Poly(hydroxybutyrate-co-valerate), PHBV, is a brittle biodegradable polymer. This study focuses on the modification of PHBV for flexible applications. Blending with nanoparticle titanium dioxide (TiO2) 1% by weight did not result in toughening. Blending with poly(butylene adipate-co-terephthalate) (PBAT or Ecoflex) at various ratios of PHBV/Ecoflex (80/20, 70/30, and 50/50 by weight) for flexibility with and without nanoparticle TiO2 also was not promising. Grafting with 2-Hydroxyethyl methacrylate (2HEMA) at ratios of PHBV/2HEMA of 90/10 and 70/30 by weight was also unsuccessful in increasing flexibility. Crosslinking PHBV in the presence of 2,5-Bis(tert-butylperoxy)-2,5-dimethylhexane (L101) resulted in significantly greater elongation at break and slightly higher tensile strength. The crosslinked PHBV had lower crystallinity than PHBV since the crosslinked network impeded crystalline formation, creating voids for favorable paths for gases resulting in higher permeation. The amount of L101 in the crosslinking reaction was investigated at 0.5, 1, 2, 3, and 4 % by weight. The neat PHBV and crosslinked PHBV sheets were not significantly different in tensile strength. The maximum elongation at break was obtained at L101 content of 2 % by weight where it was twice that of neat PHBV. Thermal analysis showed that crystallinity of the crosslinked PHBVs were lower than neat PHBV. Also, the permeability to gases increased with an increase in L101 content.
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