Experimental and molecular dynamics simulation based investigation to understand tribological performance of graphene reinforced thermoplastic polyurethane (Gr/TPU) nanocomposites

Ongoing innovative research in tribology aims to develop high-performance polymer nanocomposite (PNC) materials that offer significant improvements in efficiency, reliability, and durability across various engineering systems. Selection of appropriate nanoreinforcements is crucial for maximizing the tribological behavior in PNCs. The primary objective is to investigate how various factors, such as graphene (Gr) loadings, processing techniques, normal loading, and sliding velocity influence the tribological behavior of thermoplastic polyurethane (TPU) and graphene reinforced thermoplastic polyurethane (Gr/TPU) nanocomposites using molecular dynamics (MD) simulation and experiments. Nanocomposite materials fabricated by ultrasonication methods, test specimens are prepared in appropriate dimensions as per ASTM (American Society for Testing and Materials) and DIN (Deutsches Institut für Normung) standard. MD simulations are conducted on the developed plate and rod models under different sliding velocity, pressing and stabbing depth conditions to understand fundamental insights into the friction and wear mechanisms of Gr/TPU nanocomposites at the atomic level. Morphological studies using scanning electron microscopy (SEM) micrographs indicate no case of Gr agglomeration up to 3 wt% Gr/TPU nanocomposite. Energy dispersive spectroscopy (EDS) analysis confirms presence of Carbon (c), Nitrogen (N) and Oxygen (O) in Gr/TPU nanocomposites. Finally the obtained results from MD simulation and experiments show a significant trend of similarity. • Abrasion testing where maximum relative volume loss is found as 46.85 mm 3 in for 3 wt% Gr/TPU nanocomposite. • Minimum coefficients of static and dynamic friction values are found as 0.44 and 0.36 in coefficient of friction test. Further addition of Gr in TPU matrix cause increase in both COF and abrasion rate (AR). • From MD simulation based tribological study, it is observed that increase in sliding velocity, and both the values of COF and W R are decreased in wear models up to 3 wt% of Gr addition. But increase in sliding velocity, both the values of COF and W R are increased in friction models up to certain amount of Gr addition. • SEM micrographs show that there is no case of Gr agglomeration up to 3 wt% Gr in the Gr/TPU nanocomposite. Presence of more than 3 wt% Gr in TPU matrix, cause cracks, distortions and agglomerations which one observed in SEM micrographs. Energy dispersive spectroscopy (EDS) analysis confirms that Carbon (C), Nitrogen (N) and Oxygen (O) are present in Gr/TPU nanocomposites.