Polipropileni

Polipropileni, or polypropylene (PP), is a widely used thermoplastic polymer produced from the monomer propylene. It belongs to the polyolefin family and is represented by the repeating unit -CH2-CH(CH3)-. The material exists in different tacticities, with isotactic and syndiotactic forms being crystalline and providing stiffness, while atactic polypropylene is amorphous and softer. In practical use, isotactic PP is the most common form.

Polypropylene is lightweight, with a typical density around 0.90 g/cm3, and exhibits a relatively high melting point for a plastic, usually in the range of 160 to 170°C. It offers good chemical resistance, fatigue resistance (notably in bending and flexing applications), and electrical insulation. Its mechanical properties can be enhanced by crystallinity, copolymerization, or by adding fillers and reinforcements. PP is processable by standard plastic technologies, including injection molding, extrusion, blow molding, and lamination, making it suitable for films, packaging, containers, fibers, and molded components.

Production and history: polypropylene is produced by addition polymerization of propylene, typically using Ziegler–Natta or metallocene catalysts. The development and commercialization of isotactic PP in the 1950s, enabled by these catalysts, led to one of the most extensively used plastics in modern manufacturing. The material’s versatility continues to be expanded through copolymer formulations and compatibilized blends.

Applications and environmental aspects: polypropylene is used in packaging films and containers, automotive parts, household goods, textiles, medical devices, and more. It offers good chemical resistance and impact resistance, but is not biodegradable. PP is commonly recycled under the resin code 5, though recycling rates vary by region and product. Like other plastics, reducing contamination and improving end-of-life recovery are important for its environmental performance.