What is the pp material of the PP plastic cup?
PP is the abbreviation of Polypropylene, commonly known as pleated glue. PP is produced by the catalytic polymerization of propylene monomers using a catalyst. It is a crystalline isotactic polymer with regular molecular chains. PP can be divided into isotactic PP and random PP according to its crystallinity. Isotactic polypropylene is a highly crystalline thermoplastic resin with a crystallinity of over 95% and a molecular weight between 80,000 and 150,000; atactic polypropylene is non-crystalline and slightly viscous white wax at room temperature Substance, with a lower molecular weight of 3000-10000, has an irregular structure and lacks cohesion, so it is rarely used.
The commonly used PP raw material is isotactic polypropylene. Polypropylene is a high molecular polymer. The monomer is propylene CH2=CH-CH3. Polypropylene is obtained by addition polymerization. The chemical formula can be expressed as (C3H6)n, and the simplified structural formula can be expressed as [-CH2-CH(CH3)-]n. The molecular structure of PP is a typical main body regular structure, which is a crystalline polymer.
PP is a semi-crystalline material. It is harder than PE and has a higher melting point. Because the homopolymer PP temperature is very brittle above 0C, many commercial PP materials are random copolymers containing 1-4% ethylene or block copolymers with higher ethylene content. Copolymerized PP materials have low heat distortion temperature (100C), low transparency, low gloss, and low rigidity, but have stronger impact strength. The strength of PP increases with the ethylene content.
The Vicat softening temperature of PP is 150°C. Due to the high degree of crystallinity, this material has very good surface stiffness and scratch resistance. PP does not have environmental stress-cracking problems. Typically, PP is modified by adding glass fibers, metal additives, or thermoplastic rubber. The flow rate MFR of PP is between 1 and 40. PP materials with low MFR have better impact resistance, but lower elongation strength. For materials with the same MFR, the strength of the copolymer type is higher than that of the homopolymer type.
The shrinkage rate of PP is quite high, generally 1.8~2.5%. And the direction uniformity of shrinkage is much better than PE-HD and other materials. Adding 30% glass additive can reduce 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 has no resistance to aromatic solvents, chlorinated hydrocarbon solvents, etc., and the oxidation resistance of PP at high temperatures is not as good as that of PE.
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