Toughening of poly(3-hydroxybutyrate) with poly(cis-1,4-isoprene)

Poly(cis-1,4-isoprene) (PIP) was blended with poly(3-hydroxybutyrate) (PHB) to improve the mechanical properties of PHB. With the change in the blend composition there was virtually no shift in the T-g of either PIP or PHB, indicating that PHB and PIP were incompatible. Therefore, poly(vinyl acetate), which is compatible with PHB, was grafted onto PIP, and properties of the PHB/PIP-g-PVAc blend were characterized. As the concentration of the PIP-g-PVAc copolymer was increased in the PHB/PIP-g-PVAc blend, the T-g of the PHB rich domain was increased, while the T-g of the PIP rich domain remained nearly constant. It could be interpreted that the PVAc moiety of the graft copolymer was diffused into the PHB domain. The size of the dispersed phase of the PHB/PIP-g-PVAc blend was smaller than that of the PHB/PIP blend. The tensile properties and impact strength of the PHB/PIP-g-PVAc blends were superior to the PHB/PIP blends. (C) 1999 Elsevier Science Ltd. All rights reserved.