BINARY BLENDS OF MICROBIAL POLY(3-HYDROXYBUTYRATE) WITH POLYMETHACRYLATES

Blends of bacterial poly(3-hydroxybutyrate) (PHB) with poly(methyl met hacrylate) (PMMA) and poly(cyclohexyl methacrylate) (PCHMA) were prepa red by melt compounding followed by quenching to room temperature. PHB /PMMA blends containing up to 20 wt% PHB are single-phase amorphous gl asses with a composition dependent glass transition temperature (T(g)) . When the concentration of PHB exceeds 20 wt%, partially crystalline pure PHB coexists with a constant-composition PHB/PMMA (20/80) mixture , which represents the solubility limit of PHB in PMMA. In such blends crystallization of PHB, both isothermally from the melt and with heat ing from the rubbery state, is retarded by increasing amounts of PMMA in the blend. PHB shows no miscibility at all with PCHMA. In the PHB/P CHMA blends, two phases, consisting of the pure polymer components, ar e present over the whole composition range and PHB crystallization is unaffected by the presence of the methacrylate polymer.