ABSTRACT

A very strong stabilizing effect that surpasses the additivity has been reached in plastics and coatings by cooperative combinations of UV absorbers and HAS (29,51). It may be accepted that UV absorbers, the derivatives ofbenzotriazole 65-68 in particular, prevent the HAS-developed nitroxide from photolysis and the relevant depletion of the piperidine ring (see Sec. IV.E.3), and vice versa, the UV absorbers are protected from breaking of the H-tunneling effect by HAS (39,51,88,91). The favorable integral effect of the HAS-UV absorber combination arose in coatings and in polyolefins containing conventional processing stabilizers (10).