Theoretical and experimental studies of pyranopyrazoles and their tribological compatibility with a borate ester
Kavita and J Kuntail and DK Verma and B Kumar and AK Singh and N Shukla and I Sinha and RB Rastogi, COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS, 606, 125497 (2020).
The tribological properties of fused heterocyclic ring systems have been scarcely studied. Generally, increased heteroatoms in such molecules should make them better additives. Accordingly, antiwear behavior of substituted pyranopyrazoles (PPz-R, where R=H, methyl and methoxy), compounds with fused heterocyclic rings, have been investigated in the present research. These compounds were characterized by FTIR and NMR (H-1 and C-13) spectroscopy. Their tribological activity followed the order PPz-OMe > PPz-Me > PPz-H > ZDDP (standard). Atomic force microscopy (AFM) and scanning electron micrographs (SEM) of wear scar lubricated with pyranopyrazoles exhibited surface smoothness according to tribological results. The energy-dispersive X-ray (EDX) spectroscopy analysis revealed the heteroatoms nitrogen and oxygen of additive on the surface. XPS analysis showed that interaction of the best additive, PPz- OMe with a borate ester (Van lube 289), increased the efficiency synergistically. Results of DFT calculations on the interaction between adsorbent and substituted pyranopyrazoles are in agreement with the experimental data. The order of adsorption energies found using molecular dynamics (MD) simulations, correlated very well with the additive activity order. Furthermore, MD studies gave the conformation of the additive molecules on the adsorbing surface, paving the way to an understanding of the mechanism of adsorption and triboactivity.
Return to Publications page