The opposite of polymerisation when monomeres are joined to longer molecules called polymers. Depolymerisation occurs due to high temperature or to global radiation. The influence of high energy radiation causes fractures of the polymeric chain. The UV-component of solar radiation causes depolymerisation of many polymers.

The same process takes place in a plasma which generates high energy UV radiation. This radiation cracks polymers, mainly hydrocarbons. This process does not result immediately in saturatured monomers or shorter polymers. The result of the fracture of a polymeric chain is two unsaturatured molecular bindings. These polymer segments with an open chain end are called radicals. These radicals are very reactive because they have a strong tendency to fix an atom or another radical to their unsaturated binding..

Usually depolymerisation in a low pressure plasma results in gaseous monomers or short polymers which can be removed by the vacuum pump. This is the  processes of removing hydrocarbon layers by low pressure plasma.