Morphology and thermal properties of poly(lactic acid)/poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/graphene oxide polymeric composites

Abstract Poly(lactic acid) (PLA)/poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV) blends are typically phase‐separated, and there is limited research on using graphene oxide (GO) as their matrix filler. PLA/PHBV/GO composites using 1, 3, or 5 wt% GO were prepared by melt mixing, after which their morphology and thermal properties were determined. All the components were hydrophilic (Contact angles less than 90°), and the wetting coefficient value of 3.52 suggested that GO would be dispersed in PLA during surface energy evaluations (SEES). Scanning electron microscopy (SEM) showed that PLA/PHBV blends are immiscible and phase‐separated; however, adding GO brought partial miscibility. Differential scanning calorimetry (DSC) showed that GO plasticized the polymers at lower contents (1 wt%) and inhibited their crystallization at higher contents (3 and 5 wt%). Fourier‐transform infrared spectroscopy (FTIR) measurements showed that a chemical interaction exists between GO and the polymers, and X‐ray diffraction (XRD) results confirmed that GO inhibited crystallization in the polymers at high contents. Adding GO to the polymers generally improved the thermal stability of PLA, verifying the affinity thereof during thermogravimetric (TGA) analyses. Merging of the thermal degradation steps implied that GO induced partial miscibility on polymers. Concurrently, the polymers thermally masked the GO to prolong its lifespan. Composites with 1 wt% GO were the optimal and ideal materials. Highlights Melt mixed PLA/PHBV blends and their composites with GO as a filler. GO brought partial miscibility to the blends and favored the PLA phase. 1 wt% GO contents provide optimal thermal and morphological properties. 3 and 5 wt% GO contents form chemical bonds with the polymers. Initial GO loadings increase the crystallinity of the polymers.