Synergistic effects and comprehensive analysis of photodegradability inhibition of PVC plastics film by novel Schiff base metal complex additives: Performance and Dechlorination mechanism

Abstract

Three photo-stabilizers were prepared and designed from a complexation reaction of (2E)-2-(4-((E)-(2-hydroxyphenylimino)methyl)benzylideneamino)phenol Schiff base and three metal ions: Fe(III), Cu(II), and Ni(II). Their chemical structures were elucidated using elemental analysis, FTIR, ^1HNMR, and UV/Vis spectroscopy. The photo-stabilizers were formulated at 0.5 % in PVC sheets and tested under ultraviolet light for 0–250 h. The degradation indexes including unsaturation (I_CC), carbonyl (I_CO), and hydroxyl (I_OH) indexes of pure PVC were 0.12, 0.2, and 0.23. While, the index values were decreased moderately in the case of Cu-stabilizer to 0.025, 0.112, and 0.122, respectively. In the case of the Ni-stabilizer, the degradation indexes considerably reduced to 0.062, 0.078, and 0.110 respectively. The average molecular weight of PVC after 200 h of photo-irradiation was decreased by 80 % in the case of pure PVC, while in the case of stabilized PVC by the prepared photo-stabilizers were 69 %, 56 %, and 39 % for PVC-Fe, PVCCu, and PVCNi, respectively. The photo-stabilizing tendencies of the prepared photo-stabilizers were ascribed based on their ability for radical scavenging and were associated with their antioxidant efficiencies. The antioxidant efficiencies of the synthesized photo-stabilizers were measured and compared to 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS⁺) as standards. Copper and nickel complexes exhibited higher efficiency than ferric complexes during the photo-stabilization of PVC under the studied conditions. The role of the synthesized photo-stabilizers in the photo-stabilization mechanism was explained.