文档介绍：Effects and Optimization of Processing Parameters
in Water-Assisted Injection Molding
1 ABSTRACT:
Experiments of water-assisted injection molded polypropylene curved pipe were carried out on newly developed equipment in this lab. First, four processing parameters, including short-shot size, melt temperature, water injection delay time, and water pressure, were investigated in terms of their effects on the water ration length and residual wall thickness of curved pipe. Second, an orthogonal array of Taguchi, the S/N ratio, and ANOVA were utilized to find the optimal processing parameters resulting in maximum water ration length. Finally, the crystallization behavior difference between the beginning and the end of the water channel of the curved pipe was analyzed using differential scanning calorimetry. It was interesting to find that the crystallinity of sample from the middle is higher than those from both outer and inner layers at position near the water inlet. The samples taken from the outer layer, middle, and inner layer show similar melting peak and crystallinity at position near the end of water channel.
Key words: crystallization; differential scanning calorimetry (DSC); injection molding; poly(propylene) (PP)
2 INTRODUCTION
Over a period of recent years, fluid-assisted injection molding technologies, including gas-assisted1–6 and water-assisted7–18 injection molding, have attracted more and more attention in researches and applications, due to that they offer potential to the production plex, highly integrated parts in virtually one process step. Water- and gas-assisted injection molding (WAIM and GAIM) are similar processes and they both utilize high-pressure fluids with viscosities much lower than the polymer melt viscosity to displace the polymer melt within thick sections of the cavity. Just before demolding, the fluid is released from the core to provide a hollow but fully formed geometry. The GAIM is a well-known technology for producing hollow p