Effect of graphene oxide content on the mechanical, water absorption, and thermal properties of polyhydroxybutyrate nanocomposites

Abstract

Biopolymers such as polyhydroxybutyrate (PHB) have emerged as promising alternatives to petroleum-based plastics due to plastic pollution. In this context, this study investigates PHB/graphene oxide (GO) nanocomposites. GO was synthesized via chemical oxidation of graphite, and its formation was confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy, which evidenced increased interlayer spacing, oxygenated functional groups, and structural defects typical of GO. PHB/GO formulations containing 0 (control), 0.2, 0.5, and 1 wt% GO were prepared and processed by hot compression molding. The PHB/GO formulations were characterized by Izod impact resistance, Shore D hardness, water absorption, and thermogravimetric analysis (TGA). The incorporation of GO did not significantly affect impact resistance (~12.9 kJ/m²), indicating preserved toughness. In contrast, hardness increased from 62 to 67-68 Shore D, demonstrating enhanced surface rigidity. TGA results revealed similar thermal degradation behavior for all compositions, with no significant change in stability. However, water absorption increased with GO content, particularly at 1 wt%, suggesting higher permeability and potential effects on durability. Overall, GO improves stiffness without compromising impact performance, although higher contents may affect moisture sensitivity production.