Preparation and properties of polyhydroxybutyrate blended with different types of starch

This study examines the properties of polyhydroxybutyrate (PHB) when blended with two types of maize starch, Starch 1 (containing 70% amylose) and Starch 2 (containing 72% amylopectin). The PHB/starch blends were prepared by melt compounding at a ratio of 70/30 by weight and characterized in terms of their morphology, structure, thermal, rheological and mechanical properties. The results show that starch granules act as a filler in PHB/starch blends and also act as a nucleating agent causing a very significant reduction in the size of the PHB spherulites. There were found to be significant improvements in thermal, rheological and mechanical properties and these were greater for blends containing Starch 1 than those containing Starch 2. These improvements are attributed to enhanced hydrogen bonding between PHB and Starch 1 with high amylose content.