Polyethylene, PE for short. According to density, it can be divided into high density polyethylene [HDPE], low density polyethylene [LDPE] and linear low density polyethylene [LLDPE]. HDPE can be used as a large water pipeline, while LDPE can be used as plastic film, preservative film and plastic bag.

Polypropylene, PP for short. It can be divided into random polypropylene, syndiotactic polypropylene and isotactic polypropylene. Random polypropylene can usually be used in hot and cold water pipes for writers.

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