Study On The Injection Molding Process And Flow Induced Crystallization Of Impact Polypropylene

The processing of impact polypropylene material determines usability of finalproduct because this process changes its microstructure and molecule structure. Inorder to forecast the usability of final product, it is necessary to model thecrystallization process and molding process of impact polypropylene.This paper focus on the establishment of compressible flow model and two-phaseflow induced crystallization model, injection molding process of impact polypropylene.Using Moldflow software and Matlab tool, this paper analyzes how the productstructure and process parameter affect the crystallization process. The two-phase flowinduced crystallization model is verified usefully through dimension measuring,mechanical property testing, DSC test of actual molding samples, which moldingunder multiple different process parameters. Also a FEA simulation model is built upusing Moldflow software to verify the crystallization model.Through modeling and analysis of crystallization process of impactpolypropylene, two conclusions are drawn:1. Product structure, location and thickness affect on the crystallization processand molding process. Where the shear rate is high, the crystallization speed ishigh. Nearer the central layer, smaller the shear rate and slower thecrystallization rate.2. Packing pressure, packing time and mold temperature also affect on themolding process and crystallization process. Under higher mold temperature,slower the crystallization speed. Increasing the packing pressure and packing time will accelerate the crystallization speed. But this trend is closely reratedwith the product structure and location.The measuring results of actual molding samples are similar to the simulationresults of crystallization model, which verified the model is applicable.