Jatropha Trimethylolpropane Ester as a Sustainable Biolubricant Enhanced with rGO/MoS2 Hybrid Nanoparticles: Synthesis, Tribo-Rheological Performance, and ANN-Based Predictive Modelling

Growing environmental concerns and stringent sustainability mandates have accelerated demand for high-performance biolubricants as viable alternatives to conventional petroleum-based lubricants. This study synthesized jatropha trimethylolpropane ester (JTMPE) via esterification and transesterification processes, subsequently enhanced with reduced graphene oxide/molybdenum disulfide (rGO/MoS2) hybrid nanoparticles at concentrations of 0.1-1.0 wt%. Successful JTMPE synthesis was confirmed by FTIR spectroscopy, while Raman, XRD, and TEM analyses verified the formation of well-integrated rGO/MoS2 heterostructures and uniform MoS2 deposition on rGO layers. Rheological evaluation demonstrated Newtonian behavior at operational shear rates, with 1.0 wt% loading enhancing dynamic viscosity by 18.2% at 40°C and 38.1% at 100°C, alongside a 16.0% improvement in viscosity index. Four-ball tribological testing revealed that the 0.6 wt% formulation achieved optimal performance, yielding 27.9% friction reduction and 21.9% wear reduction relative to base JTMPE, and a lubrication ratio transition from boundary to mixed lubrication. FE-SEM and EDAX analyses confirmed the formation of chemically enriched tribofilms containing carbon, molybdenum, and sulfur at the worn interface. An artificial neural network model employing Bayesian Regularization with a 16-neuron hidden layer achieved exceptional predictive accuracy (R = 0.99964, MSE = 4.09×10−4), outperforming the Levenberg-Marquardt algorithm in generalization. These findings establish rGO/MoS2-enhanced JTMPE as a high-performance, environmentally responsible lubricant platform for demanding industrial applications.