Polymer blends based on bacterial poly(3-hydroxybutyrate)

Abstract

The phase behavior of blends of bacterial poly(3-hydroxybutyrate) (PHB) with highly substituted cellulose esters (CEs), polymethylmethacrylate (PMMA), polycyclohexylmethacrylate (PCHMA), ethylcellulose (EtC), and polyepichlorohydrin (PEC) is discussed on the basis of dynamic mechanical, calorimetric, and optical microscopy results. PHB is miscible in the melt in all proportions with CEs and PEC, is partially miscible with PMMA, and is totally immiscible with EtC and PCHMA. The rate and extent of biodegradation in activated sludge of immiscible PHB–EtC blends strongly depends on phase distribution, which is in turn dictated by composition and blending conditions. Miscible PHB–CE and PHB–PEC blends containing 80% PHB show analogous spherulitic morphology, but behave very differently in activated sludge. The blend containing PEC shows weight loss and surface erosion upon sludge exposure, whereas the one containing CE does not biodegrade over a period of 12 months. It is suggested that mobility of the amorphous mixed phase is an important parameter in determining biodegradability of miscible PHB-based blends.Key words: poly(3-hydroxybutyrate), blends, miscibility, biodegradation, morphology.