Mechanism of stabilization of polypropylene by ultraviolet absorbers

Abstract

Abstract The ultraviolet screening properties of 2‐hydroxyphenylbenzotriazoles and 2‐hydroxybenzophenones in polypropylene film were investigated by using photochemical and spectroscopic techniques. The effect of light screening on polymer photostability was examined by using filter solutions, and the fraction of ultraviolet light absorbed by stabilized film was calculated and compared to flexural failure times. It was found that the 2‐hydroxyphenylbenzotriazoles behave primarily as screeners of ultraviolet light whereas the 2‐hydroxybenzophenones are both screeners and excited‐state quenchers. The quenching characteristics of the latter have not been isolated and mechanistically examined, but it is probably similar in nature to that of the nickel chelate stabilizers.