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.
Düzenli et al. (Tue,) studied this question.