What is PP？
PP is a standard universal abbreviation in the polymer materials field, referring essentially to polypropylene—a thermoplastic resin polymerized from propylene monomer and categorized as a general-purpose plastic. Boasting advantages of light weight, chemical resistance and easy processability, it has become one of the plastic varieties with the highest output and application scale worldwide.
Core Properties and Production Process of PP
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Raw Material Sources
The core monomer is propylene, a byproduct of petroleum cracking or natural gas processing, making PP a typical petroleum-based plastic. In recent years, bio-based propylene technology has gradually matured; bio-based PP, produced from biomass fermentation products, has entered the industrialization stage, further enhancing the material’s sustainability.
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Production Process
The mainstream industrial process is coordination polymerization. With propylene as the monomer, under the action of Ziegler-Natta or metallocene catalysts, the tacticity of molecular chains (divided into isotactic PP, syndiotactic PP and atactic PP) is regulated by controlling polymerization temperature, pressure and catalyst type. Isotactic PP dominates the market due to its high crystallinity and excellent performance. After polymerization, the product undergoes secondary processing including pelletizing, extrusion, injection molding, film blowing and drawing to form various finished products.
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Key Properties
Its core advantages lie in
light weight yet high strength, excellent chemical resistance and good heat resistance: with a density of only 0.90-0.91g/cm³, it is one of the lightest common plastics; it resists acids, alkalis and organic solvents (except strong oxidizing acids) with outstanding chemical stability; its heat deflection temperature is around 100-120℃, enabling long-term use below 100℃ and resistance to boiling water sterilization. Its drawbacks are poor low-temperature toughness (prone to embrittlement and cracking at low temperatures) and inferior weather resistance (easy to age under prolonged exposure to sunlight), which can be optimized via copolymerization modification (e.g., ethylene-propylene copolymer EPP) or adding antioxidants and UV stabilizers.
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Application Scenarios
PP is widely used in packaging, automotive, home appliance, textile and daily necessities fields, such as food packaging films, food containers and plastic bottles; automotive bumpers, instrument panels and door liners; home appliance casings and washing machine inner tubs; non-woven fabrics (raw material for masks and protective clothing), ropes and woven bags. It is particularly suitable for lightweight and low-cost application scenarios.
