The Study Of The Preparation Of Hms-pp Foaming Using Water Vapor As A Blowing Agent

Due to its highly availability, easiness to recycle, cheap and excellent performance, Polypropylene (PP) is one of the most popular five resins in the world. The foamed materials have many performances such as light weight, heat insulation, sound insulation, Gushing, low cost and so on, so it has been used in national economy and daily life more and more. However, recent years , The traditional foam plastics (PE,PS and so on)are made by using CFC as blowing agent which destroyed the ozone layer of the nature and the waste of the products which are not rotten and difficult to be recycled became"white pollution". While Polypropylene (PP) and its foamed products have good elastic, high mechanical strength and easy to degradable, so it can be widely used in many fields such as packaging, automotive uses, construction and other industrial fields. Now, People attach importance to the foamed PP, therefore, the foam plastics PP is destined to be a new kind of materials in the future. But PP belongs to family of crystal polymer. The melt strength decreases rapidly after the melting point. This makes it difficult to expand and shape. Currently, it's industrialized only in several advanced country.By the analysis bases on the research in the progress on polypropylene (PP) foaming at home and abroad, the experiment uses non-continuous way to prepare PP foaming plastics, which is divided into two parts. 1. Preparing pre-foam PP particles using water as a blowing agent in the single-screw extruder. 2. Preparation of HMS-PP foaming using water vapor as a blowing agent. Use water vapor as a blowing agent has the following two advantages than other chemical foaming agents (for example AC blowing agent)and physical blowing agents such as CO2 ,butane and so on.â‘ there is no by-products while foaming.â‘¡It is cheap, will not cause the greenhouse effect and damage the ozone layer. The foaming process is non-toxic. So it is a green blowing agent.In this paper, cellular model is taken to describe 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 cellular growing can be drawn. By changing material parameter (relaxation time, viscosity, interfacial tension and so on) and technological condition (pressure, pressure drop rate), principle about how cellular grow and how these parameters influence the growth of cellular. By theory and experiments. Observing the microstructure of PP foaming material and further analyze the factors (pressure, pressure drop rate and so on) which influence the foam structure and properties. Drawing the following conclusion mainly: The pressure of water vapor influences the foaming greatly. The average diameter of bubble becoming bigger when increasing the pressure of water vapor .Which matches the theory; Pressure drop rate is the most important factor which influence the foam structure and properties, the faster the pressure drop rate is , the bigger the average diameter of bubble is ,especially when the pressure drop rate is small enough, the pre-foam PP particles can't be foamed; When the pressure of water vapor is high and the pressure drop rate is fast, we can get a big bubble diameter, low density, and high expansion ratio PP foaming products.We can improve bubbles'morphology of the produces through increasing the pressure and pressure drop rate. So the content of this paper presented have important significance to research and production for foaming plastics using water vapor as a blowing agent.