Does Acrylic Block UV Light?
Unlike glass, pure acrylic (PMMA) does not filter ultraviolet (UV) light. Acrylic can transmit UV light down to 300 nm. Standard acrylic, like e.g. Plexiglas, includes an additive to make the acrylic absorb UV light. This is not wanted by all applications, but it is necessary to keep the material from quick degradation by UV.
Acrylic Pool Windows don't Mind UV - Click for More Impressions