Regulation And Characterization Of Dynamic Environment Of Polyolefin Foaming Process

In this paper,the effect of different foaming environment on the stability of PP foaming process was observed in real time with the help of visualization equipment,and the influence law of different foaming environment on the cell formation process was analyzed through the introduction of mathematical model.At the same time,based on the stability of PP foam material,the accuracy and universality of the mathematical model were verified.The results are as follows:(1)In the study of the influence of different foaming agent content on the stability of PP foamed materials,it was found that the final cell number of the foamed materials always included the rapid reduction stage and the basic stability stage.The increase of foaming agent content did not shorten the rapid reduction stage of cell number,and the stability of the final cell number and the coincidence degree of N-t curve were not significantly improved in the stable stage of the final cell number.(2)By comparing the final number of cells at different injection temperatures,it can be found that with the decrease of injection temperature,the area where the final number of cells decreases rapidly shortens,which indicates that the reduction of injection temperature can effectively make the final number of cells reach the stable stage ahead of time.Comparing the distribution of the final number of cells in the stable stage and the coincidence degree of N-t curve,it is found that the stability of PP foam can be effectively improved by appropriately reducing the injection temperature.(3)By changing the injection temperature and foaming agent content,the N-t curve always presents the characteristics of " semi-S" curve.With the increase of injection pressure,the stage of slow increase of cell number disappears,and the N-t curve changes from "S" curve to " semi-S" curve.In the free foaming process,changing the melt temperature and foaming agent content,the N-t curve always shows a typical "S" curve;With the increase of melt pressure,the N-t curve changes from complete "S" shape to " semi-S " shape,and the stage of slow increase of cell number disappears.(4)By fitting the N-t curve of the cell formation process,it can be found that the model formula can be consistent with the experimental data whether it is in the injection molding process or the free foam molding process.It shows that the model formula has both accuracy and universality.