2013-11-02 by wsdchemicallow molecular polyethylene : (1) LDPE: low density polyethylene ( also called high-pressure polyethylene ) (2) LLDPE: linear low density polyethylene (3) MDPE: medium density polyethylene (4) HDPE: high density polyethylene ( also known as low-pressure polyethylene ) (5) UHMWPE: ultra High Molecular Weight polyethylene ( 6 ) modified polyethylene : chlorinated polyethylene (CPE), cross-linked polyethylene (PEX) (7) ethylene copolymer : ethylene - propylene copolymer material ( plastic ), EVA, ethylene - butene copolymer , an ethylene - other olefins ( such as octene POE, cyclic olefin ) copolymer , an ethylene - unsaturated ester copolymer (EAA, EMAA, EEA, EMA, EMMA, EMAH ) . Molecular weight of up to 300 million -600 Wan polyethylene called ultra high molecular weight polyethylene (UHMWPE). UHMWPE intensity is very high, it can be used to make bullet-proof vests . LDPE resin properties : tasteless , odorless, non-toxic, matte , white wax particles , density of about 0.920g/cm3, melting point 130 ℃ ~ 145 ℃. Insoluble in water, slightly soluble in hydrocarbons, such as toluene . Most of the acid-base corrosion resistant , low water absorption , can maintain flexibility at low temperature resistance, high electrical insulating properties . Production process : the main high-pressure tubular process and autoclave French. Development from the current situation, to reduce the reaction temperature and pressure , tubular high temperature method process commonly used to initiate polymerization system active agents cited in the main raw material of high purity ethylene , propylene / propane, the density adjusting agent , using high- activity initiator agent at about 200 ℃ ~ 330 ℃ ,150-300MPa polymerization conditions . Polymerization reactor, molten polymers , must be through high-pressure , medium-pressure and low-pressure cooling , separation, high pressure recycle gas is cooled , separated into high pressure (300MPa) compressor inlet , the pressure recycle gas is cooled , separated later into a higher pressure (30MPa) the compressor inlet , and the low pressure recycle gas is cooled , separated into a lower pressure (0.5MPa) recycling compressor , melted through high-pressure polyethylene , low separation into granulator for water dice in the granulation , the enterprise according to different application areas , adding suitable additives , particles packaged factory .