Polyethylene, a commonly used material in hollow sheet products, is a crystalline or semi-crystalline saturated hydrocarbon formed by ethylene addition polymerization.
There are many types of polyethylene, and there are many classification methods, such as the method of polymer synthesis, polymer molecular chain structure, polymer density and the like. In addition, in the same type of polyethylene, it can be divided into homopolymers and copolymers according to the number of synthetic monomers.
Classified according to the method of polymer synthesis, this classification method began in the early stage of industrial production of polyethylene, and it has been used until now. As polyethylene is classified according to the density of the polymer, the density of polyethylene is in the range of about 0.860 - 0.965 g/cm3. Within this range, according to the density of polyethylene, it is divided into various types of polyethylene, which is a customary classification method on the market. They are ultra low density polyethylene (ULDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), high relative molecular mass. Density polyethylene super high molecular weight denier high density polyethylene (UHMWHDPE) and so on.
Basic properties of polyethylene and its films The chemical composition of polyethylene is relatively simple. However, although the chemical composition is the same, different polymerization conditions form different molecular structures (such as linear and branched), thereby producing different types of polyethylene such as low density polyethylene, linear low density polyethylene, and high density polyethylene. . Since the chemical structure of polyethylene is relatively simple, it is easy to enter the crystal lattice, resulting in higher crystallinity. However, the branching of the chain interferes with its crystallization ability, which lowers its relative molecular mass, thereby reducing the density of polyethylene.
The hollow sheet raw material polyethylene is almost insoluble in organic solvents at normal temperature, but it will grow in contact with aliphatic hydrocarbons, aromatic hydrocarbons and halogenated hydrocarbons for a long time; it will produce permanent contact with oils (mineral oil, vegetable oil, animal fat). Sexual deformation. When the temperature exceeds 70 ° C, it can be dissolved in a small amount in a solvent such as toluene, acetic acid, valeric acid, trichloroethylene, turpentine, mineral oil or paraffin.
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