Radical Polymerization

Ethene can be polymerized with peroxide catalysts under high pressure (1000 atm  or more, literally in a cannon barrel) at temperatures in excess of 100^o. The initiation step involves formation of radicals, and chain propagation entails stepwise addition of radicals to ethene molecules.

Chain termination can occur by any reaction resulting in combination or disproportionation of free radicals.

The polyethene produced in this way has from 100 to 1000 ethene units in the hydrocarbon chain. The polymer possesses a number of desirable properties as a plastic and is used widely for electrical insulation, packaging films, piping, and a variety of molded articles. Propene and 2-methylpropene do not polymerize satisfactorily by radical mechanisms.