The production methods of polyethylene sheets mainly include the following:
High-pressure method: This method carries out polymerization under high temperature and high pressure, usually using a pressure of 100-200MPa and a temperature of 160-300 degrees. Using oxygen or organic peroxide as an initiator, ethylene monomer undergoes polymerization under solvent-free conditions. The high-pressure method is suitable for the production of low-density polyethylene, and the product has good impact resistance and toughness.
Medium-pressure method: This method carries out polymerization under lower pressure, usually using a pressure of 7-8MPa and a temperature of more than 100 degrees. Using metal oxides as catalysts, the reaction is carried out under dry and airless conditions. The medium-pressure method is suitable for the production of polyethylene with high relative molecular mass.
Low-pressure method: This method carries out polymerization under normal pressure or slightly pressurized conditions, and the temperature is 30-70 degrees. Using titanium tetrachloride and triethylaluminum as catalysts, the polymerization reaction is carried out in anhydrous alkane solvents. The low-pressure method is suitable for the production of high-density polyethylene, and the product has high tensile properties and low-temperature performance.
Radiation polymerization: This method conducts polymerization reaction under Y-ray radiation, with pressure of several to tens of MPa and temperature of 20-200 degrees. Normal aliphatic hydrocarbons or cycloalkanes are used as absorbents for ethylene monomers, and the catalyst is an alkane dispersion of titanium tetrachloride. Radiation polymerization is suitable for producing polyethylene products with specific properties.