Synthesis and characterization of gallic acid derivatives and their utilized as organic photo-stabilizers for poly (vinyl chloride)

The photo-stabilization of poly (vinyl chloride) containing 1,3,4-thiadiazole derivatives derived from Gallic acid as additives were studied. The four different substituents of 1,3,4-thiadiazole-gallic derivatives, 2-(4-substituted-phenyl)-5-(3,4,5-trimethoxyphenyl)-1,3,4-thiadiazole, (R1-R4) were prepared starting from Gallic acid and characterized by FTIR, ¹HNMR and elemental analysis. The 5% concentration by weight of these derivatives (R1-R4) in PVC polymer was used to study the photo-stabilization of PVC. The photo-stabilization of PVC films were studied at room temperature under irradiation of U.V light with λ = 385 nm and an intensity of 7.75 × 10^?7 Einstein dm^?3 s^?1. The photo-stabilization activity of these compounds was determined by monitoring the carbonyl (I_CO), polyene (I_po) and hydroxyl (I_OH) indices and weight loss method with irradiation time. It was found that the (I_CO), (I_po) and (I_OH) index values increased with the irradiation time increase, this increase found to depend on the type of additives, also it was found that the PVC films in the presence of additives (R1-R4) were arranged as the following trend: PVC + R1 > PVC + R2 > PVC + R3 > PVC + R4.