Miscibility and Biodegradation Behavior of Melt-Processed Blends of Bacterial Poly(3-Hydroxybutyrate) with Poly(Epichlorohydrin)

The miscibility of melt processed blends of bacterial poly(3-hydroxybutyrate) (PHB) with poly(epichlorohydrin) (PEC) is investigated over the whole range of compositions by means of differential scanning calorimetry, dynamic-mechanical analysis, and hot-stage optical microscopy. PHB and PEC are miscible in the melt in all proportions. After melt quenching, PHB/PEC blends show a single glass transition that linearly changes with composition between the T g s of the pure components (PHB = 2°C, PEC = −21°C). At room temperature all PHB/PEC blends are partially crystalline, owing to crystallization of a constant fraction (58%) of the PHB present in each blend. A spacefilling spherulitic morphology develops upon blend crystallization from the melt. Isothermal crystallization measurements show that over the range of crystallization temperatures (40°C < T e < 130°C) and compositions (20% < PEC < 80%) explored, the spherulite radial growth rate (G) decreases with increasing PEC content. Biodegradation experiments, carried out in activated sludge and in enzymatic solution (PHB-depolymerase from Aureobacterium saperdae) on the blend containing 80% PHB, show both weight loss and surface erosion. The biodegradation results are discussed in terms of PHB chain-mobility.