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- Apr 13, 2018 -

Polypropylene is a thermoplastic resin made from propylene polymerization. According to the position of methyl arrangement, it can be divided into three kinds: isotactic polypropylene, random polypropylene and syndiotactic polypropylene.

Industrial products are mainly composed of isotactic materials. Polypropylene also contains propylene and a small amount of ethylene copolymer. It is usually semitransparent and colorless solid, odorless and nontoxic. Because the structure is regular and highly crystallized, the melting point can be as high as 167 degrees. Heat resistance, corrosion resistance and steam sterilizing are the outstanding advantages of products. Small density, the lightest general plastic. The disadvantages are low temperature resistance, low impact and easy aging, but they can be overcome by modification.

The copolymer type PP materials have lower thermal deformation temperature (100), low transparency, low gloss and low rigidity, but have stronger impact strength. The impact strength of PP increases with the increase of ethylene content. The softening temperature of VEKA in PP is 150 C. Because of the high crystallinity, the material has good surface stiffness and scratch resistance. There is no environmental stress cracking in PP.

The melt mass flow rate (MFR) of PP is usually 1~100. Low MFR PP material has better impact resistance but lower extension strength. For the same MFR material, the impact strength of the copolymer is higher than that of the homopolymer. Because of the crystallization, the shrinkage rate of PP is quite high, generally 1.6~2.0%.

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