Effects of Core-Shell Particles on Fracture Micromechanisms of PP/PC/SEBS Ternary Blends

Abstract

PP/PC, PP/SEBS binary blends and a PP/PC/SEBS ternary blend were produced via melt blending in a co-rotating twin-screw extruder. The phase morphology, bending and impact behaviors of the blends were studied. Transmission optical microscopy (TOM) of the crack tip damage zone, scanning electron microscopy (SEM) of impact fractured surfaces and transmission electron microscope (TEM) were performed to characterize the fracture mechanism. The core-shell particles in PP/PC/SEBS ternary blends do not have a significant influence on the crack initiation resistance but SEBS particles in PP/SEBS binary blend cause reduction of the crack initiation resistance and PC particles in PP/PC binary blend cause the greatest reduction of the crack initiation resistance. In PP and PP/PC binary blend samples no sign of plastic deformation was observed, while TOM micrographs in R30 and BR30 samples indicates that shear yielding mechanisms have also occurred around the crack tip and crack wake, also the fracture surfaces of R30 and BR30 shows ductile deformation. Preliminary analysis of micromechanical deformation suggested that the high impact toughness observed for R30 and BR30 was attributed to the cavitation of rubber particles and consequently shear yielding of the matrix. As illustrated in TOM observation in R30 the intensity of the damage zone and number of crazes is less than BR30, indicating cavitation capability of the core-shell particles is higher than pure rubber particles. In R30 due to the presence of the core-shell particles, cavitation can occur easily and small cavities connect to each other and form large cavities.