Photo-stabilising action of metal chelate stabilisers in polypropylene: Part VIII—Pigment interactions

The interaction of four metal chelates—Cyasorb UV 1084, Irganox 1425, Irgastab 2002 and Sanduvor NPU—with five commercial pigments, anatase and rutile titanium dioxide, cadmium yellow, Vynamon Blue B and Monolite Yellow G, is examined using infra-red spectroscopy. Individually, four pigments offer some stabilisation to processed polypropylene. Their order of stabilisation is Monolite Yellow G > Vynamon Blue B > cadmium yellow ～ rutile titanium dioxide. Anatase titanium dioxide showed mild sensitising action. When mixed with the metal chelates their order of stabilisation is variable. The effect of a commercial antioxidant, Irganox 1010, is also examined. It is found that the antioxidant tends to suppress any synergistic effects that may be present between the chelate and the pigment.