Synthesis and Tribological Assessment of TMP Ester Bio-Lubricant Derived from Stearic Acid Via Sequential Esterification and Transesterification Reactions

9 pages•Published: August 6, 2026

Zulhanafi Paiman, Syahrullail Samion, Aiman Yahaya and Inna Salsabila Nazhifah

Abstract

The transition toward sustainable lubrication systems has driven significant research into chemically modified bio-based lubricants as alternatives to conventional mineral oils. Although mineral lubricants remain dominant in industrial applications, their low biodegradability, toxicity concerns, and reliance on non-renewable resources pose environmental challenges. Fatty acid-derived esters, particularly trimethylolpropane (TMP) esters synthesized from stearic acid, have emerged as promising candidates due to their superior lubricity, high viscosity index, and enhanced oxidative stability. However, the physicochemical and tribological performance of TMP esters is highly dependent on synthesis conditions, especially the reactant molar ratio, which governs conversion efficiency, molecular structure, and final lubricant properties. This study investigates the influence of varying molar ratios on TMP ester yield, physicochemical characteristics, and tribological behavior. Stearic acid was initially esterified with methanol, followed by transesterification with TMP. Sixteen samples with different molar ratios were synthesized within a 3 hours reaction period. Chemical transformation was verified using FTIR spectroscopy while tribological performance was evaluated using a four-ball tribotester, following ASTM D4172 standard and supported by optical microscopy analysis of wear scars. The highest conversion (98.26%) was achieved at a 5:1 molar ratio. FTIR analysis confirmed the existence of ester group in TMP backbone after the transesterification process. The 4:1 ratio exhibited the lowest coefficient of friction, achieving a 18.1% reduction compared to neat TMP, while the 3:1 ratio produced the smallest wear scar diameter, reduced by 11.12%. These findings demonstrate that molar ratio optimization plays a critical role in enhancing esterification efficiency and improving tribological performance of TMP ester bio-lubricants.

Keyphrases: esterification, stearic acid, tmp ester, transesterification, tribology

In: Numpon Mahayotsanun (editor). Proceedings of The 11th International Conference on Tribology in Manufacturing Processes & Advanced Surface Engineering, vol 4, pages 104-112.

Links:	https://easychair.org/publications/paper/xwdC
	https://doi.org/10.29007/ktkc

BibTeX entry

@inproceedings{ICTMP2026:Synthesis_Tribological_Assessment_TMP,
  author    = {Zulhanafi Paiman and Syahrullail Samion and Aiman Yahaya and Inna Salsabila Nazhifah},
  title     = {Synthesis and Tribological Assessment of TMP Ester Bio-Lubricant Derived from Stearic Acid Via Sequential Esterification and Transesterification Reactions},
  booktitle = {Proceedings of The 11th International Conference on Tribology in Manufacturing Processes & Advanced Surface Engineering},
  editor    = {Numpon Mahayotsanun},
  series    = {EPiC Series in Technology},
  volume    = {4},
  publisher = {EasyChair},
  bibsource = {EasyChair, https://easychair.org},
  issn      = {2516-2322},
  url       = {/publications/paper/xwdC},
  doi       = {10.29007/ktkc},
  pages     = {104-112},
  year      = {2026}}

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