Chapter 2 - PE Processes

Abstract

This chapter focuses on the manufacturing process of various polyethylene (PE) such as low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene linear low density polyethylene (m-LLDPE), high density polyethylene (HDPE), very low density polyethylene (VLDPE), and enhanced polyethylene (EPE). The basic raw material for polyethylene is the monomer ethylene. Ethylene is a colorless gas with a slightly sweet smell and is obtained by cracking (thermal decomposition) ethane at high temperatures (800° C) in a cracker or steam furnace. Ethane is found in natural gas or can be obtained from oil or naphtha and when ethylene is compressed to high pressure and, at the right temperature and with an initiator, polyethylene (PE) molecules are produced. There are several copolymers of polyethylene that are of commercial significance which include ethylene vinyl acetate (EVA), ethylene methyl acrylate (EMA), ethylene acrylic acid (EAA), ethylene methyl acrylic acid (EMAA), ethylene butyl acrylate (EBA), ethylene carbon monoxide (ECO), and ionomers (ION). The transition metal catalyst chemistry developed by Zeigler and Natta led to several processes that produce linear PE molecules which include gas phase, solution, loop slurry, and slurry. The first PE made with Z–N catalyst was high density polyethylene (HDPE) in 1953. In the late 1970s, linear low density polyethylenes (LLDPE) were introduced by copolymerizing with alpha olefins to create SCB.