Enhanced thermal, mechanical and migration properties of extruded PHBV/graphene hybrids for packaging
Description
Aiming to improve the properties of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), hybrid materials were prepared. PHBV was mixed with poly(ethylene-co-vinyl acetate) (EVA) by extrusion at different compositions, in the presence of a plasticizer and a graphene derivative. A reduced graphene oxide-zinc oxide composite (rGO-ZnO) was added as a nucleating agent. X-ray diffractometry (XRD) showed that rGO-ZnO, added at 0.5 and 1.0 mass%, was well-dispersed within the polymer matrix. XRD and differential scanning calorimetry results indicated that the crystallinity of the PHBV phase was reduced in the hybrids. However, an increase in crystallinity was observed for the PHBV/EVA hybrids at 50:50 and 25:75 compositions, when the rGO-ZnO content was increased to 1.0%. This increase in crystallinity was associated to the formation of smaller spherulites. Tensile tests showed improved mechanical properties for the hybrids in relation to PHBV and the neat blends. For the hybrids, while a reduction in Young’s modulus was observed, elongation at break values varied from 307.5% to 822.6%. Finally, overall migration tests revealed that the hybrids with PHBV/EVA at 50:50 composition presented migration levels lower than those required by the European legislation for fat food packaging.