the ultraviolet light radiation stability as manifested , for instance , by the resistance to yellowing is improved for polyphenylene ether resins and blends by including a combination of a benzotriazole - based screening - type uv stabilizer and a hindered dipiperidinyl antioxidant - type uv stabilizer . the combination of the two stabilizers exhibits syneristic behavior in the compositions , conferring better resistance to yellowing than can be predicted and expected from the observed effects of each stabilizer alone . flame retardant embodiments are illustrated .