Study On Microcellular Foam And Cellular Morphologic Control

Due to its unique structure and excellent performance, microcellular foam plastics has been paid comprehensive attention, and many countries have conducted industrial research on developing microcellualr foam plastics. Control of cellular morphologic is the most important factor of forming microcellular foam plastics, which is related to many aspects, for example, technological design and performance of product. So it goes without saying that control of cellular morphologic is of great importance to form microcellular foam. Using polypropylene to form microcellular foam by supercritical CO₂ is a new technology. Compared with polystyrene foaming, it has the advantage of environment - protection and economical efficiency.In this paper, cellular model is taken to descirbe the physical model of cellular growing, and equation of continuity,equation of momentum and constitutive equation are taken as control equation. Through these above, mathematical model of cellula growing can be drawn. The principle how radius and growing rate of cellula change can be gained. Compared with experimental data under similar condition given by predecessor, author proves the correctness of this model. Through adjusting material parameter (diffusion coefficient of gas,relaxation time) and technological condition (pressure of injecting gas,temperature), principle about how cellula grows and how these parameters influence cellula's growth is studied.Before polymer starts foaming, if obturator foramen is opened in order to form connected pore inside polymer, this will endow polymer with some new function, such as selective penetrance, which will make cell-connectivity have higher research value and use value. And this kind of open pore structure is named as opening polymer microcellular material. On the basis of cellula growing model, according to research on melt tension, process of cell-connectivity is simplified and reseasonal assumptation is made, then author proposes the condition of forming cell-connectivity. As a result, take polystyrene as a case, author analyses material parameter and mechanical & technological condition of forming cell-connectivity,and draws a conclusion about under what condition cell-connectivity can be formed during foaming extrusion process. This provides some guidance for pratical production.