Effect of High Molecular Mass Tail in the Mol Mass Distribution of Polypropylene on Injection Molding

R. Qian; M. Guo; S. Li

doi:10.1515/217.870174

Article

Effect of High Molecular Mass Tail in the Mol Mass Distribution of Polypropylene on Injection Molding

R. Qian , M. Guo and S. Li

Published/Copyright: April 9, 2022

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From the journal International Polymer Processing Volume 2 Issue 4

Abstract

The effect of high molecular mass (MM) tail in the molecular mass distribution (MMD) of polypropylene (PP) on injection molding has been studied using injection molded tensile bars from a commercial PP resin and two samples of the above resin deprived of the high MM tail in different degrees by controlled degradation during extruder reaction with an added processing aid named Promax. The central portions of the tensile bars were studied by polarizing microscopy of microtomed sections parallel and perpendicular to the melt flow direction, and by density and birefringence profiles across the thickness of the bar. Mechanical properties and acoustic emission behavior in stretching of these injection molded tensile bars are also discussed. The experimental results show that by stripping off the high MM tail in the MMD the injection molded tensile bar has smaller degree of crystallization, less frozen orientation, improved uniformity across the thickness and the thickness of the skin part is greatly reduced. Better quality of the fabricated articles is to be expected by using Promax with PP for injection molding.

* Mail address : Dr. Qian Renyuan, Institute of Chemistery, Academis Sinica, Beijing, China.

** Yong Liu, Tiangui and Changhua Xu of Institute of Chemistry, Academia Sinica and Hanling Wang of Beijing Institute of Aeronautics took part in the work of this paper.

Acknowledgement

The authors would like to express their thanks to Mr. Xie Ping for the GPC data, and to Mr. Wang Shuzhong, Beijing Research Institute of Chemical Industry, Ministry of Chemical Industry, for injection molding of the tensile bars used in this investigation.

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Published Online: 2022-04-09

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