Linear low-density polyethylene (LLDPE) is a substantially linear polymer (polyethylene), with significant numbers of short branches, commonly made by copolymerization of ethylene with longer-chain olefins. Linear low-density polyethylene differs structurally from conventional low-density polyethylene (LDPE) because of the absence of long chain branching. The linearity of LLDPE results from the different manufacturing processes of LLDPE and LDPE. In general, LLDPE is produced at lower temperatures and pressures by copolymerization of ethylene and such higher alpha-olefins as butene, hexene, or octene. The copolymerization process produces a LLDPE polymer that has a narrower molecular weight distribution than conventional LDPE and in combination with the linear structure, significantly different rheological properties.
LLDPE is being used in extrusion coating applications where it helps protect the contents of liquid containers, primarily for paper and paperboard packaging.
Non-food packaging applications are requiring stronger films such as consumer, industrial and agricultural uses.
The injection moulding sector, which accounts for around 5% of LLDPE demand, has outlets such as lawn and garden products, kitchen accessories, luggage and furniture parts, recreational products and toys.
The development of metallocene or single site catalyst technology has resulted in new LLDPE resins which allow significant downgauging of films as well as faster film processing and more stable operations. Easy processing LLDPE grades are also being introduced.
Applications include multi-layer cast stretch film, agricultural greenhouse film, medium to heavy duty bags and lamination packaging film. Metallocene-based LLDPE can also be coextruded with LDPE in multilayer film barriers used in drink cartons. Metallocene-based LLDPE may also penetrate non-polyethylene markets such as metals, paper and polyvinyl chloride (PVC).