Study On The Influence Of Polypropylene Melt Strength On Foaming

Due to its highly availability, light weight, easiness to recycle, and excellent performance, Polypropylene(PP) is one of the world's most popular resin. PP foamed material has become the hot spot in the plastic industry because of is unique properties. Firstly, PP foam has low cost, high elasticity, rigidity. It is durable and performs well under environmental pressure. Particularly, when compared with foamed materials made from PS and PE, PP foam products have better heat-resistance, insulation and obstructive ability. Secondly, the process of making PP foam doesn't involve florin and chlorine carbides, and there is no harm to the ozone layer. Therefore PP Styrofoam is environment friendly and is called "green foam".PP belongs to family of crystal polymer. The melt strength decreases rapidly after the melting point. This makes it difficult to expand and shape. Therefore, it's a key factor to control the melt strength of the PP foaming. Currently, it's industrialized only in several advanced country such as US, Japan and Germany. In our country, it's still a blank area. Also the theoretical research is space. This thesis, based on the results from the previous, focused on the internal relationship between the melt strength andfoaming, researched into the process and functions of ingredients for making PP foam. The detailed research areas are as follows,1. Systematically discussed the factors that affect the melt strength of the PP foaming. The important factors can be divided into three categories: Firstly, the property of rheology of the polymer, such as the stickiness, surface tension etc. Secondly, the molecular weight, molecular structure and the branching degree of the polymer under microscope. This is also the theoretical foundation of the improved process and integrants. Thirdly, the process conditions determine adjustment range of ingredients in making PP foam.2. As an integrated system, it researched the methods for modification on PP, and the effects on melt strength. It also introduced the mechanism of modification, and the relationship to the melt strength. The normal ways of modification are cross-linking, branching, blending and adding etc.3. It proposed a physical model of the molecular structure that is suitable for foam expansion. In order to obtain the desired molecular structure to meet the requirement of the expansion, the only way is through integrated modification including cross-linking, branching, blending ,adding-it's one of the effective ways to achieve the desired molecular structure, based on a rudiment research.4. The area of the die and the temperature greatly affect the structure and property of the PP. The smaller the die's area is, the bigger the...