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-hydroxybu tyrate) (PHB) with poly(epichlorohydrin) (PEC) is investigated over th e whole range of compositions by means of differential scanning calori metry, dynamic-mechanical analysis, and hot-stage optical microscopy. PHB and PEC are miscible in the melt in all proportions. After melt qu enching, PHB/PEC blends show a single glass transition that linearly c hanges with composition between the T(g)s of the pure components (PHB = 2 degrees C, PEC = -21 degrees C). At room temperature all PHB/PEC b lends are partially crystalline, owing to crystallization of a constan t fraction (58%) of the PHB present in each blend. A space-filling sph erulitic morphology develops upon blend crystallization from the melt. Isothermal crystallization measurements show that over the range of c rystallization temperatures (40 degrees C < T-c < 130 degrees C) and c ompositions (20% < PEC < 80%) explored, the spherulite radial growth r ate (G) decreases with increasing PEC content. Biodegradation experime nts, carried out in activated sludge and in enzymatic solution (PHB-de polymerase from Aureobacterium saperdae on the blend containing 80% PH B, show both weight loss and surface erosion. The biodegradation resul ts are discussed in terms of PHB chain-mobility.