Introduction to Ultraviolet UV Stabilisation

Whereas the use of thermo-oxidative stabilisers can be regarded as largely optional for aromatic polyesters unless particularly harsh conditions are likely to be met in service, the light stabilisation of these polymers is more of a requirement in any situation where an article made thereof is going to be exposed to short-wavelength light, or a combination of this with oxygen. 

Additives formulated with polymers to improve their photostability must carry out one or more of the following functions effectively to protect their host polymer [1,2]  

From what is known of the initial photophysical and photochemical processes involved in polyester photodegradation, it would appear 

As was noted in Chapter 4, polyesters such as polyethylene terephthalate (PET) degrade mainly in a thin surface layer under the influence of light and oxygen. This suggests that photostabilisation in the bulk of an article will not be optimally used at best, portions of the additive distributed in the interior will act as a reservoir to replace stabiliser lost in the outer regions during any of the chemical or physical processes under way. 

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