Polypropylene PP

• High rigidity and low density (0.90—0.91), high tensile strength (especially after stretching), excellent transparency, stress crack resistance, chemical resistance, high heat resistance, The melting point reaches 164 degrees, and it can be used for a long time below 100-120 degrees. It has good electrical insulation and good folding resistance.
• After being filled and reinforced, the mechanical properties of polypropylene are sufficient to compete with higher-cost engineering plastics in many applications.
• Good injection molding processability.
• It can be stretched and oriented to produce fibers and stretched films.
• The disadvantage is that it is easy to be brittle at low temperature, insufficient wear resistance, poor aging resistance, not easy to dye, and large molding shrinkage.

1. Classification by structure

• Homopolymer polypropylene: polymerized from the same monomer, including polypropylene (PP), high crystal polypropylene (HOPP), high tear polypropylene (IRP), refractory polypropylene (HPP), etc.
• Copolymer polypropylene: polymerized from two or more monomers, which can be specifically divided into random copolymers, ordered copolymers, isolated copolymers, etc. Among them, copolymer polypropylene is further divided into block (impact-resistant) copolymer polypropylene (PP-B) and random (random) copolymer polypropylene (PP-R).

2. Classification by production process:

• Melt method: polypropylene prepared by melt polymerization, including ordinary polypropylene and high melt index polypropylene.
• Solution method: polypropylene prepared by solution polymerization, including heterogeneous polypropylene, sample polypropylene, etc.
• Gas phase method: including gas phase polymerization, synchronous gas phase polymerization and post-treatment gas phase polymerization.

3. Classification by use:

• Food grade polypropylene: suitable for food packaging and utensils, fresh-keeping bags, etc.
• Engineering polypropylene: including modified polypropylene, enhanced polypropylene, etc., suitable for automotive parts, home appliances, toys, etc. Among them, high-efficiency enhanced polypropylene is a high-strength polypropylene chloride plastic polymerized by the combined action of a synergistic catalyst and additives. PP resin has excellent heat resistance, mechanical properties and corrosion resistance. It is usually used for automotive parts, oil pumps, fuel tanks, wheel covers and other parts and industrial valves and pipes.

4. Medical polypropylene: suitable for medical moldings, medical consumables, etc.

5. Other classification methods:

• Random polypropylene: a common polymer without a physical crosslinking agent, polymerized from propylene monomers, with low crystallinity, uncertain melting point, and translucent at room temperature.
• Block polypropylene: a polypropylene plastic with a special structure. There are regular different structural blocks in the molecular structure. It has the characteristics of high melting point, crystallinity and mechanical strength. It is generally used to make high-performance films, industrial pipes and molded parts.