Phenylthiourea derivatives as organic stabilizer for polystyrene against photodegradation

N-phenylthiourea derivatives have been prepared and investigated as photostabilizers for polystyrene by measuring the extent of weight loss [%], the amount of formed gel as well as the average molecular weights of the soluble fractions [M[v]] of the degraded polymers. The results indicated a reasonable stabilizing effect of these derivatives compared with phenyl salicylate UV-absorber. A synergistic effect is achieved when the investigated stabilizers are mixed with the phenyl salicylate in a weight ratio of 25% of the thiourea derivative and 75% of the reference stabilizer. A probable radical mechanism is proposed to account for the stabilizing action of the organic investigated materials