Investigation Of The Molding And Performance Of Biopolymer Materials(PHAs)

Poly (3-hydroxybutyrate-co-4-hydroxybutyrate)[P(3HB-co-4HB)] with0%,5%,10%and20%of4HB molar contents were selected as raw materials. The melting point, thermal decomposition temperature, spherulite morphology, mechanical properties, fracture morphology, Vicat softening temperature and melt rheological properties etc. were charac tcrized by DSC, TGA, POM, Capillary rheometer, Brabender plastics instrument, etc. The effect of4nucleating agents on thermal properties, crystalline properties, mechanical properties of P(3HB-co-4HB)-5was investigated. P[(3HB-co-4HB)-5]/cornstarch blends was prepared and its thermal properties, mechanical properties and rheological properties, etc. were researched.The results show that (1) With the increase of4HB content, the melting point of P(3HB-co-4HB) decreased significantly than that of P(3HB), while the initial deco-mposition temperature is almost constant, which widened the processing temperature ran-ge. The spherulites of P(3HB-co-4HB) copolyester are of typical black cross extinction and the extinction and concentric ring can be observed. In addition, there are a number of cracks in P(3HB) spherulites disappeared in P(3HB-co-4HB),which indicating that the cracks can be effectively inhibited by4HB.There is a maximum crystallization rate temperature for various P(3HB-co-4HB), which decreases with the increase of4HB content. With the increase of4HB content, the breck elongation and notched impact strength of P(3HB-co-4HB) increase, but the tensile strength and bending strength show a contrary tendency.(2) The spherulite size, thermal decomposition temperature and notched impact strength of the copolyesters can be effectively refined and improved by various nucleating agents, but the Vicat softening temperature was little influenced by the nucleating agents. The tensile strength and break elongation of the copolyesters can be improved by organic and inorganic nucleating agents respectively. Nucleating agentIV has the most significant nucleating efficiency in P(3HB-co-4HB), which resulted in the coarsest fracture morp-hology and the best impact strength.(3) P(3HB-co-4HB)-5and cornstarch are partially compatible. Cornstarch has a little effect on the thermal decomposition temperature of the P(3HB-co-4HB)-5.With the increase of cornstarch, the tensile strength of the P(3HB-co-4HB)-5/cornstarch blends decrease and becomes flat after40portion. The break elongation of P(3HB-co-4HB)-5/cornstarch first increases and then decreases with the increasing of the cornstarch and reaches the optimum at20portion cornstrach. The brittle-ductile transition occurs with the cornstarch adding, which shows that cornstarch can serve as a filler as well as play a toughener for the blending materials. The melts of the P(3HB-co-4HB)-5/cornstarch blend-ing materials are pseudoplastic fluids. The melt viscosity decreases with the increseing of shear rate. The water absorption increased with the increase of cornstrach content.