Facilities Raw Materials - Analysis of Properties of Polypropylene

Polypropylene (PP) is a semi-crystalline thermoplastic. With high impact resistance, strong mechanical properties, resistance to a variety of organic solvents and acid-base corrosion. Widely used in the industry, it is one of the common polymer materials. Australian and Canadian plastic coins are also made of polypropylene.

Facilities Raw Materials - Analysis of Properties of Polypropylene

Polypropylene structure:

The repeating unit of polypropylene consists of three carbon atoms. Two of the carbon atoms are in the main chain and one carbon atom is in the form of a branched chain. The methyl groups are arranged on the same side of the molecular backbone as isotactic polypropylene; if the methyl groups are randomly arranged on both sides of the molecular backbone, atactic polypropylene; when the methyl groups alternate between the two sides of the molecular backbone Polypropylene.

Polypropylene properties:

1, physical properties

Polypropylene is a non-toxic, odorless, odorless, milky white, highly crystalline polymer with a density of only 0.90--"0.91g/m3, which is one of the lightest species in all plastics. It is particularly stable to water, The water absorption rate in water is only 0.01%, and the molecular weight is about 80,000 to 150,000. The moldability is good, but the shrinkage rate is large (1% to 2.5%). The thick-walled products are easily sag and have high dimensional accuracy. Parts, it is difficult to meet the requirements, the product surface gloss is good, easy to color.

2, mechanical properties

Polypropylene has high crystallinity and regular structure, so it has excellent mechanical properties. However, at room temperature and low temperature, due to its high degree of structural regularity, the impact strength is poor. The most prominent property of polypropylene is its resistance to bending fatigue.

3, thermal performance

Polypropylene has good heat resistance, and the product can be disinfected and sterilized at a temperature of 100° C. or higher, and is not deformed at 150° C. under the condition of no external force. The embrittlement temperature is -35°C, and embrittlement will occur below -35°C. Cold resistance is inferior to polyethylene.

4, chemical stability

Polypropylene has good chemical stability. It is stable to other chemical agents except that it can be eroded by concentrated sulfuric acid and concentrated nitric acid. However, low molecular weight aliphatic, aromatic and chlorinated hydrocarbons can soften polypropylene. Swelling, while its chemical stability with the increase in the degree of crystallinity has increased, so polypropylene is suitable for the production of a variety of chemical pipelines and accessories, anti-corrosion effect is good.

5, electrical properties

Polypropylene has excellent high-frequency insulation properties. Since it absorbs almost no water, the insulation properties are not affected by humidity. It has a high dielectric coefficient and can be used to make heated electrical insulation products as the temperature rises. Its breakdown voltage is also very high, suitable for use as electrical accessories. The resistance to voltage and arc resistance is good, but the degree of static electricity is high and it is easy to age with contact with copper.

6, weather resistance

Polypropylene is very sensitive to ultraviolet rays. Adding zinc oxide, dilauryl thiodipropionate, carbon black or similar cream fillers can improve its aging resistance.

Polypropylene features:


1, the relative density is small, only 0.89-0.91, is one of the lightest varieties of plastic.

2, good mechanical properties, in addition to impact resistance, other mechanical properties are better than polyethylene, molding process performance is good.

3, with high heat resistance, continuous use temperature up to 110-120 °C.

4, good chemical properties, almost no water absorption, and most chemical products do not react.

5, pure texture, non-toxic.

6, good electrical insulation.

7. The transparency of polypropylene products is better than that of high-density polyethylene products.


1. The product has poor cold resistance and low impact strength at low temperature.

2. The products are susceptible to the effects of light, heat and oxygen during use.

3, poor coloring.

4, easy to burn.

5, poor toughness, high static electricity, poor dyeing, printing and adhesion.

Polypropylene classification:

According to the position of branched atoms, polypropylene can be classified into atactic, isotactic and syndiotactic.

Branched atoms of atactic polypropylene are randomly distributed on both sides of the main chain.

Isotactic polypropylene branched atoms are distributed on the same side of the backbone.

The syndiotactic polypropylene branch atoms are symmetrically spaced on both sides of the main chain.

Polypropylene applications:

1, film products

Polypropylene film products are transparent and glossy, and have low permeability to water vapor and air. It is divided into blown film, cast film (CPP), biaxially oriented film (BOPP) and so on.

2, injection products

Can be used for automotive, electrical, mechanical, instrumentation, radio, textile, defense engineering accessories, daily necessities, turnover boxes, medical and health equipment, building materials.

3, extruded products

Can do pipes, profiles, monofilaments, fishing ropes, strapping, tying ropes, woven bags, fibers, composite coatings, sheets, plates and so on.

4, other

Low foaming, calcium plastic board, synthetic wood, laminate, synthetic paper, high foaming can be used as structural foam.

Related Reading:

"Professional Introduction of Random Copolymer Polypropylene PPR Plastics"


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