POLYMER BLENDS CONTAINING POLY(3-HYDROXYALKANOATE)S

The remarkable properties of poly(3-hydroxyalkanoate)s (PHAs) have res ulted in a growing interest in these polymers. They offer a wide varie ty of useful mechanical properties and show excellent biodegradability . However, they are still expensive and poly(3-hydroxybutyrate) (PHB) in particular is quite brittle. Polymer blending offers interesting po ssibilities to prepare less expensive biodegradable materials with use ful mechanical properties. In this review the literature concerning PH A-containing blends has been summarized. Blends incorporating either P HB or copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate (P(HB-HV)) were discussed. The thermal and crystallization behaviour of the blen ds, their mechanical properties, morphology and biodegradability have been reviewed. Among the conclusions drawn from the literature, it is evident that PHAs can form miscible blends with polymers containing th e appropriate functional groups via hydrogen bonding and/or donor-acce ptor interactions. The crystallization behaviour of the PHAs is influe nced by both the miscible and immiscible components. Immiscible PHA-co ntaining blends show improved apparent biodegradability when compared to miscible blends. Their apparent biodegradability (weight loss) is m ostly controlled by the blend morphology. Blends of PHA with other bio degradable polymers also usually show improved biodegradability when c ompared with pure PHAs.