Polyolefiinit

Polyolefiinit, commonly known in English as polyolefins, are a family of thermoplastic polymers produced from olefin (alkene) monomers such as ethylene and propylene. The primary members are polyethylene (PE) and polypropylene (PP). Polyolefiinit are typically nonpolar, chemically resistant, lightweight, and have good electrical insulation properties. They can be highly crystalline (HDPE, isotactic PP) or less crystalline (LDPE, atactic PP), with properties tunable by branching, copolymerization, and tacticity. Common variants include high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and various polypropylene copolymers.

Production and processing: Polyolefiinit are produced by addition polymerization using catalysts such as Ziegler-Natta or metallocene catalysts. Polymerization can occur in gas-phase, slurry, or bulk processes. High-pressure processes produce LDPE; coordinated catalyst processes yield HDPE, LLDPE, and PP. In processing, they are widely shaped by extrusion, injection molding, blow molding, and film casting.

Applications: They are used in packaging films and bags, containers, piping, automotive parts, toys, and consumer products. The broad chemical resistance and processability make them dominant in many sectors.

Environmental aspects: Polyolefin products are widely recycled, primarily as PE and PP; recycling streams are well established but quality depends on additives and contamination. Life-cycle considerations include energy use in production and end-of-life disposal challenges.