Photodegradation of TiO2 composites based on polyesters

The knowledge of the photodegradation mechanisms and the possibility to modify them is a very important topic, especially for the novel biopolymers, as their durability with respect to the petro-plastics is yet an open question. Among the biopolymers, aliphatic polyesters are an emerging class of materials, thanks to the possibility of preparing them from renewable resources and their potential environmental degradability. In this study two aliphatic molecular structures, containing 1,4-cyclohexylene units, have been used: poly(butylene 1,4-cyclohexanedicarboxylate) (PBCHD) and poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) (PCCD). Moreover, in order to increase the durability, titanium dioxide (TiO2), known for its capability of absorbing UV radiation, was incorporated into the polymer. Therefore, composites containing different amount of titania, in the anatase and rutile crystalline phases separately, have been prepared by using a Brabender mixer. Both matrixes and composites were exposed to UV irradiation in an accelerated photo-ageing device and the modifications in their chemical structures were analysed by UV and IR spectroscopies. It results that the photodegradability of PBCHD, containing only one cycle per repeating unit, is lower than that of PCCD and that the composites have a photodegradability lower than those of the homopolymers. The well dispersion of the particles and the good adhesion between TiO2 and polymer have been checked by SEM observations. The protection of TiO2 against the photooxidation increases with the particle content and results higher for the anatase crystalline phase.