Fabrication and Improved Performance of Poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) for Packaging By Addition of High Molecular Weight Natural Rubber

The packaging industry is searching for alternative materials to attain environmental sustainability. PHBV (poly (3-hydroxybutyrate-co-3-hydroxyvalerate)) is a semi-crystalline polymer that meets this sustainability goal since it is bio-derived and bio-degradable. However, its brittle nature and relatively high water permeation and transmission rates make it unsuitable for packaging applications. In addition, PHBV has poor mechanical, thermal, and rheological properties above 160ºC, limiting its use in cast sheets and thermo-formed packaging applications. To improve these properties, new blends of PHBV with high molecular weight natural rubber at 5, 10, 15, and 25% by weight were fabricated, and physico-chemical properties of the blends were characterized. The rubber in the blends aided in the following: increased thermal stability since the complex viscosities of the blends were improved by one log over pure PHBV at 170ºC, created more uniform melting peaks attesting to improved homogeneity, decreased water permeation to a level similar to that of traditional thermoplastics; increased the elongation at break, and stabilized the Young’s modulus. Therefore, these blends can potentially be used in-place of traditional, petroleum-based thermoplastics in cast sheets and thermoforms.