Crosslinking and Chain Scission
Modifying the molecular structure of some polymers enhances their physical characteristics such as resistance to heat and abrasion. Electron beam and gamma irradiation are well-established technologies for initiating these changes at the molecular level in polymers; the absorption of the radiation energy can lead to either cross-linking or chain scission of the macro-molecular chains. Electron beam accelerators frequently carry this out, although gamma radiation is used in some instances.
The chemical structure and morphology of the polymer plays an important role with regards to its tendency to degrade or to cross-link. For some polymers the aim is to change the thermoplastic materials into thermosets. The molecules in the thermoplastic materials tend to slip and slide over one another fairly freely. As temperatures rise, these uncross-linked materials soften and finally melt. When they are cross-linked, molecular movement is impeded and becomes more stable against heat.