反应降解聚丙烯的高速挤出流动稳定性

High speed extrusion stability of PP melts prepared by reactive degradation

采用双毛细管流变仪研究了反应降解聚丙烯试样的挤出稳定性。结果表明:基础树脂聚丙烯PP-2401的挤出压力随剪切速率增高呈阶梯状稳定增高,而降解聚丙烯的挤出压力随剪切速率增高出现不规则波动;低相对分子质量降解聚丙烯的压力波动主要发生在口模入口区;发生波动的原因与聚丙烯分子链结构特征有关,同时与熔体在口模区的Weissenberg准数和Reynolds准数较大有关。

The extrusion flow stability of reactive degraded polypropylene （PP） samples was studied by a double capillary rheometer. The results indicate that the extrusion pressure of basic resin PP-2401 increases stably and step by step with the rise in the shear rate, but the extrusion pressure of the degraded PP samples is irregular undulated by higher shear rate. Such pressure instability of degraded PP with low relative molecular mass happens mainly at the entrance area of die. The causes of this instability are related to the chain structure of PP, larger Weissenberg number and Reynolds number of melts at the entrance area of die.