PP polypropylene resin is a colorless, odorless , non-toxic powder or granular combustible matter , density of 0.90 ~ 0.91g/cm3, a low density resin . It is more transparent than polyethylene , lighter , breathable lower.
Regular molecular structure of the polypropylene is a crystalline polymer having a spherulite structure in general . Crystallinity polymer isotacticity with relevant regulations , etc. The higher the degree of crystallinity larger . The crystallinity of the polypropylene is generally from 30 to 70% . Density directly affects the degree of crystallinity , density polypropylene crystalline portion of 0.94g/cm3, the density of Titanium dioxide rutile the non- crystalline portion of 0.85g/cm3, and therefore the higher the crystallinity, the greater its density . Surface hardness than the high -density polyethylene polypropylene big . Its tensile strength than polyethylene , polystyrene, and styrene - butadiene - acrylonitrile copolymer (ABS) large, especially when the temperature exceeds 80 ℃ still maintain high strength , PVC stabilizer even at 100 ℃ stretching , half strength retained at room temperature . Polypropylene at high temperatures have a high impact strength , low temperature impact strength but worse than polyethylene. Polypropylene has excellent flex fatigue resistance , which is one of the unique properties of polypropylene . Polypropylene is the best inexpensive resin a heat-resistant , can be used in harsh conditions of 100 ℃ . The melting point of the polypropylene 164 ~ 170 ℃ ( pure isotactic polypropylene mp 176 ℃). As polypropylene and polyethylene , has excellent electrical insulating properties , and because it does not absorb water ( water absorption < 0.02% ) , and therefore not affected by humidity , the Plastic impact modifier dielectric constant and dielectric loss is small , with excellent high frequency characteristics. Polypropylene has good chemical stability , its chemical stability increased with increasing degree of crystallinity , except for a few medium is stable for most media Han , PVC stabilizer is usually an inorganic acid , base or salt solution , in addition to a strong by oxidation , the temperature is 100 ℃ at almost no damage to the polypropylene . The presence of a tertiary carbon atom in the polypropylene molecule , and therefore susceptible to oxidative corrosion medium . Polypropylene is very stable polar organic solvents , alcohols , phenols , aldehydes , ketones, carboxylic acids , etc. do not make the most of the swelling Aluminum hydroxide of polypropylene , aromatic and chlorinated hydrocarbons , but when the polypropylene has above 80 ℃ dissolution.
