Poly(β-hydroxybutyrate-co-β-hydroxyvalerate) (PHBV) was modified with endic anhydride grafted poly(propylene carbonate) (EA-PPC), and then PHBV/EA-PPC composite polymers were prepared by melt blending under the catalysis of stannous octoate (Sn(Oct)2). The blends were characterized by an electronic universal testing machine, cantilever impact testing machine, and differential scanning calorimeter (DSC), as well as dynamic mechanical analysis (DMA) and field emission scanning electron microscopy (FESEM). Effects of the amount of Sn(Oct)2 on the mechanical properties, thermal properties, and morphology of the blends were discussed. The results showed that the addition of Sn(Oct)2 promoted the transesterification reaction between PHBV and EA-PPC, and the compatibility between PHBV and PPC was greatly improved. When the amount of Sn(Oct)2 was 3 wt%, the impact strength and elongation at break of the PHBV/EA-PPC blend increased from 3.7 kJ/m2 and 4.1% to 5.9 kJ/m2 and 387.5%, respectively, and there was no significant decrease in tensile strength. Additionally, four esterification reaction mechanisms for PHBV/EA-PPC blends were proposed.
Keywords: endic anhydride; graft modification; poly(propylene carbonate); poly(β-hydroxybutyrate-co-β-hydroxyvalerate).