Polyethylene (PE) is a thermoplastic resin obtained by polymerizing ethylene. In industry, copolymers of ethylene with small amounts of alpha-olefins are also included. Polyethylene is odorless, non-toxic, feels like wax, has excellent low temperature resistance (minimum operating temperature can reach -100~-70°C), good chemical stability, and can resist most acid and alkali erosion (not resistant to oxidation nature acid). It is insoluble in common solvents at room temperature, with low water absorption and excellent electrical insulation.
Chemical formula: (C2H4)n
Molecular weight: 190.09
CAS number: 9002-88-4
EINECS Accession Number: 618-339-3
Melting point: 85 to 110 ℃
Water solubility: soluble in water, the aqueous solution is acidic, soluble in glycerol, slightly soluble in ethanol
Density: 0.962 g/cm³
Appearance: low molecular weight is colorless liquid, high molecular weight is colorless milky white waxy granules or powder
Flash point: 270 ℃
High pressure polyethylene: more than half is used for film products, followed by pipes, injection molded products, wire wrapping layers, etc.
Medium and low pressure polyethylene: mainly injection molding products and hollow products.
Ultra-high pressure polyethylene: Due to the excellent comprehensive properties of ultra-high molecular polyethylene, it can be used as engineering plastics.
Polyethylene resin is a non-toxic, odorless white powder or granule, milky white in appearance, with a wax-like feel, and low water absorption, less than 0.01%. The polyethylene film is transparent and decreases with increasing crystallinity. The polyethylene film has low water permeability but high air permeability, which is not suitable for fresh-keeping packaging but suitable for moisture-proof packaging. Flammable, with an oxygen index of 17.4, low smoke when burning, with a small amount of molten droplets, the flame is yellow on top and blue on the bottom, with paraffin odor. Polyethylene has better water resistance. The surface of the product is non-polar, difficult to bond and print, and has been improved by surface treatment. More branched chains have poor resistance to photodegradation and oxidation.
Its molecular weight is in the range of 10,000 to 100,000. If the molecular weight exceeds 100,000, it is ultra-high molecular weight polyethylene. The higher the molecular weight, the better its physical and mechanical properties, and the closer to the required level of engineering materials. But the higher the molecular weight, the more difficult it is to process. Polyethylene has a melting point of 100-130°C and has excellent low temperature resistance. It can still maintain good mechanical properties at -60 °C, but the operating temperature is 80~110 °C.
It is insoluble in any known solvent at room temperature, and can be dissolved in a small amount in toluene, amyl acetate, trichloroethylene and other solvents above 70°C.