molecular spectroscopic studies of ZDDP—PIBS interactions

Abstract

The effect of the nature and alkyl chain length of zinc dialkyldithiophosphate (ZDDP) (R = C4 to C8) on its interactions with polyisobutenyl succinimide (PIBS) has been investigated using 31P‐NMR and infrared spectroscopy. 31P‐NMR spectra of ZDDP in the presence of PIBS showed both broad (35–850 Hz) and sharp (50–100 Hz) resonance signals due to different modes of interaction, mainly cluster formation and specific complexation, respectively. Single‐ended mono‐PIBS exhibit stronger interactions compared to the double‐ended bis‐PIBS. The proportion of sharp signals due to specific complexes in 31P‐NMR spectra of ZDDP—PIBS blends are in the order: C8 > C5 > C4+C8 > C6 = aryl ZDDP. The effect of PIBS concentration on the strength of complexes has also been studied.

Ultralow Boundary Lubrication Friction by Three-Way Synergistic Interactions among Ionic Liquid, Friction Modifier, and Dispersant

“…While there is no report for the interaction between PIBSI and MoDTC, PIBSI and MoDDP (similar structure to MoDTC) have been found to form a complex structure by the electron pairs of the nitrogen of PIBSI and the Mo of MoDDP. , This may explain how PIBSI suspends/disperses MoDTC in oil. In the meantime, PIBSI was also reported to interact/react with ZDDP , and the interaction/reaction largely depends on the chemical structures of both PIBSI and ZDDP. When PIBSI has a stronger interaction/reaction with ZDDP than with MoDTC in fluid, there would be two negative effects: (i) less ZDDP available leading to weaker wear protection and (ii) less PIBSI available to suspend/disperse MoDTC in oil causing agglomeration/precipitation of MoDTC and consequently deteriorated friction behavior.…”

“…This observation is contrary to some previously reported synergistic effects for MoDTC and ZDDP working together. 21−24 One reason might be the influence of a dispersant/detergent that had been reported to significantly affect the interactions between MoDTC and ZDDP, 23 and certain dispersants 47,48 including PIBSI 49 could react with ZDDP to cause antagonistic effects. Most literatures 21−23 reporting synergism for MoDTC + ZDDP did not use any dispersant/detergent, and the one 24 that used a dispersant/detergent did not disclose the chemistry.…”

“…50,51 This may explain how PIBSI suspends/disperses MoDTC in oil. In the meantime, PIBSI was also reported to interact/react with ZDDP 47,49 1. Compared with the mean COFs, 0.11 and 0.12, and wear volumes, 9.0 × 10 7 and 8.0 × 10 7 μm 3 , for using [N 888 H][DEHP] alone and together with PIBSI in the base oil (see Table S1 and Figure S1), there seems to be a synergistic effect among [N 888 H][DEHP], MoDTC, and PIBSI.…”