聚丙烯分子量对其注射成型试样的拉伸和抗冲特性的影响

通过对聚丙烯及其经化学降解后的一系列不同分子量聚丙烯的注射成型样条的密度、结晶度、形态、取向、常温拉伸特性和低温抗冲性等方面的实验,讨论了分子量对这些性能的影响。分子量对密度、结晶度影响不大,但对形态及内外层的取向结构影响较大,而低温抗冲性能随分子量下降较多,常温抗拉特性随分子量变化较复杂,就其综合性能而言,以分子量在某一范围内较好。

EFFECT OF MOLECULAR WEIGHT ON TENSILE AND IMPACT PROPERTIES OF INJECTION MOLDED POLYPROPYLENE

In this paper the density, degree of crystallization, morphology, frozen orientation, tensile and impact properties have been studied for injection molded PP bars. The polypropylene specimens having different molecular weight were prepared by controlled chemical degradation. The effect of molecular weight on tensile and impact mechanical properties have been discussed. The experimental results show that by suitably decreasing Mw and stripping off tke high molecular weight tail in the MWD the injection molded bar has smaller degree of crystallization, less frozen orientation and thinner thickness of the skin part. Better duetility is to be expected in tensile test, but the impact intensity decreases.