In industry, polyethylene also includes * * * polymers of ethylene and a small amount of α-olefins. Polyethylene is odorless and non-toxic, feels like wax, and has excellent low temperature resistance (the lowest service temperature can reach-100 ~-70℃), good chemical stability and resistance to most acids and bases (not oxidative acids). Insoluble in general solvents at room temperature, low water absorption and excellent electrical insulation.
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chemical property
Polyethylene has good chemical stability, and can resist dilute nitric acid, dilute sulfuric acid and any concentration of hydrochloric acid, hydrofluoric acid, phosphoric acid, formic acid, acetic acid, ammonia water, amines, hydrogen peroxide, sodium hydroxide, potassium hydroxide and other solutions at room temperature. But it is not resistant to strong oxidation corrosion, such as mixed solution of fuming sulfuric acid, concentrated nitric acid, chromic acid and sulfuric acid.
At room temperature, the above solvents will slowly corrode polyethylene, while at 90 ~ 100℃, concentrated sulfuric acid and concentrated nitric acid will rapidly corrode polyethylene, causing it to be destroyed or decomposed. Polyethylene is prone to photooxidation, thermal oxidation and ozone decomposition, and is easily degraded under the action of ultraviolet rays. Carbon black has a good shading effect on polyethylene. After irradiation, reactions such as crosslinking, chain breaking and formation of unsaturated groups will occur.
mechanical properties
Polyethylene has general mechanical properties, low tensile strength, poor creep resistance and good impact resistance. Impact strength LDPE > LLDPE >; HDPE, other mechanical properties LDPE
It is mainly affected by density, crystallinity and relative molecular weight. With the improvement of these indexes, its mechanical properties are improved. Environmental stress cracking resistance is not good, but it increases with the increase of relative molecular weight. Good puncture resistance, LLDPE is the best.
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