Metals and ceramics do not tend to experience any degradation as a result of UV-C exposure. Polymers can over time break down, with some polymers being more susceptible than others. Of course, this all depends on the frequency of application.
- Metals are almost entirely unaffected by UV because of the availability of free electrons to absorb photon energy without undergoing energy transitions or bond dissociation.
- Ceramic ions have tightly bound electrons, hence they have a high bond strength, withstand extreme temperatures, are usually extremely chemically inert and are strong electrical insulators. It is this high bond strength and chemical inertness that make ceramics completely unaffected by UV exposure.
- Since most polymers consist of covalently bonded organic constituents, most are susceptible to damage by UV. The most basic and prevalent UV damage mechanism in polymers is called chain scission by photolysis – the breaking of long chains into shorter ones by the direct action of high-energy photons breaking the “backbone” of the molecule. This reduction in molecular weight of a polymer almost always results in a degradation of physical properties such as strength and ductility and a degradation of aesthetic properties such as color and texture. There is a class of high-performance engineering polymers called fluoropolymers that exhibit excellent UV resistance.