I got curious about styrene vs acrylic.
A few links of interest:
What is UV Degradation? UV degradation can be a primary factor in signs substrates yellowing over time. The simulation shown easily demonstrates how other styrene facers can quickly degrade and yellow simply from exposure to interior lighting. UV degradation occurs due to oxidation of polymers...
ultraboard.com
As with any sign substrate, the quality of core raw materials utilized in manufacturing is key. The components used in making sign facer styrene have properties such as whiteness and opacity that can affect how UV light interacts with the polymers of the material. Higher quality materials assist in creating a more substantial barrier that protects against light permeation below the face of the styrene, leading to photodegradation and rapid yellowing.
Yellowing in films of polystyrene and poly(styrene-altmethyl methacrylate) induced by 254-nm radiation in vacuum and in air has been investigated by absorption and emission spectroscopy. In polystyrene, yellowing is more rapid in air than in vacuum; species related to 1,3-diphenyl-1,3-hutadiene are major emissive contributors to yellowing. Photooxidation produces diene and species related to 1-phenyl-1,3-butanedione which quenches excimer in the polymer. Poly(styrene-alt-methyl methacrylate) initially yellows more rapidly than polystyrene. Rates of yellowing are greater in vacuum than in air and decrease with time. Yellowing is caused by species related to 1,5-diphenyl-1,3,5-hexatriene. Photolysis and photooxidation of the triene reduce the rate of yellowing. Fluorescence quenching occurs at the same rate in vacuum and air and may result from ketones formed by inter-unit interaction within the copolymer.