长支链聚丙烯微注射成型的研究

Study on Long Chain Branched Polypropylene in Micro-injection Molding

研究了长支链聚丙烯微注射试样的形态结构、结晶形态和力学性能,探讨了微注射试样的结构与性能之间的关系。结果表明,长支链聚丙烯微注射试样的皮层区域为串晶结构,芯层区域为球晶结构,长支链结构引入使得芯层区域球晶数量增加,晶粒细化;当单体三羟甲基丙烷三丙烯酸酯(TMPTA)含量超过0.7 mL时,长支链聚丙烯微注射皮芯结构消失,层与层之间的界面模糊,原因在于支链结构导致了熔体松弛时间增加,最终成型微制品芯层分子延流动方向进行取向;通过力学性能分析,发现长支链聚丙烯微注射试样的拉伸强度增至41.22~41.32 MPa,增长幅度为14.27%。

The morphologies, crystallization and mechanical properties of long chain branched polypropylene （LCB） micro-parts were studied systematically, and the relationship between structure and property of the LCB micro-parts was investigated. The results show that the shish-kebab structure appears in the region of skin layer, and spherulite structure in the region of core layer. With the addition of trimethylolpropane triacrylate （TMPTA）, the size of spherulites decreases and the quantity increases markedly. As the TMPTA content is above 0. 7 mL, the typical skin-core structure of LCB micro-parts disappears and the boundary between skin layer and core becomes obscure. These changes of morphologies should be related to the increase in the relaxation time of LCB melt, which leads to molecular orientation in the region of core layer of LCB micro-parts. The tensile strength of LCB micro-part increases by 14.27% , and the corresponding tensile strength of LCB micro-part is in the range of41.22-41.32 MPa.