Aruna Kukrety

Alkyl-chain-grafted hexagonal boron nitride nanoplatelets as oil-dispersible additives for friction and wear reduction.

Hexagonal boron nitride (h-BN), an isoelectric analogous to graphene multilayer, can easily shear at the contact interfaces and exhibits excellent mechanical strength, higher thermal stability, and resistance toward oxidation, which makes it a promising material for potential lubricant applications. However, the poor dispersibility of h-BN in lube base oil has been a major obstacle. Herein, h-BN powder was exfoliated into h-BN nanoplatelets (h-BNNPs), and then long alkyl chains were chemically grafted, targeting the basal plane defect and edge sites of h-BNNPs. The chemical and structural features of octadecyltriethoxysilane-functionalized h-BNNPs (h-BNNPs-ODTES) were studied by FTIR, XPS, XRD, HRTEM, and TGA analyses. The h-BNNPs-ODTES exhibit long-term dispersion stability in synthetic polyol ester lube base oil because of van der Waals interaction between the octadecyl chains of h-BNNPs-ODTES and alkyl functionalities of polyol ester. Micro- and macrotribology results showed that h-BNNPs-ODTES, as an additive to synthetic polyol ester, significantly reduced both the friction and wear of steel disks. Elemental mapping of the worn area explicitly demonstrates the transfer of h-BNNPs-ODTES on the contact interfaces. Furthermore, insight into the lubrication mechanism for reduction in both friction and wear is deduced based on the experimental results.

Development of new ecofriendly detergent/dispersant/antioxidant/antiwear additives from L-histidine for biolubricant applications

Two novel overbased Ca salts of histidine Schiff base esters Ca-HDS-L and Ca-HDS-M were synthesized following a three-step reaction sequence. The histidine Schiff base (HDS) was synthesized first by imine coupling of histidine with salicylaldehyde. Then its phenolic group was esterified using lauroyl chloride and myristoyl chloride to obtain HDS-L and HDS-M, respectively. Finally in the third step, their respective overbased salts Ca-HDS-L and Ca-HDS-M were synthesized by reaction with Ca(OH)2. All the synthesized compounds were characterized using FT-IR, NMR, CHN and TG analysis. Panel coker federal test (FTM 3462), blotter spot test (ASTM D7899), universal oxidation test (IP-306) and four ball test (ASTM 4172A) were used for the evaluation of detergent, dispersant, antioxidant and antiwear activity, respectively, of the synthesized additives in polyol base oil. Both the additives are active but overall Ca-HDS-L is more effective as detergent and dispersant while Ca-HDS-M is more effective as antioxidant and antiwear multifunctional biolubricant additive.

Capacity of thiourea Schiff base esters as multifunctional additives: synthesis, characterization and performance evaluation in polyol

A novel thiourea Schiff base ester TSBE was synthesized following a two step reaction. At first, thiourea and salicylaldehyde were reacted in ethanol to obtain thiourea Schiff base TSB. In the second step, esterification of TSB was done with lauroyl chloride catalyzed by 4-(dimethylamino)pyridine (DMAP) in N,N-dimethylacetamide (DMAc) solvent to obtain the final product TSBE. The synthesized compounds were characterized using CHN analysis, FT-IR and NMR. The antioxidant properties of this additive were assessed via the universal oxidation test (IP-306) and rotary bomb oxidation test (ASTM D2272) while antifriction and antiwear properties were evaluated in terms of the average friction coefficient and average wear scar diameter respectively by doing the four ball test (ASTM D4172). Studies revealed that TSBE had good antioxidant properties. Tests carried out by a four ball test machine indicated that the additive TSBE could reduce the friction to 45.6% and wear to ∼20% when compared with the pure polyol base oil.

Synthesis of a novel efficient antioxidant for use in lubes and biodiesel

A novel phenolic ester Bz-3-tBz was synthesized by reaction between 1,3,5-benzenetricarboxylic acid chloride and 3,5-di-tert-butyl-4-hydroxybenyl alcohol using N,N’-dimethylacetamide solvent and N,N’-dimethylaminopyridine as catalyst. The additive Bz-3-tBz was characterized by CHN, FT-IR, NMR and TG. The Bz-3-tBz was then evaluated as antioxidant additive in polyol by the rotatory bomb oxidation test (RBOT) as per ASTM D2272. The RBOT time for the blank sample containing only polyol base was observed to be 6 min 43 sec. It was observed that Bz-3-tBz in 3000 ppm concentration enhanced the RBOT time to the 15 min 46 sec. It was a significant increase of 2.35 times. The oxidation stability of biodiesel was also found to be increased when Bz-3-tBz was added in to it. The value of induction time determined by the Rancimat test for the biodiesel at 130°C was 0.60 h which was increased to 3.14 h at 2000 ppm Bz-3-tBz concentration.