Synergistic and Destructive Effect of Processing Additives on the Extrusion of Poly(3-hydroxybutyrate)

Polyhydroxyalkanoates have attracted academic and industrial attention owing to their promising mechanical properties, inherent biodegradability, and biobased nature. However, thermal processing of the most prevalent of these polyesters, poly(3-hydroxybutyrate) (P3HB), is challenging due to thermo-mechanical and thermo-oxidative degradation during melt processing. In this work, we explore the impact of three different additives on P3HB processing. Irganox 1010, a phenolic antioxidant, Stabaxol I, an antihydrolysis agent, and Joncryl ADR4400, a chain extender, are evaluated in isolation and combination to optimize an additive package for improved processability. Each additive improved tensile strength at yield relative to the additive-free control, with the largest improvement seen with the combination of 1 wt % Irganox 1010 and 1.25 wt % Joncryl ADR4400, while combinations of antioxidant and antihydrolysis agents were destructive in effect. Color analysis delineated a relationship between tensile strength at yield and the absolute color difference, highlighting the potential use of color analysis as a nondestructive analytical tool for predicting mechanical performance. Together, these results suggest that additives will play an important role in improving Bioplastic processing and performance.