Extrusion Counterpressure Microcellular Foam And Numerical Simulation Of Bubble Growth

With applications of porous foam products becoming more widely, industrial application requirements for performance foam products are becoming more stringent. For the study of porous foam products preparation process of industrialization and related theories is also increasing. During industrialization process porous foam products, processing and production equipment are important factors in determining the performance of the plastic foam material. The research of bubble growth in microcellular foam processing has an important role to improve the performance of microcellular foam.Firstly, this paper analyzed and compared the advantages and disadvantages of existing microcellular foaming process, proposed the extrusion counterpressure process subsequently. Secondly, the paper analyzed the principle of counterpressure foaming process feasibility, designed the extrusion counterpressure foaming experimental device, the corresponding gas counterpressure injection system, temperature control system and data acquisition system, built a extrusion counterpressure microcellular foaming experiment platform. It was verified by experiment that the feasibility of extrusion counterpressure foaming process and experimental apparatus. Minimum average cell size of foaming samples prepared in experiment is 61.7μm, and cell density is 6.18x107/cm3.A parametric study was conducted to examine the effects of process parameters on cell morphology of PS/CO2 foam samples. It was found that the effect of filling time and dwell time on cell size and cell density is not monotonous. With the autoclave temperature or the counter pressure increasing, the cell size of foam sample becomes smaller, the cell density increases. With the counter pressure increasing, the effect of counter pressure on the cell size becomes small gradually, because of the competition of cell nucleation and growth. Extrusion counterpressure foaming experiments were designed and analyzed by DOE method. It shows that autoclave temperature impacts cell size and apparent density of foam samples most significantly; the higher autoclave temperature, the larger cell size of foam samples, the smaller apparent density.This paper established the non-isothermal bubble growth model based on cell model in PS/CO2 system, obtained numerical simulation solution of non-isothermal bubble growth, and studied the effect of material parameters and foaming process parameters on bubble growth. It shows that diffusion coefficient and viscosity have greater influence on bubble growth. This paper combined non-isothermal mathematic model of bubble growth and experimental analysis of DOE. The bubble growth and rate profiles were predicted. The results show that the system pressure has the most significant affection.