Polyolefins are produced by the polymerization of olefins or alkenes (molecules with the general formula CnH2n) such as ethylene, propylene, butene, isoprene, pentene, etc. The name “olefin” means “oil-like” and refers to the oily character of the materials.
The most important commercial polyolefins are polyethylene (PE), polypropylene (PP) and ethyl vinyl acetate (EVA). Polyethylene is classified according to its density as Very Low Density Polyethylene (VLDPE), Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE), Medium Density Polyethylene (MDPE), and High Density Polyethylene (HDPE).
Polyethylene and polypropylene are two of the top polymer resins used in the world today. These resins can be tailored to achieve wide range of mechanical and chemical properties, making it possible to use them in a myriad of applications such as agricultural films, garments, tapes, stretch films, retail bags, bottles, containers, pipes, etc.
The selection of a polyolefin for a particular application depends on the resin’s type and grade, which are determined by the manufacturing technology or process, the catalyst, and the raw feedstock used in production. In turn, the polyolefin grade is determined by key properties such as molecular weight, molecular weight distribution (MWD), crystallinity, branching and density that affect how and where each resin is used. Two distinctive process sections can be identified in polyolefin production, a wet-end and a dryend process.