Polyolefinen

Polyolefinen, or polyolefins, denote a family of polymers derived from olefin (alkene) monomers by addition polymerization. The most important members are polyethylene (PE) and polypropylene (PP). Together they account for a large share of global plastic production and are valued for lightweight, chemical resistance and versatile processability.

Most polyolefins are produced from simple olefin monomers such as ethylene, propylene and butenes. The polymer chains are saturated hydrocarbons. Polyolefins are synthesized mainly by coordination polymerization using Ziegler–Natta or single-site metallocene catalysts, giving well-defined tacticity and crystallinity. High-pressure free-radical processes are used to make low-density polyethylene (LDPE), which is highly branched and more flexible. Industrial processes include gas-phase, slurry and solution polymerizations. Major grades are HDPE, LDPE and linear low-density polyethylene (LLDPE) for polyethylene, and isotactic, syndiotactic or atactic polypropylene. Physical properties depend on molecular weight, branching and crystallinity: densities roughly 0.91–0.95 g/cm3 for PE and 0.90–0.92 g/cm3 for PP; melting points about 105–115 C (LDPE), 120–130 C (HDPE) and 160–170 C (isotactic PP). They offer excellent chemical resistance, good electrical insulation and relatively low cost; mechanical properties range from flexible films to rigid moldings.

Applications include packaging films, bags, bottles and containers, pipes and fittings, automotive parts and consumer goods. Polyolefins are widely recycled, commonly identified with resin codes 2 (HDPE), 4 (LDPE/LLDPE) and 5 (PP); recycling streams may require sorting and cleaning. Environmental concerns relate to single-use packaging and fossil-carbon footprint, prompting ongoing efforts in recycling, alternative feedstocks and improved recyclability.