PLLA and cassava thermoplastic starch blends: crystalinity, mechanical properties, and UV degradation

The effect of the addition of cassava thermoplastic starch on the general properties and the photodegradation behavior of poly(L-lactic acid) (PLLA) was evaluated by blending PLLA with TPS in different weight percentages (5, 10, 15, 20 and 25 wt%). The blends were studied through differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and mechanical properties. All the studies were performed before and after the photo-degradation in a climatic chamber. It was found that TPS was immiscible with PLLA and reduced Tg, Tm, and Tcc and influence Xc of PLLA, indicating an interaction of the TPS phase with the PLLA matrix, probably due to plasticizer migration. The tension test showed a decrease in the mechanical resistance of the blends, especially at the lowest TPS content; however, an increase in TPS lead to an increase in ductility. On the other hand, the UV degradation resistance was higher for the blends than for L100, possibly due to the protective effect of glycerol. It was concluded that the films obtained were fully biobased and biodegradable with higher UV resistance than the PLLA and with similar ductility.