Natural Antioxidants as Thermal Stabilizers in Fully Biobased <scp>PHBV</scp> Compounds

ABSTRACT In the transition from fossil based to biobased polymers polyhydroxyalkanoates (PHA) stand out as good candidates. However, their high sensitivity to oxidative and thermal degradation makes processing of PHA challenging. This paper aims to investigate the oxidative and thermal stability of a commercially available poly(3‐hydroxybutyrate‐ co ‐3‐hydroxyvalerate) (PHBV) with natural antioxidants in order to develop a biobased, biodegradable and thermally resistant polyester using a continuous manufacturing approach. The effect of the antioxidant on the rheological properties as well as the thermal stability is investigated. The results show that thermo‐oxidative degradation is negligible, but processing is mainly responsible for thermal degradation. Regenerative additives effectively stabilized the material, as shown by thermal and rheological tests. Although macroscopic changes occur (change in viscosity and molecular weight, aging effects due to oven storage and a change in thermal properties), no changes in the chemical structure or composition molecular‐level structural alterations were detected, and IR spectroscopy showed no chemical modifications as well. Overall, regenerative additives improved the thermal stability of biobased polymers without compromising their molecular structure.