Films of PLLA/PHBV: Thermal,morphological, and mechanical characterization

Blends of poly(L ‐lactic acid)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PLLA/PHBV), both semicrystalline polymers, were prepared in different compositions (100/0, 80/20, 60/40, 50/50, 40/60, 20/80, and 0/100) and characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), polarized light microscopy (PLM), and tensile tests. Although PLLA/PHBV blends do not present clear phase separation by SEM, the analyses by TGA, DSC, and DMA showed that the PLLA/PHBV blends are immiscible. The cross sections observed by SEM showed that the morphology of the blends changes from porous to dense, due to the composition. DSC and DMA data showed two distinct glass transition and melting temperatures. However, the DMA analysis related to frequency variation showed partial molecular interactions between PHBV and PLLA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2898–2906, 2002