Polyhydroxyalkanoates (PHAs) is a family of microbial polyesters, which can be synthesized by a wide range of microorganisms. A direct correlation between the blend morphology and the biodegradability and mechanical properties of polymer blends containing the most commonly found PHAs member; the polyhydroxybutyrate (PHB) is established in this study. Poly-∈-caprolactone (PCL) and Poly(3-hydroxybutyric acid) poly(3-hydroxyvaleric acid) copolymer (PHBV) are selected as the second blend component with PHB to demonstrate the correlation with the aid of several characterization techniques, including DSC, in situ studies on the crystallization process, micro-Raman spectroscopy, TEM and SEM observation on the degraded samples....[ Read more ]

Polyhydroxyalkanoates (PHAs) is a family of microbial polyesters, which can be synthesized by a wide range of microorganisms. A direct correlation between the blend morphology and the biodegradability and mechanical properties of polymer blends containing the most commonly found PHAs member; the polyhydroxybutyrate (PHB) is established in this study. Poly-∈-caprolactone (PCL) and Poly(3-hydroxybutyric acid) poly(3-hydroxyvaleric acid) copolymer (PHBV) are selected as the second blend component with PHB to demonstrate the correlation with the aid of several characterization techniques, including DSC, in situ studies on the crystallization process, micro-Raman spectroscopy, TEM and SEM observation on the degraded samples.

Macrophase separation is observed in PHB-PCL blends and found to be immiscible by the presence of two melting peaks. Crystallization of PHB is observed to be independent of PCL inclusion. As PCL is found to be non-degradable by Alcaligenes eutrophus (ATCC 17699), the apparent enhanced degradation rate observed on the PHB major blend is attributed by the defragmentation of PCL from the PHB integrity during microbial attack, this is first reported by means of Raman spectroscopy.

Defragmentation is not observed in PHB-PHBV blends, though the miscibility is varyng with composition as deduced by the crystallization process. SEM and TEM micrographs show clearly that enzymatic hydrolysis took place on the surface only, and preferentially degraded the amorphous region first. In this system, the PHB major blend is found to have a significant improvement on both the mechanical properties and the degradation rate compared to the individual components.