Polyethylene, Linear Low Density

Abstract

Linear low density polyethylene (LLDPE) resins are copolymers of ethylene and α‐olefins with a low α‐olefin content; their density ranges from 0.915 to 0.925 g cm −3 . These resins are semicrystalline materials that are produced in catalytic copolymerization reactions. Various types of LLDPE resins differ in several respects: (a) the type of the α‐olefin used in copolymerization with ethylene (1‐butene, 1‐hexene, 4‐methyl‐1‐pentene, or 1‐octene); (b) the content of the α‐olefin in the copolymers (between 2.0 and 3.5 mol%); (c) density and crystallinity degree; and (d) compositional uniformity of the copolymers. LLDPE resins are produced in industry with three classes of catalysts: Ziegler catalysts based on titanium compounds, catalysts utilizing metallocene complexes, and Phillips catalysts based on chromium oxides. The resins are manufactured on a commercial scale in three types of polymerization processes: in the gas phase, in solution, and in slurry. LLDPE resins are major commodity products with a combined 2012 worldwide manufacture volume exceeding 26 × 10 6 ton yr −1 . Film is their largest application market. It is used to manufacture grocery sacks, bags for produce, trash bags, and bags for merchandise packaging, garments, etc, as well as for non‐packaging applications such as industrial sheeting and agricultural mulch film. Injection molding products represent the second largest market for LLDPE resins; they are mostly used for housewares. These resins are also used for blow molding of bottles and drums; for rotational molding of toys, large containers, and tanks; for manufacture of pipe and tubing; and for wire coating in electrical and telephone industry.