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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
Polymer Engineering and Science (15482634)64(3)pp. 1258-1273
Today, the use of biodegradable polymers has become widespread in a wide range of industries. This research scrutinized the physical, mechanical, and rheological properties of poly (lactic acid)/poly (ethylene oxide)/carbon nanotube (PLA/PEO/CNTs) blend nanocomposites, as a good candidate for usage in the packaging industry. PEO and CNTs were added at various concentrations to improve the flexibility, toughness, gas permeability, thermal stability, and mechanical properties of PLA via solution blending. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Field Emission Scanning Electron Microscope (FESEM), water contact angle (WCA), rheometric mechanical spectrometer (RMS) test, gas permeability, and tensile characterization were performed to characterize the properties of the prepared blends and nanocomposites. The experimental results revealed that the addition of 25 wt% PEO to the PLA matrix made a partially miscible blend with a droplet-matrix morphology. PEO at this concentration increased the elongation at break (from 2.2% to 18%) while reducing the modulus (from 25 to 6 MPa). Also, the experimental results indicated that the miscibility of PLA and PEO was enhanced by the addition of 1 wt% CNTs to the prepared blend, associated with diminished entropy of mixing in the LCST phase diagram. Theoretical calculations predicted that the CNTs would be localized in the PLA phase which increased the total crystallinity of the sample by 28%, considerably reducing the amount of gas permeation into the nanocomposite. In addition, the introduction of the CNTs to the blend increased the elongation at break and tensile strength by 13% compared to pure PLA and lowered the rate of thermal degradation effectively. Also, the final results showed that the COOH-CNTs located in the PEO phase caused a decline in the crystallinity and an increase in the gas permeability of the prepared nanocomposite. Highlights: Improvement of physical properties of PLA by blending with PEO and CNTs. A deep investigation on rheological behavior of the prepared nanocomposite. Increasing the crystallinity degree of PLA/PEO blend by adding CNTs. Improvement of the miscibility between PLA and PEO in the presence of CNTs. Controlling the CNTs localization by surface modification. © 2024 Society of Plastics Engineers.
Thermal Science and Engineering Progress (24519049)47
Encapsulation of phase change materials (PCMs) is an intelligently effective way to overcome the challenges of PCMs usage in heat storage and transfer applications. At the first stage of the current study, a novel magnetic nanoencapsulated PCM (M−NEnPCM) consisting of n-Octadecane (n-C18) coated with a poly methyl methacrylate (PMMA) shell was synthesized through the miniemulsion ultrasonic-assistant polymerization technique. The magnetic property was introduced to the nanocapsules by adding surface-modified Fe3O4 nanoparticles into the core during the formation step. The dynamic light scattering (DLS) results showed an average nanocapsule size of 78 nm. The scanning electron microscope (SEM) along with transmission electron microscope (TEM) images confirmed the spherical shape with a core/shell structure of the M−NEnPCM. According to the differential scanning calorimetry (DSC), M−NEnPCM had melting and crystallization latent heats of 116.47 and 124.71 J/g, respectively. Moreover, based on vibrating sample magnetometry (VSM) results, the superparamagnetic property of M−NEnPCM is proved. At the second stage, the performance of water suspensions containing different amounts of the as-prepared nanocapsules in enhancing the natural convection in a cube cavity was investigated under various heat fluxes and magnetic field flux densities. The results illustrated that the use of nanocapsules leads to enhance the natural convection up to 2 times higher than that of pure water; while there are optimum levels of M−NEnPCM concentration and magnetic field flux density at which the heat transfer coefficient is maximized. © 2023 Elsevier Ltd
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.
Polymers for Advanced Technologies (10427147)33(3)pp. 760-769
A conductive polymer composite (CPC) based on polylactic acid (PLA)/poly (styrene-co-acrylonitrile) (SAN)/multi-walled carbon nanotubes (MWNT) blend was prepared and used as a sensitive layer for detecting methanol, ethanol, toluene, and water vapor. The response behavior of polymer blend nanocomposite in comparison with PLA-MWNT and SAN-MWNT sensitive layers was studied as well as the influence of solution blending on the morphology, electrical behavior, and performance parameters of prepared sensitive layers. The scanning electron microscopy micrograph results showed that the PLA/SAN solution blended with a 50/50 wt% ratio had formed the co-continuous morphology. In addition, the electrical conductivity investigation revealed that the percolation threshold of sensitive layers decreased from 1.5 vol%, related to PLA-MWNT, to 0.8 vol%, related PLA/SAN blend nanocomposite. Thermodynamic investigation revealed that, in the solution blended conductive composites, MWNTs are preferentially localized in the PLA phase. The relative response (Rrel) of blended conductive composite, in comparison with PLA-MWNT, was increased toward ethanol and toluene vapor while it was decreased against the methanol vapor. The sensitivity behavior of polymer blend composite was investigated based on the double percolated conductive network as well as the thermodynamic parameters such as Flory-Huggins interaction parameter and solubility parameters. © 2021 John Wiley & Sons Ltd.
Polymers for Advanced Technologies (10427147)32(1)pp. 391-401
The nonsolvent-induced phase separation (NIPS) method was employed to fabricate the porous films based on polyvinyl chloride loaded with carbon nanotubes (CNTs). The combinational addition of CNTs and a proper nonsolvent (ethanol) resulted in a porous surface layer with the nano-size nodular structure possessing an exact superhydrophobic behavior (water contact angle [WCA] = 157° and sliding angle [SA] <5°). The size of PVC nodules at the surface layer varies in the range of 200 to 800 nm depending on the nonsolvent concentrations, and polymer molecular weight. The effects of various nonsolvent concentrations as well as PVC molecular weight on the surface properties of the films were also investigated. Morphological and roughness analyses revealed the pronounced role of PVC molecular weight on the size of nodules, and the structural uniformity of the surface morphology based on the thermodynamic parameters such as relaxation time and dynamic of polymer chains. The concurrent use of CNTs and nonsolvent led to promote the NIPS process due to the nucleating role of CNTs, which were localized within the polymer-rich phase leading to an ultra-fine and packed nodular surface structure. Transmission electron microscopy results also proved the very well dispersion quality of CNTs. Glass transition temperature of PVC was also assessed, and the results were correlated to the associating ability of CNTs with polymer chains during the phase separation process. Overall, the promising potential of CNT/ethanol combination on the surface porosity and hydrophobicity of PVC nanocomposite films was revealed in this study, which could further extend its application window. © 2020 John Wiley & Sons Ltd
Polymer Engineering and Science (15482634)60(7)pp. 1631-1641
A smart porous conductive polymer composite (CPC) consisting of cellulose acetate as matrix and multiwalled carbon nanotubes as conductive filler was prepared to detect a set of lung cancer biomarkers. The solvent evaporation-induced phase separation was used to introduce porosity into the conductive composite. The prepared sensitive layers exhibited high response intensity, low response time, and good recovery behavior toward the mentioned analytes. A thorough investigation was conducted on the morphology, response behavior, sensitivity, and selectivity of the prepared CPC transducer. The selectivity of responses was considered based on the thermodynamic and kinetic characteristics of polymer and analytes such as Hansen solubility parameters, Flory-Huggins interaction parameter, and diffusion coefficient of analytes into the polymer membrane. Moreover, the microstructure of porous layers was characterized by using SEM, contact angle, and BET. The volume porosity and specific surface area of the sensitive layers were increased by the introduction of porosity into the polymer composite, causing the improvement of sensing parameters. The obtained responses further confirmed the promising potential of the prepared porous CPC structure, for the detection of lung cancer biomarkers, from exhaled breath as an inexpensive, repeatable, accurate, and noninvasive method. © 2020 Society of Plastics Engineers
Iranian Journal of Polymer Science and Technology (10163255)33(2)pp. 147-158
Hypothesis: Introducing the porosity into the conductive polymer composite (CPC) sensitive layer improves the performance parameters of the prepared gas detectors. Methods: In this research, porous poly(vinyl alcohol)/carbon nanotube (CNT) composite was used as the sensitive layer for detecting methanol, ethanol, and water (as lung cancer biomarkers). Vapor-induced phase separation method was used for introducing the porosity into the polymer matrix. The solution consisted of 2% (by wt) polymer in water and 4% (by wt) CNT. The film was exposed to the acetone vapor for introducing the porosity. The morphology of the prepared porous composite was investigated by SEM and BET tests. The responses of prepared sensitive layers toward the target analytes were analyzed by a home-made apparatus. Findings: The SEM images indicated the porous structure of the composite with nodular structures. Also, the BET test indicated the remarkable increase in the specific surface area of the porous composite in comparison with the dense one. The results showed that the specific surface area was increased to10.93 m2/g for porous composite. The final results illustrated the remarkable improvement in performance parameters such as response time and sensitivity in porous composites. The lower level of detection (LLD) of dense and porous composites toward water vapor was equal to 1000 and 50 ppm, respectively. Such enhancement was related to the increasing the specific surface area of the composite, and consequently, increasing the accessibility of analyte molecules to the sensitive sites of CPCs. Also, the response of the prepared sensitive layer was investigated based on the thermodynamic. The final investigations indicated that δa correctly explained the sensitivity of prepared CPCs. © 2020 Iran Polymer Society. All rights reserved.
Abbasi, P.M.,
Soleimani E.,
Aghamiri, S.,
Shabanian, M.,
Soleimani E.,
Aghamiri, S.,
Abbasi, P.M.,
Shabanian, M. Iranian Polymer Journal (10261265)29(4)pp. 341-350
A new structure of a polymer composite was designed to be used as a vapor sensor for detection of a set of volatile organic compounds (VOCs), namely ethanol, methanol, isopropyl alcohol (IPA), toluene and water as moisture in the atmosphere. Picric acid was used for physical decoration of graphene (Gr), as a conductive filler, and then, the modified graphene (Gr.PA) was added to polyvinyl alcohol (PVA) to design a conductive polymer composite (CPC) sensitive layer for detection of polar vapor analytes. The Fourier transfer infrared spectroscopy (FTIR) was used to study the physical adsorption of picric acid molecules on the surface of Gr. The experimental results revealed that the sensitivity of the prepared CPC transducer was dramatically improved through the decoration of Gr surfaces with PA molecules. The enhanced sensitivity was related to the addition of –OH and –NO2 functional groups on the surface of Gr (due to picric acid molecules). Those polar functional groups increased the diffusion driving force of polar analytes into the polymer composite. On the other hand, upon adding PA molecules, Gr–Gr junctions were tuned as sensitive sites, and the adsorbed vapor molecules increased the distance of Gr platelets, which, consequently, decreased the electron tunneling conductivity of the prepared CPC. The experimental results also proved that one could change the electrical conductivity of Gr as a p-type semiconductor through adsorption of analyte molecules on its surface. All in all, the attained results demonstrated that tuning the conductive filler junctions could be regarded as an exceptional strategy to improve the sensitivity of CPC transducers. © 2020, Iran Polymer and Petrochemical Institute.
Iranian Polymer Journal (10261265)28(3)pp. 203-211
A conductive polymer composite (CPC) was designed as a gas sensor for the detection of lung cancer biomarkers. A poly(ether-imide) with aromatic bulky pendant groups was synthesized and used as a CPC transducer by introducing multi-walled carbon nanotubes for the detection of acetone, toluene, methanol, ethanol and water vapor as lung cancer biomarkers. The following trend in CPC response was observed for different vapors: AR (acetone) > AR (toluene) > AR (ethanol) > AR (methanol) > AR (water). The sensing ability of the conductive polymer composite towards the above biomarkers was evaluated based on Hansen solubility parameters of the analytes. The prepared sensitive layer showed a good sensitivity against a wide range of analytes with various polarities. The good sensitivity of designed sensitive layer was attributed to the non-polar –CH3 groups besides the bulky aromatic pendant groups of the as-synthesized polymer. The aromatic pendant groups have established relatively strong attractions with the carbon nanotube (CNT) surfaces leading to the creation of significant active sites in the CNTs’ junctions. As a result of adsorption of the analyte molecules on those active sites, especially at low concentrations, the bulky aromatic groups were found much to improve the sensitivity of the prepared gas detector by affecting the electron tunneling of 3-D nano-conductive filler architecture. The experimental results illustrated that the synthesized CPC has a promising potential as a lung cancer biomarker detector. © 2019, Iran Polymer and Petrochemical Institute.
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.
Iranian Polymer Journal (10261265)27(2)pp. 77-86
A novel proton-exchange polymer composite membrane was synthesized using Nafion®, tetraethoxysilane-modified carbon nanotubes (CNTs) and phosphotungstic acid-modified carbon nanotubes with the aim of using direct methanol fuel cells (DMFCs). Physicochemical properties of the modified CNTs and fabricated composite membranes were investigated by Fourier transform infrared spectroscopy, field emission scanning electron microscopy, water uptake, thermogravimetric analysis, ion exchange capacity, proton conductivity and methanol permeability tests. It was demonstrated that chemical surface modification of CNTs and introduction of the phosphotungstic acid (PWA) groups effectively improved the performance of DMFC. It was found that the presence of PWA groups on the surface of CNTs led to the formation of strong electrostatic interactions between the PWA groups and clusters of sulfonic acid in Nafion® macromolecules. Hence, the incorporation of inorganic phosphotungstic super-acid-doped silicon oxide-covered carbon nanotubes (CNT@SiO2-PWA) into Nafion® matrices enhanced the proton conductivity of the prepared membranes. Moreover, the methanol permeability was reduced to 2.63 × 10−7 cm2 s−1 in comparison with the recast Nafion® membrane (2.25 × 10−6 cm2 s−1). Enhancing the proton conductivity and reducing the methanol permeability, the selectivity of the prepared nanocomposite membranes was enhanced to a greater value of 330,700 S s cm−3 as compared to the value of 38,222 S s cm−3 for recast Nafion®. © 2017, Iran Polymer and Petrochemical Institute.
Journal of Macromolecular Science, Part B: Physics (1525609X)56(4)pp. 234-244
A new polymer nanocomposite membrane based on Nafion and functionalized carbon nanotubes (CNTs) was developed for proton exchange membrane fuel cell (PEMFC) applications. Histidine, an imidazole-based amino acid, was used for modifying the surface of CNTs. The modification of CNTs was characterized by means of Fourier transform infrared spectroscopy (FTIR) and their Zeta potential. The imidazole groups, due to forming and breaking of hydrogen bonding, can facilitate proton transport across the polymer matrix by the Grotthuss mechanism. The final structure of the Nafion/CNT nanocomposites was investigated by small angle X-ray scattering (SAXS). The results confirm that the transport properties of the fabricated new membranes were significantly improved in comparison with unmodified and conventional Nafion® membranes. The power density of the imidazole-CNT (Im-CNT) Nafion® composite membranes was about three times more than Nafion® membranes. Also, the experimental results showed that the proton conductivity for the conventional Nafion® membranes decreased over 100°C but the conductivity for the Nafion®/Im-CNT remained at a nearly constant value above 100°C up to 120°C. Thus, the nanocomposite based on Nafion/imidazole functionalized CNT can be considered as an anhydrous PEMFC membrane for high-temperature applications. © 2017 Taylor & Francis Group, LLC.
Journal of Materials Science: Materials in Electronics (09574522)27(5)pp. 4879-4886
Cobalt ferrite, titanium dioxide nanoparticles and finally magnetic CoFe2O4–TiO2 nanocomposites were synthesized via a simple hydrothermal reaction using. The effect of various precipitating agents such as ammonia, sodium hydroxide, ethylene diamine, hydrazinium hydroxide and different surfactants on the morphology of the products was investigated. For preparation of magnetic nanocomposite, CoFe2O4 was added to poly vinyl alcohol. The magnetic properties of the product were also investigated using a vibrating sample magnetometer. The nanoparticles exhibit various ferromagnetic behaviours by changing in surfactants at room temperature. The photocatalytic behaviour of CoFe2O4–TiO2 nanocomposite was evaluated using the degradation of various organic dyes aqueous solution under UV light irradiation. The results confirm that CoFe2O4–TiO2 nanocomposites have suitable performance in photo-catalytic applications. The results show that the CoFe2O4–TiO2 can enhance the flame retardant property of the PVA matrix. © 2016, Springer Science+Business Media New York.
Polymer Composites (02728397)37(9)pp. 2803-2810
Chitosan (CS) and hydrophobic-modified chitosan (HM-CS) chains were wrapped onto multiwalled carbon nanotubes (MWNTs) and introduced to polyvinyl alcohol (PVA) matrices as nanohybrid conductive polymer composites (CPCs) for detection of polar vapors. The effect of grafted alkyl groups on polarity of CS chains were studied by quantum mechanics (QM). The designed composites were applied as sensitive layers to clarify the response mechanism in CPCs gas sensors. It was realized that the wrapped biopolymers intensely influenced the sensitivity of the composites. Experiment results specified that the nature of biomacromolecules and their interactions with vapor molecules affects the resistance change in CPCs. The higher interaction of CS with polar vapor molecules caused more plasticization of polymer segments in the MWNTs connections. Such phenomenon enhanced the resistance change in the presence of analytes. Moreover, it was inferred that the semiconductor character of MWNTs has an important effect in the final signals. The more polar structure of CS in comparison with HM-CS enhanced the adsorption of vapor molecules on the surface of MWNTs, and the electron donor analytes decreased the conductivity of p-type MWNTs increasing the final responses. The presented results corroborate that the performance of CPCs gas sensors could be finely tuned through manipulation of the nanointerfaces. POLYM. COMPOS., 37:2803–2810, 2016. © 2015 Society of Plastics Engineers. © 2015 Society of Plastics Engineers
RSC Advances (20462069)4(58)pp. 30906-30913
A new nanohybrid conductive composite was designed for detection of polar vapours and characterized based on thermodynamic parameters to investigate the sensor response. Poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA)-carbon nanotubes (CNTs) nanocomposite sensors were introduced to various organic vapours such as methanol, ethanol, isopropyl alcohol (IPA), chloroform and water. The response of these sensors was investigated based on thermodynamic parameters. Although, affinity is one of the most important parameters that can affect the response of sensors, the interaction parameter (χ) proposed by Flory and Huggins, cannot clarify the response trend for these series of nanocomposite transducers. We interpreted the response trend of transducers based on the polarity contribution of the Hansen solubility parameter. Thus, by designing a new nanohybrid nanocomposite, the sensor response against polar vapours was improved. New active sites in conductive polymer composites (CPCs) were designed by decoration of CNTs with chitosan (a polar biopolymer) and introducing of these new conductive particles to PVA and PEO. The wrapping of chitosan around CNTs was further investigated by molecular dynamics (MD) simulations. The polar functional groups of chitosan enhanced the driving force for diffusion of polar molecules into the nanohybrid composite and adsorption on the surface of CNTs and subsequently improved the sensor response. © 2014 the Partner Organisations.
Asgari, M.S.,
Nikazar, M.,
Abbasi, P.M.,
Hasani-sadrabadi, M.M. International Journal of Hydrogen Energy (03603199)38(14)pp. 5894-5902
Here we show preparation and characterization of a new type of composite membrane based on Nafion®/histidine modified carbon nanotube by imidazole groups (Im-CNT), for direct methanol fuel cell (DMFC) applications. Due to the presence of this imidazole-based amino acid on the surface of CNT, new electrostatic interactions can be formed in the interface of Nafion ® and Im-CNT. Physical characteristics of these nanocomposite membranes are investigated by water uptake, methanol permeability, ion exchange capacity, proton conductivity, as well as fuel cell performance results. Especially at elevated temperatures, Nafion®/CNT-0.5% membranes exhibit higher proton conductivities plus lower methanol crossover in comparison with commercial Nafion® membranes. Power density of nanocomposite membranes reached to 61 mW cm-2 in contrast with 42 mW cm-2 for Nafion®117 (at 0.5 V and 5 M methanol concentration). Obtained results exposed that Nafion®/Im-CNT-0.5% membranes can be utilized as promising polyelectrolyte membranes for direct methanol fuel cell applications. Copyright © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
Sensors and Actuators B: Chemical (09254005)155(2)pp. 562-567
The fabrication of novel porous conductive composite vapor sensors characterized by different porosities and specific surface areas is described in this study. These samples were obtained by the dry-cast non-solvent induced phase separation (NIPS) method. Porous composite structures have been studied by the SEM, BET and water evaporation methods. Testing different concentrations of several organic vapors, the porous sensors showed improved sensitivities and response times as compared to their dense counterpart. Improved characteristics of the sensor response were correlated to better sorption and diffusion properties of sensing film due to increased porosity and specific surface area obtained by this method of film fabrication. A competition theory was proposed that describes the optimum porosity and thickness of sensing films in which the highest sensitivities were observed. © 2011 Elsevier B.V. All rights reserved.
Smart Materials and Structures (09641726)20(10)
A novel vapor sensor was fabricated by multi-walled carbon nanotube (MWCNT) porous composite. Poly(methyl methacrylate) (PMMA) was used as a matrix. Porous sensing films were obtained by the dry-cast non-solvent-induced phase separation (NIPS) method. The experimental results showed a remarkable improvement in sensitivity and response time of conductive porous composite vapor sensors in comparison with dense composites. The response of porous films was about five times greater than dense ones with comparable thicknesses. In addition, the effect of surface modification of nanotubes on sensitivity of porous sensors was evaluated. It was observed that functionalized CNT/PMMA porous composite sensors show higher responsiveness towards a series of organic vapors. Their response was approximately ten times greater than the response of similar sensors without functionalization of CNTs, which was explained on the basis of polar interactions of vapors on the surface of CNTs and better dispersion of nanotubes in the polymer matrix. © 2011 IOP Publishing Ltd.
Novel non-fragile porous conductive nanocomposite vapor sensors with variant volume porosities and specific surface areas have been fabricated from PMMA and carbon nanoparticles. Sensing films were obtained by well known drycast non-solvent induced phase separation (NIPS) method. Porous composite structures have been characterized by SEM, BET and water evaporation methods. Response behavior of fabricated porous sensors toward various organic vapors in different concentrations were measured and compared to response of their conventional dense counterparts in dynamic mode. Both sensitivity and response speed of vapor sensors have been improved remarkably with introducing porosity to the sensing layer. Similar results were observed when nano-sized carbon black as conductive filler in composite was replaced with multiwall carbon nanotube. Improved characteristics of the sensor response were related to better sorption properties of sensing film due to increased porosity and specific surface area obtained by this method of thin film preparation. These porous sensitive layers showed non-fragility that particularly will be promising in fabrication of wearable sensors. Simplicity and versatility of both fabrication method and sensing mechanism of these porous conductive composite vapor sensors make them advantageous wherever sensing materials with low cost and high performance needed. ©2009 IEEE.
AIP Conference Proceedings (0094243X)1137pp. 361-364
We describe herein the fabrication of novel porous conductive composite vapor sensors characterized by different porosities and specific surface areas. These samples were obtained by dry-cast non-solvent induced phase separation (NIPS) method. We have studied porous composite structures by SEM, BET and water evaporation method. Testing to different concentrations of several organic vapors, the porous sensors showed improved sensitivities and response times, compared to their dense counterpart. Improved characteristics of the sensor response were related to better sorption properties of sensing film due to increased porosity and specific surface area obtained by this method of film fabrication. © 2009 American Institute of Physics.
