Simultaneously enhanced thermal conductivity and fracture toughness in polystyrene/carbon nanofiber composites by adding elastomer

The common strategy to enhance the thermal conductivity of the polymer composites through increasing filler content usually results in the deterioration of the fracture toughness of the composite articles, which greatly restricts the real engineering application of the composites. In this work, carbon nanofibers (CNFs) and elastomer (styrene-ethylene/butylene-styrene, SEBS) were simultaneously incorporated into polystyrene (PS) through melt-compounding method. The dispersion state of CNFs and the processing flowability of the composites were comparatively investigated. The results show that SEBS tailors the dispersion of CNFs and promotes the formation of CNF assemblages and simultaneously, the processing flowability of the composites is improved to a certain extent. The thermal conductivity of the composites gradually increases with increasing CNF content, and it can be further enhanced by adding SEBS. The PS/20CNF and PS/20CNF/30SEBS composite samples show thermal conductivities of 1.074 and 1.358 W/m·K, respectively, which are 496.6% and 654.5% higher than that of the pure PS sample. Furthermore, incorporating SEBS greatly improves the fracture toughness of the composite samples. For example, the PS/20CNF/30SEBS composite sample shows impact strength of 45.2 kJ/m2, which is 407.9% higher than that of the PS/20CNF composite sample (8.9 kJ/m2). The simultaneously enhanced thermal conductivity and fracture toughness endow the ternary PS/CNF/SEBS composites with great potential applications in the fields relating to heat transfer and mechanical impact.