Compatibilization of poly(lactic acid)/poly(3‐hydroxybutyrate‐<i>co</i>‐hydroxyvalerate) blends using multifunctional epoxy‐based chain extender

Abstract In this study, the influence of the multifunctional epoxy‐based Joncryl ADR‐4468 as a chain extender (CE) for homopolymers and compatibilizer for blends of polylactide (PLA) and poly(hydroxybutyrate‐ co ‐hydroxyvalerate) (PHBV) is investigated. Firstly, dissolving Joncryl in acetone enabled precise dosing through the extruder feed zone during reactive extrusion of various blends with low Joncryl concentrations. The chosen composition ratio with 30 wt% PHBV led to a droplet‐matrix morphology with spherical PHBV droplets in the matrix of PLA. The increased compatibility of the PLA/PHBV blends was achieved by the addition of Joncryl. The average size of PHBV droplets decreased with increasing Joncryl concentration. Rheological measurements clearly revealed the influence of the interfacial tension between PLA and PHBV on the storage modulus. Specifically, the shoulder of the storage modulus at low frequencies shifts to lower frequencies with an increasing concentration of Joncryl in the blend. Moreover, an improvement of compatibility and interfacial adhesion between the PLA and PHBV phases is demonstrated by tensile tests under uniaxial loading, as the blends clearly become more ductile with higher Joncryl concentration. Highlights Dissolving Joncryl in acetone ensures precise low dosing in reactive extrusion. Joncryl reduces PHBV droplet size in the PLA matrix. Joncryl compatibilizes PLA/PHBV blends, enhancing adhesion and strain at break. Joncryl increases dynamic moduli and viscosity of PLA, PHBV, and their blends.