Effect of agitation speed on microencapsulation of healing agent in PMMA shell and study on the mechanical properties of epoxy/PMMA microcapsules

Abstract

In this study, the effect of agitation speed as a key process parameter on the morphology and particle size of epoxy-Poly (methyl methacrylate) (PMMA) microcapsules was investigated. Thus, a new interpretation is presented to relate between the microcapsule size to rotational speed so as to predict the particle size at different agitation speeds from the initial capsule size. The PMMA shell capsules containing EC 157 epoxy and hardener as healing materials were fabricated through the internal phase separation method. The process was performed at 600 and 1000 rpm mechanical mixing rates. Scanning electron microscopy (SEM) revealed the formation of spherical microcapsules with smooth surfaces. According to static light scattering (SLS) results, the average diameter size of the epoxy/PMMA capsules at two mixing rates were 7.49 and 5.11 µm for 600 and 1000 rpm, respectively, indicating that the mean size increased as the mixing rates of the process increased. The D50, D90 and mean particle size values were the lowest for hardener/PMMA microcapsules at 1000 rpm. Moreover, the Fourier transform infrared (FTIR) spectroscopy was conducted to describe the chemical structure of epoxy and hardener PMMA capsules. To investigate the reinforcing role of microcapsules, they embedded in EPL-1012 epoxy resin with various amounts of 1 and 2.5 wt.% epoxy/PMMA capsules. The investigation also involved the effect of microcapsules on mechanical behavior as well as the reinforcement of polymer composite material. Experimental results showed that the tensile strength of the self-healing polymer composite slightly increased by 1 wt.% PMMA microcapsules prepared at 1000 rpm and then reduced with an increase in the concentration and mean size diameter of PMMA microcapsules. In addition, a similar trend of Young’s modulus was seen for pristine epoxy matrix and microcapsule-loaded epoxy composite. Copyright © 2021 Techno-Press, Ltd.