Experiment Study On Extrusion Swell Of PS/SCCO₂ Foaming System

The swell of the polypropylene foaming is the normal appearance in moulding of polymer. This dissertation summarized various factors that affect the swell of the PS/SCCO₂ foaming system. The factors are divided into two categories: one are the effects of the specification,variety,capability and the dosage of the raw and processed materials, the other is the effect of the process parameters. This article focuses on craft parameter which influence the PS/ SCCO₂ foaming system swelling and the final quality, this dissertation focuses on two issues: (1)Theoretical analysis and numerical simulation of the extradate swell of the PS/ SCCO₂ foaming system; (2) Theoretical analysis and experimental research of the relationship between the extradate swelling of the foam and the size of the bubble.First, as for the swell behaviors of the foaming system, we study on the mathematical model of the viscous-elastic extrudate swell and the theoretical model of the cell swell, as well as how the capillary number using in the extrusion. Then we put forward the swell ratio forecast model of the PS/ SCCO₂ foaming system. In this model, not only the effects of the CO₂ foaming blister, but also the temperature and pressure. There are many factors affecting the quality of micrecellor. In which,the patter and effect of import are very imponent. In the extruding technics of microcellular, the CO₂ vesicent without pollution take place of the chemical vesicant which is detrimental to make the advantageous microcellor foaming. which makes wide-ranging concern. First, we make the regression of the viscosity from the experimental data, and then regresses the expression of the swell ratio and the capillary number, at last, the swell ratio forecast model is gained by the formula translation. The swell ratio forecast model can predict the extrudate swell ratio well. The swell ratio forecast model can predict the extrudate swell ratio well.Secondly, the orthogonal experimental method and the data statistic means are used in this dissertation. The issues in reality are very complicated, and the factors that affect on the experiment are various. The orthogonal experiment in this dissertation includes three factors, three levels, nine takes experiments, which is time-saving, material-saving and collecting the data correctly. And the advanced experimental data statistic software such as SPSS,Excel are also used to find out the most significant factors that affect the experiment most. The software regressed the expression of the shear rate and the stress of the PS/SCCO₂ foaming system, and the expression of the swell ration and the capillary number.As for experiment, This article uses the digital camera to record the entire squeezing process of PS/SCCO₂ foaming system from the mouth mold. The methods in detail are as follow: fix the plotting paper and the electron stop watch under the exit of the capillary; digital camera shot the time and the locomotion of the extrudating on the same picture. From the pictures, the parameters of extrusion, such as the average speed of the extrudate, the flow rate, the viscosity and the die swell ratio, can be calculated.As for the cell dimension, we analyze the digital camera pictures of the extrudate in the orthogonal experiments. We rebuild the swell ratio forecast model to be the cell diameter forecast model by using the expression of the capillary number and the cell dimension, so that we can predict the cell size in micro view from the swell ratio in the macro view.By establishing the theoretical model of the PS/SCCO₂ system and carring experimental research, we can know that the forecasting model results and the experimental results extremely tallies. Thus we can confirmed the forecasting model feasibility, and providing formulating craft condition and enhancing squeezing quality with the reliable theory basis and the promotion application value.