| The foamed material has many performances such as light weight, heat insulation, sound insulation, cushing, low cost and so on, so it has been used in national economy and daily life more and more. However, recent years, owing to destroying the ozone layer of the nature by using CFC and "white pollution" to the environment caused by the waste products which are not rotten and difficult to be recycled, the UN environment-protection organization decided to stop to produce and use foamed PP all over the world from year 2005. and China declared that from year 2000 the disposal foamed PS tableware. As the fastest increasing resin, Polypropylene (PP) and its foamed products have good heat resistance and mechanical strength, and also better environmental effect than that of foamed PS, foamed Polyethylene (PE). People attach importance to the foamed PP, since it can be widely used in many fields such as packaging, food, short order, automotive uses, construction, heat insulation, physical culture and so on.Nevertheless foaming processing of PP is very difficult because of its high crystallinity and poor melt strength. Up to now, only several developed countries such as U.S.A., Japan and Germany have realized the industrial production, and it is vacant in China, in addition, the correlative theory is still absent. Basing on the achievements of domestic and abroad research, the author carry out preliminary study on the chemical extruding free foaming of PP.The main achievements and conclusions are as following:1. Using domestic common PP resin as basic material, by means of conventional single-screw extruder and conventional die, the chemical extruding free foaming processing of PP in one step was realized. In comparison to normal pressure foaming processing and extruding foaming of foreign countries, this technology has some characteristics such as short flow process, simple equipment, easy adjustment of products and good economy and so on.2. Through crosslinking extrusion and blending extrusion, the meltstrength of common PP resin was improved, with the rheological properties that the dropping rate of melt viscosity with temperature becomes slow. And then the extruding foaming of PP from the low expansion to high expansion ( ratio: 6~8 ) with high resilience was realized through (slight) crosslinking extruding foaming and non-crosslinking blending extruding foaming methods.3. The physical-chemical reaction process and mechanism was analyzed synthetically from decomposing of crosslinking agent and foaming agent up to forming of PP polymer/gas solution, and the phase transformation of melting crystal and the effect of crystallinity on diffusion and solution of gas was discussed.4. The whole cell forming process from nucleation to cell growth to solidification was analyzed theoretically. The physical and mathematical model of PP cell expansion on the basis of "cell" model was established. Through the coupling of momentum, mass and energy transfer equation, the controlling equation for the cell expansion was obtained. Compared with the past studies in the model, this model is more integrate and more close to reality since some factors were taken account including nonisothermal condition, change of melt density, compressibility of foam body, real gas state equation and crystal latent heat of PP.5. Through a lot of experiments, by means of changing combination of parameters for formula, technology and equipment structure, the effect of foaming under different processing variable on micro-structure of cell and macro property of foam was studied. The relationship between the variables and the foaming effect was educed, which is important to guide the controlling of cell structure and properties.6. Introducing the concept of "instantaneous change flow", in virtue of explosion theory, the "instantaneous change flow" character of PP foaming, namely instantaneousness and oscillation, was put forth and proved. The "instantaneous change" characteristic for high ratio foaming was discovered. It was found through c...
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