Synergistic effects of β-modification and impact polypropylene copolymer on brittle-ductile transition of polypropylene random copolymer

摘要

In this work, the synergistic effects of β-modification and impact polypropylene copolymer (IPC) on brittle-ductile (B-D) transition behavior of polypropylene random copolymer (PPR) have been investigated. It is interesting to find that adding both IPC and β-nucleating agent into PPR has three effects: (i) leading to a significant enhancement in β-crystallization capability of PPR, (ii) contributing to the shift of B-D transition to lower temperatures, (iii) increasing the B-D transition rate. The reason for these changes can be interpreted from the following two aspects. On one hand, the transition of crystalline structure from α-form to β-form reduces the plastic resistance of PPR matrix, thus causing the initiation of matrix shear yielding much easier during the impact process. On the other hand, the well dispersed rubbery phase in IPC with high molecular mobility at relatively low temperatures is beneficial to the shear yielding of PPR matrix and, subsequently, the great improvement in impact toughness of the ternary blends.