Non-isothermal crystallization of P(3HB-co-4HB)/PLA blends: Crystallization kinetic, melting behavior and crystal morphology

A series of P(3HB- co -4HB)/PLA blends with different mass ratios were prepared via solution blending. Non-isothermal crystallization kinetic, melting behavior and morphology of the blends at various cooling rates were investigated by differential scanning calorimetry, wide-angle X-ray diffraction and polarized optical microscopy (POM). Mo’s theoretical model was applied to describe the process of non-isothermal crystallization. The results show that the blends form crystal structure of P(3HB- co -4HB) and PLA simultaneously, and Mo’s method could describe the non-isothermal crystallization of P(3HB- co -4HB)/PLA blends very well. The crystal morphologies of P(3HB- co -4HB)/PLA blends with different mass ratios by polarizing microscope (POM) clearly show that typical spherulite morphology with “Maltese Cross” extinction pattern can be found in all samples. Neat P(3HB- co -4HB) and P(3HB- co -4HB)/PLA at PLA mass ratio ≤20 % exhibit typical banded spherulites as PHB or PHBV. The blends with P(3HB- co -4HB) and PLA mass ratio 70–90 % form classic non-banded spherulites as neat PLA. The spherulitic morphologies of the blends are very complex when the mass ratios of P(3HB- co -4HB) and PLA are 70/30, 60/40, 50/50 and 40/60, respectively.