Bio‐based blends from poly(3‐hydroxybutyrate‐<i>co</i>‐3‐hydroxyvalerate) and natural rubber for packaging applications

Abstract

ABSTRACT Poly(3‐hydroxybutyrate‐ co ‐3‐hydroxyvalerate) (PHBV) is a promising bioplastic but has limited packaging applications due to its brittleness and poor processability. Incorporation of highly viscous high‐molecular‐weight natural rubber (HMW‐NR, gel extracted from NR) into PHBV can improve these properties. HMW‐NR is not commercially available, impeding commercialization of the PHBV/rubber blends. Therefore, an organic peroxide was used to selectively crosslink NR to increase its viscosity during its melt blending with PHBV. The PHBV/NR blends were fabricated through a two‐step extrusion process using a twin‐screw extruder. The blends contained two phases with crosslinked rubber being dispersed in PHBV, and had clear rubber loading‐dependent differences in performance. The thermal stability and melt strength of the blends were enhanced over pristine PHBV, indicating improved processability. The flexibility and toughness of the blends were improved by 59 and 20%, respectively, compared with pristine PHBV, and were comparable to commercial petroleum‐based plastics. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47334.