Types of Polyolefins and Their Properties

High-density polyethylene (HDPE) was first made with Ziegler-Natta catalysts. When produced as a homopolymer, HDPE has no short-chain branches, but a 

Linear low-density polyethylene (LLDPE) is a copolymer of ethylene and a-olefins (generally 1-butene, 1-hexene, or 1-octene) with densities in the range 0.915-0.94 g cm . Products with even lower densities, down to 0.88 g cm, are sometimes called very low-density polyethylene (VLDPE) but are chemically identical to LLDPE. Copolymerization of ethylene with increasing amounts of a-olefins disrupts the order of the linear polyethylene chains by introducing short-chain branches. As a consequence, the density, crystallinity, and rigidity of LLDPE are lower than for HD PE. Linear low-density polyethylene is used predominantly in films, and shares the market with LDPE. 

Olefins are commonly polymerized in a single reactor or in two or more reactors in series. Single reactors are used when a polyolefin with more uniform composition is required, while reactors in series are employed for the commercial produc- 

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