Influence of filler particles on deformation and fracture mechanism of isotactic polypropylene

This study is focussed on the role of calcium carbonate particles on the deformation and fracture mechanism in PP/CaCO3 composites. Several composites with different amounts of calcium carbonate were examined. Tensile test, three- and four-point bending test were conducted. The results of tensile tests show that the addition of CaCO3 to PP decreases yield strength and elongation at break while causes to promote modulus. Optical microscopy taken from the polished surfaces of tensile test illustrates presence of the damage zones in all specimens. Looking at in more details via scanning electron microscope (SEM) show the damage zone included some crazes and some voids owing to poor adhesion between filler and matrix. Briefly the dominant mechanism of deformation in PP/CaCO3, observed in this work, appears to be a craze type of damage, propagating via repeated cavitation. The results of three-point bending tests show that the fracture toughness of PP decreases with increasing of CaCO3 content. The results of four-point bending tests display that a wide spread damage zone in front of the pre-crack while SEM photographs appears that the damage zone including craze which is followed by repeated cavitation and debonding.