水辅助注塑聚丙烯制品的晶体结构研究

通过偏光显微镜(PLM)观察了水辅助注塑(WAIM)聚丙烯(PP)制品靠近注水喷嘴和远离注水喷嘴两个位置的晶体结构,发现WAIM制品沿壁厚方向都可以分为表层、中芯层和水道层,并且发现两个位置水道层和中芯层的晶体结构比较相似,表层晶体结构出现了较大的差异;靠近注水喷嘴位置表层晶体结构出现明显的取向现象,而在远离注水喷嘴位置没有出现。在晶体结构分析的基础上,初步探讨了水辅助注塑制品晶体结构的形成机理。结果表明:水的穿透对于熔体内部剪切的增加和取向结晶的形成有明显的促进作用。

Study on Crystal Structure of Water-assisted Injection Molded Polypropylene Parts

The crystal structure of both gate end and non-gate end of polypropylene(PP) parts,which were molded by water-assisted injection molding,were investigated by using the polarizing microscope(PLM).The results indicated that the residual wall of water assisted injection molded(WAIM) parts could be divided into several different layers,such as skin layer,middle core layer and water channel layer.The results also indicated that the crystal structure was similar in water channel layer and middle core layer but was rather distinct in the skin layer.Highly oriented structure was formed in the skin layer at gate end,but much less oriented structure was formed in the skin layer at non-gate end.Based on the crystal structure analysis,the formation mechanism of the crystal structure of WAIM parts was also investigated.The results showed that the presence of water penetration notably enhanced the melt internal shear and the oriented crystal.