Polypropylene, a thermoplastic resin produced by the polymerization of propylene. According to the position of the methyl group is divided into three types of polypropylene, random polypropylene and polypropylene.
The methyl group is arranged on the same side of the molecular chain, said the order of the order of the methyl group in the molecular chain of the two sides called random polypropylene, when the methyl alternately arranged on both sides of the molecular chain said the regulation of polypropylene. In general industrial production of polypropylene resin, the content of the structural content of about 95%, and the rest for the random or inter - regulation. Industrial products as the main components of the composition. Polypropylene also includes a copolymer of propylene and a small amount of ethylene. Usually semi transparent, colorless solid, non - toxic, non - toxic. Because the structure is regular and highly crystallized, the melting point can be as high as 167. Heat resistance, corrosion resistance, products can be used as steam disinfection is a prominent advantage. Density is small, is the lightest of general plastic. The disadvantage is that the low temperature impact resistance is poor, more easy to aging, but can be overcome by modifying.
The copolymer type PP material has a lower thermal deformation temperature (100 degrees C), low transparency, low gloss, low rigidity, but has a stronger impact strength, the impact strength of PP increased with the increase of ethylene content. PP VEKA softening temperature is 150. Due to the high degree of crystallinity, the surface stiffness and scratch resistance of this kind of material are very good. PP does not exist the problem of environmental stress cracking.
The melt mass flow rate (MFR) of PP is usually in the 1~100. Low PP MFR material has better impact resistance but lower ductility. For the same MFR, the impact strength of the copolymer is higher than that of the copolymer. Due to crystallization, the shrinkage rate of PP is quite high, generally 1.6~2.0%.