Imidazolium-bis(salicylato)borate Ionic Liquids as Lubricant Additives: the Effect of Alkyl Chain Lengths on the Tribological Performance†

doi:10.7503/cjcu20170205

Abstract

Abstract:

Seven environmental-friendly ionic liquids containing chelated organoborate anions having different alkyl chain lengths were synthesized and then evaluated as potential lubricant additives. The ¹H NMR, TGA and DSC were employed to characterized the structure and thermal properties of synthesized ionic liquids. The tribo-performacne were systematically studied by four-ball machine and SEM-EDX as well. The synthesized ionic liquids were found to be quite stable at room temperature and showed remarkable improvement in the anti-wear properties of the poly(ethylene) glycol(PEG200) lube base. The results showed that ionic liquids as additives significantly reduced the wear of PEG200, and particularly the variation in substituted alkyl chain length on the imidazolium ring monitored the degree of reduction in wear. C₆ImC₈BScB shows the excellent friction reducing properties among all the synthesized ionic liquids, the coefficient of wear scar diameter lubricated by PEG under 392 N corresponding reduced with mass fraction of 27.49%.

Key words: Ionic liquid, Environmental-friendly, Bis(salicylato)borate anion, Alkyl chain length, Anti-wear

CLC Number:

O621

TrendMD:

SUN Liwen, ZHANG Yunxiao, CAI Tao, SHANG Wangji, LIU Dan, TONG Dingyi, LIU Shenggao. Imidazolium-bis(salicylato)borate Ionic Liquids as Lubricant Additives: the Effect of Alkyl Chain Lengths on the Tribological Performance^†[J]. Chem. J. Chinese Universities, 2017, 38(12): 2198.

Figures/Tables 9

References 32

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Compd.	¹H NMR(400 MHz, CDCl₃), δ
D-C₄ImBScB	0.831(t, J=4.0 Hz, 6H, CH₃), 1.159—1.252(m, 4H, CH₂), 1.654—1. 729(m, 4H, CH₂), 4.052(t, J=7.4 Hz, 4H, CH₂), 6.874(dd, J=8.4, 13.2 Hz, 4H, C₆H₄), 7.129(s, 2H, C₆H₄), 7.387(t, J=7.6 Hz, 2H, C₆H₄), 7.858(d, J=7.6, 8.0 Hz, 2H, Imi—CH—CH—), 9.274(s, 1H, Imi—CH)
D-C₆ImBScB	0.813(t, J=6.8 Hz, 6H, CH₃), 1.185[s, 12H, (CH₂)₃], 1.717(t, J=6.4 Hz, 4H, CH₂), 4.056(t, J=7.6 Hz, 4H, CH₂), 6.846—6.898(m, 4H, C₆H₄), 7.015(d, J=2.4 Hz, 2H, C₆H₄), 7.360—7.408(m, 2H, C₆H₄), 7.865(d, J=1.2 Hz, 2H, Imi—CH—CH—), 9.307(s, 1H, Imi—CH)
D-C₈ImBScB	0.855(t, J=6.8 Hz, 6H, CH₃), 1.194—1.271[m, 20H, (CH₂)₅], 1.739(t, J=5.6 Hz, 4H, CH₂), 4.087(t, J=7.6 Hz, 4H, CH₂), 6.845—6.922(m, 4H, C₆H₄), 7.082(d, J=1.6 Hz, 2H, C₆H₄), 7.367—7.410(m, 2H, C₆H₄), 7.859(dd, J=1.6, 8.0 Hz, 2H, Imi—CH—CH—), 9.363(s, 1H, Imi—CH)
D-C₁₀ImBScB	0.871(t, J=6.8 Hz, 6H, CH₃), 1.186—1.298[m, 28H, (CH₂)₇], 1.713—1.763(m, 4H, CH₂), 4.075(t, J=7.2 Hz, 4H, CH₂), 6.837—6.901(m, 4H, C₆H₄), 7.103(d, J=1.6 Hz, 2H, C₆H₄), 7.353—7.396(m, 2H, C₆H₄), 7.850(dd, J=1.6, 7.8 Hz, 2H, Imi—CH—CH—), 9.394(s, 1H, Imi—CH)
C₄ImC₈BScB	0.834(q, J=7.4 Hz, 6H, CH₃), 1.165—1.256[m, 12H, (CH₂)₅ and CH₂], 1.665(dt, J=7.6, 15.4 Hz, 4H, CH₂), 4.039(t, J=7.2 Hz, 4H, CH₂), 6.865(t, J=8.0 Hz, 4H, C₆H₄), 7.144(s, 2H, C₆H₄), 7.379(t, J=7.8 Hz, 2H, C₆H₄), 7.857(d, J=7.6 Hz, 2H, Imi—CH—CH—), 9.260(s, 1H, Imi—CH)
C₆ImC₈BScB	0.789—0.863(m, 6H, CH₃), 1.165—1.242[m, 16H, (CH₂)₅ and (CH₂)₃], 1.684—1.736(m, 4H, CH₂), 4.037(t, J=7.4 Hz, 4H, CH₂), 6.864(t, J=8.6 Hz, 4H, C₆H₄), 7.139(s, 2H, C₆H₄), 7.357—7.399(m, 2H, C₆H₄), 7.855(dd, J=2.8, 9.4 Hz, 2H, Imi—CH—CH—), 9.257(s, 1H, Imi—CH)
C₁₀ImC₈BScB	0.862(q, J=7.2 Hz, 6H, CH₃), 1.186—1.279[m, 24H, (CH₂)₅ and (CH₂)₇], 1.713—1.763(m, 4H, CH₂), 4.073(t, J=7.4 Hz, 4H, CH₂), 6.844—6.913(m, 4H, C₆H₄), 7.092(s, 2H, C₆H₄), 7.384(t, J=7.8 Hz, 2H, C₆H₄), 7.857(d, J=7.6 Hz, 2H, Imi—CH—CH—), 9.331(s, 1H, Imi—CH)

Compd.	¹H NMR(400 MHz, CDCl₃), δ
D-C₄ImBScB	0.831(t, J=4.0 Hz, 6H, CH₃), 1.159—1.252(m, 4H, CH₂), 1.654—1. 729(m, 4H, CH₂), 4.052(t, J=7.4 Hz, 4H, CH₂), 6.874(dd, J=8.4, 13.2 Hz, 4H, C₆H₄), 7.129(s, 2H, C₆H₄), 7.387(t, J=7.6 Hz, 2H, C₆H₄), 7.858(d, J=7.6, 8.0 Hz, 2H, Imi—CH—CH—), 9.274(s, 1H, Imi—CH)
D-C₆ImBScB	0.813(t, J=6.8 Hz, 6H, CH₃), 1.185[s, 12H, (CH₂)₃], 1.717(t, J=6.4 Hz, 4H, CH₂), 4.056(t, J=7.6 Hz, 4H, CH₂), 6.846—6.898(m, 4H, C₆H₄), 7.015(d, J=2.4 Hz, 2H, C₆H₄), 7.360—7.408(m, 2H, C₆H₄), 7.865(d, J=1.2 Hz, 2H, Imi—CH—CH—), 9.307(s, 1H, Imi—CH)
D-C₈ImBScB	0.855(t, J=6.8 Hz, 6H, CH₃), 1.194—1.271[m, 20H, (CH₂)₅], 1.739(t, J=5.6 Hz, 4H, CH₂), 4.087(t, J=7.6 Hz, 4H, CH₂), 6.845—6.922(m, 4H, C₆H₄), 7.082(d, J=1.6 Hz, 2H, C₆H₄), 7.367—7.410(m, 2H, C₆H₄), 7.859(dd, J=1.6, 8.0 Hz, 2H, Imi—CH—CH—), 9.363(s, 1H, Imi—CH)
D-C₁₀ImBScB	0.871(t, J=6.8 Hz, 6H, CH₃), 1.186—1.298[m, 28H, (CH₂)₇], 1.713—1.763(m, 4H, CH₂), 4.075(t, J=7.2 Hz, 4H, CH₂), 6.837—6.901(m, 4H, C₆H₄), 7.103(d, J=1.6 Hz, 2H, C₆H₄), 7.353—7.396(m, 2H, C₆H₄), 7.850(dd, J=1.6, 7.8 Hz, 2H, Imi—CH—CH—), 9.394(s, 1H, Imi—CH)
C₄ImC₈BScB	0.834(q, J=7.4 Hz, 6H, CH₃), 1.165—1.256[m, 12H, (CH₂)₅ and CH₂], 1.665(dt, J=7.6, 15.4 Hz, 4H, CH₂), 4.039(t, J=7.2 Hz, 4H, CH₂), 6.865(t, J=8.0 Hz, 4H, C₆H₄), 7.144(s, 2H, C₆H₄), 7.379(t, J=7.8 Hz, 2H, C₆H₄), 7.857(d, J=7.6 Hz, 2H, Imi—CH—CH—), 9.260(s, 1H, Imi—CH)
C₆ImC₈BScB	0.789—0.863(m, 6H, CH₃), 1.165—1.242[m, 16H, (CH₂)₅ and (CH₂)₃], 1.684—1.736(m, 4H, CH₂), 4.037(t, J=7.4 Hz, 4H, CH₂), 6.864(t, J=8.6 Hz, 4H, C₆H₄), 7.139(s, 2H, C₆H₄), 7.357—7.399(m, 2H, C₆H₄), 7.855(dd, J=2.8, 9.4 Hz, 2H, Imi—CH—CH—), 9.257(s, 1H, Imi—CH)
C₁₀ImC₈BScB	0.862(q, J=7.2 Hz, 6H, CH₃), 1.186—1.279[m, 24H, (CH₂)₅ and (CH₂)₇], 1.713—1.763(m, 4H, CH₂), 4.073(t, J=7.4 Hz, 4H, CH₂), 6.844—6.913(m, 4H, C₆H₄), 7.092(s, 2H, C₆H₄), 7.384(t, J=7.8 Hz, 2H, C₆H₄), 7.857(d, J=7.6 Hz, 2H, Imi—CH—CH—), 9.331(s, 1H, Imi—CH)

Temp./℃	Kinematic viscosity/(mm²·s^-1)
Temp./℃	PEG200	D-C₄ImBScB	D-C₆ImBScB	D-C₈ImBScB	D-C₁₀ImBScB	C₄ImC₈BScB	C₆ImC₈BScB	C₁₀ImC₈BScB
40	22.99	24.09	24.41	24.05	23.83	24.56	24.24	24.28
100	4.20	4.18	4.22	4.19	4.21	4.16	4.21	4.26

Temp./℃	Kinematic viscosity/(mm²·s^-1)
Temp./℃	PEG200	D-C₄ImBScB	D-C₆ImBScB	D-C₈ImBScB	D-C₁₀ImBScB	C₄ImC₈BScB	C₆ImC₈BScB	C₁₀ImC₈BScB
40	22.99	24.09	24.41	24.05	23.83	24.56	24.24	24.28
100	4.20	4.18	4.22	4.19	4.21	4.16	4.21	4.26

Oil sample	Element	Mass fraction(%)	Atomic fraction(%)
PEG200	C	6.81	23.81
	O	3.12	8.18
	Si	0.27	0.41
	Cr	1.72	1.39
	Fe	88.07	66.21
PEG200 and C₆ImC₈BScB	C	8.12	25.69
	O	2.87	6.81
	Si	0.23	0.31
	Cr	1.63	1.19
	Fe	84.63	57.57
	B	1.99	7.01
	N	0.53	1.43