水辅注射成型聚丙烯制品的取向结晶

Crystalline orientation of the water-assisted injection molded polypropylene

应用小角X射线散射研究了水辅注射成型(WAIM)等规聚丙烯制品中串晶(shish-kebab)结构的形成、分布以及片晶取向行为。结果表明:根据取向度不同,WAIM制品沿壁厚方向可明显分为表层、芯层和水道层。表层和水道层均有shish-kebab结构生成,且在表层生成的数量比水道层多,而芯层则没有这种结构。这种shish-kebab结构使表层和水道层区域内的片晶取向明显,表层取向度的最大值(0.63)大于水道层(0.52);而片晶在芯层的取向不明显,取向度很小(接近于0),制品内部基本呈各向同性。

The formation and distribution of shish-kebab structure and the lamellae orientation of the waterassisted injection molded（WAIM） isotactic polypropylene（/PP） part were studied by small-angle X-ray scattering （SAXS）. The results indicate that the WAIM part can be divided into three different layers along the wall thickness direction： surface layer, core layer and water channel layer, according to the different degrees of orientation. The shish-kebab structure forms in the surface and water channel layers of the WAIM part, and the quantity of the shish-kebab structure formed in the surface layer is more than that of the water channel layer, but the structure does not appear in the core layer of the WAIM part. The formation of shish-kebab structure makes lamellae in the surface layer and water channel layer be oriented remarkably; the former＇s maximum degree of orientation （0.63） is larger than the latter＇s value （0.52）. However, the orientation degree of the lamellae in the core layer is close to 0, indicating the preponderant isotropy inside the part.