Degradation of polylactic acid and polylactic acid/natural rubber blown films in aquatic environment

This research investigated the degradation of polylactic acid (PLA) and polylactic acid/natural rubber (PLA/NR) films submerged in water by focusing on the effect of film constituents, which were natural rubber and an organic peroxide, as well as an exposure to outdoor sunlight. The degradation of film samples was characterized by the changes in molecular structure, toughness, morphology, thermal properties and weight loss of the films and pH of water. It was found that hydrolysis was the primary degradation mechanism of the films submerged in purified water in the indoor condition, while photo-degradation was more prominent in the outdoor condition. Moreover, the presence of NR in PLA led to faster degradation of the films in aqueous environment both indoor and outdoor, while the addition of 0.02 wt% organic peroxide did not delay the degradation of PLA/NR films. These results indicate the potential of NR as it not only improved the toughness of PLA films during their useful life but also accelerated the films' degradation in aqueous environment after use.