UV and its effect on plastics: an overview
In much the same way as our skin can be prone to damage when it comes into contact with harmful ultraviolet (UV) rays (i.e. the sun), plastic can be affected, too. What that means for engineers is that projects requiring the use of plastics may not run so smoothly, resulting in the risk of operational downtime and stretched budgets.
The good news is there are multiple ways of providing resistance to these often-damaging effects.
But what about plastic – how is it affected by the varying types of UV?
If plastic has been affected by ultraviolet rays, you may notice:
- a chalky appearance
- the component surface becoming brittle
- a colour change on the surface of the material In terms of the components more likely to be at risk of UV damage, automotive parts are high on the list. The effects will predominantly result in a change of the material’s surface layer – and some plastics, if damaged by UV, will ultimately lead to the component failing altogether – not good news when a project is near completion or has been finalised.
Free radicals and UV energy
- When absorbed by plastics, UV energy can excite photons. This, in turn, can create free radicals. Then, before you know it, degradation occurs, as catalyst residues will often act as receptors. The fact is, lots of pure plastics simply cannot absorb UV radiation, putting your project and its components at severe risk. You can, of course, avoid UV degradation in plastics. Blockers, stabilisers or absorbers can be used to great effect, while titanium dioxide may also be beneficial. Meanwhile, benzophenones and other organic compounds can absorb the UV and re-emit it as heat, which isn’t nearly as harmful. A few examples of materials where UV stabilisers or other solutions can completely eliminate the problem of UV deterioration include:
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- Polyolefin: Heat Shrink Tubing and End Caps
- Nylon: Cables ties and cable tie mounts Never assume, however, that either of these materials are UV resistant. They’re usually not and must be specially treated. Always look for ‘UV resistant’ in the product details. A material called carbon black, which offers black colouration, can reduce the risk of such degradation, as it will provide protective surface coatings. The latter can include metallization or paint, though carbon black is a typically low-cost option. It can also be as effective as the alternatives.
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