Preparation And Properties Of Poly(lactic Acid)/Acetylated Starch Composite Films

In this study, we tried to prepare biodegradable poly(lactic acid) composite films mainly consisting of poly(lactic acid) (PLA) and potato starch since the traditional petroleum plastic packages cause lots of environmental problems. The compatibility between PLA and starch and the optimum ratio of PLA and starch were studied. The results may promote the application of biodegradation PLA-based composite materials, for example, as common package materials.PLA is a kind of biodegradable material with excellent properties, which can degrade to water and carbon dioxide in the environment. But there are some disadvantages about PLA, such as high cost, brittleness and so on, so that the application of PLA is usually limited. In the early studies, many efforts had been made to develop the PLA/starch blends to reduce the cost, but the results showed that the PLA/starch blends had rather poor interfacial compatibility. They are the typical thermodynamically immiscible, and the mechanical properties of the blends were decreased significantly.In order to improve the compatibility between starch and PLA, different methods were tried. In this work, the starch was modified to prepare the acetylated starch (AS). It was found that the compatibility between PLA and AS in the blends was increased. Also different plasticizes were used to improve the mechanical properties of PLA/AS composite films. 1. ATBC is a kind of environment friendly plasticizer. With ATBC, the compatibility of PLA/AS was increased according to SEM. With the increase of ATBC content, the continuous phase in the composite films was formed. When the ATBC content was 20wt%, the elongation at break of composite films reached the largest at 31.85%, but the tensile strength decreased sharply to the lowest at the ATBC content of 30wt%. 2. PEG with different molecular weighs of 400 and 1000 were used. PEG could improve the elongation at break of composite films. The tensile strength of composite films with PEG was higher than that with same content of ATBC. Moreover, PEG400 was better than PEG1000, because small molecular weight of PEG could penetrate into the internal of PLA and AS. 3. We changed the ratio of PLA to AS while keeping the content of PEG at 20wt%. The results showed that the mechanical properties of the composite films were the ideal when the content of AS was less than 15wt%. 4. High molecular weight of PEO could not only increase the tensile strength and the elongation at break of the composite films, but also increase the storage modulus. The comprehensive performance of composite films was good under high molecular weight of PEO.