[Science Stickers] Polypropylene-the difference between copolymerization and homopolymerization

Polypropylene (PP) is divided into homopolypropylene (PP-H), block (impact-resistant) copolymer polypropylene (PP-B) and random (random) copolymer polypropylene (PP-R).

1. Homopolypropylene (PP-H)v

PP-H is homopolypropylene, which is what we call type I polypropylene. We can know that it is polymerized from a single polypropylene monomer and does not contain ethylene monomer in the molecular chain. The regularity of the PP-H molecular chain is very high, so the material has high crystallinity and poor impact resistance.

Main performance: high molecular chain regularity, good high temperature resistance, poor low temperature impact resistance, poor light aging resistance.

Application fields: generally used in chemical pipelines or other engineering purposes.

2. Block (impact resistance) copolymer polypropylene (PP-B)

PP-B is a block copolymer polypropylene, which is what we call type II polypropylene. Its ethylene content is relatively high, generally 7-15%. In the molecular sequence, the probability that two vinyl monomers and three monomers are connected together is very high, indicating that the vinyl monomers only exist in the block phase. The ethylene segment in the form of blocks greatly improves the impact strength of the material, but because the isotacticity of the PP-H molecular chain cannot be reduced, the crystallinity, melting point and heat resistance of the material cannot be fundamentally improved. . 

Main performance: good low temperature impact resistance, low temperature embrittlement point of -5℃, poor high temperature resistance, applicable temperature range of 0-60℃.

Application field: Generally suitable for cold water system or low pressure water system with temperature lower than 60 degrees.

3. Random (random) copolymer polypropylene (PP-R)

PP-R is random copolymer polypropylene, which is what we call type III polypropylene. It is obtained by copolymerization of propylene monomer and a small amount of ethylene monomer under heating, pressure and catalyst. The ethylene monomer is randomly distributed in the propylene long chain, and the ethylene monomer is generally controlled between 3-5%. The random addition of ethylene monomer reduces the crystallinity and melting point of the polymer, and improves the impact performance and heat resistance.

Main performance: General low-temperature impact resistance, good creep resistance under high temperature, applicable temperature range is 0-80℃.

Application field: widely used in cold and hot water systems of buildings.

This article comes from the Internet, only for learning and communication, no commercial purpose.

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