Study On Internal Friction Behavior Of Microcellular Foaming Process Of Polymer

The microcellular plastic molding technology is polymer materials research focus of the twenty-first century, with broad prospects. The three stages of the microcellular plastic foam molding plays a decisive role on the microstructure and mechanical properties of the final product, therefore its quite detailed and in-depth research to find some of the parameters of the law, these conclusions focus on bubbles nucleated static process. Must exist in the microcellular foam molding process the melt flow behavior is bound to its internal friction in the flow process of impact molding process. In this paper, the microcellular foam molding process mechanism departure from the angle of internal friction behavior and its influencing factors were studied.Studied from the angle of internal friction behavior of supercritical fluid diffusion in the polymer melt and polymer/super critical fluid viscosity of the homogeneous system; friction can be studied from the point of view of energy balance on the bubble nucleation process the impact, to make up for the lack of classical nucleation theory bubble nucleation behavior as a static equilibrium analysis process, more accurately express the actual microcellular foam molding process of bubble nucleation behavior. Moldflow simulation software to simulate the the microcellular foam injection molding process, and the results were analyzed to verify the correctness of the theoretical analysis; finally, the by targeted experimental study to final validation of theoretical research and simulation.Theoretical studies:With the increase of the content of the supercritical fluid and the screw speed is increased in the viscosity of the polymer melt can be reduced to improve the flow properties of the mixture, effectively enhance the rate of diffusion in the polymer melt to promote its that the degree of mixing with the polymer melt to accelerate significantly reduce the formation time of the homogeneous system, the viscosity is calculated on the content of the supercritical fluid and the fluid velocity gradient homogeneous system. In the steady-state flow field analysis of the law of friction can promote bubble nucleation and related factors, and the friction energy to overcome the Gibbs free energy barrier of bubble nucleation contribution formula is based on energy conservation, more reasonable explanation the phenomena appear in the actual micro-foam production.For the polymer microcellular foaming process and friction factors analysis, concluded:bubble nucleation behavior strongly depend on the content of the supercritical fluid, affecting the size and density of the foam; improve the steady-state flow rate can increase the friction energy, promote bubble nucleation and bubble growth, promote foam more uniform dispersion, the bubble density is greater, to reduce the product density, is conducive to the microcellular plastic molding, However, the cell morphology will occur in excessive shear stress on the direction of orientation, or even destruction of the foam structure is not conducive to the quality of the foamed article. Reflect the correctness of the theoretical research and experimental results from a macro point of view.