LIGHT STABILIZERS OF HALS TYPE WITH REGULATED MOLECULAR-MASS

A new class of high molecular weight light stabilizers containing a light sensitive unit in their structure has been synthesized and tested in polypropylene. They are terpolymers of 2,2,6,6-tetramethyl-4-piperidyl acrylate (TMA) with 1-phenyl-2-propenone (VPK) and n-octadecyl acrylate (ODA) prepared by radical polymerization. VPK is a light sensitive unit while TMA provides light stabilization action. Under irradiation, the molecular weight of the stabilizer decreases and the presence of ODA in the fragments ensures migration throughout the stabilized polymer. The stabilizing efficiency depends on the VPK content. The higher the content of the VPK units in terpolymers with the same molecular weights and the same TMA and ODA contents, the higher the stabilizing efficiency, due to smaller fragments with higher migration ability.