Thermal, mechanical, electrical properties of poystyrene/poly (styrene-b-isobutylene-b-styrene/carbon nanotube nanocomposites

Abstract

In this study, high impact polystyrene (HIPS) materials was prepared by using a styrenic elastomer (10, 20, 30 wt%) and carbon nanotube (CNT) (3, 5, 7, 10 phr) by melt blending technique as alternative to commercial HIPS including polybutadiene rubber. The poly (styrene- b-isobutylene- b-styrene) (SIBS) was used as thermoplastic elastomer with polystyrene (PS) to improve its poor impact resistance and CNT was added to PS/SIBS blend matrix to maintain its strength and stiffness. The modulus, tensile strength and toughness values of the blends decreased while those of impact resistance increased in comparison to neat PS. The impact strength of PS20SIBS blend containing 20 wt% SIBS was found to be approximately 530% higher than pure PS. The nanocomposites of the PS20SIBS exhibited a decrease in the size of SIBS particles with increasing CNT compared to PS20SIBS. This was ascribed to the increased viscosity of PS matrix via CNT filler, preventing the coalescence of the elastomer domains. Compared to the PS20SIS, its nanocomposites showed higher strength, modulus and toughness, but lower impact strength. The toughness of the nanocomposite containing 5 phr CNT (PS20SIBS-5CNT), increased by 117% while its creep deformation decreased by approximately 40%, in comparison with PS20SIBS blend. Although PS20SIBS-5CNT exhibited lower impact strength than the PS20SIBS blend due to the dispersion of smaller SIBS particles in the PS matrix, it still increased the impact strength of pure PS by 188%. The PS20SIBS-5CNT nanocomposite, which improved impact strength and creep resistance with optimal toughness and tensile modulus can be used as a novel HIPS material that tunes the hardness-toughness/impact balance effectively. Moreover, the same nanocomposite was found to reach the conductivity threshold by exhibiting 106 times lower electrical resistance in comparison with that containing 3 phr CNT, leading to a conductive filer network with 5 phr loading of the nanotubes into the system.