Study On Maize Starch-based Biodegradable Film

As science advanced and public awareness of environmental protection enhanced, much attention is paid to global environmental and resource issues. The problem of "white pollution" caused by used plastic is becoming increasingly serious, in which plastic shopping bags play an important role. The State Council of the Chinese government issued a ban on plastics bags in supermarkets, department stores and all the markets on June 1,2008, which meant that plastic bags used to be free of charge would not be provided to the customers. In recent years, the research on biodegradable materials, especially biodegradable plastic, has become a hot topic. As one of the most promising natural materials, maize starch-based biodegradable materials have been developed rapidly.In this paper, with waxy, normal and high-amylose maize starch as research objects, the effect of amylose contents of starches on compatibility and film-forming properties of maize starch and polyvinyl alcohol (PVA) blend pastes were studied, the optimal operating conditions of starch thermal-plastic cast film were discussed, and the film properties were also characterized. The main results were as follow:The starch/PVA pastes and blend films was prepared by PVA and maize starch with different amylose contents. The influence of amylose contents of starches on the compatibility of the blend pastes was quantitatively evaluated by the initial demixing time and subsidence ratio. The results demonstrated that with the increasing amylose contents of the pastes, the initial rate and the degree of the phase separation decreased markedly, and the pastes stability increased. With the higher amylose contents of starch/PVA film, the films had better miscibility, compactness and mechanical properties according to the test result by scanning electron microscopy (SEM) and tensile test.The starch/PVA composite film was prepared by normal maize starch treated by high temperature with PVA. The effect of reaction temperature on the mechanical properties and water-resistance of the film was discussed. By X-ray diffraction (XRD), differential scanning calorimetry (DSC), SEM and biodegradation experiment, the crystallinity, thermal stability, microstructure and biodegradability of the film were studied respectively. The results showed that the film-forming properties of the film showed differences by temperature treatments from 90℃to 150℃. The film treated at 110℃had lower crystallinity, better thermal stability, miscibility and compactness than the others, and its mechanical properties and water-resistance increased markedly. The starch/PVA film had good biodegradability.The biodegradable films were prepared with high-amylose maize starch and PVA as raw materials by casting method. The mechanical properties, water-resistance, microstructure and biodegradability of the film were studied, by tensile test, water-absorption experiment, SEM and biodegradation experiment, respectively. The results showed that the gelatinization temperature of the high-amylose maize starch was obviously higher than that of normal maize starch; the high-amylose maize starch was gelatinized completely at 130℃. Comparing with normal maize starch/PVA composite film, high-amylose maize starch/PVA composite film treated at 130℃had better miscibility and compactness mechanical properties, water-resistance and biodegradability.