The Research Of Technology And Die In Continuous Extrusion Of Microcellular Plastics

As a new macromolecular material, microcellular plastics is a hot research field in polymer processing molding, since it was born in the1980s, and it has a vast potential for application with its excellent performance. Continuous extrusion is generally used with its efficient production rate and low cost in polymer process, but the technology in continuous extrusion of microcellular plastics is immaturity.Rapid formation of the polymer melt/gas homogeneous phase system and an effective forming die are the key points in microcellular plastics continuous extrusion. According the solubility of CO2in polymer melt to determine the volume flow rate, and select the method of supercritical CO2injection into the melt and an appropriate acceleration device to improve the mixture effect of polymer melt and CO2for the rate of industrial production. Compared the theory of classical nucleation and summed up the results of previous experiments to analyze the factor of the melt nucleation in the forming die. Offer a suggestion that the gas-assisted extrusion instead of the rapid decompressive die by exploring the problem of the traditional molding die, and make a feasibility study of the effect and advantage in microcellular plastics.Select decompressive die as a prototype, design the microcellular plastic extrusion molding die. Take a numerical simulation of PS/CO2homogeneous phase system in different geometric parameters, process conditions and gas-assisted through the finite element analysis software polyflow. Through these factors which impact on the pressure and velocity fields in the melt to analyze the impact on nucleation melt. Verify the superiority of the gas-assisted extrusion by the results of traditional and gas-assisted extrusion from the numerical simulation.Build an experimental platform by summary of the earlier studies and simulated results, and use supercritical CO2and polypropylene PP for the experiments of the states which are different process parameters and gas-assisted extrusion, and analyze the impact in different parameters and advantage of the gas-assisted extrusion through the results in the experiment. Analyze the experimental products and summarize the problems which were encountered in the experiment to give advices of the improvement measures on the experimental program and the molding die.