Partially Dehydrated Castor Oil-Based Isoalkyl and Polyol Esters as Potential Base Stocks for Industrial Applications

Thirupathi Azmeera1,2, Rajini Punyamurthy2, M.S.L. Karuna2, Siddaiah Vidavalur1,* and Devarapaga Madhu3,*,

1Department of Organic Chemistry, Food, Drugs and water, Andhra University, Visakhapatnam-530003, India

2Centre for Lipid Science & Technology, CSIR-Indian Institute of Chemical Technology, Hyderabad-500007, India

3Department of Chemistry, Indian Institute of Technology Varanasi, Varanasi-221005, India

*Corresponding authors: E-mail: sidduchem@gmail.com; devarapagamadhu4@gmail.com

Abstract

Partially dehydrated castor oil (PDCO) which is of less use in the paint and furniture coating formulations has been modified to develop biolubricant base stocks. PDCO (44.1%, non-conjugated linoleic acid; 32%, conjugated linoleic acid (18:2) isomers and 15.3% ricinoleic acid) obtained from a local industry was hydrolyzed under alkaline conditions. The fatty acids obtained (PDCFAs) in 98% yields were reacted with polyols namely 2-ethyl hexanol, neopentyl glycol, trimethylol propyl, pentaerythritol to obtain respective isoalkyl erters and esters of polyol with >95% yield. The base stocks exhibited very high viscosity indices (187.288 to 187.687), excellent pour point (-25 to -40 ºC) and high flash points (212 to 317 ºC) required for a variety of industrial applications namely metal working, hydraulic, forging, cutting fluid, gear oil applications. The tribological properties of PDCO, exhibited very low WSD (0.72-0.79 mm) and WSVs (0.82-0.83 mm3) with high load carrying capacities (180-220 kg) indicating low friction and less energy losses between the sliding surfaces. This was also accompanied by very high thermo-oxidation stabilities [Oxidation stability (230-242 ºC); Onset temperature (300-381 ºC)] of the base stacks due to branching. Overall all the PDCO isoalkyl and polyol esters exhibited excellent properties suitable for a wide range of industrial applications on par with mineral oil based lubricants.

Keywords

Partially dehydrated castor oil, Polyols, Lubricant base stocks, Oxidation stability, Wear scan.

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