Materials intended for outdoor usage will be exposed to direct sunlight (ultraviolet radiation). This may cause undesirable degradation of the (plastic) materials such as colour change or loss of elongation (elasticity, stretch). Some plastics are inherently UV resistant or "stable", but most plastics (polymers) need UV stabilisers to withstand the adverse effects of ultraviolet (UV) light or weathering.
UV light stabilisers (or absorbers) are additives that prevent deterioration of plastics and rubbers caused by exposure to sunlight. Examples of UV stabilisers are benzotriazole and benzophenone which are both on the SIN list.
Examples of "UV stable" plastics are acrylic, PVDF (polyvinylidene fluoride) and PTFE (polytetrafluoroethylene).
Outdoor products may contain chemical additives to protect them against sunlight and weathering.
For the chemical risk assessment of materials this is essential information from your supply chain.