Poly(Hydroxybutyrate‐ Co ‐Hydroxyvalerate)/Thermoplastic Starch Blends for Application in Biodegradable Mulch Films

ABSTRACT Poly(hydroxybutyrate‐ co ‐hydroxyvalerate) (PHBV)/thermoplastic starch (TPS) blends were produced for application in biodegradable mulch films. Pure films and blends in the proportions of PHBV (P) and TPS (T) (80P20T, 70P30T, and 60P40T wt.:wt.) were prepared by melt mixing. SEM micrographs revealed a two‐phase morphology of the blends, with the change from droplets to co‐continuous phases as the percentage of TPS increased. Blends were more flexible compared to PHBV film. Young's modulus decreased by up to 67% versus pure PHBV with increased amount of TPS and a slight increase in elongation at break was observed. All blends were less hydrophilic compared to pure TPS, with a decrease in the rate of water vapor permeation, water and moisture absorption. Partial solubilization of TPS in the blends occurred after 14 days in water, but solubilization was lower than the pure TPS. A lower melting temperature was achieved, especially at the 70P30T ratio (157°C) compared to PHBV (167°C), promoting a lower processing temperature. Therefore, this set of results indicates that the properties of the materials might be adjusted for the intended application according to the blend composition.