Graphene and Carbon Nanotubes as Fillers in Polymer Nanocomposites: Synthesis, Properties, and Applications

Both carbon nanotubes (CNTs) and graphene have been called two of the most eye-catching nanofillers to synthesize advanced polymer nanocomposites, thanks to their outstanding structural, mechanical, thermal and electrical properties. Both the synthesis techniques and intrinsic characteristics of graphene and CNT-reinforced polymer nanocomposites (PNCs) are reviewed critically with a unified framework, thereby emphasizing the complementary role of graphene and CNT, and showing the synergistic behavior. The rationale behind co-reviewing these fillers is due to their common sp2-carbon structure, the processing techniques they use, and that the combination of these fillers has been reported to provide a synergistic improvement of the composite properties. Focus is placed on the performance and comparison of graphene and CNTs compared to traditional fillers like clay, carbon black and silica, and understanding the mechanism of action that provides improved properties of PNCs. Recent advances are included from 2020 to 2026, such as hybrid graphene/CNT systems that have been able to deliver multifunctional performance which would not have been possible using only a single type of filler. The challenges to scalable synthesis, filler dispersion and toxicological characterization are discussed, and solutions to these emerging challenges are presented.