What are the advantages of polypropylene over thermoplastics?

Polypropylene (PP) has excellent comprehensive performance, is easy to process and form, and has low production cost, so its use is wide. The disadvantages are poor low temperature toughness, high brittle fracture temperature (about 8 ° C), and easy aging. In recent years, modified products have been obtained by methods such as copolymerization and blending, and their low-temperature resistance, impact resistance, and aging resistance have been improved.
The main chemical and physical properties of polypropylene have a weight average molecular weight of about 3 to 7105; light weight, density of about 0.91 g / cm 3; melting temperature of about 174 ° C; high strength, hardness, wear resistance and chemical resistance; Good to use, can be used at 120 ° C; its performance is not affected by environmental humidity. Its products are excellent in bending fatigue resistance and can withstand hundreds of thousands of bends without damage. Good processing performance and low shrinkage during processing.
Polypropylene is polymerized by using propylene monomer as a main component. Industrial production methods include solvent method, liquid phase bulk method, gas phase bulk method and solution method, but the solvent method is generally used, followed by the bulk method.
Polypropylene is classified into a homopolymerization grade and a copolymerization grade according to the monomer composition participating in the polymerization. The homopolymer grade is polymerized from a single propylene monomer and thus has a high degree of crystallinity, high mechanical strength and heat resistance. Copolymer grade polypropylene is obtained by copolymerizing a small amount of ethylene monomer during polymerization. According to the copolymerization method, there are two types of block copolymer polypropylene and random copolymer polypropylene. Copolymer grade polypropylene has a high impact strength, and random co-polypropylene has good transparency in addition to high impact strength.
Compared with other general-purpose thermoplastics, polypropylene has the advantages of small specific gravity, good rigidity, high strength, flex resistance, heat resistance temperature higher than 100 ° C and good chemical resistance. The deficiency of polypropylene is that the low-temperature impact resistance is poor, the aging is easy, and the molding shrinkage rate is large.
According to the requirements and uses of the product, polypropylene can be modified by blending, filling, reinforcing, adding additives, as well as copolymerization, blending, crosslinking and the like. For example, calcium carbonate, talc, minerals, etc. may be added to improve hardness, heat resistance, dimensional stability; glass fiber, asbestos fiber, mica, glass beads, etc. may be added to improve tensile strength, improve low temperature impact resistance, and resistance. Creep; addition of rubber, elastomers, and other flexible polymers to improve impact properties, transparency, and the addition of various special additives to impart properties such as weather resistance, antistatic, flame retardancy, electrical conductivity, and Electroplating, nucleation, copper resistance, etc.
Polypropylene can be produced by injection molding, extrusion molding, blow molding, thermoforming, rotational molding, plastic coating, foaming, etc. Because various processing methods have different requirements on the melting properties of polypropylene, the injection molding grade, extrusion grade, blow molding grade, coating grade, fiber grade, film grade, rotational molding grade, etc. are formed to meet different processing requirements. .
The use of polypropylene is quite extensive. Through injection molding, polypropylene can be made into various industrial parts, electrical appliances, building materials and daily necessities; extrusion pipe production of pipes, sheets, profiles, flat yarns, fibers, ropes; blow molding to produce various small Containers and bottles; IPP film and CPP film are produced by blown film method and flat film method, and high strength and high transparency OPP film can be obtained through stretching; large chemical storage tanks and containers can be produced by rotational molding.

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