What is PP material?

PP (polypropylene)

PP performance

　　PP is a crystalline polymer. PP is the lightest among the commonly used plastics, with a density of only 0.91g/cm3 (smaller than water). Among general-purpose plastics, PP has the best heat resistance, its heat distortion temperature is 80-100°C, and it can be cooked in boiling water. PP has good resistance to stress cracking and has a high bending fatigue life, commonly known as "100% plastic".

　　PP's overall performance is better than PE material. PP products are light in weight, good in toughness and good in chemical resistance. Disadvantages of PP: low dimensional accuracy, insufficient rigidity, poor weather resistance, easy to produce "copper damage", it has post-shrinkage phenomenon, after demolding, easy to aging, brittle, and easy to deform. PP has always been the main raw material for making fibers because of its coloring ability, wear resistance, chemical resistance, and favorable economic conditions.

　　PP is a semi-crystalline material. It is harder than PE and has a higher melting point. Since the PP temperature of the homopolymer type is very brittle when it is higher than 0°C, many commercial PP materials are random copolymers containing 1 to 4% ethylene or block copolymers with a higher ratio of ethylene content. Copolymer PP materials have lower heat distortion temperature (100℃), low transparency, low gloss, and low rigidity, but have stronger impact strength. The strength of PP increases with increasing ethylene content.

　　PP has a Vicat softening temperature of 150°C. Due to the high crystallinity, this material has good surface stiffness and scratch resistance.

　　PP does not have the problem of environmental stress cracking. Generally, PP is modified by adding glass fiber, metal additives or thermoplastic rubber. The flow rate MPP of PP ranges from 1 to 40. PP materials with low MFR have better impact resistance but lower ductility.

　　 Due to crystallization, the shrinkage of PP is quite high, generally 1.8 to 2.5%. And the direction uniformity of shrinkage is much better than that of HDPE and other materials. Adding 30% glass fiber additive can reduce the shrinkage to 0.7%.

　　 Both homopolymer and copolymer PP materials have excellent moisture absorption resistance, acid and alkali corrosion resistance, and solubility resistance. However, it is not resistant to aromatic hydrocarbon (such as benzene) solvents, chlorinated hydrocarbon (carbon tetrachloride) solvents, etc. PP, like PE, still has oxidation resistance at high temperatures.