Polyethylene polyethene and polypropylene polypropene

Low-density polyethylene (LDPE) is produced by a free radical process, initiated with traces of oxygen or peroxides, at temperatures of 200°C to over 3(WC and pressures up to 3000 atm. Over half of this low-melting point, flexible product is used for packaging film manufacture. 

Yields in all these processes are in the range 97-99% of theory overall, giving feedstock energy inputs of 72-73 GJ/tonne with ethylene at 2MJ/mol. Processing requirements add 10-12 GJ/tonne for the high pressure (LDPE) process and 6-7 GJ/tonne for the low pressure (HDPE, LLDPE) processes. 

---