Study on the biodegradability of modified starch/polylactic acid (PLA) composite materials

In this work, polylactic acid/thermoplastic acetylated starch (PLA/TPAS) composites were prepared using PLA as a matrix material and TPAS as a modifier. TPAS is based on acetylated starch, which is plasticized using glycerin. Analysis of the mechanical, thermal, and dynamic mechanical properties, and morphological structures of the PLA/TPAS composites shows that with an increase in the TPAS content, the toughness of the PLA/TPAS composites significantly improves. When the amount of TPAS added is 40% by weight, the elongation at break is increased 4 times. At the same time, the addition of TPAS has little effect on the thermal stability of the composites. Differential scanning calorimetry (DSC), dynamic mechanical analysis and scanning electron microscopy (SEM) analysis results show that PLA is incompatible with TPAS. The addition of TPAS promotes the crystallization of PLA, resulting in a decrease in the thermal stability but limits the degradation behavior during the processing of the material, which has little effect on the performance of the material. High temperature and high humidity soil degradation and ultraviolet radiation aging experiments on PLA/TPAS composites show that the PLA/TPAS composites have good biodegradability. In soil burial degradation experiments, the degradation rate of the pure PLA material is slow, and its final mass retention rate is high. The PLA/TPAS composites degrade fast. In ultraviolet radiation aging experiments, the tensile strength of the PLA/TPAS composites was improved to a certain extent after exposure to ultraviolet radiation. With an increase in the ultraviolet irradiation time, the tensile properties of the PLA/TPAS composites gradually decreased.