Effects of UV/Photo-Initiator Treatments on Enhancement of Crystallinity of Polylactide Films and Their Physicochemical Properties

Effects of UV/photo-initiator treatments on crystal formation and properties of polylactide (PLLA) films are investigated. Camphorquinone and riboflavin photo-initiator solutions in methanol are employed in the treatment of amorphous quenched PLLA films. Results from FTIR, ATR-FTIR, DSC, XRD, and SEM show evidence of crystalline domain formation dispersed throughout the film. ¹H NMR and GPC results suggest that the molecular weights of the polymer slightly decrease after the treatment. This indicates that the treatment leads to a diffusion of the photo-initiators molecules through the film matrix, resulting in a low degree of PLLA chain scissions, and formation of carboxylic acid and hydroxyl polar end groups. This, in turn, induces PLLA crystallization, which imposes profound effects on surface wettability and physical and mechanical properties of the samples. The process can be applied in optimizing properties of PLLA films with shorter treatment times, compared to other methods, which is suitable for use in various fields; especially those that require specific characteristics like biomedical, packaging and environmental applications.