Effect of poly(styrene-ethylene-butylene-styrene) block copolymer on thermomechanical properties and morphology of polypropylene/poly(styrene-ethylene-butylene-styrene)/polycarbonate ternary blends

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.