PMMA-driven morphology modification and dramatic improvement in ductility for PVDF/PLA blends

Poly(methyl methacrylate) (PMMA) was incorporated as compatibilizer in immiscible poly(vinylidene fluoride) (PVDF)/poly(lactic acid) (PLA) blends at different ratios. Scanning electron microscopy results revealed that, after adding PMMA, the phase morphology of PVDF/PLA blends evidently changed and the boundary became diffused, indicating improved interaction between PVDF and PLA. The sea-island biphasic morphology of PVDF/PLA (1:1) blend transferred to pseudo co-continuous morphology with the incorporation of PMMA. Differential scanning calorimetry and polarized light microscopy results showed that the presence of pre-crystallized PVDF facilitated the crystallization of PLA on cooling from the melt, but the molten PLA slightly retarded the crystallization of PVDF. With the inclusion of PMMA in the blends, PVDF crystal growth was further inhibited due to its miscibility with PMMA, and its crystallinity was also decreased. The elongation at break (ductility) of PLA and PVDF/PLA blends increased drastically by up to 27.8 and 11.1 times respectively, after formation of ternary PVDF/PLA/PMMA blends. Dynamic mechanical analysis results showed that the individual glass transition temperatures of PVDF and PLA in the blends shifted to higher temperatures after adding PMMA. PMMA showed more affinity to PVDF than to PLA. Rheological property measurements confirmed the increase in complex viscosity and storage modulus of the blends with increasing PMMA loading.