Study On Composite Modification Of Poly (3-hydroxybutyrate-co-4-hydroxybutyrate)

Poly(3-hydroxyllbutyrate-co-4-hydroxylbutyrate)[P(3HB-co-4HB)] with nucleating agents BN, P250, CaC03and Tm-3respectively were prepared via melt molding. Polarized optical microscopy (POM), differential scanning calorimetry (DSC), thermal gravimetric analyzer (TGA) and scanning electron microscope (SEM) etc. were used to characterize the effects of various nucleating agents and their dosage on the spherulitic morphology, melting point, thermal decomposition temperature, mechanical properties and fracture morphology of the samples. Composite material of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)[P(3HB-co-4HB)] and poly(L-lactide)(PLA) or composite material of poly(3-hydroxybutyrate-co-4-hydroxybutyrate)[P(3HB-co-4HB)] and poly(ethylene glycol)(PEG) were prepared by melt-mixing and subsequent injection molding, and their fracture morphology, thermal decomposition temperature and mechanical properties were investigated. The results show that:(1) The various nucleating agents can effectively refine the spherulite, improving the melting point and thermal decomposition temperature of the P(3HB-co-4HB) copolyesters. There is a dosage of nucleating agents at which the mechanical properties of copolyesters are the optimum. The comprehensive properties of the copolyesters are the best with BN as nucleating agent at5wt%o～8wt%o.(2) The research of thermal properties shows that with the increase of PLA content, the thermal decomposition temperature is increased. The vicat softening temperature almost unchanged when the PLA content less than60wt%, while as PLA content continuously increases, the vicat softening temperature changes rapidly, whereas the PLA content up to80wt%, the vicat softening temperature basically approach the neat PLA. When the PLA content up to40wt%, the melt viscosity was lowest. With the increase of PLA content, the tensile strength and the bending strength of the blends increase. The notched impact strength and the elongation at break of P(3HB-co-4HB)/PLA=60/40blend are lowest and a phase inversion occurs at composition with40wt%of PLA in the blend.(3) The addition of PEG can increase the melting point and thermal decomposition temperature of the P(3HB-co-4HB), improve the rheological properties and hydrophilcity, but the vicat softening temperature, the tensile strength and the bending strength of the blends decreased rapidly, while the notched impact strength and the elongation at break were increased with moderate content of PEG. The comprehensive properties of the copolyesters are the best with PEG content up to5wt%-10wt%.