Susceptible Polymers
Common synthetic polymers which may be attacked include polypropylene and LDPE where tertiary carbon bonds in their chain structures are the centres of attack. The ultra-violet rays activate such bonds to form free radicals, which then react further with oxygen in the atmosphere, producing carbonyl groups in the main chain. The exposed surfaces of products may then discolour and crack, although in bad cases, complete product disintegration can occur.
In fibre products like rope used in outdoor applications, product life will be low because the outer fibres will be attacked first, and will easily be damaged by abrasion for example. Discolouration of the rope may also occur, thus giving an early warning of the problem.
Polymers which possess UV-absorbing groups such as aromatic rings may also be sensitive to UV degradation. Aramid fibres like Kevlar for example are highly UV sensitive and must be protected from the deleterious effects of sunlight.
Read more about this topic: UV Degradation
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