Ultraviolet-C (UV-C) is high-energy radiation that can cause degradation in susceptible materials. UV-C-induced photochemical damage remains superficial because short wavelengths do not penetrate far – only a few micrometers – into the material.
Three factors should be considered when deciding whether an object or device is suitable to be exposed to UV-C in the BioShift chamber:
- Material composition
Generally, the susceptibility of a material to UV-C degradation is determined by its atomic bonding characteristics. Ceramics (ionic/covalent bonding) are completely unaffected by UV-C. Metals (metallic bonding) are almost entirely unaffected, while most polymers (weak covalent bonding) are susceptible to UV-C degradation to some degree.
- Chemically inert plastics such as PTFE (Teflon®), FEP or PVDF, are quite resistant.
- Papers, rubber, PVC, methacrylate polymer, alkyloid paint, wood, wool, and nylon show some levels of degradation
- Plastic polymers such as polycarbonate, polypropylene, and polyethylene are particularly vulnerable
Any plastic material may contain catalyst residues and other impurities in trace amounts, which can accelerate the breakage of polymer bonds by UV-C. Volatile by-products of the degradation process can also be released into the surrounding environment. On the other hand, organic or inorganic fillers might have been added to the polymer for UV stabilization.
- Tolerance for UV-C degradation
UV-C irradiation may cause some materials, especially white or clear plastics, to turn yellow. Other colors or pigments may change hue or become bleached over time. The failure modes are typically micro cracks in the surface (embrittlement), local cratering, change of surface roughness (texture), weight loss, bleaching, blistering, chalking, reduced strength and ductility.
- Expected lifetime dose
Longer or repeated exposures increase the possible negative effects of UV-C exposure.
Evaluate the risk according to the considerations outlined above. If the risk is acceptable, approach cautiously. The objects or materials should be routinely inspected for any undesired effects. Discontinue use before the effects become intolerable. Lifetime dose testing is available upon request at your ONCE representative.