PP material main performance

PP material main performance

Polypropylene (PP plastic) is another excellent resin developed after nylon. It is a kind of high density, non-side chain and high crystallinity linear polymer with excellent comprehensive performance.

Physical properties

Polypropylene is non-toxic, odorless, tasteless milky white crystalline polymer, density of only 0. 90 - "0. 91g / cm3, is one of the lightest varieties of all plastic.It is particularly stable to water, The water absorption rate of only 0.01%, molecular weight of about 81,000 to 150. Good shape, but due to shrinkage (1% ~ 2.5%). Thick-walled products prone to depression, for some high-dimensional accuracy Parts, it is difficult to meet the requirements, product surface gloss.

Mechanical properties

Polypropylene high crystallinity, structured, and therefore has excellent mechanical properties. The absolute value of the mechanical properties of polypropylene is higher than polyethylene, but still in the plastic material is low varieties, the tensile strength can only reach 30 MPa or slightly higher level. Polypropylene with larger isotactic index has higher tensile strength, but with the increase of isotactic index, the impact strength of the material decreases, but does not change after falling to a certain value.

The temperature and loading rate have a great influence on the toughness of polypropylene. When the temperature is higher than the glass transition temperature, the impact failure ductile fracture, brittle fracture below the glass transition temperature, and a substantial decrease in the value of impact strength. Increasing the loading rate increases the temperature at which the ductile fracture transitions to brittle fracture. Polypropylene has excellent bending fatigue resistance, its products can be bent at room temperature 106 times without damage.

However, at room temperature and low temperature, because of its high molecular structure regularity, so the impact strength is poor. Polypropylene performance is the most prominent resistance to bending fatigue, commonly known as 100% plastic.

Thermal performance

Polypropylene has good heat resistance, products can be sterilized at temperatures above 100 ℃, without external conditions, 150 ℃ nor deformation. Embrittlement temperature of -35 ℃, below -35 ℃ will occur embrittlement, cold resistance as polyethylene. For polypropylene glass transition temperature reported value of a 18qC, 0qC, 5 ℃, etc., which is also due to the different samples, which contain different proportions of crystalline and amorphous phase, the molecular chain of amorphous part of the chain length is different Due. The melting temperature of polypropylene is about 40-50% higher than that of polyethylene, about 164-170 ° C. The melting point of 100% isotactic polypropylene is 176 ° C.

Chemical stability

Polypropylene chemical stability is very good, in addition to be concentrated sulfuric acid, concentrated nitric acid erosion, the other chemical reagents are relatively stable, but low molecular weight aliphatic hydrocarbons, aromatic hydrocarbons and chlorinated hydrocarbons can make polypropylene soften and Swelling, and its chemical stability with the increase in crystallinity has also increased, so polypropylene for the production of various chemical pipes and fittings, anti-corrosion effect is good.

Electrical properties

It has a high dielectric constant, and with the temperature rise, can be used to make heated electrical insulation products. Its breakdown voltage is also high, suitable for use as electrical accessories. Anti-voltage, arc resistance is good, but high static electricity, contact with copper easy to aging.

Weatherability

Polypropylene is very UV sensitive. The addition of zinc oxide, dilauryl thiodipropionate, carbon black or similar milky filler can improve its anti-aging properties.

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