Dynamic Conditions Of Microcellular Plastics With Supercritical Co <sub> 2 </ Sub> Foam Nucleation

This paper studies the main performances of polymer solutions when using supercritical CO₂ fluid as a foam agent, studies the kinetics and mechanism of the bubble nucleation under the effect of shear and elongate flow field in the process of extruding microcellular.One of the studying keystones of this paper is supercritical CO₂ fluid for such causes: it can dissolve quickly in the polymer melt, it can increase greatly fluidity of the polymer melt and reduce the viscosity of it greatly, it can also depress the extruding temperature of the melt.The nucleation of bubble is a key stage of the process of extruding microcellular when using supercritical CO₂ fluid as foaming agent. In order to carry out this process, uniform phases solutions containing polymer melt and supercritical CO₂ fluid must be formed in the first place. The forming of this solution is involved in diffusing and dissolving of supercritical CO₂ fluid. This paper traverses the characteristics of this fluid such as diffusibility and solubility in polymer melt, and presents the corresponding account method for them.The presence of supercritical CO₂ fluid brings a great deal of changes of rheology performance of polymer melt, and the extruding conditions changes greatly for it. This affects the forming and growing of bubbles directly, it also affects the performance and configuration of the final product. This paper studies the rheology performance of polymer solutions containing supercritical CO₂ fluid using freedom volume fractional, studies the reciprocity mechanism of polymer melt and supercritical CO₂ fluid.This paper studies detailedly the process and the kinetics of bubble nucleation when using supercritical CO₂ fluid as foaming agent, studies the critical Gibbs free energy variety for bubble nucleating by using interfacial tension of gas-liquid in the solution. This paper also present the method of bubble nucleation velocity at the base of bubble impacting model.In the actual extrusion foaming process, the formation of nuclei is under the effect of shear action of extruding flow field and elongate action of convergent die. This paper introduces the effects of dynamic factors into the calculation of bubble nucleation kinetics. On the basis of Talyor's Deformation...