH2-MIL-101 (Cr) along with 2.5% poly(butyl acrylate-block-styrene) to the epoxy adhesive, the lap shear strength of samples increased from 1.05 ± 0.08 MPa to 5.25 ± 0.06 MPa compared to the neat epoxy adhesive. According to the TGA test, the highest thermal stability is related to the sample containing 0.3 wt% of NH2-MIL-101 nanoparticles and 2.5 wt% of the copolymer. The image of the fracture surface of the sample containing 0.3 wt%. NH2-MIL-101 (Cr) and 2.5 wt% block copolymer shows that the interface of nanoparticles and the matrix improved due to the chemical reaction of functional groups of nanoparticles and adhesive matrix. © 2023 John Wiley & Sons Ltd.
Publication Date: 2024
pp. 51-79
Hydrogen is considered the energy carrier of the future since it produces only water when it is fed to polymer electrolyte membrane fuel cells. Currently, hydrogen is mainly produced by methane steam reforming, which is an energy-intensive process emitting approximately 9kg-CO2/kg-H2-produced. However, using alcohols from biofeedstock could reduce the CO2 emission. In addition, green hydrogen could be produced if a membrane reactor (MR) is used. The MR has the main benefit to intensify the process in terms of energy and efficiency since hydrogen is produced and simultaneously separated from the CO2 by a membrane. In this chapter, the relevant progress in topics of alcohol reforming via MR technology and the effect of operating conditions on the reforming reaction in MRs are reviewed and discussed. Moreover, mathematical models used for modeling reforming processes in MRs are discussed. © 2025 Elsevier Inc. All rights reserved.
Publication Date: 2024
Thermal Science and Engineering Progress (24519049) 55
Metal–organic frameworks (MOFs) are known for their excellent physical and thermal properties. In the current paper, the use of thermally stable MOFs in the preparation of epoxy composites were studied and their tolerance to high temperatures was investigated in terms of degradation kinetics and operating temperature. UiO-66 and UiO-66-NH2 were used to prepare a series of novel composites from epoxy resin and Novolac (EU and EUN samples, respectively). The effect of the amine groups presented in the UiO-66-NH2 structure on the thermal stability was studied using decomposition activation energy (Ea). The Flynn–Wall–Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Ozawa models were used to study the Ea, where it was increased from 166.7 kJ·mol−1 in neat epoxy samples to 238.58 kJ·mol−1 in EUN samples by using only 0.5 Phr of the UiO-66-NH2. Moreover, the operating temperature of the prepared composites was calculated and compared for four sets of heating rates. Up to 10 % mass loss, the mean operating temperature for using the neat epoxy, EU, and EUN composites for 20,000 h, was found to be 184.17 ℃, 246.26 ℃, and 247.73 ℃, respectively. This approach can pave the way for using MOFs as fillers in preparing innovative thermoset composites. © 2024 Elsevier Ltd
Publication Date: 2024
Journal Of The Iranian Chemical Society (1735207X) 21(2)pp. 549-559
PAN‐based carbon fiber surface properties modified by electrochemical oxidation process were studied by different methods. Functional groups created during the electrochemical oxidation process were characterized by potentiometric titration and spectroscopic (ATR-FTIR) methods. Hydrogen atoms of carboxylic groups on surface of modified carbon fiber react with hydroxyl groups of sodium hydroxide and pristine alkalis were determined by titration method. The increase in oxygen content on the carbon fiber surface modified by ammonium oxalate monohydrate electrolyte’s ((NH4)2C2O4.H2O) was shown by EDX spectrum. The surface topography and effect of electrochemical alteration were studied using atomic force microscopy (AFM). The AFM results showed that the porosity of the modified carbon fiber surface increased during the electrochemical oxidation process. The results showed that with the increase of 30% of carboxylic groups on the surface of carbon fiber and the increase in surface etching, the chemical properties and morphology of the fiber surface improved by 25–30% during the electrochemical oxidation process. Graphical abstract: (Figure presented.). © Iranian Chemical Society 2023.
Publication Date: 2024
International Journal of Hydrogen Energy (03603199) 51pp. 624-636
Material characterization, hydrogen permeation, and separation properties of a novel ternary Pd82Ag15Y3 membrane were evaluated by feeding single gases and several mixtures at temperature and pressure ranges of 300–600 °C and 1.0–3.0 bar (abs), respectively. The Pd82–Ag15–Y3 membrane was prepared by cold rolling and was characterized by ∼38 μm of thickness. When exposed to air at different temperature and constant pressure of 1 bar, the membrane showed good thermal and chemical stability. In particular, its surface area increased from 615 μm2 at 25 °C to 685 μm2 at 500 °C indicating a potential improvement of hydrogen permeation. However, several agglomerates consisting of metal oxides were formed on the surface at the highest temperature. The temperature was -then- kept constant at 400 °C and the pressure was varied to analyze the effects of singles gases and several mixtures on the hydrogen permeation characteristics. When exposed to pure gases, such as H2 and N2, the membrane showed an H2 permeability of 9.1 × 10−11 mol m−1 s−1.Pa−0.9 and “n” value of 0.9 due to the presence of Y, while no N2 was detected in the permeate stream, respectively. So, the membrane was considered to be completely selective towards H2 permeation. When mixtures were used, the hydrogen permeation decreased by its original value due to the presence of other gases, such as N2, CH4, CO2 and CO. The presence of CO particularly affected the H2 permeating flux due to the competitive adsorption of both gases on the Pd-alloy surface. Finally, the Scanning Electron Microscope (SEM), Energy Dispersive X-Ray Spectroscopy (EDS), Atomic Force Microscope (AFM) and X-ray diffraction (XRD) analysis were performed to observe any changes in the surface and structure of pristine and used membrane. © 2023 Hydrogen Energy Publications LLC
Publication Date: 2024
Energy and Fuels (08870624) 38(21)pp. 19992-20014
The emission of greenhouse gases (GHGs) has escalated to unprecedented levels due to the extensive use of fossil fuels for industrial development and population growth. Consequently, the transition to clean and renewable energy sources is critical for mitigating climate change. Hydrogen is considered a promising energy carrier that can be produced from both conventional (fossil fuels) and renewable resources (biofuels and water). Among renewable sources, ethanol is favored over other bioalcohols because it has a high energy content and is less toxic than hydrocarbon fuels. In addition, ethanol reforming represents a viable method of efficiently producing renewable hydrogen. To enhance this process, innovative technologies have been developed, particularly through the use of a membrane reactor (MR) technology. In MRs, the reaction and separation processes occur simultaneously, which improves the selectivity and yield while reducing operating conditions and preventing coke formation. This study aims to highlight recent advancements in ethanol reforming reactions─including steam reforming, partial oxidation, and autothermal reforming reactions─to produce renewable, low-carbon hydrogen using MR technology. In particular, the central focus is to provide a comprehensive analysis of the performance of different MRs, shedding light on their efficacy, scalability, and potential limitations in the context of renewable hydrogen production from ethanol reforming. By exploring these aspects, this study attempts to inform strategic decisions and advancements in sustainable energy technologies, facilitating the transition toward a greener, more resilient energy landscape. © 2024 American Chemical Society.
Publication Date: 2024
Polymers for Advanced Technologies (10427147) 35(9)
Epoxy adhesives become very brittle after curing due to their high-crosslinking degree. For increasing the toughness of epoxy adhesives, the addition of different toughening agents has been proposed. In this study the diglycidyl ether of bisphenol A (DGEBA)/dicyandiamide epoxy network has been modified by adding an emulsion latex containing core–shell rubber particles (CSPs) prepared by means of seeded emulsion polymerization. The CSPs consist of poly (butyl acrylate) (PBA) as core and methyl methacrylate (MMA) copolymerized with glycidyl methacrylate (GMA) as shell. The effects of adding various amounts of the emulsion latex on the mechanical properties, thermal stability, adhesion, and microstructure of the cured epoxy resin were investigated. The CSPs were analyzed by transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The mechanical properties, thermal stability, adhesion to aluminum plates, and microstructure of the cured epoxy resin were investigated by stress–strain, thermal gravimetric analysis (TGA), single lap shear test, and field emission scanning electron microscopy (FESEM), respectively. The addition of 7 wt.% emulsion latex to epoxy enhanced the tensile strength and the toughness of the dumbbell-shaped samples by 421% and 4388% with respect to neat epoxy, respectively. Furthermore, the single lap shear strength increased in 33% and an increase of 71°C in the initial decomposition temperature of the epoxy was obtained by adding 7 wt.% CSP, without affecting the maximum decomposition temperature. The FESEM micrographs of the fractured surfaces indicated that the major toughening mechanisms were CSP de-bonding, plastic void growth, and shear bond yielding. © 2024 John Wiley & Sons Ltd.
Joseph, T.M. ,
Azat, S. ,
Ahmadi, Z. ,
Moini jazani, O. ,
Esmaeili, A. ,
Kianfar, E. ,
Haponiuk, J. ,
Thomas, S. Publication Date: 2024
Case Studies in Chemical and Environmental Engineering (26660164) 9
It is difficult to reuse wastes from polymers due to the mismatch between the amount of contaminants and the secondary polymers and the quality of the feed. This type of operation is much more expensive and cost-effective than the production of polymer raw materials from the latest materials. However, the reuse of recyclable polymers is beneficial if used extensively in the production of various concrete products and wood-polymer boards. This is done only if cleaning and sorting are not particularly important for the production of polymer products. Polyethylene terephthalate (PET) is a widely used polymer in various industries due to its excellent physical and chemical properties. Besides, the increasing use of PET products has led to a global crisis in waste management, as improper disposal of products has caused significant environmental damage. PET is a major source of accumulated waste in landfills, and to address this issue, recycling methods have evolved. In this regard, the present review examines various techniques involved in the recycling of PET. Conventional recycling methods and the influence of diverse depolymerization reaction variables were discussed, and the upsides and downsides of each technique were considered. The review summarizes major advances in recycling technologies for plastic waste, focusing on the bio-recycling of PET, aiming for sustainable, economical solutions in the circular economy. © 2024 The Authors
Publication Date: 2024
Colloids and Surfaces A: Physicochemical and Engineering Aspects (18734359) 687
Objectives: Epoxy adhesives are advanced materials, but suffer from high brittleness and low toughness due to their high crosslinking degree, which limits their service life in structural applications. The lack of appropriate thermal stability at high temperatures is another constraint of epoxy adhesives. The main aim of this research was to increase the thermal stability and toughness of epoxy adhesives using phenolic resin, zinc oxide (ZnO) nanoparticles, and poly (butyl acrylate-block-styrene) copolymer as a toughening agent. Furthermore, the mechanical properties of epoxy adhesives were predicted by designing two feed-forward multilayer perceptron (MLP) networks. Methods: Epoxy adhesives with different contents of phenolic resin (10, 20, and 30 phr), copolymer (1.25, 2.5, and 3.75 phr), and ZnO (0.5, 1, 2, and 5 phr) nanoparticles were synthesized under mechanical mixing by using xylene as solvent. Then, the epoxy adhesive samples for tensile and lap shear tests were cured at room temperature for 7 and 2 days, respectively. The mechanical properties of adhesive samples were measured by tensile and lap shear tests. The thermal stability of the epoxy adhesive samples was investigated by thermogravimetric analysis (TGA). The kinetics of the curing reaction of the optimum epoxy adhesive samples was also studied by differential scanning calorimetry (DSC). Results: The toughness of epoxy adhesive containing 10 phr phenolic, 2.5 phr block copolymer, and 2 phr ZnO nanoparticles increased by 20%, and shear strength by 99% compared to pure epoxy adhesive, notifying a significant synergistic effect. The TGA results showed that all three mentioned additives have increased the thermal stability of pure epoxy. The highest thermal stability was observed for epoxy adhesive containing 2.5 phr block copolymer and 2 phr ZnO nanoparticles. In addition, DSC analysis proved the positive effect of ZnO nanoparticles incorporation and block copolymer on the curing kinetics of epoxy adhesive. Moreover, the predicted tensile strength, tensile modulus, toughness, and shear strength of epoxy adhesives by MLP networks showed a very good consistency between the experimental data and the model predictions (e.g., MRE < 1.1 for lap shear). Significance: In the current study, the artificial neural networks (ANN) results showed that there was very good consistency between the ANN predictions and the experimental data. © 2024 Elsevier B.V.
Publication Date: 2023
Polymer Composites (02728397) 44(12)pp. 8353-8365
The present study was an attempt to improve the toughness, mechanical and adhesion properties, and thermal stability of a two-phase epoxy DGEBA/Resole phenolic resin through the use of carboxyl-modified multi-walled carbon nanotubes (c-MWCNTs) and ground rubber tire (GRT) powder. The effect of a hybrid reinforcement containing GRT and c-MWCNT blend on the mechanical properties, thermal stability, and microstructure of the epoxy-phenolic adhesive were evaluated by tensile test, TGA, and FESEM, respectively. The formulated adhesive was utilized in a lap joint metal to a composite in order to peruse the adhesion features, where the composite was an epoxy resin reinforced with carbon fibers and the metal was stainless steel 316 L. According to the tensile test, there were 32% rise in tensile strength, 27% rise in modulus, and a 64% rise in toughness with adding 0.5% wt c-MWCNTs and 15 phr waste GRT powder to the epoxy-phenolic matrix. Furthermore, adding 1% wt c-MWCNTs of nanoparticles and GRT powder has resulted in a 15% increase in lap shear strength. It also can be seen that thermal stability for the formulated samples has experienced an upward trend compared to the neat epoxy composite. Highlights: Epoxy adhesives based on GRT Powder, c-MWCNTs particles and phenolic resin have been successfully prepared. The hybrid uses of GRT Powder and c-MWCNTs particles can synergistically increase the tensile and lap shear strength The addition of c-MWCNT nano particles and GRT Powder in an epoxy adhesive can have a dramatic rise in the toughness system compared to the neat epoxy adhesive. Maximum degradation temperature of the produced newly adhesive has increased considerably in contrast with the neat epoxy adhesive. © 2023 Society of Plastics Engineers.
Publication Date: 2023
Chemical Engineering and Processing - Process Intensification (02552701) 189
The development of sustainable and new technologies based on renewable energy sources is mandatory due to the anthropogenic climate changes and the depletion of fossil fuels. Hydrogen is considered a clean alternative able to produce only water and energy when consumed in fuel cell. However, the main issue for large-scale hydrogen commercialization is its storage and transportation. One way to solve this problem is to use energy carriers, such as methanol, which is liquid at ambient conditions, low reforming temperature, holds relatively highly H/C ratio and can be produced by biomass. So, hydrogen can be later produced on-demand by methanol steam reforming reaction. In order to produce carbon-low hydrogen alternative technologies are considered. In particular, membrane reactors are raising attention. The use of membrane reactor enables to increase the process selectivity, lower the temperature of the reaction while avoiding the formation of coke, and obtain a high pure hydrogen stream. This review provides an overview of the recent progress to produce hydrogen from methanol reforming in convectional and membrane reactors. © 2023
Publication Date: 2023
Materials Chemistry and Physics (02540584) 308
Film adhesives made from epoxy resin are typically used in different industries including transportation and aerospace to attach aluminum substrates together. These film adhesives offer a series of advantages including ease of application and handling, control over the adhesive thickness, minimal waste and uniform product as compared to other forms of adhesive like paste adhesives. Here, we try to improve the mechanical and thermal properties of these adhesives as well as to address poor ductility and weak fracture toughness of cured epoxy as major disadvantages. We used two dimensional (2D) Ti3C2Tx nanoparticles (NPs) which is the most well-known member of the emerging MXene family. MXenes a recent class of 2D transition metal carbides, nitrides and carbonitrides, have attracted many attentions since they were synthesized in 2011.The particular structural and functional characteristics of MXenes make them good candidate for multifunctional composites. The addition of inorganic MXene NPs to epoxy matrix at 1 phr accompanied by phenolic resin (novolac type) improves the tensile strength, modulus, and toughness of the adhesive by 16.49%, 43.51%, and 17.19%, respectively. Using MXene NP-containing epoxy film adhesives for attaching aluminum pieces together, we realized that the presence of MXene increases the single-lap shear strength and T-peel strength by 32.69% and 37.94%, respectively.in addition, the thermal stability of the MXene NP-containing film adhesives was improved, as indicated by 10.51% increase in the initial degradation temperature. © 2023
Nikkhah varkani, M. ,
Moini jazani, O. ,
Sohrabian, M. ,
Torabpour esfahani, A. ,
Fallahi, M. Publication Date: 2023
Journal of Inorganic and Organometallic Polymers and Materials (15741443) 33(11)pp. 3595-3616
Epoxy adhesives are one of the polymers used as high-performance matrix in adhesives. However, the high brittleness and low toughness of epoxy adhesives are critical challenges during their service in structural applications due to their high-crosslinking degree. The lack of appropriate high-temperature thermal stability is another drawback of these valuable materials. This study addressed the effect of hybrid reinforcement comprising zirconium oxide nanoparticles (NPs), phenolic resin (resol type), and poly (butyl acrylate-block-styrene) copolymer (BCP) on mechanical, adhesion, thermal, and morphological properties of the epoxy adhesive. Mechanical properties, thermal stability, and microstructure of the epoxy adhesive was assessed using tensile test, TGA, and FESEM tests, respectively. The adhesion features of the formulated adhesive were evaluated in lap joint bonding of an aluminum to aluminum. A new approach was developed to design advanced adhesives with high mechanical, adhesion, and thermal properties by adding hybrid additives. Based on the tensile test results, adding 5 phr of zirconium oxide nanoparticles to the epoxy adhesive increased the tensile strength, modulus, and the toughness of the dumbbell-shaped samples by 69, 33 and 175% compared to the neat epoxy adhesive, respectively. Furthermore, the sample containing 10 phr phenolic resin, 5 phr zirconia NPs, and 2.5 phr block copolymer exhibited the highest improvement (420%) in the shear strength in the single lap joint increment compared to pure epoxy, reflecting the synergistic impact of these compounds at the mentioned percentage. The TGA results indicated the highest initial degradation temperature in the sample containing 5 phr zirconia NPs which was 54.4 °C higher than that of the pure epoxy. The images of the fracture surface of the optimal samples in the tensile test showed the cavitation, shear band formation, crack deviation, and crack tip blunting as major mechanisms in the toughness enhancement of the samples. Graphical Abstract: [Figure not available: see fulltext.] © 2023, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
Publication Date: 2023
pp. 67-94
Ammonia is currently considered as an energy carrier because it allows for hydrogen storage in liquid-phase under mild conditions. Although ammonia can be directly employed for energy application, its use in proton-exchange membrane fuel cells (PEMFC) requires two steps: decomposition into hydrogen and nitrogen, and separation of hydrogen. The combination of ammonia decomposition and in situ separation of hydrogen via membrane reactor (MR) can lead to relax the thermodynamic constraints, reduce the footprint of this technology, and intensify the process. Indeed, in the field of hydrogen production and separation, the use of MR induces the selective hydrogen removal from the reaction zone through the membrane enabling a higher conversion and hydrogen yield compared to the conventional reactor. In this chapter, the relevant progress achieved so far, the most relevant topics of ammonia decomposition via MR technology and the effects of the most important parameters affecting the reaction in MRs are described and critically reviewed. In addition, an overview on the mathematical models used for simulating ammonia decomposition in MR is also presented and discussed. © 2024 Elsevier Inc. All rights reserved.
Publication Date: 2023
Chemical Engineering Journal (13858947) 471
Epoxy (EP) adhesives as high-shear strength permanent adhesives have been used in various engineering applications, particularly aerospace and automotive. However, these adhesives suffer from disadvantages such as high fragility, poor tensile strength, and toughness, which limits adhesion efficiency in structural bonding. Here, a novel EP nanocomposite adhesive-based SiO2-nanoscale ionic materials (SiO2-NIMs) with excellent adhesives strength, transparency, thermal stability, and mechanical properties was prepared via a solvent-free process. To prepare SiO2-NIMs, the sulfonated-SiO2 nanoparticles (SiO2-SO3H) were ionically tethered as a core-corona with Jeffamine-ED-2003 chains as a canopy. Then, SiO2-NIMs/EP nanocomposites with various SiO2-NIMs contents were fabricated. We demonstrate that SiO2-NIMs as high-performance additives, unlike conventional additives, via an exclusive mechanism can simultaneously improve interfacial bond strength, stiffness, and toughness of EP adhesive. The RMS and DMTA tests averred the liquid-like SiO2-NIMs played a magnificent multi-functional role that acts as nonvolatile solvents, reinforcing-agent particles, and toughening agents, causing improved shear strength and resistance to crack growth of epoxy adhesives. The core-corona-canopy parts of SiO2-NIMs make hydrogen bonds and ionic-electrostatic interactions between the adhesive and adherent layers. The single lap shear under different temperatures, TGA, tensile, and SEM tests were applied to investigate adhesion strength, thermal and mechanical properties, and fracture surface morphology of EP adhesives, respectively. For example, the 5 phr SiO2-NIMs/EP showed increased lap shear strength at RT, tensile toughness, tensile strength, stiffness, elongation% and char-yield% by 54%, 240%, 92%, 36%, 91%, and 50% compared to neat EP, respectively. This study introduces SiO2-NIMs as promising additives for high-performance EP adhesives. © 2023 Elsevier B.V.
Kaveh, A. ,
Moini jazani, O. ,
Fallahi, M. ,
Asghari, S. ,
Mirmohammadi, S.M. ,
Hajizamani, E. ,
Taghavi, M.R. ,
Namvar asl, A. Publication Date: 2023
Colloids and Surfaces A: Physicochemical and Engineering Aspects (18734359) 676
Background: Epoxy-based adhesives are widely used in different industries in various forms. Among them, epoxy film adhesives are particularly applicable in constructing honeycomb structures in aerospace systems. However, these adhesives suffer from brittleness, low flexibility, and thermal stability. In the current paper, the effect of pure and functionalized SiO2 and ZrO2 nanoparticles (NPs), the addition of a block copolymer (butyl acrylate-block-styrene), and Novolac resin on the mechanical, thermal, and adhesive properties of the epoxy film adhesive were thoroughly studied. Methods: The mechanical properties, thermal stability, and surface morphology of the epoxy adhesive samples were evaluated using tensile, thermogravimetric analysis (TGA), and field emission scanning electron microscopy (FE-SEM) images, respectively. More importantly, the Lap shear and Peel tests were utilized to investigate the adhesive properties. Significant findings: Pure and functionalized NPs were added to the prepared epoxy adhesive samples. Intriguingly, compared to the non-functionalized NPs, by only adding 1 phr of each functionalized NPs to the formulation, the tensile modulus, tensile strength, and toughness increased to 66 %, 197 %, and 553 %, respectively. More importantly, the single lab shear and T-peel strength were increased as high as 121 % and 101 %, respectively, indicating a synergistic effect. After optimizing the parameters effective on the properties, FE-SEM images of the fractured surface of optimized samples were used to study the possible fracture mechanisms, including crack deflection, crack pinning, nanoparticle debonding, and shear band formation. Also, this synergistic effect was observed in the thermal stability where the only addition of 1 phr of functionalized NPs increased the decomposition onset temperature up to 40 ℃ higher than the neat one. This simple and applicable method can pave the way for using functionalized NPs in modifying epoxy adhesives. © 2023 Elsevier B.V.
Publication Date: 2023
Brazilian Journal of Chemical Engineering (01046632)
In this study, the effect of nanosilica (SiO2) reinforcement on the gas separation properties of polyurethane/polyethylene glycol (PU-PEG) nanocomposite membrane was investigated. Formulation optimization of PU-PEG-SiO2 triple nanocomposite membrane was performed using experimental design and the Taguchi method. The effects of different formulation variables including nanosilica content, PEG content and molecular weight on the permeability and selectivity of CO2, N2, O2 and CH4 gases were investigated. The morphological and structural properties of the membranes were investigated by SEM, XRD, and FTIR analysis. Finally, the selectivity of optimal nanosilica-reinforced membrane was evaluated by Robeson's upper bound diagram. The obtained results showed that increasing the PEG content improves the gas permeability of the membrane due to its plasticizing effect. However, PEG plasticizing effect decreased at higher molecular weights and resulted in permeability reduction. By increasing the nanosilica content, the permeability of all the gasses reduced but the selectivity of the membrane for CO2 over CH4 and N2 improved. Finally, PU-20% PEG6000-5% SiO2 formulation which had the best selectivity for CO2/CH4 gases and was closer to Robeson’s upper bound line was chosen as the optimal composition. In conclusion, PEG/nanosilica-reinforced Polyurethane nanocomposite membrane could serve as a promising candidate for efficient gas separation applications. © 2023, The Author(s) under exclusive licence to Associação Brasileira de Engenharia Química.
Publication Date: 2022
Polymer Composites (02728397) 43(3)pp. 1637-1655
In this research, phenolic resin and poly (butyl-acrylate-block-styrene) copolymer were used in the formulation of epoxy adhesive to improve its thermal stability and toughness. Also, in order to improve the mechanical properties such as the modulus and tensile strength, aluminum oxide nanoparticles (NPs) were added to the epoxy based resin. Effects of different factors such as percent contents of phenolic resin, toughening agent, and aluminum oxide NPs on the microstructure, mechanical properties, and thermal stability of the epoxy-based adhesives were investigated. Thermogravimetric analysis, Fourier transform infrared spectroscopy, and field-emission scanning electron microscopy were used to investigate the thermal, mechanical, and morphological properties of the prepared epoxy adhesive samples. In addition, the curing kinetics of the optimal specimens was studied based on differential scanning calorimetry (DSC). The experimental results indicated that the phenolic decreased strength of dog-bone samples, while increased the adhesion strength in metal-to-metal single-lap strength. On the other hand, addition of block-copolymers as toughening agent led to a consistent decrease in the modulus as well as increasing the tensile strength. Also, results of single-lap strength tests showed that, in the optimal quad system, the four components exhibit synergetic effects and show a single-lap strength that is 152% higher than that of pure epoxy. The DSC analysis indicated that the presence of alumina NPs and block-copolymers tend to reduce the initial curing temperature while increasing the curing reaction heat. © 2022 Society of Plastics Engineers.
Publication Date: 2022
Journal Of Computational Applied Mechanics (24236713) 53(1)pp. 55-65
In order to investigate and improve the destructive effects of maneuvers that the flying body has during a flight in space, it is necessary to know the forces acting on the flying body. In this paper, an analysis of the composite sandwich structure of a launch vehicle fairing is considered. This study explores carbon-fiber-reinforced skins with different cores used to deploy satellites and can be used as a space habitat. In order to calculate the effective forces on sandwich skins, finite element method (FEM) was used to determine three-dimensional stress and strain. Three types of structural models with honeycomb and solid core under dynamic loads were compared and evaluated. Models were compared in three category of stress distribution, strain and weight. The honeycomb core pattern helps reduce the structure's weight up to half of the structure compared to a solid core. The effect of mesh size sensitivity applied on simulations. The results showed that the amount of stress and strain were the same in all models and only differed in dispersion. However, the composite sandwich structure with aluminum core showed more strength against the applied forces. © 2022 PAGEPress Publications. All rights reserved.
Publication Date: 2022
Polymers for Advanced Technologies (10427147) 33(6)pp. 1944-1955
Polythioether is an elastomer with proper thermal resistance and elongation at break, which can be used in various high-temperature and high-pressure sealing applications. This research is aimed to determine the suitable thiol/vinyl ratio and the branching agent content to synthesize a novel polythioether and the polythioether/multiwall carbon nanotube (MWCNT) composite using two monomers, including dimercapto dioxaoctane (DMDO) and triethylene glycol divinylether. For each synthesis process, the gel permeation chromatography (GPC) was used to measure the molecular weight and the polydispersity index of the polymer chains. Fourier transforms infrared spectroscopy and Nuclear Magnetic Resonance were used to study the bond formation, while the glass transition of the polymer was evaluated by differential scanning calorimetry. Tensile and lap adhesion tests were also used to assess the mechanical properties of the samples. Field emission scanning electron microscopy was utilized to observe the dispersion of nanoparticles in polythioether/MWCNT nanocomposite. GPC results showed that the thiol/vinyl ratio of 0.5 and branching agent molar ratio of 0.2 (relative to vinyl monomer) led to the most suitable average molecular weight (2022 g/mol) which had the highest mechanical properties. The nanocomposite containing 1 wt% MWCNT, showed the highest tensile strength and elongation at break up to 2.12 MPa and 303%, respectively. A considerable increase of 30°C is obtained in maximum degradation temperature of the produced nanocomposite compared to neat polythioether. © 2022 John Wiley & Sons Ltd.
Publication Date: 2022
pp. 424-426
Hydrogen permeation and separation properties of a ternary Pd-alloy are evaluated at temperature and pressure range of 300 °C and 600 °C and 2-5 bar (abs), respectively. The membrane Pd82-Ag15-Y3 is unsupported, prepared by cold rolling and it is characterized by ~ 35 μm of thickness. The membrane shows good thermal and chemical stability when exposed to air and at different temperature. In particular, its surface area increases by 2.5x from room temperature to 600 °C indicating a potential improvement of hydrogen permeation. The permeation characteristics of the membrane and the effects of the other gases on hydrogen permeation will be investigated by varying temperature and pressure evaluating the effects of dilution, depletion, concentration polarization, and competitive adsorption on the H2 permeating flux. © 2022 Proceedings of WHEC 2022 - 23rd World Hydrogen Energy Conference: Bridging Continents by H2. All rights reserved.
Publication Date: 2022
Journal Of Chemical And Petroleum Engineering (24236721) 56(1)pp. 37-52
Polyacrylonitrile (PAN)-based carbon fibers were chemically modified with a different ratio of Sulfuric acid (SA) to Nitric acid (NA), then reinforced Polyurethane (PU) composites in the presence of carbon fibers were prepared. The structural and surface characteristics of the modified carbon fibers were investigated by scanning electron microscopy (SEM), Fourier transforms infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The FTIR results showed the presence of the carbonyl groups in a higher ratio of NA and the formation of carboxyl groups in a lower ratio of NA. The interaction between carbon fiber and PU matrix was studied by the dynamic mechanical thermal analysis (DMTA) method. The DMTA results showed with increasing carbon fiber/PU matrix interaction, the intensity of glass transition temperature decreased. Matching the DMTA results with the power-law model and Cole-Cole diagram showed that the process of carbon fiber modification can increase the amount of chain with a long relaxation time in the PU matrix. © 2022 Vascular and Endovascular Review. All rights reserved.
Publication Date: 2022
Polymer Composites (02728397) 43(6)pp. 3794-3808
In this study, non-isothermal curing kinetics of the prepared samples was studied using differential scanning calorimetry (DSC) to evaluate the effect of methyl phenyl silicone resin (MPS), acrylonitrile butadiene styrene (ABS), and graphene oxide (GO) on the cure reaction of epoxy resin. Chemical and microscopic structure of prepared nanocomposites was investigated using Fourier-transform infrared spectrophotometry (FTIR) and scanning electron microscopy (SEM), respectively. Izod impact strength of modified epoxy resin with 5 phr MPS, 2 phr ABS, and 0.1 phr GO was about 53% higher than pure epoxy resin. Evaluation of activation energy (Ea) by Kissinger, Ozawa, FWO and Friedman methods showed that the presence of GO facilitates the curing reaction by reducing Ea about 30% which is due to the catalytic effect of hydroxyl groups presented on the surface of GO for epoxy ring opening. According to Friedman's plots, curing reaction remained autocatalytic for all of samples. The presence of GO increased the autocatalytic term of the reaction (n) from 0.26 to 0.32. Non-isothermal DSC diagrams obtained from experimental data fitted well with data obtained from theoretical relations. © 2022 Society of Plastics Engineers.
Publication Date: 2022
Journal of Applied Polymer Science (00218995) 139(1)
Herein the kinetics of network formation (cross-linking) and network degradation (thermal decomposition) in a complex system based on epoxy resin reinforced with hyperbranched amino polymer-functionalized nanoparticles (HAPF) were discussed. Five classes of nanoparticles, that is, nano-SiO2, halloysite nanotubes (HNTs), HNTs@nano-SiO2 core/shell, HAPF/nano-SiO2, HAPF/HNTs@nano-SiO2 core/shell were loaded at 0.5, 1.0, 2.0 (optimal loading among prepared samples), and 5 wt% were examined. Parameters of the cure kinetics and degradation were correlated, and the mechanical properties were interpreted in terms of microstructure and rheological analyses. The isothermal chemorheological cure kinetics study (60, 70, and 80°C) revealed a low activation energy for epoxy/HAPF/HNTs@nano-SiO2 core/shell nanocomposite (72.21 kJ/mol), compared with the blank epoxy (79.99 kJ/mol). Correspondingly, gel time of the system decreased from 1040 to 515 to 237 s upon isotherms of 60, 70, and 80°C, respectively. Tensile strength was also increased vividly (ca. 32%), possibly due to the strong interfacial adhesion, which reflected in an induced shear yielding. Nitrogen-mediated thermal decomposition kinetics suggested an average degradation activation energies of ca. 150 and 210 kJ/mol for the assigned nanocomposites and the blank epoxy, respectively. Overall, there was a complete agreement between the kinetics of network formation and network degradation in the studied epoxy nanocomposite. This work enables understanding of structure-properties-performance in complex epoxy nanocomposites. © 2021 Wiley Periodicals LLC.
Publication Date: 2022
Iranian Polymer Journal (10261265) 31(2)pp. 153-167
The impact of styrene–butadiene–styrene (SBS) and maleated styrene–ethylene–butylene–styrene (SEBS-g-MA) weight ratios was studied on the microstructure and ultimate performance of PP/PBT/(SBS + SEBS-g-MA) (70/15/15) blends. Morphological observations revealed a gradual change in the dispersions state of modifier domains from isolated phases to stack formation and then to encapsulation morphology as the SEBS-g-MA proportion was steadily increased. This was accompanied by improved blend homogeneity and finer dispersion of PBT domains (a drop in particle size from ~ 3 μm to ~ 0.3 μm) with increase of SEBS-g-MA concentration in the rubbery fraction of the blend. The alteration of morphology was manifested in macroscopic mechanical properties of the blends. Young’s modulus declined (~ 20%) whereas yield stress (~ 17%), tensile strength (~ 16%), and tensile ductility (~ 210%) were steadily enhanced with increase of SEBS-g-MA concentration in the rubbery fraction of the blend. The notched Izod impact strength also monotonically rose (~ 150%) as SBS:SEBS-g-MA weight ratio was reduced. The improvement of mechanical properties of the blends was attributed to improved blend compatibility and interfacial adhesion followed by more homogeneous mixing state between blend components upon progressive replacement of SBS component with SEBS-g-MA phase. The crystalline- and phase structure of the blends were studied by DCS and DMTA analyses, respectively and correlated with the blend composition and morphology. The impact-fractured surface of the toughened blends was examined and the deformation mechanisms were clarified. Increased resistance against particle debonding along with the development of microvoids induced by rubber phase was responsible for the enhanced impact fracture energy of these blends. Graphic abstract: [Figure not available: see fulltext.] © 2021, Iran Polymer and Petrochemical Institute.
Publication Date: 2022
Polymer Composites (02728397) 43(3)pp. 1665-1684
To improve thermal, mechanical and adhesion properties, epoxy resin was modified with methyl phenyl silicone (MPS), acrylonitrile butadiene styrene (ABS) and graphene oxide (GO). In order to increase compatibility and stability, MPS intermediate was grafted on epoxy resin through condensation reaction. Transmission electron microscopy images showed well dispersion of GO particles in the system proving successfully preparation of the MPS grafted epoxy/ABS/GO nanocomposite. Single lap shear strength for steel-epoxy/carbon fiber composite joint in sample containing 15% MPS and 2% ABS improved up to 108% compared to neat epoxy. Such an improvement occurred when only 5% MPS, 2% ABS and 0.1% GO were used showing GO could decrease required content of modifiers in this case. Tensile strength of sample containing 5% MPS and 2% ABS was 49.89 MPa and it reached 55.23 MPa by adding 0.1% GO while it was 37.12 MPa in pure epoxy. Nanocomposite modified sample had a residual char of 20 wt%. at 600°C and increment of 30°C in initial degradation temperature and 7°C in maximum degradation temperature compared to pure epoxy. These finding beside 23% increasing in calculated activation energy using Kessinger's and FWO method's proved significantly improved thermal stability of modified epoxy resin. Scanning electron microscope images of fractured surface of specimens showed micro size domains obtained by phase separation cause toughness improvement and crack energy absorption. © 2022 Society of Plastics Engineers.
Publication Date: 2022
Journal Of Chemical And Petroleum Engineering (24236721) 56(2)pp. 193-201
The flow responses of aramid and cellulose nanowhisker (fibrids) or CNCs (cellulose nanocrystal) suspended in a sulfuric acid and water respect at loadings of about 17% weight fraction was determined in transient shear flow. The effect of temperature and shearing conditions were examined. Aramid solution exhibits strong shear thinning with power-law indices of about 0.2-0.3, and cellulose nanowhisker suspension indices is below 0.15. Formation of an interacting flocculated network at rest is the reason for the large relative viscosity and offers the least flow resistance during shear flow. The structure formed at rest is easily destroyed, and this is the reason for the observed shear thinning. Evolution of shear stress data versus time over four of shear rate were described the structure of nematic phase in aramid\sulfuric acid solution. Also, nanowhisker/water suspension shear rheology results show shear thinning behavior, and behave as a plastic system at different temperatures. For the spinning process, the aramid\sulfuric acid dope through the air gap entered cold water. Orientation of polymer solution emerged from the spinneret and, through very high extensional shear in the air gap, resulted in excellent tensile properties of the final spun fibers. © Amir Kaveh, Omid Moini Jazani, Morteza Ahmadi Lashaki, Mehrzad Mortezaee, Mahmoud Razavizadeh.
Publication Date: 2021
Journal of the Taiwan Institute of Chemical Engineers (18761070) 123pp. 310-327
In this study, the effect of hybrid reinforcement comprising silica nanoparticles (SNPs) and a blend of equal percentages of acrylamide-modified waste tire powder and polyethylene terephthalate (PET) on mechanical, thermal stability, and microstructure of the epoxy-phenolic adhesive was assessed using tensile test, TGA, and FESEM tests, respectively. To investigate the adhesion features, the formulated adhesive was applied in lap joint bonding of a stainless steel 316L to epoxy resin/carbon fiber composite. Based on the tensile test results, adding 10 wt.% modified waste tire powder- PET blend and 1 wt.% SNPs to the epoxy-phenolic adhesive increased the tensile strength, modulus, and the toughness of the dumbbell-shaped samples by 65.24%, 58.95% and 98.80% as compared with the neat epoxy-phenolic adhesive, respectively. Furthermore, the highest improvement of shear strength, modulus, and toughness in the steel-composite single lap joint was observed in the sample containing 10 wt.% modified waste tire powder-PET blend and 0.5 wt.% SNPs of 237.22%, 25.64%, and 279.66%. TGA results also indicated that the addition of 10 wt.% PET powder and 1 wt.% SNPs enhanced the initial decomposition temperature, maximum decomposition temperature, and residue char by 5.94°C, 3.64°C, and 59.45% respectively. The images of the fracture surface of the optimal samples in the tensile test showed that the debonding of nanoparticles, plastic void growth, and deviation from the main crack path are among the major mechanisms in the increase of the toughness of the samples. © 2021 Taiwan Institute of Chemical Engineers
Publication Date: 2021
Iranian Polymer Journal (10261265) 30(11)pp. 1181-1200
The effects of processing conditions were studied on the phase morphology and mechanical properties of the polypropylene/polybutylene terephthalate (PP/PBT) blends toughened by styrene-butadiene triblock copolymer thermoplastic elastomers. Highly toughened PP-based blends that exhibited increased impact strength (seven- to ninefold) and little loss of stiffness (< 15%) in comparison with neat PP resin were successfully developed through manipulation of the dispersion state and interfacial interactions in the blend systems. A combination of core–shell and separately dispersed morphologies was predicted theoretically and identified by scanning electron microscopy (SEM) observations. It was found that the mixing order and intensity (screw speed) significantly affected the dispersion state of the modifier domains in the blends, which in turn, profoundly influenced the mechanical performance of the resulting blends. The phase interactions and crystalline structure of the blends were examined by DMTA and DSC analyses. The results indicated that the two-step melt blending approach with properly selected mixing parameters was more effective in producing toughened PP/PBT blends with superior impact resistance than the one-step melt mixing procedure. The toughened blends revealed enhanced crystallization behavior in the form of higher cold-crystallization temperature of the PP matrix and larger crystallinity degree over the neat PP resin. Fractography analysis showed numerous voids in the matrix and around the dispersed PBT domains which affected the energy absorbing mechanism during impact loading. Graphic abstract: [Figure not available: see fulltext.] © 2021, Iran Polymer and Petrochemical Institute.
Publication Date: 2020
Journal of Vinyl and Additive Technology (15480585) 26(4)pp. 548-565
Properties of silicone thin films and coatings are strongly hooked on curing reaction. We discussed about cure process of silicone nanocomposites containing halloysite nanotube (HNT) at different loading levels (0.5, 1.0, and 2.0 phr), both qualitatively and quantitatively. Systems containing pristine and aminosilane-functionalized HNT were cured nonisothermally and heat buildup of the reaction was recorded by differential scanning calorimetry (DSC) in terms of the time and the temperature varying the heating rate. Integral and differential isoconversional methods suggested that apparent activation energy (Ea) was strongly affected by the loading level and surface treatment of HNT. The exponent of the autocatalytic reaction (m) was decreased by the introduction and increasing the amount of pristine, and more remarkably the functionalized HNT to the silicone, where the Friedman method suggested 0.249, 0.119, and 0.045 values of m for the neat silicone rubber, and the nanocomposites containing 1 phr of pristine and functionalized HNT, respectively. The logarithm of frequency factor, ln A was also increased due to the enhanced collisions between curing moieties in the presence of pristine and functionalized HNTs form 23.57 seconds for silicone rubber to 24.25 seconds and 25.19 seconds for silicone nanocomposite containing 2 phr of pristine and functionalized HNT, respectively. The theoretical rate of reaction was in agreement with experimental data. © 2020 Society of Plastics Engineers
Publication Date: 2020
Journal of Vinyl and Additive Technology (15480585) 26(4)pp. 502-510
Ternary polymer blends based on polypropylene (PP)/poly(styrene-ethylene-butylene-styrene) (SEBS)/polycarbonate (PC) compatibilized through maleic anhydride-grafted SEBS were prepared using a twin-screw extruder. Four different compositions in which the weight ratio of SEBS constituent was varied from 5% up to 30% were formulated in order to assess the relation between morphology and mechanical properties and SEBS/SEBS-g-MA weight ratio was set to be 1. Samples were characterized using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and mechanical properties measurements. Microscopic observation confirmed the formation of core-shell droplets dispersed in the PP matrix in which the rubbery phase encapsulated PC droplets. Individual fibril-like PC rods were also observed beside the encapsulations. Accordingly, impact resistance progressively improved (28.57-fold at 30 wt% of SEBS) compared to neat PP while only 6.8% decrease was detected in the yield strength of this sample. SEM micrographs also showed that the population and size of the individual PC particles are higher in the samples containing 5 and 10 wt% of SEBS compared to those containing 20 and 30 wt%, which endow the former with higher chance of heterogeneous nucleation and correspondingly higher crystallization temperature confirmed by DSC results. Introduction of SEBS rubber phase intensified the elastic behavior of the blends supported by DMTA thermograms. © 2020 Society of Plastics Engineers
Jouyandeh, M. ,
Moini jazani, O. ,
Navarchian, A.H. ,
Shabanian, M. ,
Vahabi, H. ,
Saeb, M.R. Publication Date: 2019
Applied Surface Science (01694332) 479pp. 1148-1160
Hydroxyl-rich halloysite nanotube (HNT)/silica nanosphere (SiO 2 ) core/shell particles were functionalized with multi-arm hyperbranched polyethylenimine macromolecule to develop epoxy superadhesives for metal/polymer composite interfaces. A variety of techniques including FTIR, TGA, XRD, XPS, and TEM were employed to precisely monitor the surface and bulk chemistry of HNTs flecked with silica particles and subsequently with hyperbranched polymer. Amine groups of the functionalized core/shell nanoparticles were exchanged with imide ones through the reaction with pyromellitic acid dianhydride to make the system thermally stable. Incorporation of the developed reactive bushy-surface hybrid nanoparticles into epoxy resulted in a highly crosslinkable superadhesive with exceptional thermal and mechanical properties; so that addition of only 0.5 wt% of core/shell nanoparticles caused a rise of about 31 °C in glass transition temperature with respect to the blank epoxy, suggesting very high potential of particles to cure with epoxy. Cure of adhesives containing 2 wt% of bushy-surface hybrid nanoparticles via nonisothermal differential scanning calorimetry was indicative of facilitated crosslinking, as detected by a higher enthalpy of ca. 106 J/g at low heating rate of 5 °C min −1 in a narrower temperature interval of ca. 13 °C compared to blank epoxy, visualized by the Cure Index universal dimensionless criterion. From property standpoint, a rise of ca. 130% in lap shear strength was surprisingly observed for adhesives containing bushy-surface hybrid nanoparticles. © 2019 Elsevier B.V.
Jouyandeh, M. ,
Karami, Z. ,
Moini jazani, O. ,
Formela, K. ,
Paran, S.M.R. ,
Jannesari, A. ,
Saeb, M.R. Publication Date: 2019
Progress in Organic Coatings (03009440) 126pp. 129-135
Epoxy resins can be cured with a wide variety of curing agents such as amines and anhydrides, but anhydride curing would be more favorable for research purpose because of epoxy-anhydride curing taking place slowly at room temperature. Incorporation of natural nanosized minerals into epoxy is of environmental importance. Halloysite nanotubes (HNTs) display chemical properties similar to those of silica and alumina, and hydroxyl groups positioned somewhere in between or at the edge of HNTs layers give them potential to participate in epoxy ring-opening. Curing epoxy/anhydride systems containing HNTs at various concentrations (0.5, 1 and 2 wt.% based on 100 parts by weight of epoxy) via nonisothermal differential scanning calorimetry at three heating rates (5, 10 and 15 °C.min−1) is discussed here to study the effect of HNTs concentration on epoxy-anhydride curing reactions. The extent of crosslinking reaction was promoted at 0.5 and 1 wt.% of HNTs as a result of participation of hydroxyl groups of HNTs in epoxide ring-opening, while at 2 wt.% of HNTs a hindered curing was the case, which has been speculated on account of probable deactivation of anhydride curing agent by the internal surface of HNTs pursued by anhydride molecules diffusion into the lumen of HNTs. © 2018 Elsevier B.V.
Publication Date: 2019
Progress in Organic Coatings (03009440) 136
Brittleness and low thermal stability of epoxy confines its usage as adhesive for metal-polymer interfaces. In this work, epoxy formulations containing phenolic resin (X1 (wt.%), for thermal stability), recycled tire powder (X2 (wt.%), economically reasonable for toughening), and clay nanoplatelets (X3 (wt.%), for modulus enhancement) were optimized based on L9 Taguchi experimental design approach. The main effects of X1, X2, and X3 on mechanical properties of epoxy adhesives including tensile strength, Young's modulus, and toughness, were studied by taking into account signal-to-noise ratio (S/N) as well as the analysis of variance (ANOVA). It was found that at X1 level of 50 wt.%, X2 level of 10 wt.%, and X3 level of 2 wt.% an increase of about 39% was observed in the single-lap shear strength compared to blank epoxy adhesive formulation. Scanning electron microscopy revealed crack mechanism in the form of deviation of crack growth pathway when encountered with large platy nanoclays. Thermal stability of epoxy was also improved by 16% based on degradation peak temperature monitoring. © 2019 Elsevier B.V.
Publication Date: 2019
Progress in Organic Coatings (03009440) 136
In this work, the effects of the graphene oxide (GO) content and composition of waste blends of poly(ethylene terephthalate) (W-PET) and ground rubber tire (GRT) on the mechanical properties and lap-shear strength of epoxy adhesives have been discussed. Adhesives based on diglycidyl ether of bis-phenol A (DGEBA) were developed in which extrusion-blended waste blends of W-PET/GRT were incorporated at variable composition (80/20, 50/50, 20/80) together with maleic-anhydride grafted SEBS (SEBS-g-MAH) as a binding agent. Dumbbell-shaped samples and adhesively bonded steel-(epoxy/carbon fiber composite) joints were used to evaluate tension properties of adhesives. The results indicated that addition of 10 phr of SEBS-g-MAH compatibilized 20/80 w/w blend of W-PET/GTR with 0.3 phr GO to epoxy formulation resulted in an increase of modulus, tensile strength and toughness to 33.2, 247.9, and 551.2%, respectively. The stiffness of GO together with its proper adhesion to epoxy/(W-PET/GTR) was responsible for this behavior. The overall shear strength of the composite-metal samples adhered by developed epoxy formulation was increased by 101% compared to the neat epoxy matrix. © 2019 Elsevier B.V.
Publication Date: 2019
Progress in Organic Coatings (03009440) 133pp. 376-386
Epoxy adhesives are prone to brittle failure and thermal degradation. Nanotechnology allows for developing advanced epoxy adhesives, but attempt to design high-performance epoxy adhesives must be made by starting inexpensive trials in micron scales by the use of recycled and waste materials. Phenolic resin, recycled tire powder, and alumina microfillers were systematically mixed here as epoxy toughening agent and modulus/strength modifier, respectively. Incorporation of phenolic resin to epoxy compensated for low thermal stability. Taguchi experimental design was used to study the main effects of waste tire powder, alumina microparticles, and phenolic resin contents on tensile, single-lap joint and thermogravimetric properties of epoxy adhesive. The results suggest that addition of 40 wt. % alumina microparticles, 15 wt. % recycled tire powder, and 30 wt. % phenolic resin to epoxy led to a drastic rise of ca. 80% in the lap shear strength with respect to the neat epoxy. Microscopic analyses unraveled blocking mechanism for cracking, as evidenced by a deviation in crack growth pathway at the vicinity of alumina microparticles. A considerable increase of ca. 34 °C in degradation peak temperature of epoxy was also noticeable. The outcome of this work enlightened future perspective on nanostructured epoxy adhesives. © 2019
Publication Date: 2019
Progress in Organic Coatings (03009440) 136
Epoxy adhesives based on recycled poly(ethylene terephthalate) (PET), ground rubber tire (GTR), and graphene oxide (GO) nanoflakes were designed and their thermal and mechanical properties were discussed. By changing the amounts of the aforementioned components (recycled polymers and GO nanosheets), adhesive formulations were tested for tensile and single-lap shear strength applied at the interface between epoxy/carbon fiber and stainless steel. The best and the worst samples in regard to mechanical strength were specified and selected for thermal degradation analyses base on thermogravimetric analysis (TGA). The dispersion state of PET and GTR were also studied by the use of field-emission scanning electron microscopy (FE-SEM). It was found that addition of 10 phr of 75/25 (w/w) PET/GTR mixture to 100 parts by weight of epoxy together with 0.1 phr of GO could surprisingly enhance ca. 29, 260 and 585% the Young's modulus, tensile strength, and the toughness of epoxy, respectively. It was also proved that introduction of GO to the adhesive enhanced thermal stability of epoxy/(PET/GTR). © 2019 Elsevier B.V.
Publication Date: 2019
Progress in Organic Coatings (03009440) 136
Rubber/clay nanocomposites (RCNs) have attracted an emerging interest from academia and industry alike due to their outstanding tunable properties. The present paper addresses the viscoelastic behavior of silicone/clay systems in order to get an understanding of physical interactions in the RCNs systems as well as making possible interpretation of the effect of nanoparticle shape and surface functionality on viscoelastic behavior of molten RCNs. Rheological behavior determination of silicone/clay composites provides insight into dependency of properties of resulting nanocomposite coatings on processing and preparation conditions. The effect of bare and (3-aminopropyl) triethoxysilane (APTES) functionalized platy and tubular clays on viscoelastic behavior of silicone rubber nanocomposites were investigated by rheometric mechanical spectrometer (RMS). The analysis was set to the strain and frequency sweep tests, where the linear viscoelastic zone of the uncured nanocomposites were determined by dynamic strain sweep and then frequency sweep to probe into the role of dispersion of nanoparticles in silicone matrix. Well-known Han, Cole-Cole and van Gurp-Palmen models were applied to peruse silicone/clay interaction and to find additional information on rheological properties of nanocomposites under the influence of the shape, surface chemistry and content of nanoparticles. The findings depicted the effective role of physical interactions on APTES-functionalized clay on appropriate dispersion of clays throughout silicone matrix. This effect was more obvious in the presence of platelet-like clays in view of improved intercalation and/or exfoliation. © 2019 Elsevier B.V.
Karami, Z. ,
Moini jazani, O. ,
Navarchian, A.H. ,
Karrabi, M. ,
Vahabi, H. ,
Saeb, M.R. Publication Date: 2019
Progress in Organic Coatings (03009440) 129pp. 357-365
Silicone elastomer coatings are known for their softness and high elongation properties, but not for faithful service over time because of their inadequate adhesion, thermal, and mechanical properties. Addition of nanofillers to silicone would be the solution to such long-standing shortcomings, but yet there is a little guarantee of success because of silicone crosslinking being significantly hindered by filler incorporation. In this work, well-cured 3D silicone networks are formed by peroxide curing in the presence of pristine and silane-functionalized halloysite nanotubes (HNTs). Nanofillers are incorporated into silicone at different loadings and the curing potential of the resulting nanocomposite coatings are evaluated by dimensionless indexes of T* and ΔH* calculated from nonisothermal differential scanning calorimetry. Regardless of the content and surface chemistry of the HNTs, silicone nanocomposite was outstandingly cured by peroxide thanks to reactive surface of nanofillers. Overall, ΔH* value of ≈ 2 was indicative of a two-fold rise in the amount of heat release in silicone nanocomposites whatever heating rate. Moreover, T* values obtained were slightly lower than 1, a signature of an unhindered curing. The excellence of facilitated crosslinking brought about by the use of HNTs was featured by an improved polymer-filler interaction, which seems promising for coating applications. © 2019 Elsevier B.V.
Publication Date: 2018
Progress In Color, Colorants And Coatings (20082134) 11(3)pp. 149-164
The effect of alumina and tough nylon 66 on microparticles' presence the mechanical and thermal properties of epoxy adhesives is assessed here. In order to distribute the adhesive formulation components, in a uniform manner a mechanical stirrer is applied. The effect a combined percentage of nylon 66 at (20, 30, 40 pph) and alumina micro-particles 20 μ (50,60,70 pph) selected based on Taguchi experimental design method on the mechanical and thermal properties of the adhesives is assessed. The tensile test results reveal that the sample containing 20 pph nylon 66 and 70 pph alumina micro particles has the highest Young's modulus and tensile strength compared to other examples designed in Taguchi Table and Sample containing 30 pph nylon 66 and 50 pph alumina micro particles has the highest degree of toughness compared to other specimens. The results of TGA reveal that the sample with the highest mechanical properties has a degradation startup temperature and more residual coal than pure epoxy. All this is due to the presence of nylon 66 that contains active hydrogen which in turn can increase cross-linking and degree of networking high and ultimately a higher thermal stability than the epoxy matrix. The results obtained from the FT-IR test indicate that amide groups of nylon 66 are capable of interaction with epoxy rings. © Institute for Color Science and Technology.
Publication Date: 2018
Progress In Color, Colorants And Coatings (20082134) 11(2)pp. 103-112
Polysulfide is well known elastomer for use in aerospace applications due to providing flexible coating and chemically resistant sealants. In this work, the effects of carbon black content on curing behavior of polysulfide elastomer were investigated and rheological properties for samples with different filler content (15, 20 and 25 phr) were evaluated by rheometric mechanical spectrometer (RMS). According to RMS analysis, sample with 20 phr carbon black had minimum gel point temperature and loss factor and highest elasticity. Also, the time sweep test for the optimal sample resulted from temperature and frequency sweep at 90 °C was done and gel time obtained less than a few minutes. From the dynamic differential scanning calorimetry (DSC) diagram for polysulfide sample with 20 phr carbon black observed one exothermic peak in heat flow for uncured sample that corresponded to the formation of cross-linking network and curing of polysulfide elastomer. © Institute for Color Science and Technology.
Publication Date: 2018
Progress In Color, Colorants And Coatings (20082134) 11(4)pp. 199-207
Epoxy coatings are usually reinforced by the use of nanofillers, but reactive nanofillers having physical tendency towards epoxide ring opening are preferable. In this work, nanosilica (SiO2) and halloysite nanotubes (HNTs) known for their hydroxyl-contained surface are used and their effects on the curing behavior of an epoxy/amine coating is compared. The spherical and tubular nanoparticles used in epoxy led to somewhat different crosslinking. Epoxy/amine systems containing equivalent amount of silica spherical and halloysite nanotube particles were compared for their cure characteristics, i.e. temperatures of starting and ending of curing reaction (TONSET and TENDSET), the exothermal peak temperature (Tp), the temperature range among which curing reaction was completed (ΔT= TENDSET - TONSET) and the total heat of curing reaction (ΔH). Fourier-transform infrared spectrophotometry and scanning electron microscopy analyses were used to assess formation of SiO2. Nonisothermal differential scanning calorimetry was performed at different heating rates and cure characteristics together with values of glass transition temperature of two kinds of systems containing SiO2 and HNTs were calculated, where both nanofillers revealed accelerating role in epoxy curing reaction. © Institute for Color Science and Technology.
Publication Date: 2018
Separation Science and Technology (15205754) 53(3)pp. 573-583
This paper investigates the synthesis of graphene oxide (GO)-incorporated polyamide thin-film nanocomposite (TFN) membranes on polysulfone substrate for forward osmosis applications. The GO nanosheets were embedded into polyamide layer using different concentrations (0.05−0.2 wt%). The results represented the alteration of polyamide surface by GO nanosheets and enhancing the surface hydrophilicity by increasing the GO loading. The results showed that the water flux for 0.1 wt% GO embedded nanocomposite (TFN) membrane was 34.7 L/m2 h, representing 90% improvement compared to the thin-film composite, while the salt reverse diffusion was reduced up to 39%. © 2017 Taylor & Francis.
Publication Date: 2018
Iranian Polymer Journal (10261265) 27(3)pp. 193-205
Poly(vinyl alcohol) (PVA) hydrogel membranes were prepared through three different preparation methods including freeze-thawing (FT), solution casting (SC) followed by thermal annealing, and phase separation (PS). The prepared hydrogels were characterized by Fourier transform-infrared spectroscopy, X-ray diffractometry, and scanning electron microscopy. Nitrofurazone (NFZ) was then loaded in the hydrogels. FT and SC methods led to obtaining dense membranes, while PS method resulted in an asymmetric one. The effects of hydrogel preparation method on water absorption, gel fraction, water vapor and oxygen permeabilities, bacterial barrier, tensile properties, and drug release profiles were investigated. The water vapor permeability of the hydrogel prepared through PS method was about 1.5 times higher than those obtained through FT and SC methods. Gel formation in PS method is probably responsible for the highest degree of crystallinity, and consequently the maximum gel fraction for the corresponded membrane. The elongation-at-break for this membrane in wet state was 41% higher than that made by FT method and 18% greater than that of SC method. Membranes prepared by all three methods showed excellent barrier property against bacterial penetration during 1 week. The results showed that PS membrane could control the release of NFZ more effectively as compared with the other two samples. © 2018, Iran Polymer and Petrochemical Institute.
Publication Date: 2018
Progress in Organic Coatings (03009440) 125pp. 222-233
Properties of a rubber/clay nanocomposite coating depend on rubber network formed in the presence of clay platelets. Not surprisingly, however, a few is known about the state of cure in silicone nanocomposites. In this work, nanoclay flakes are modified with trifunctional silane, fully characterized, and then added to silicone coatings. The resulting nanocomposites are underwent nonisothermal differential scanning calorimetry (DSC) varying heating regime. Fourier-transform infrared spectrophotometry, X-ray diffractometry, and thermogravimetric analysis (TGA) techniques were employed to quantify grafting reaction efficiency and thermal stability of modified nanoclay. Cure characteristics of nanocomposites (exothermal peak temperature as well as cure enthalpy) containing pristine and silane-modified nanoclays were discussed in terms of clay content under different DSC heating rates. The mysterious state of cure in silicone/clay nanocomposite coatings was unraveled and then explained by solving curing puzzle for silicone/clay systems through comparison between newly defined T* and ΔH* dimensionless indexes dedicated to the crosslinked nanocomposite networks with respect to blank silicone coating. The progressive/diffusional crosslinking and complete/partial/imperfect curing were respectively evaluated by analyzing fluctuations in T* and ΔH* values, where the effects of clay content and surface chemistry were satisfactorily quantified. © 2018
Jouyandeh, M. ,
Moini jazani, O. ,
Navarchian, A.H. ,
Shabanian, M. ,
Vahabi, H. ,
Saeb, M.R. Publication Date: 2018
Applied Surface Science (01694332) 447pp. 152-164
Curing behavior of epoxy-based nanocomposites depends on dispersion state of nanofillers and their physical and chemical interactions with the curing moieties. In this work, a systematic approach was introduced for chemical functionalization of nanoparticles with macromolecules in order to enrich crosslinking potential of epoxy/amine systems, particularly at late stages of cure where the curing is diffusion-controlled. Super-reactive hyperbranched polyethylenimine (PEI)-attached nanosilica was materialized in this work to facilitate epoxy-amine curing. Starting from coupling [3-(2,3-epoxypropoxy) propyl] trimethoxysilane (EPPTMS) with hyperbranched PEI, a super-reactive macromolecule was obtained and subsequently grafted onto the nanosilica surface. Eventually, a thermally-stable highly-curable nanocomposite was attained by replacement of amine and imine groups of the PEI with imide and amide groups through the reaction with pyromellitic acid dianhydride. Fourier-transform infrared spectrophotometry, X-ray diffractometry, X-ray photoelectron spectroscopy and transmission electron microscopy approved successful grafting of polymer chains onto the nanosilica surface. Thermogravimetric analyses approved a relatively high grafting ratio of ca. 21%. Curing potential of the developed super-reactive nanoparticle was uncovered through nonisothermal differential scanning calorimetry signifying an enthalpy rise of ca. 120 J/g by addition of 2 wt.% to epoxy at 5 °C/min heating rate. Even at low concentration of 0.5 wt.%, the glass transition temperature of epoxy increased from 128 to 156 °C, demonstrating prolonged crosslinking. © 2018 Elsevier B.V.
Moini jazani, O. ,
Rastin, H. ,
Formela, K. ,
Hejna, A. ,
Shahbazi, M. ,
Farkiani, B. ,
Saeb, M.R. Publication Date: 2017
Polymer Bulletin (14362449) 74(11)pp. 4483-4497
Glycidyl methacrylate (GMA) has been grafted on polypropylene (PP) with the aid of styrene (St) comonomer, by changing dicumyl peroxide initiator content, GMA level, and St concentration. The performance of the resulting PP-g-GMA reactive material towards static and dynamic mechanical properties of poly (ethylene terephthalate) (PET) was monitored in terms of grafting reaction variables and compatibilizer content. Fourier transform infrared spectroscopy, scanning electron microscopy, mechanical properties, melt flow rate, and impact strength analyses were applied to correlate structural changes due to grafting (or undesired chain scission) with blends’ properties. The competition between the desired reaction, i.e., GMA grafting onto PP chain, and undesired chain scission of PP macroradicals due to thermal degradation, was discussed based on torque–time curves and mechanical properties. Manipulation of grafting variables was responsible for a special behavior over properties, means that optimal or ascending/descending trends, which noticed high sensitivity of PET toughening to GMA grafting efficiency. © 2017, Springer-Verlag Berlin Heidelberg.
Publication Date: 2017
Construction and Building Materials (09500618) 134pp. 157-166
Waste poly(ethylene terephthalate) (wPET)/ground tire rubber (GTR) blends with variable compositions were applied as low-cost modifiers into bitumen and their performance has been evaluated via morphological, thermal and rheological analyses. Depending on the weight ratio of wPET/GTR, dispersion of single/composite domains of waste polymers in the bitumen has promoted the interaction between bitumen and blend components. Fourier transform infrared spectroscopy confirmed an adequate physical interaction between bitumen and wPET/GTR blend, while morphological analyses suggested deterioration of interaction upon increase of GTR content, which can be ascribed to the cross-linked structure of GTR. Increasing wPET/GTR content led to an improved rheological properties and thermal stability of the bitumen, especially for wPET/GTR blends composed mainly of wPET due to its thermoplastic character. The present work indicates that rheological and thermal properties of bitumen can be satisfactorily modified varying composition and content of wPET/GTR in the bitumen matrix. © 2016 Elsevier Ltd
Publication Date: 2016
Journal of Polymer Engineering (21910340) 36(5)pp. 513-519
This work seeks to explore the permeability dependence of polyurethane (PU)/polyethylene glycol (PEG) blend membranes on the molecular weight and composition of PEG constituent polymer. In this regard, gases with different polar nature were mixed (CO2/N2, CO2/CH4, and O2/N2) and subjected to a series of PU/PEG blends prepared via solution casting method. With the alteration of the molecular weight (1000, 2000, and 6000 g/mol) and composition (0, 10, 15, and 20 wt.%) of PEG in the blend films, the potentials of membranes in controlling the permeation of gas molecules within the films were quantified, compared, and discussed. It is known that the introduction of PEG into PU-based membranes causes the films to become more flexible, which brings advantages from an application point of view. Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, and scanning electron microscopy analyses were used to study the microstructural changes in the prepared PU/PEG blend membranes. The selectivity of the films was obviously displaced by the introduction of PEG, particularly when higher-molecular-weight PEGs were used and the resulting hybrid membranes were subjected to a mixture of CO2/CH4 or CO2/N2 gases. © 2016 by De Gruyter.
Publication Date: 2016
Journal of Reinforced Plastics and Composites (07316844) 35(23)pp. 1685-1695
Epoxy-based adhesives reinforced with silica and alumina fillers (20, 40, and 60 phr) were prepared and successfully applied for lap-joint bonding of carbon fiber composite with steel. The mechanical properties of adhesives were assessed as different cure temperatures to find optimum cure temperature. Morphology of the reinforced epoxy adhesives was observed by optical microscopy to disclose the interplay between composite properties and distribution fashion of the silica and alumina fillers within the epoxy matrix. Thermal stability and interfacial interaction situation were explored by thermogravimetric and Fourier transform infrared spectroscopy analyses, respectively. Rheological behavior of the composite samples was also studied. Lap shear test was an indication for a considerable improvement of about 12% and 20%, compared to unfilled epoxy/hardener systems, for composites containing 60 phr of alumina and silica, respectively. However, the presence and population of voids in case of samples cured at elevated temperature deteriorated lap shear strength. Of note, the storage and loss modulus of the latter adhesive have been increased by 797% and 472%, respectively. Thermal stability on the basis of initial degradation temperature and char yield (> 500.,) of the assigned adhesive under N2 and air have also been enhanced. Higher performance of silica-based adhesives was mechanistically and morphologically discussed on the bedrock of formation of a 3D inter-connected network of filler particles. © SAGE Publications.
Publication Date: 2016
Journal of Polymer Research (15728935) 23(11)
Structure–property relationship in typical polypropylene/polycarbonate/poly[styrene-b-(ethylene-co-butylene)-b-styrene] (PP/PC/SEBS) ternary blends containing maleated SEBS (SEBS-g-MAH) was investigated. Three grades of PC with different melt viscosities were used, and changes in blend morphology from PC/SEBS core–shell particles partially surrounded by SEBS-g-MAH to inverse SEBS/PC core–shell particles in PP matrix were observed upon varying the viscosity ratio of PC to SEBS. It was found that the viscosity ratio completely controls the size of the core–shell droplets and governs the type, population, and shape of the dispersed domains, as evidenced by rheological, mechanical, and thermomechanical behavioral assessments. Dynamic mechanical analysis of samples with common (PC–SEBS) and inverse (SEBS–PC) core–shell particles revealed that they show completely different behaviors: blends containing PC–SEBS presented a higher storage and loss modulus, while blends containing SEBS–PC exhibited a lower β-transition temperature. Moreover, ternary blends with PC cores showed the highest Young’s modulus values and the lowest impact strength, due to the different fracture modes of the blends containing PC–SEBS and SEPS–PC core–shell droplets, which present debonding and shell-fracture mechanisms, respectively. Morphological observations of blends with high-molecular-weight PC demonstrated the presence of detached droplets and rods of PC in the PP matrix, along with composite core–shell and rod-like particles. Micrographs of the fracture surfaces confirmed the proposed mechanisms, given the presence of stretched (debonded) PC (SEBS) cores encapsulated by SEBS (PC), which require more (less) energy to achieve fracture. The correlation between the mechanical and morphological properties proves that decreasing core diameter and shell thickness has positive effects on the impact strength but decreases the Young’s modulus. © 2016, Springer Science+Business Media Dordrecht.
Publication Date: 2016
JOURNAL OF THERMOPLASTIC COMPOSITE MATERIALS (08927057) 29(3)pp. 297-311
Polypropylene/polycarbonate (PP/PC), PP/poly(styrene-b-(ethylene-co-butylene)-b-styrene) (PP/SEBS) binary blends, and PP/PC/SEBS ternary blend were produced via melt blending in a co-rotating twin-screw extruder. The phase morphology, tensile, and impact behaviors of the blends were studied. Transmission optical microscopy and atomic force microscopy investigations of the necking region in tensile tests and scanning electron microscopy of tensile fractured surfaces were performed to characterize the fracture mechanism. In the PP/PC/SEBS ternary blend, core-shell morphology (PC particles as a core and the SEBS phase as a shell) was formed. Analysis of micromechanical deformation suggested that crazing occurred in PP and shear yielding did not occur during tensile tests. Rubber particles cavitation, shear yielding, and crazing occurred in both the PP/SEBS binary blend and PP/PC/SEBS ternary blend. Results showed that Corte and Leibler's theory was unable to describe the effect of core-shell particles in these blends.
Publication Date: 2015
Journal of Vinyl and Additive Technology (15480585) 21(4)pp. 245-252
The effects of using maleated poly[styrene-b-(ethylene-co-butylene)-b-styrene] triblock copolymer (SEBS-g-MAH) and unmodified SEBS (unSEBS) on the phase morphology and mechanical properties of immiscible polymer blends of polyamide-6 (PA-6) and polycarbonate (PC) are investigated. Different binary, ternary, and quaternary blends were prepared by using a Brabender® co-rotating twin-screw extruder. The weight ratio of unSEBS to SEBS-g-MAH was changed to probe the phase morphology and mechanical properties. The results revealed that the mechanical properties of (PA-6)/PC/(unSEBS/SEBS-g-MAH) blends were considerably governed by the unSEBS to SEBS-g-MAH weight ratio. Morphological investigation based on the spreading coefficient concept confirmed the results of scanning electron microscopy, indicating encapsulation of unSEBS domains around the PC core-forming component in the presence of reactive SEBS-g-MAH precursor. Moreover, larger unSEBS-PC composite droplets appeared throughout PA-6 matrix upon increasing the ratio of unSEBS to SEBS-g-MAH, until reaching a maximum value. In the case of the (PA-6)/PC blend compatibilized with a 50/50 combination of unSEBS and SEBS-g-MAH, the highest mechanical properties, i.e., tensile strength, impact resistance, and strain at break, were achieved owing to compatibilizing effect of virgin and maleated SEBS constituents. J. VINYL ADDIT. TECHNOL., 21:245-252, 2015. © 2014 Society of Plastics Engineers.
Publication Date: 2014
Journal of Macromolecular Science, Part B: Physics (1525609X) 53(6)pp. 1103-1115
Ternary blends of polypropylene/polycarbonate/poly(styrene-b-(ethylene-co- butylene)-b-styrene) (PP/PC/SEBS) with varying SEBS contents were produced via melt blending in a co-rotating twin-screw extruder. The phase morphology of the resulting ternary blends and its relationship with bending and impact behaviors were studied. Transmission optical microscopy (TOM) of the crack tip damage zone and scanning electron microscopy (SEM) of impact fractured surfaces were performed to characterize the fracture mechanism. With increasing SEBS content in the PP/PC/SEBS ternary blends, the number of PC/SEBS core-shell particles increased and the size of the core-shell particles enlarged. It was shown that with an SEBS content of 5%, the crack initiation resistance decreased and then was almost unchanged with further increase of SEBS content, while resistance to crack growth increased continuously with increasing of SEBS content. Preliminary analysis of the micromechanical deformation suggested that the high impact toughness observed for samples containing 20 and 30 wt% of SEBS could be attributed to cavitation of the rubbery shell and, consequently, shear yielding of the matrix. This plastic deformation absorbed a tremendous amount of energy. Due to low interfacial adhesion between PC particles and PP matrix in samples containing 5 and 10 wt% of SEBS, debonding occurred too early, so the occurrence of matrix shear yielding was delayed and resulted in premature interfacial failure and, hence, rapid crack propagation. © 2014 Taylor & Francis Group, LLC.
Saeb, M.R. ,
Khonakdar, H.A. ,
Moghri, M. ,
Razban, M. ,
Moini jazani, O. ,
Alorizi, A.E. Publication Date: 2014
Polymer - Plastics Technology and Engineering (15256111) 53(11)pp. 1142-1149
This article seeks to address morphological evolutions in polyolefinic ternary blends. To catch this target, different binary and ternary blends comprising HDPE, PP, and PA-6 constituents were prepared varying the type of polyolefinic matrix and composition in minority phase. Afterward, development of microstructure was monitored based upon theoretical and experimental analyses. In case of HDPE-based ternary blends, experimental microstructure observations agreed well with predictions, whereas SEM images provided from PP-based systems did not give strong evidence for encapsulation of PA-6 by HDPE minor domains. Analysis of stress-transfer across the matrix/shell/core provided a profound sense of morphological changes in these systems. © 2014 Copyright Taylor & Francis Group, LLC.
Publication Date: 2014
Chinese Journal of Polymer Science (English Edition) (02567679) 32(2)pp. 137-142
Ethylene polymerization was carried out by immobilization of rac-ethylenebis(1-indenyl)zirconium dichloride (Et(Ind)2ZrCl2) and rac-dimethylsilylbis(1-indenyl)zirconium dichloride (Me2Si(Ind)2ZrCl2) preactivated with methylaluminoxane (MAO) on calcinated silica at different temperatures. Polymerizations of ethylene were conducted at different temperatures to find the optimized polymerization temperature for maximum activity of the catalyst. The Me2Si bridge catalyst showed higher activity at the lower polymerization temperature compared to the Et bridge catalyst. The highest catalytic activities were obtained at temperatures about 50 °C and 70 °C for Me2Si(Ind)2ZrCl2/MAO and Et(Ind)2ZrCl2/MAO catalysts systems, respectively. Inductively coupled plasma-atomic emission spectroscopy results and polymerization activity results confirmed that the best temperature for calcinating silica was about 450 °C for both catalysts systems. The melting points of the produced polyethylene were about 130 °C, which could be attributed to the linear structure of HDPE. © Chinese Chemical Society Institute of Chemistry, CAS Springer-Verlag Berlin Heidelberg 2014.
Publication Date: 2014
Fibers and Polymers (12299197) 15(6)pp. 1230-1235
A proper collector is designed and examined in electrospinning process to produce electrospun nanofibers with favored mechanical propertied. The quality of product was controlled by changing and optimizing the process variables, namely electrospinning time, gap distance, and collector rotating speed in a manner that well-aligned yarns were fabricated from polyacrylonitrile (PAN) dilute solutions. It was found that the tensile characteristics of fabricated yarns are greatly dependent on the process variables. Incorporation of multi-walled carbon nanotubes (MWCNTs) into the polymer solution revealed improvement to the yarn strength because of enhancement in alignment of the filaments. The state of fiber alignment and dispersion of MWCNTs were detected by means of scanning electron microscopy. It was illustrated that combination of nanofibers and microfibers gives PAN/MWCNTs composite nanofibers with high surface area and high porosity to satisfy sophisticated users. © 2014 The Korean Fiber Society and Springer Science+Business Media Dordrecht.
Moini jazani, O. ,
Arefazar a., A. ,
Jafari, S.H. ,
Peymanfar, M.R. ,
Saeb, M.R. ,
Talaei, A. Publication Date: 2013
Polymer - Plastics Technology and Engineering (15256111) 52(9)pp. 954-954
Publication Date: 2013
Polymer - Plastics Technology and Engineering (15256111) 52(15)pp. 1595-1603
PP/PC, PP/SEBS binary blends and a PP/PC/SEBS ternary blend were produced via melt blending in a co-rotating twin-screw extruder. The phase morphology, bending and impact behaviors of the blends were studied. Transmission optical microscopy (TOM)of the crack tip damage zone, scanning electron microscopy (SEM)of impact fractured surfaces and transmission electron microscope (TEM)were performed to characterize the fracture mechanism. The core-shell particles in PP/PC/SEBS ternary blends do not have a significant influence on the crack initiation resistance but SEBS particles in PP/SEBS binary blend cause reduction of the crack initiation resistance and PC particles in PP/PC binary blend cause the greatest reduction of the crack initiation resistance. In PP and PP/PC binary blend samples no sign of plastic deformation was observed, while TOM micrographs in R30 and BR30 samples indicates that shear yielding mechanisms have also occurred around the crack tip and crack wake, also the fracture surfaces of R30 and BR30 shows ductile deformation. Preliminary analysis of micromechanical deformation suggested that the high impact toughness observed for R30 and BR30 was attributed to the cavitation of rubber particles and consequently shear yielding of the matrix. As illustrated in TOM observation in R30 the intensity of the damage zone and number of crazes is less than BR30, indicating cavitation capability of the core-shell particles is higher than pure rubber particles. In R30 due to the presence of the core-shell particles, cavitation can occur easily and small cavities connect to each other and form large cavities. © 2013 Copyright Taylor and Francis Group, LLC.
Moini jazani, O. ,
Arefazar a., A. ,
Jafari, S.H. ,
Peymanfar, M.R. ,
Saeb, M.R. ,
Talaei, A. Publication Date: 2013
Polymer - Plastics Technology and Engineering (15256111) 52(2)pp. 206-212
This article highlights the effect of using maleic anhydride-assisted SEBS compatibilizer precursor on the morphology and mechanical properties of the polypropylene (PP)/poly (trimethylene terephthalate) (PTT)/poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS) 70/15/15 ternary blends. In all ternary blends, the amounts of PP and PTT, respectively as the matrix and the primary minor components were kept constant at 70 and 15 wt%; in turn, the amount of constituent polymers within the secondary minor phase containing reactive maleic anhydride grafted SEBS (SEBS-g-MAH) and nonreactive SEBS was changed. The mentioned compatibilizing system was first melt-blended in a co-rotating twin screw extruder and then added into the blend. Theoretical models were also employed to make a comparison with experimental values obtained from morphology characterization through the ternary systems. Accordingly, it is found that the blend containing only non-reactive SEBS exhibited fine dispersion of core-shell particles; however, by diminishing SEBS to SEBS-g-MAH weight ratio, the morphology changed from the pure core-shell to a multi-phase system consisting of both core-shell and detached particles. Eventually, this transition in the phase morphology caused some consequences and/or advantages on the mechanical properties, so that the blend consisting of 50/50 weight ratio of SEBS/SEBS-g-MAH exhibited the minimum value of modulus; in contrast, the impact strength of that sample was considerably higher than that of neat PP specimen. These alterations in mechanical properties could be ascribed to the formation of some especial microstructures, in another word, the impact of particle size and particle size distribution, which has been well-established through scanning electron micrographs. © 2013 Copyright Taylor and Francis Group, LLC.
Jahromi, A.E. ,
Arefazar a., A. ,
Moini jazani, O. ,
Sari, M.G. ,
Saeb, M.R. ,
Salehi, M. Publication Date: 2013
Journal of Applied Polymer Science (00218995) 130(2)pp. 820-828
Applying the Taguchi method of experimental design, we prepared various polyamide 6 (PA6)/acrylonitrile butadiene rubber (NBR)/nanoclay nanocomposites under different processing conditions by melt mixing in an internal mixer. The effects of the processing variables, including the rotor speed, chamber temperature, and mixing order on the morphology, that is, the rubber particle size and interlayer distance, and the mechanical properties, that is, the tensile modulus and impact strength, were then investigated. As demonstrated with the Taguchi approach, the lower temperature associated with higher rotor speeds improved the mechanical properties of the 90/5/5 PA6/NBR/nanoclay systems. However, it was revealed that the mixing order did not affect the mechanical properties for the assigned composition. Hence, the simultaneous mixing of all the ingredients is seemingly the simplest way of mixing to obtain the desired mechanical properties. These results were confirmed with transmission and scanning electron microscopy observations and X-ray diffraction measurements. Image analysis corresponding to the mean particle size of the NBR constituent was also performed. The optimum processing condition to achieve the appropriate mechanical properties is ultimately predicted by the Taguchi analysis and corresponded to a chamber temperature of 230°C and a screw speed of 80 rpm. Moreover, the simultaneous mixing of all of the ingredients was suggested for convenience. © 2013 Wiley Periodicals, Inc.
Moini jazani, O. ,
Arefazar a., A. ,
Peymanfar, M.R. ,
Saeb, M.R. ,
Talaei, A. ,
Bahadori, B. Publication Date: 2013
Polymer - Plastics Technology and Engineering (15256111) 52(13)pp. 1295-1302
The work aims to study the role of NBR-g-GMA compatibilizer on the morphology and mechanical characteristics of PET/PC/NBR ternary blends. The compatibilizer content and amount of constitutive polymers are changed to correlate morphology development with mechanical properties. Various ternary samples are prepared using a twin-screw extruder whereat weight percent of rubbery dispersed phase (NBR+NBR-g-GMA) is changed. Analyzing the morphology of produced samples and interpretation of mechanical properties corroborated the role of the mentioned factors on the type of morphology and also the size of both individual and composite domains in these sorts of ternary blends. Based on this attempt, the mechanical properties of 50/50 blends of NBR/NBR-g-GMA, showed maximum toughness value compared to pure PET specimen. Also, the results revealed that by increasing the rubber content, the rodlike structures were disappeared; besides, toughness was increased. On the contrary, by increasing PC content, rodlike structures have seen by morphological study; however, core-shell droplets formed in the blend structure caused enhancing the impact strength and reducing Young's modulus. Ultimately, the ternary blend of 63/7/30 of PET/PC/ (NBR+NBR-g-GMA) revealed the best mechanical properties due to proper interaction between the PET matrix and rubbery domains in the presence of reactive compatibilizer. © 2013 Copyright Taylor and Francis Group, LLC.
Publication Date: 2012
Polymer Bulletin (14362449) 68(8)pp. 2187-2197
This article describes the application of the chemical surface re-modification of carboxylated multi-walled carbon nanotubes (MWCNTs) through in-situ esterification of oligomeric unsaturated aliphatic hydroxyl terminated polyesters. The Fourier transform infrared spectroscopy and the thermogravimetric analysis proved covalent treatment of MWCNTs. Consequently, the acid-base titration method was employed to determine the population of the re-modified sites within the polyester chains. The dispersion state of the re-modified MWCNTs was investigated by the transmission electron microscopy relevant to the cured nano-composite sample along with the Ultraviolet-Visible spectroscopy while using various solvents. The degree of dispersion was correlated to the Hansen solubility parameters. In summary, our study shows an appropriate dispersion of the remodified MWCNTs into the solvents with a high dispersive fashion. In addition, the rheological properties of the re-modified MWCNTs/epoxy resin having various nanoinclusions were considerably studied and discussed. Also, an improved rheological response was observed in the case of the re-modified MWCNT nanocomposite samples. © Springer-Verlag 2012.
Publication Date: 2011
Journal of Applied Polymer Science (00218995) 121(5)pp. 2680-2687
In this work, five ternary blends based on 70% by weight (wt %) of polypropylene (PP) with 30% wt of polycarbonate (PC)/poly(styrene-b-(ethylene- co-butylene)-b-styrene)(SEBS) dispersed phase consists of 15 wt % PC and 15 wt % reactive (maleic anhydride grafted) and nonreactive SEBS mixtures at various ratios were prepared in a co-rotating twin screw extruder. scanning electron microscopy (SEM) micrographs showed that the blends containing only nonreactive SEBS exhibited a fine dispersion of core-shell particles. With decreasing the SEBS/SEBS-g-Maleic Anhydride (MAH) weight ratio, the morphology changed from the core-shell particles to a mixed of core-shell, rod-like and individual particles. This variation in phase morphology affected the thermal and mechanical properties of the blends. DSC results showed that the blends containing only nonreactive SEBS exhibited a minimum in degree of crystallinity due to the homogeneous nucleation of core-shell particles. Mechanical testing showed that in the SEBS/SEBS-g-MAH weight ratio of 50/50, the modulus and impact strength increased compared with the PP matrix while the yield stress had minimum difference with that of PP matrix. These effects could be attributed to the formation of those especial microstructures revealed by the SEM studies. © 2011 Wiley Periodicals, Inc.
Publication Date: 2011
Journal of Polymer Engineering (21910340) 31(2-3)pp. 237-241
In this study, nine ternary blends of polypropylene (PP)/poly [styrene-b-(ethylene-co butylene)-b-styrene] tri-block copolymer (SEBS)/polycarbonate (PC) were produced at different processing conditions through twin screw extruder. Accordingly, die temperature, screw speed, and blending sequences were altered based on L9 Taguchi experimental design as indications of processing variables. Consequently, the impact strength of each produced sample is considered as the responding variable. Analyzing two important aspects, namely main and interactive effects by using Taguchi analysis, was the especial point of view in our contribution; as a result, not only was the PP/SEBS/PC ternary system studied for the first time, but the SEBS-g-MAH compatibilizer also showed sufficient effects on morphology development. It was observed that the impact strength of PP/SEBS/PC ternary blends is not affected by die temperature significantly, whereas screw speed and blending sequence have had effective impacts. Besides, the optimum processing condition, which is proportional to the highest value of impact strength, is recommended through the mentioned ternary blends. These results are also confirmed while applying image analysis on morphology micrographs. © 2011 by Walter de Gruyter. Berlin. Boston.
Publication Date: 2010
Journal of Applied Polymer Science (00218995) 116(4)pp. 2312-2319
In this work, ternary polymer blends based on polypropylene (PP)/polycarbonate (PC)/poly(styrene-b- (ethylene-co-butylene)-b-styrene) (SEBS) triblock copolymer and a reactive maleic anhydride grafted SEBS (SEBS- g- MAH) at fixed compositions are prepared using twin-screw extruder at different levels of die temperature (235-245- 255°C), screw speed (70-100-130 rpm), and blending sequence (M1-M2-M3). In M1 procedure, all of the components are dry blended and extruded simultaneously using Brabender twin-screw extruder, whereas in M2 procedure, PC, SEBS, and SEBS-g-MAH minor phases are first preblended in twin-screw extruder and after granulating are added to PP continuous phase in twin-screw extruder. Consequently, in M3 procedure, PP and SEBS-g-MAH are first preblended and then are extruded with other components. The influence of these parameters as processing conditions on mechanical properties of PP/PC/SEBS ternary blends is investigated using L9 Taguchi experimental design. The responding variables are impact strength and tensile properties (Young's modulus and yield stress), which are influenced by the morphology of ternary blend, and the results are used to perform the analysis of mean effect as well. It is shown that the resulted morphology, tensile properties, and impact strength are influenced by extrusion variables. Additionally, the optimum processing conditions of ternary PP/PC/SEBS blends were achieved via Taguchi analysis. © 2010 Wiley Periodicals, Inc.
Publication Date: 2010
E-Polymers (16187229)
In this study, nine ternary polymer blends based on polypropylene (PP)/polycarbonate (PC)/styrene-ethylene-butylene-styrene triblock copolymer (SEBS) with the same compositions (70%wt PP, 15%wt PC, 7.5%wt SEBS and 7.5%wt maleic-anhydride grafted SEBS (SEBS-g-MAH) as a compatibilizer) are prepared using twin screw extruder at different levels of die temperature (235-245-255 °C), screw speed (70-100-130rpm) and blending sequence (M1-M2-M3) . In M1 procedure, all of the components are dry blended and extruded simultaneously using Brabender twin-screw extruder. In M2 procedure, PC, SEBS, and SEBS-g-MAH minor phases are first pre-blended in twin screw extruder and after granulating are added to PP continuous phase in twin screw extruder. Consequently, in M3 procedure, PP and SEBS-g-MAH are first pre-blended and then are extruded with other components. The influence of these parameters as processing conditions on mechanical properties of PP/PC/SEBS ternary blends is investigated using L9 Taghuchi experimental design. The responding variables are impact strength and tensile properties (young modulus and yield stress) which are influenced by the morphology of ternary blend and the results are used to perform the analysis of variance (ANOVA). It is shown that the resulted morphology, tensile and impact strength are influenced by extrusion variables. Additionally the optimum processing conditions of ternary PP/PC/SEBS blends from Taguchi analysis was achieved.
Publication Date: 2008
Macromolecular Symposia (10221360) 263(1)pp. 67-69
Modified SBR was blended with dried PET bottle wastes in an internal mixer. During the process mechanical and morphological properties were studied. When PET bottle wastes were blended with unmodified SBR, the final blend had a rough morphology and low impact strength. In contrary, blending of PET with modified SBR lead to smooth and fine morphology. Utilizing grafted SBR in PET blends creates an enormous difference in particle size and morphology, which is a result of powerful interactions and effective chemical bonding between the components of the blend. The final product had high impact strength in comparison with PET and unmodified SBR blend/These results are mainly related to formation in situ of PET/SBR graft copolymer in interface, which is produced by chemical reaction among active maleic anhydride groups and active PET groups. Copyright © 2008 WILEY-VCH Verlag GmbH & Co. KGaA,.
Publication Date: 2006
Journal of Applied Polymer Science (00218995) 102(2)pp. 1615-1623
Styrene butadiene rubber (SBR) was modified by the grafting reaction of maleic anhydride (MAH) in the presence of the initiator benzoyl peroxide (BPO). This modified elastomer was then blended with poly(ethylene terephthalate) (PET) bottle waste, and the mechanical and morphological properties of the resulting blends were studied. The amount of grafted MAH was determined by chemical titration. The results revealed that the concentrations of MAH and BPO strongly affected the grafting process. The morphology of the dispersed phase for blends of PET waste and SBR-g-MAH was quite different from that of a simple blend of PET waste and SBR. Dynamic mechanical thermal analysis revealed suitable compatibility between PET waste and styrene butadiene rubber-graft-maleic anhydride (SBR-g-MAH). The enhanced compatibility resulted in better impact properties. The better compatibility was concluded to result from bond formation between the carbonyl group of SBR-g-MAH and the hydroxyl or carboxyl end groups of PET. © 2006 Wiley Periodicals, Inc.
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