Sains Malaysiana 44(3)(2015): 405–412

Lubricity and Tribological Properties of Dicarboxylic Acid and Oleyl Alcohol Based Esters

(Sifat Pelinciran dan Tribologi Ester Berasaskan Asid Dikarboksilik dan Alkohol Oleil)

JUMAT SALIMON*, WALED ABDO AHMED, NADIA SALIH, MOHD AMBAR YARMO

& DARFIZZI DERAWI

School of Chemical Sciences and Food Technology, Faculty of Science and Technology

Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor Darul Ehsan, Malaysia

Diserahkan: 23 April 2014/Diterima: 26 September 2014

ABSTRACT

Synthesis of new lubricants nowadays is increasing to improve the lubricity properties and the quality of lubricant. In the current study, eight diesters with different chemical structures were tested in terms of their suitability as lubricants. The esterification reaction was carried out using Dean-Stark distillation method with some modification. Fourier transformation infra-red (FTIR), proton and carbon nuclear magnetic resonance (1H-NMR and 13C-NMR), were used to verify the chemical structure of the diesters. The results showed that the dioleyl pimelate (DOlP), dioleyl adipate (DOlA), dioleyl glutarate (DOlG), and dioleyl succinate (DOlSuc) showed good low temperature properties with pour point values at -10, -12, -16 and -20°C, respectively. The dioleyl dodecanedioate (DOlD) indicated remarkable flash point value at 305°C and had slightly high oxidative stability temperature (OT) at 183°C. The flash point increased with the number of carbons for dicarboxylic acid used, while oxidative stability was affected by the unsaturated of oleyl alcohol. Tribological study showed that the diesters were non-Newtonian except DOlD, which was Newtonian fluid. All the diesters were found to be boundary lubricants with low coefficients of friction (COF). Overall, the results indicated that all the diesters studied can be used as lubricating base oils.

Keywords: Coefficients of friction; flash point; oxidative stability; pour point; tribological properties

ABSTRAK

Sintesis pelincir pada masa ini telah meningkat untuk menambahbaik sifat pelinciran dan kualiti sesuatu minyak pelincir. Dalam kajian ini, lapan jenis ester berlainan struktur kimia telah diuji kesetabilannya untuk kegunaan pelincir. Tindak balas pengesteran telah dilakukkan dengan menggunakan penyulingan Dean-Stark dengan sedikit pengubahsuian. Struktur kimia diester terhasil dibuktikan dengan menggunakan transformasi Fourier inframerah (FTIR), nuklear magnetik resonan proton dan karbon (1H-NMR dan 13C-NMR). Hasil kajian menunjukkan dioleil pimelat (DOlP), dioleil adipat (DOlA), dioleil glutarat (DOlG) dan dioleil suksinat (DOlSuc) mempunyai sifat suhu rendah yang baik dengan nilai takat tuang masing-masing pada -10, -12, -16 dan -20°C. Dioleil dodekanedioat (DOlD) pula menunjukkan nilai takat kilat yang tinggi pada 305°C dan mempunyai kestabilan oksidatif (OT) yang agak tinggi pada 183°C. Takat kilat ester meningkat dengan peningkatan bilangan karbon asid dikarboksilik yang digunakan, sementara kestabilan oksidatif dipengaruhi oleh ketaktepuan alkohol oleil. Kajian tribologi menunjukkan diester yang terhasil bersifat bukan-Newtonian kecuali DOlD, yang bersifat bendalir Newtonian. Kesemua diester menunjukkan sifat pelincir sempadan dengan pekali geseran (COF) yang rendah. Secara keseluruhannya, hasil kajian menunjukkan kesemua diester kajian boleh digunakan sebagai minyak asas pelincir.

Kata kunci: Kestabilan oksidatif; pekali geseran; sifat tribologi; takat kilat; takat tuang

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*Pengarang untuk surat-menyurat; email: jumat@ukm.edu.my