Preparation, Structure And Properties Characterization Of TPS/WPU Biodegradable Plastic

The general plastics have many advantages, such as light, good performance and low cost, so they are widely applied in all kinds of departments of national economy. But there are two major problems of general plastics, first, the materials of general plastics is oil. As we all know, oil resource is very shortage and its price is very high; second, general plastics are hard to degrade, and "white pollution" seriously threat to human survival environment. Therefore, Starch-based biodegradable plastics are more attractive to a number of research workers. Now there are some starch plastics are put into production use, but they still face poor water resistance, mechanical properties and high cost of production el ct.Previously, the laboratory had done a large amount of research work on starch-based biodegradable plastics and achieved great achievements, but there are also some problems to be solved, such as plasticity, aging discoloration, hot sealing and poor water-resistance. This experiment using glycerol as plasticizers, corn starch and acetate starch as raw material prepared starch thermoplastics(TPS), then add a certain amount of waterborne polyurethane, which is biodegradable, in order to improve the water resistance and mechanical properties of TPS. The strong cohesive force of WPU can improve the heat sealing TPS/EAA, and it can also improve the compatibility between starch and hydrophobic polyester. Joining the amount of antioxidants, the late-like WPU would wrap up the starch and antioxygen, which can isolate O2 when they are in extrusion processing. As a result, this can improve the efficiency of antioxidants and solve the problem of aging discoloration. The different proportion of the raw materials is prepared into biodegradable plastics after some procedures, then study the chemistry structure and microstructure, mechanical properties, water resistance, thermal properties and biodegradability of biodegradable plastics.(1) According to Fourier infrared spectrum analysis:after melting and blending, WPU and starch formed in the hydrogen bonding interaction and built network structure, which helps improving the mechanical properties and water resistance of TPS, and improving the compatibility between EAA and starch. So this improves the mechanics performance of TPS/WPU/EAA.(2) The results of SEM:joined with WPU, the unplasticated starch reduced and the size of plastic starch decrescent, which improves the plasticity of TPS/WPU; after WPU and starch extrusion melting, they formed a "embedding" structure, which is helpful to improve the water resistance of starch and starch’s surface, also is helpful to improve the compatibility of starch and EAA, thereby improving the mechanical propertiesof TPS/WPU/EAA.(3) MFR shows that joined with WPU, the liquidity melt of TPS improved. When the bending system contains 15% WPU, the molten index of TPS/WPU increases from 1.06g/10min to 4.26g/10min; the molten index of TPS/WPU/EAA increased from 22.1g/10min to 57.1g/10min, in other words, they are increased 3 times and 1.5 times.(4) According to the mechanical properties test and analysis, with the increase content of plasticizer, the tensile strength of TPS first increased and then reduced. When the TPS contains 35% plasticizer, the tensile strength of TPS is 6.63MPa. Because WPU has strong force, it can forme the hydrogen bonding interaction and "embedding" structure with starch, which is helpful to improve the compatibility of starch and EAA, so joined with WPU, the mechanics performance of TPS/WPU and TPS/WPU/EAA are improved. When the bending system contains 9% WPU, the mechanics performance of TPS/WPU and TPS/WPU/EAA are best, and the tensile strength of TPS/WPU and TPS/WPU/EAA are 12.6MPa and 14.3MPa. More than nine, the tensile strength increasing amplitude decreases. While the modified starch acetate esters, its hydroxyl and plasticity improve greatly. The mechanics performance is improved when the acetate starch are used for TPS/WPU. When the bending system contains 9% WPU, the tensile strength is 13.3MPa.(5) Water resistance test indicates that WPU can improve the water resistance of starch and starch’s surfaces, it also can improve the mechanics performance of TPS/WPU and TPS/WPU/EAA after they absorbed water. Because WPU has strong force, it can forme the hydrogen bonding interaction and "embedding" structure with starch, and can effectively restrain the water absorption. In 100% RH environment, after the bending system absorbing water for 120h, the tensile strength of TPS/WPU reduce only 32.3% and TPS/WPU/EAA reduced only 14.9%,which is far below TPS(80.5%).(6)According to TG test and analysis, with the increase content of WPU, the decomposition of TPS/WPU in high thermal zone decreased which can be explain as follows, the late-like WPU would wrap up the starch and antioxygen, which can isolate O2 when they are in extrusion processing. As a result, this can improve the efficiency of antioxidants and enhance the thermal stability of oxygen, and in the end solving the problem of aging discoloration.(7) According to the heat distortion temperature test, with the increase content of WPU, the heat distortion temperature of TPS/WPU and TPS/WPU/EAA increased and the heat-resistant strengthened. When the bending system contains 9% WPU, the thermal deformation temperature increase to 31.0℃and 28.1℃respectively.(8) The dynamic thermal mechanical analysis(DMA) results show that along with the increase of the content of WPU, energy-storage modulus of TPS/WPU/EAA increase gradually when the temperature is below 25℃.This means that WPU can form hydrogen with starch molecules and built network structure. In this way, it improves the material’s resistance to deformation, as the infrared spectrum analysis. As the temperature increases, the peak temperature and corresponding energy-storage inodulu of TPS/WPU/EAA in different frequency tends to the same; on the Eventuallylost-Temperature curve, TPS/WPU/EAA has only one temperature peak. The glass transition temperature unchanged when we added a little WPU, but the glass transition temperature of TPS/WPU/EAA would increase from -26℃to-22℃when the content of WPU increased.(9) According to the simulation of soil degradation experiments, as the content of TPS/WPU and TPS/WPU/EAA increased, the biodegradable cycle extended, but they still had biodegradable ability. Pure TPS would crack and get lighter and lighter when it was buried in the soil after a month. Five months later, the 12 content WPU of TPS/WPU/EAA would bagin getting crack and appear a lot of mildew spot on its surface,but it still had good mechanical strength.