What environmental factor breaks down urethane?

Urethane is particularly susceptible to degradation from UV rays due to the nature of its chemical structure. When urethane is exposed to ultraviolet radiation, it can undergo photodegradation, which leads to the breakdown of its molecular chains. This process may result in discoloration, reduced flexibility, and overall weakening of the material. UV rays can cause the formation of free radicals, which break chemical bonds, thereby compromising the integrity of urethane compounds.

The other factors, while they affect various materials, do not have the same pronounced impact on urethane as UV radiation does. While heat can alter the properties of urethane, it is primarily UV exposure that specifically targets its molecular structure leading to significant degradation over time.