Introduction of Polypropylene PP plastic material

Source:   Release time:2018-09-25 10:03:07  Visit:

Polypropylene, with abbreviation of PP, is also called polypropene, together with PE (polyvinyl chloride)PVC (polyethylene) are three most common plastic material. PP material is a kind of thermoplastic resin obtained by the polymerization of propylene. The monomer is propylene (CH2=CH-CH3).

PP is a semi-crystalline material. It is more rigid than PE and has a higher melting point. As the homo-PP products is very brittle when then temperature is higher than 0  , therefore many commercial PP material is added 1 to 4% ethylene random copolymer, or a higher ratio of ethylene. Copolymer PP (co-PP) materials have a lower heat distortion temperature (100 °C), low transparency, low gloss, low rigidity, but have a stronger impact strength. The Strength of co-PP increased with the ethylene increasing. The Vicat softening temperature of PP is 150 °C. Because of high degree crystallinity, this material's surface stiffness and resistance to scratches is very good. PP does't exist the problem of environmental stress cracking.

Generally, we adopts adding glass fiber, metal additives or thermoplastic rubber into PP to obtain modified PP (or called compounded PP). PP turnover MFR range is from 1 to 40. Low MFR PP material have better impact properties, but the extension intensity are lower. For the same MFR PP material, the strength of copolymer-type co-PP are higher than dimer type homo-PP. PP contraction rate is very high, typically 1.8 to 2.5%, due to crystallization.
Homopolymer PP and copolymer PP materials both have excellent resistance to moisture absorption, resistance to acid-base corrosion, anti-solubility. However, it have no resistance to aromatic hydrocarbons (such as benzene) solvents, chlorinated hydrocarbons (carbon tetrachloride) solvents etc.
Not like PE, PP did not still in the high temperature oxidation resistance.

Polypropylene (PP) is a mild form common plastic with excellent electrical properties, which can be used as high frequency heat-resistant insulating material. PP is a crystalline polymer and shows a larger shrinkage tate (1.0% -1.5%) when melt condensation as the volumn changes a lot and the molecular orientation degree is high.  When PP in molten state, there is little effect by heating to reduce its viscosity. Therefore, in the molding process, we mainly adopts improving the injection pressure and the shear rate to improve the molding quality of the products.

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