Solid-liquid Phase Photodegradation of Vulcanized Rubbers in the Presence of Sensitizer

Abstract

It was investigated that photodegradation of vulcanized rubber in solid-liquid phase in the presence of sensitizer. Shredded vulcanized rubbers were dipped in a small quantity of solvent, with addition of a sensitizer, and ultraviolet irradiation was applied for 72h. Significant decreases in the molecular weights of vulcanized IR and NR were confirmed. In particular, anthraquinone reduced the sample molecular weight to around 2,000. This reduction was ascribed to the small amount of energy required for first excitation of the polycyclic aromatic quinone, which allowed this substance to easily change into an active species. Degradation product had highly enhanced solubility, being soluble in alcohol, ketone, and many other organic solvents. From the structure analysis results of the degradation product, it is suggested that the reaction that reduced the molecular weight is ascribable to auto-oxidation reaction.