A comparative study on the impact of graphene oxide and reduced graphene oxide in polypropylene composites

This study systematically investigates the effects of graphene oxide (GO) and reduced graphene oxide (rGO) on the structural, thermal, mechanical, rheological, and morphological properties of polypropylene (PP). PP/GO and PP/rGO composites containing 1–10 wt% filler were fabricated via melt blending using a twin-screw extruder, followed by injection molding. FTIR analysis confirmed the presence of oxygen-containing functional groups in GO and rGO, while the reduced peak intensity in rGO-filled samples, suggesting improved compatibility with the non-polar PP matrix. XRD and DSC results showed that both fillers acted as nucleating agents; however, rGO exhibited a significantly stronger effect, evidenced by a 17°C increase in crystallization onset temperature (Tc,onset) at 10 wt% loading and the formation of more stable α-phase crystallites. SEM observations revealed agglomeration and weak interfacial bonding in GO composites, whereas rGO provided uniform dispersion, strong interfacial interaction, and crack-deflection behavior. Mechanical testing confirmed the superior reinforcing effect of rGO, with increases of 37.6% in tensile strength (PP/rGO5) and 67.1% in impact strength (PP/rGO10). Rheological and TGA analyses further demonstrated enhanced chain restriction and thermal stability with rGO. Overall, this study provides clear evidence that rGO is a more effective nanofiller for PP than GO.