① Mechanical properties Polypropylene has high mechanical properties such as strength, rigidity and hardness compared to polyethylene and has good gloss, but it is still low in plastic materials. If high strength is required, you can choose high crystalline polypropylene or choose filler or reinforced polypropylene.
The impact strength of polypropylene is related to relative molecular weight, crystallinity, crystal size and other factors, and is highly dependent on temperature, and the impact strength of polypropylene is low under low temperature conditions. In addition, polypropylene has excellent flex resistance and fatigue resistance, so it can be bent 106 times at room temperature without damage.
②Electrical properties Polypropylene is a non-polar polymer with excellent electrical insulation. Electrical performance is basically not affected by changes in environmental humidity and electric field frequency, and it can be used as a high-frequency insulation material with excellent dielectric and electrical insulation materials.
The arc resistance of polypropylene is very good (130~180 seconds), which is a high level among plastic materials. Polypropylene, under the influence of low-temperature brittleness, has much inferior application in the field of insulation compared to polyethylene and polyvinyl chloride, and is mainly used for insulation of telecommunication cables and electrical enclosures.
③ Thermal performance Polypropylene has excellent heat resistance, so it can be used at 100°C or higher, 120°C under light load, maximum continuous operating temperature of 120°C under no-load conditions, and short-term operating temperature of 150°C.
Polypropylene has excellent resistance to boiling water and steam, making it particularly suitable for the manufacture of medical autoclave products. The thermal conductivity of polypropylene is about 0.15~0.24W/(m·K), which is lower than that of polyethylene and is an excellent insulator.
④ Environment Polypropylene has poor weather resistance, and hydrogen in tertiary carbon atoms is easily oxidized and is very sensitive to ultraviolet rays, so it is easy to decompose by oxidation and the action of ultraviolet rays. Stabilizer-free polypropylene deteriorates rapidly if left indoors for 4 months, and becomes brittle after high temperature aging at 150°C for 0.5-3.0 hours or exposure to air for 12 days.
Therefore, polypropylene resin must be added together with antioxidant and light stabilizer. In the presence of copper, the rate of oxidative decomposition of polypropylene is accelerated hundreds of times, requiring the addition of a copper inhibitor such as salicylidene ethylenediamine, benzoyl hydrazide or benzotriazole.