Polyurethane elastomers will degrade due to prolonged ultraviolet (UV) light exposure. The UV light targets certain chemical linkages depending on the type of chemistry used for a particular compound. When a part begins to degrade due to UV exposure, the first evidence is discoloration or yellowing on the surface of the part. Further degradation will be in the form of surface cracks that closely resemble ozone attack in rubbers.
Several strategies can be used to combat UV degradation. The simplest and most common method for combating UV attack is adding pigments to the urethane. The pigment will block the UV light, making it unavailable for UV degradation reactions. For extreme cases of UV exposure, UV stabilizers can be added to the urethane. UV stabilizers work to further absorb UV radiation and neutralize any free radicals generated by the UV exposure.
Another method for protecting against UV light exposure is to select an aliphatic urethane compound. Typically, the elastomers produced by Gallagher Corporation are aromatic urethane compounds. Aliphatic polyurethanes are less susceptible to UV light degradation. The drawback to using aliphatic compounds is that the raw materials are significantly more expensive and cure cycle is much longer, which leads to lower production.