Preparation And Properties Study On The PLA/starch Blend Materials

This dissertation introduced the research progress of PLA, multiple modification methods principle and properties of final products. Adding starch into PLA can reduce the cost without affecting its bio-degradability. But poor fluidity of starch and compatibility of PLA/starch need be modified by adding appropriate plasticizer and reactive compatibilizer. PLA/starch blends were prepared by adding appropriate plasticizer and reactive compatibilizer in twin-screw extruder. Properties were characterized by universal mechanical tester, impact tester, DSC, DMA, TG, FTIR, and rotation rheometer.The research results showed that two-phase interface between PLA and starch was clear, existed obvious phase separation without compatibilizer. With the increasing of starch, mechanical properties, Tg and Tm, degree of crystallinity and thermal decomposition temperature were decreased. Simultaneously the increase in starch content reduces the water resistance of the blend system but increase the rate of degradation.The results indicated that the effects of plasticization of ATBC and PEG on the properties than that of glycerol were better, with lower water absorption and migration rate. As the plasticizer content increased, the elongation at break and degradation resistance of composites increased, while heat resistance decreased.Mechanical test, TG and rheology test results showed that the mechanical properties and thermal stability of this system were enhanced. According to FTIR and DMA results, the enhanced properties of PLA/starch blend could be explained by the in situ formation of copolymer in the interface of PLA and starch granule, which increase the adhesion of PLA and starch granule.The grafting or cross-linking reaction made decreased of mobility and regularity of molecular chains making crystallization difficult. The addition of TDI dimer could enhance the processing stability of the blends and water resistance, but reduced the rate of degradation.The influence of thermoplastic elastomer TPU on mechanical properties, thermal properties, crystalline properties, rheological properties and water resistance of PLA/starch blends were also characterized. The results showed that thermoplastic elastomer TPU could significantly improve the toughness of the material, elongation at break and impact strength, but reduced the tensile strength of blends. Viscosity stability of blends was also increased as the addition of TPU. But TPU had no significant effect on water absorption in PLA/starch blends.In this study, PLA/starch blends with high mechanical strength, good heat resistance; water resistance and fully biodegradable properties were obtained.