Polypropylene PP

• Physical properties. Its density is between 0.90-0.91 g/cm³, the lowest among general-purpose plastics. The appearance ranges from translucent to milky white with excellent gloss, and can be blended into a variety of colors using masterbatches to meet diverse appearance requirements. And the melting point of PP polypropylene resin is 165-170°C, making it stable at higher temperatures and suitable for products requiring high temperature tolerance, such as microwaveable tableware.
• Chemical properties. It exhibits excellent chemical resistance, with good resistance to most acids, bases, salt solutions, and organic solvents such as alcohols and esters. It is an ideal material for corrosion-resistant equipment such as chemical pipelines and storage tanks. Its extremely low water absorption, less than 0.03%, makes it virtually unaffected in humid environments, ensuring stable operation.
• Mechanical properties. This resin material possesses high tensile strength and impact strength, meeting the structural strength requirements of most products. Its high rigidity and elastic modulus ensure excellent dimensional stability. PP exhibits outstanding fatigue resistance and maintains good mechanical properties even under repeated loading and unloading, making it ideal for reusable parts such as hinges.
• Excellent processing properties. The excellent flowability allows pp resin to be easily formed into various shapes through various processing methods, including injection molding, extrusion, and blow molding. And polypropylene pp resin has a wide molding temperature range and resists decomposition during processing, improving production efficiency. Furthermore, despite its high shrinkage, appropriate dimensional compensation can be used to ensure product accuracy, making it highly processable.

1. Classification by structure

• Polypropylene Homopolymer: polymerized from the same monomer, including polypropylene (PP), high crystal polypropylene (HOPP), high tear polypropylene (IRP), refractory polypropylene (HPP), etc.
• Polypropylene Copolymer: 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.