Bio-based silsesquioxanes nano hybrids for enhancing the tribological performance of silicone oil: A DFT and experimental study

Abstract

A novel, eco-friendly nanohybrid solid lubricant additive was synthesized using oleic acid, a readily available green material. By esterifying the 18-carbon chain of ethyl oleate (EO) and subjecting it to hydrosilylation with triethoxysilane (TES), the ethyl 9-(triethoxysilyl)octadecanoate (S2EO) was created. Nanosized Polymethyl silsesquioxanes (PMSQ) particles (P-NPs) were then modified with S2EO to produce the lubricant additive P-NPs-S2EO for enhancing silicone oil’s tribological performance. The synthesis processes were verified by FTIR, H-NMR, SEM, and EDS, while TGA demonstrated the nanohybrid’s superior thermal stability, showing only 1.8% weight loss at 200 °C. Tribological tests using a pin-on-disk tribometer with P-NPs and P-NPs-S2EO in silicone oil revealed a friction reduction of up to 93%, outperforming traditionally used borax and other silicone-based lubricants. The sustainable synthesis of P-NPs-S2EO, confirmed by Density Function Theory (DFT) calculations, underscores its thermal stability and efficiency as a lubricant additive.