Injection Molding Shrinkage and Mechanical Properties of Polypropylene Blends

Abstract

Polypropylene (PP) blends based on isotactic polypropylene (iPP), propylene-ethylene block copolymer (bPP), and propylene–ethylene random copolymer (rPP) were prepared by melt blending and the effects of content of bPP and rPP on the shrinkage during solidification and storage and mechanical properties of the blends were studied. It was found that the addition of polypropylene copolymer could effectively reduce the processing shrinkage of iPP and the lowest shrinkage of the blends was achieved at a loading of 2 wt% bPP or rPP. The flexural modulus and tensile strength of the blends decreased a little while the impact strength and elongation at break were improved greatly compared with those of iPP.

Keywords:

• injection molding
• mechanical properties
• polypropylene blends
• shrinkage

Acknowledgments

The authors gratefully acknowledge the financial support of National Natural Science Foundation of China (Grant No. 20734005 and 50873068), the Program for New Century Excellent Talents in University (NCET-08-0382).