Viscoelastic, spectroscopic and microscopic study of the photo irradiation effect on the stability of PVC in the presence of sulfamethoxazole Schiff's bases

The photostabilization of poly(vinyl chloride) (PVC) films having five Schiff's bases derived from sulphamethoxazole has been investigated. The casting method was used to produce PVC films containing sulphamethoxazoles (0.5% by weight), in tetrahydrofuran. The photostabilization activities of five additives were determined by monitoring the hydroxyl, polyene and carbonyl indices with irradiation time. In addition, the quantum yield of the chain scission (Fcs) and the changes in viscosity average molecular weight of PVC films containing Schiff's basses were evaluated with irradiation time. The rate of photostabilization for PVC films in the presence of five Schiff's base additives was found to be the highest in the case of 2-hydroxybenzylidene derivative and the lowest in the unsubstituted benzylidene derivative. Several mechanisms have been suggested to explain the photostabilization of PVC in the presence of Schiff's bases that mainly act as UV absorbers and radical scavengers for photostabilizers.