Permanent UV stability in liquid urethane products is not possible. Ultimately, the only option is to delay the degrading effects (color change and surface break down) of ultraviolet light on these materials.
Sun Devil® is a one component liquid additive that will slow color change and physical degradation due to UV exposure for many Smooth-On liquid urethane products. Sun Devil® is added by weight (gram scale required) to the urethane rubber, plastic or foam system.
Results will vary and will depend on intensity and duration of exposure to UV light to the cured material over time.