ATR-FTIR spectroscopy study of the photodegradation protective properties of BP-4 and 4HBP in polyvinyl acetate thin films

•The photostability of two UV absorbers added in polyvinyl acetate films was studied.•Photodegradation of PVAc films was studied in inert and real conditions.•ATR-FTIR was used for quantitative and qualitative analysis of degradation products.•Photodegradation pathways for studied films were proposed.

In this paper the protective properties of 4HBP (4-hydroxybenzophenone) and BP-4 (5-benzoyl-2-hydroxy-4-methoxybenzenesulfonic acid) in polyvinyl acetate thin films have been studied. UV-irradiation on the films was applied in real humidity and inert atmosphere for 1, 2 and 4 h accelerated weathering. ATR-FTIR and UV-VIS spectroscopies have been used for qualitative and quantitative estimation of photodepletion of the UV-absorbers and photostability of polyvinyl acetate films. Both UV-absorbers have demonstrated good protective properties in inert atmosphere compared to real humidity. The mechanisms of photochemical reactions of 4HBP (4-hydroxybenzophenone) and BP-4 (5-benzoyl-2-hydroxy-4-methoxybenzenesulfonic acid) were attributed to photoenolization of carbonyl and hydroxyl groups. The experimental results demonstrated that 4HBP (4-hydroxybenzophenone) has higher protective properties than BP-4 (5-benzoyl-2-hydroxy-4-methoxybenzenesulfonic acid). The photodegradation mechanisms of polyvinyl acetate films in inert atmosphere and real humidity were assigned based on the Norrish type I and II reactions.

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