Abstract
The influence of the Nโalkyl group of tertiary hindered amines on the photostabilization of polymers was studied. The photostabilizing effects of the tertiary amine derivatives of 4โbenzoyloxyโ2,2,6,6โtetramethylpiperidine (1a) in polypropylene were compared. All tertiary amine derivatives having ฮฑโH to hindered N showed higher effectiveness than 1a. Model liquid phase photoxidations were carried out by irradiating (UVโlamp) the solutions of tertiary hindered amines containing tertโbutyl hydroperoxide as a photoinitiator. The tertiary hindered amines were oxidized more easily than corresponding parent hindered amine and converted to the parent amine, which was identified as its salt, resulting from the carboxylic acid produced from the Nโalkyl group by oxidation. The thermal reaction of the tertiary hindered amines with tertโbutyl hydroperoxide was also studied in the liquid phase. The tertiary hindered amines decomposed tertโbutyl hydroperoxide more rapidly than the parent secondary hindered amine, and generated the parent amine. It was also found that the photostabilizing effects of tertiary hindered amines for polyolefins were higher than that of the parent secondary hindered amine.