titanium complex greases

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O R I G I N A L P A P E R

Synthesis, Characterization, and Tribological Behaviorof Neopentyl Polyol Ester-Based and Mixed Oil-BasedTitanium Complex Grease

Jiguo Chen

Received: 26 September 2009 / Accepted: 22 June 2010 / Published online: 6 July 2010

Springer Science+Business Media, LLC 2010

Abstract Four types of titanium complex grease weresynthesized using a 3-l reaction vessel, and their friction

and wear behavior were evaluated using a four-ball tester

in the presence of two base oils: neopentyl polyol ester and

a mixture oil of neopentyl polyol ester, 650SN, and

epoxidized soy bean oil (4.5:2.5:1), with two compositions:

benzoic acid/stearic acid and sebacic acid/stearic acid. The

results indicate that mixed oil-based titanium complex

grease has excellent tribological properties. Moreover,

compositions affect the physical characteristics of titanium

complex grease but have little effect on the friction-

reduction, antiwear, and load-carrying capability of the

same types of oil-based titanium complex grease. Inaddition, base oils also affect the tribological property of

titanium complex grease. Based on scanning electron

microscopy and x-ray photoelectron spectrometer of the

worn surfaces of steel balls lubricated with the different

types of grease, synergistic boundary lubrication was pro-

posed to illustrate the friction-reduction and antiwear

properties of titanium complex grease.

Keywords Titanium complex greaseFriction and wear

Load-carrying capacity Scanning electron microscope

(SEM) X-ray photoelectron spectroscope (XPS)

1 Introduction

A number of studies on thermorheological behavior, tri-

bological performance, application, and effects of different

additives on lubricating grease have been conducted in thepast few years. However, these studies are generally lim-

ited to lithium grease, calcium grease, aluminum grease,

and other types of grease [110].

As one of the most used type of lubricating grease,

titanium complex grease is a high-performance grease with

a high drop point, oxidation resistance, extreme pressure

property, antiwear property, long life, and excellent phys-

icalchemical properties at elevated temperatures [11],

making it suitable for the various tribological applications

of steel plants, power plants, packaging, and fertilizer

industries [12]. Kumar et al. [13, 14] report that the wear

scar diameters of rapeseed oil, diisodecyl adipate, dii-sooctyl azelate, and polyol ester-based titanium complex

grease are 0.6, 1.0, 0.85, and 0.7 mm, respectively,

whereas the friction coefficients are not mentioned. In

addition, little data are currently available on the tribo-

logical behavior and lubricating mechanism of the titanium

complex grease of different components.

Thus, the tribological behavior and lubricating mecha-

nism of four types of titanium complex grease were inves-

tigated in detail, and their physical characteristics were also

characterized in this study. The results can provide guidance

to the tribological applicationof the titanium complex grease

of different components in industrial application.

2 Experimental Details

2.1 Synthesis of Titanium Complex Grease

All materials and additives used in this article were com-

mercial products and were used without further purifica-

tion; all reagents used in the synthesis were of analytical

grade. The base oils used in the experiments were mixed

J. Chen (&)

School of Mechatronics Engineering, Harbin Institute of

Technology, Harbin 150001, Peoples Republic of China

e-mail: [email protected]

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Tribol Lett (2010) 40:149154

DOI 10.1007/s11249-010-9650-0

http://www.paper.edu.cn


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oil and neopentyl polyol ester with a viscosity of

150 mm2 s-1 at 40 C and a flash point[250 C. The

mixed oil was composed of neopentyl polyol ester, 650SN

with kinematic viscosity of 120135 mm2 s-1 at 40 C and

a flash point[255 C, and epoxidized soy bean oil

(4.5:2.5:1, absolute weight) with a flash point[255 C,

iodine values of 60.0 mg I2 g-1

, and acid value\0.35. 2,6-di-tertiary butyl paracresol (BHT) was used as antioxi-

dant of the different types of lubricating grease.

The process was performed in a 3-l reaction vessel using

a mechanical stirrer. The synthetic details and procedure

are as follows: Stearic acid, benzoic acid or sebacic acid,

titanium (IV) isopropoxide (1:1:1 equivalent ratio), and

base oil were mixed at 80 C. Once the saponification

reaction was completed, the mixture was slowly heated to

200210 C after adding water. Afterward, 3060 wt% of

the total base oil was added into the mixture to help it cool

down, as well as 1 wt% BHT. The mixture was then

allowed to cool to ambient temperature and homogenize bya three-roller mill. The whole synthetic process occurred

over a period of 8 h on the average. Therefore, the resulting

grease consisted of 17 wt% titanium complex soap, 1 wt%

antioxidant, and 82 wt% base oil.

2.2 Characterization

The dropping point and penetration of the different types of

titanium complex grease were measured according to

national standards GB/T 3498 (similar to ASTM D2265)

and GB/T 269 (similar to ASTM D217), respectively. The

average values of at least three times tests were reported.Meanwhile, tribological properties were examined at

ambient temperature on an SQ-III four-ball tester (Xiamen,

China). The friction and wear tests were conducted at a

rotating speed of 1450 rpm and loads of 200, 300, 400, and

500 N for 60 min. The maximum non-seizure loads were

evaluated. The PB values were recorded at room tempera-

ture for 10 s. The balls tested were made of GCr15 bearing

steel (AISI 52100) with an HRC 5961. The wear scar

diameters on the steel balls were measured using an optical

microscope to a resolution of0.005 mm. The friction

coefficients were measured and recorded with a strain

gauge equipped with a four-ball tester. For comparison, thetribological properties and physical characteristics of

650SN-based and mixture-based (the mixture of 650SN

and neopentyl polyol ester, 1:1.8, absolute weight) titanium

complex grease were also investigated.

The morphologies of the wear scars were observed by an

S-570 scanning electron microscope (SEM, Hitachi, Japan).

The chemical states of the elements on the wear scars were

determined using a PHI-5700 multifunctional x-ray photo-

electron spectroscope (XPS) to explore the possible tribo-

chemical changes involved in the tribological process. The

XPS analysis regions were about 2 nm to 0.8 mm, and the

exciting source was Mg Karadiation. The binding energies

of the target elements were determined at a pass energy of

29.35 eV with a resolution of0.3 eV, and the binding

energy of carbon (C1s: 284.6 eV) was used as reference.

Before each test, all specimens were cleaned using ultrasonic

bath in petroleum ether and dried at room temperature.

3 Results and Discussion

3.1 Physical Characteristics of Titanium Complex

Grease

The results of the dropping point and penetration of the

different types of titanium complex grease show that neo-

pentyl polyol ester-based titanium complex grease has a

No. 4 (NLGI grade) consistency; the corresponding drop-

ping point of benzoic acid/stearic acid titanium complexgrease is 144 C, and that of sebacic acid/stearic acid

titanium complex grease is 154 C. However, 650SN-

based, mixture-based (the mixture of 650SN and neopentyl

polyol ester, 1:1.8), and mixed oil-based (the mixture of

neopentyl polyol ester, 650SN and epoxidized soy bean oil,

4.5:2.5:1) titanium complex grease has a No. 2 (NLGI

grade) consistency, while the dropping point of mixture-

based (the mixture of 650SN and neopentyl polyol ester,

1:1.8) sebacic acid/stearic acid titanium complex grease is

277 C, but that of 650SN-based benzoic acid/stearic acid

titanium complex grease is 268 C. Moreover, the drop-

ping point of mixed oil-based (the mixture of neopentylpolyol ester, 650SN and epoxidized soy bean oil, 4.5:2.5:1)

benzoic acid/stearic acid titanium complex grease is

266 C, while that of mixed oil-based (4.5:2.5:1) sebacic

acid/stearic acid titanium complex grease is 280 C.

Therefore, when the consistency concentration is 17%, the

synthetic capability of neopentyl polyol ester-based tita-

nium complex grease is better than that of other types of

oil-based titanium complex grease, and the reactive degree

of benzoic acid/stearic acid and sebacic acid/stearic acid

titanium complex grease is above 80%. Furthermore, the

results also show the dropping point of sebacic acid/stearic

acid titanium complex grease is higher than that of benzoicacid/stearic acid titanium complex grease, i.e., composi-

tions affect the dropping point of different types of titanium

complex grease.

3.2 Tribological Behavior

Figure1 shows friction coefficient as a function of test

duration lubricated by different types of titanium complex

grease at 400 N for 60 min. The friction coefficient of

650SN-based titanium complex grease is much lower than

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that of other types of oil-based titanium complex grease,and this becomes slightly different with an increase in time.

In addition, with the exception of 650SN-based titanium

complex grease, the friction coefficients of other types of

oil-based titanium complex grease are basically similar.

The mean friction coefficient in 60 min is shown in Fig.2.

The friction coefficients of benzoic acid/stearic acid and

sebacic acid/stearic acid titanium complex grease have

minor differences, indicating that compositions have little

effect on the friction coefficients of the same types of oil-

based titanium complex grease.

Figure3 shows the wear scar diameter lubricated by

different types of titanium complex grease at 400 N for60 min. Indeed, the wear scar diameters lubricated by

mixed oil-based (4.5:2.5:1) titanium complex grease are

2225% lower than those lubricated by neopentyl polyol

ester-based titanium complex grease. At the same time, the

wear scar diameter lubricated by mixed oil-based

(4.5:2.5:1) benzoic acid/stearic acid titanium complexgrease is reduced by 31.5% as compared to that of 650SN-

based benzoic acid/stearic acid titanium complex grease,

and the wear scar diameter lubricated by mixed oil-based

(4.5:2.5:1) sebacic acid/stearic acid titanium complex

grease is reduced by 11.2% as compared to that of mixture-

based (the mixture of 650SN and neopentyl polyol ester,

1:1.8) sebacic acid/stearic acid titanium complex grease.

These prove that 12.5 wt% epoxidized soy bean oil is

important in the antiwear property of mixed oil-based

(4.5:2.5:1) titanium complex grease. These wear scar

diameters results are consistent with those of Kumar et al.

[11,14]. In addition, the minor differences of these resultsindicate that compositions have little effect on the antiwear

capacity of the same types of oil-based titanium complex

grease.

Figure4 shows friction coefficient and wear scar

diameter as a function of applied load lubricated by dif-

ferent types of titanium complex grease. The friction

coefficient and wear scar diameter of the different types of

titanium complex grease varied in a similar manner with

increasing load and had minor differences, indicating that

friction systems can be lubricated effectively even up to

loads of 200500 N. The minor differences in these results

also indicate that compositions have little effect on theantiwear and friction-reduction capacity of the same types

of oil-based titanium complex grease at 400 N.

Table1 gives the load-carrying capacity lubricated by

different types of oil-based titanium complex grease. The

results show that the PB values of mixed oil-based

(4.5:2.5:1) titanium complex grease are equal to 1100 N.

These values are higher than those of other types of oil-

based titanium complex grease, indicating a 37.5%

increase. This is because 12.5 wt% epoxidized soy bean oil

provides a high load-carrying capacity under boundary

Fig. 1 Friction coefficient as a function of test duration lubricated by

different types of titanium complex grease at 400 N for 60 min

Fig. 2 Mean friction coefficient lubricated by different types of

titanium complex grease at 400 N for 60 min

Fig. 3 Mean wear scar diameter lubricated by different types of

titanium complex grease at 400 N for 60 min

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lubrication. At the same time, the results also show that

compositions have no effect on the load-carrying capacity

of the same types of oil-based titanium complex grease.

3.3 Surface Analysis

In order to understand the lubrication mechanism of dif-

ferent types of titanium complex grease, the morphologies

and spectra of typical elements on wear scar are investi-

gated by SEM and XPS. Figure5 shows the SEM mor-

phologies of the wear scar of steel balls lubricated withdifferent types of titanium complex grease at 400 N for

60 min. The worn surface of the steel ball lubricated by

different types of oil-based titanium complex grease is

characterized by slightly adhesion wear (Fig.5a, c, e, g),

while that lubricated by mixed oil-based (4.5:2.5:1) tita-

nium complex grease is smooth and shows signs of fine

scratch (Fig.5eh). Moreover, the wear scar diameters

lubricated by mixed oil-based (4.5:2.5:1) titanium complex

grease (Fig.5e, g) are smaller than those lubricated by

neopentyl polyol ester-based titanium complex grease

(Fig.5a, c). Those resultsagree with the above-mentioned

wear scardiameters (Fig.3).Figure6shows the XPS spectra of typical elements on

the wear scar of steel balls lubricated by differenttypes of

titanium complex grease at 400 N for 60 min [5,15]. The

corresponding relative atomic concentrations on the wear

scar are shown in Table2. The C1s relative atomic con-

centration (Table2) shows a decreased tendency after

sputtering for C=O, which can be ascribed to the adsorbed

titanium complex grease, and this can be confirmed by the

detailed scan ofthe C1s region at a peak of approximately

286.2 eV (Fig.6a). The binding energy of approximately

399.9 eV (Fig.6c) is attributed to the N of the contami-

nated source. There is an indication of above 1.5% N1s on

the worn surfaces (5060 A) lubricated by neopentyl polyol

ester-based titanium complex grease after 2 min sputtering,

while the relative atomic concentration of N is 0% under

the lubrication of mixed oil-based (4.5:2.5:1) titanium

complex grease. In this case, a relatively high wear scar

diameter under the lubrication of neopentyl polyol ester-

based titanium complex grease can be partly ascribed to the

contamination in the tribo-layer. However, different anti-

wear performances are observed, which can mainly beattributed to the different base oils. In addition, peaks at

709.5, 710.9, and 711.4 eV (Fig. 6b) in the Fe2p region are

attributed to FeO, Fe2O3, and FeOOH, respectively, and the

relative atomic concentration of Fe increases after sput-

tering. This indicates that a lubrication film containing the

different types of titanium complex grease is formed,

which can effectively reduce the friction coefficient. The

Ti2p at a binding energy of 458.7 eV corresponds to tita-

nium dioxide (Fig.6e, f). At the same time, an increased

tendency of the relative atomic concentration can be found

for Ti2p after sputtering. Titanium chemical sediment is

also argued to be present during the tribological process,and titanium dioxide on the worn surface can result in

better antiwear performance. Moreover,the O1s at binding

energies of 529.9 and 530.4 eV (Fig.6d) corresponds to

TiO2 and Fe2O3, respectively.

Based on the above analysis, we found that a lubrication

film is formed during the friction process under the lubri-

cation of titanium complex grease. The lubricant layer

consists of absorbed organic materials coming from the

titanium complex grease itself. In addition, the atomic

concentration of Ti is increased after sputtering. This might

Fig. 4 Friction coefficient and

wear scar diameter as a function

of applied load lubricated by

different types of titanium

complex grease: a Friction

coefficient,b Wear scar

diameter. BS benzoic acid/

stearic acid, SS sebacic acid/

stearic acid, NPEneopentyl

polyol ester, MBO mixed base

oil, SN650SN

Table 1 Load-carrying capacity lubricated by different types of oil-based titanium complex grease

Benzoic acid/stearic acid Sebacic acid/stearic acid

650SN Neopentyl polyol ester Mixed oil (4.5:2.5:1) 650SN and NPE (1:1.8) Neopentyl polyol ester Mixed oil (4.5:2.5:1)

PB(N) 800 800 1100 800 800 1100

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Fig. 5 SEM morphologies of the wear scar of steel balls lubricated

with different types of titanium complex grease at 400 N for 60 min:

a Benzoic acid/stearic acid (neopentyl polyol ester-based oil 9100),

b Benzoic acid/stearic acid (neopentyl polyol ester-based oil 9500),

c Sebacic acid/stearic acid (neopentyl polyol ester-based oil 9100),

d Sebacic acid/stearic acid (neopentyl polyol ester-based oil 9500),

e Benzoic acid/stearic acid (mixed base oil 9100), f Benzoic acid/

stearic acid (mixed base oil 9500),g Sebacic acid/stearic acid (mixed

base oil9100), and h Sebacic acid/stearic acid (mixed base

oil 9500)

Fig. 6 XPS spectra of the typical elements on the wear scar of steel balls lubricated by different types of titanium complex grease at 400 N for

60 min: a C1s, b Fe2p, c N1s, d O1s, e Ti2p, and fTi2p. BS benzoic acid/stearic acid, SS sebacic acid/stearic acid

Tribol Lett (2010) 40:149154 153

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indicate that the tribochemcial reaction of titanium oxide

occurs on the worn steel surface at tribological conditions

to form TiO2, which can deposit on the rubbing surface

firmly and enhance the antiwear capability of titanium

complex grease.

4 Conclusions

From the above experimental results, we draw the fol-

lowing conclusions:

(a) The antiwear property and load-carrying capability of

mixed oil-based (4.5:2.5:1) titanium complex grease

are better than those of neopentyl polyol ester-based

titanium complex grease. Furthermore, compositions

affect the physical characteristics of titanium complex

grease, but have little effect on tribological properties

of the same types of oil-based titanium complex

grease. In addition, different base oils have an impact

on the friction-reduction and antiwear properties of

titanium complex grease.

(b) XPS analyses indicate that a tribochemical titanium

sediment is formed, and lubrication films are thick

under the lubrication of mixed oil-based titanium

complex grease. The synergistic boundary lubrication

film contributes to the significantly improved tribo-

logical performance of mixed oil-based titanium

complex grease.

Acknowledgments The author thanks Professor Jianjun Qu of the

School of Mechatronics Engineering, and Harbin Institute of Tech-

nology for supplying the four-ball tester.

References

1. Delgado, M.A., Valencia, C., Sanchez, M.C., Franco, J.M.,

Gallegos, C.: Thermorheological behaviour of a lithium lubri-

cating grease. Tribol. Lett. 23(1), 4754 (2006)

2. Marchetti, M., Jones Jr, W.R., Street, K.W., Wheeler, D., Dixon,

D., Jansen, M.J., Kimura, H.: Tribological performance of some

Pennzane-based greases for vacuum applications. Tribol. Lett.

12(4), 209216 (2002)

3. Martn-Alfonso, J.E., Valencia, C., Sancheez, M.C., Franco, J.M.,

Gallegos, C.: Development of new lubricating grease formula-tions using recycled LDPE as rheology modifier additive. Eur.

Polym. J. 43, 139149 (2007)

4. Suek, M.W., Bocho-Janiszewska, A.: The effect of metal

8-Hydroxyquinolinates as lubricant additives of the friction pro-

cess. Tribol. Lett. 15(3), 301307 (2003)

5. Wang, L.B., Wang, B., Wang, X.B., Liu, W.M.: Tribological

investigation of CaF2nanocrystals as grease additives. Tribol. Int.

40, 11791185 (2007)

6. Yi, H.L., Dang, K.Y., Zeng, X.Q., Shao, H.Y., Ren, T.H.: Tri-

bological studies of S-N type triazinyl-containing polysulfides as

additives in biodegradable grease. Ind. Lubr. Tribol. 60(2), 7985

(2008)

7. Joly-Pottuz, L., Vacher, B., Ohmae, N., Martin, J.M., Epicier, T.:

Anti-wear and friction reducing mechanisms of carbon nano-

onions as lubricant additives. Tribol. Lett. 30, 6980 (2008)8. Martins, R., Seabra, J., Brito, A., Seyfert, Ch., Luther, R., Igartua,

A.: Friction coefficient in FZG gears lubricated with industrial

gear oils: biodegradable ester vs. mineral oil. Tribol. Int.39, 512

521 (2006)

9. Spikes, H.: Origins of the friction and wear properties of antiwear

additives. Lubr. Sci. 18, 223230 (2006)

10. Lugt, P.M.: A review on grease lubrication in rolling bearings.

Tribol. Trans. 52, 470480 (2009)

11. Kumar, A., Nagar, S.C., Naithani, K.P., Rail, M.M., Bhatnagar,

A.K.: Enhancing further performance properties of titanium

complex grease. NLGI Spokesman 62(6), 2027 (1998)

12. Kumar, A., Nagar, S.C., Mittal, B.D., Kumar, A., Naithani, K.P.,

Bhatnagar, A.K.: Titanium complex grease for girth gear appli-

cations. NLGI Spokesman 63(6), 1519 (1999)

13. Kumar, A., Naithani, K.P., Sayanna, E., Singh, M.M., Rai, M.M.,Bhatnagar, A.K.: Titanium complex grease: a product of high

potential. NLGI Spokesman 59(9), 1218 (1995)

14. Kumar, A., Mittal, B.D., Singh, M.P., Naithani, K.P., Rai, M.M.,

Bhatnagar, A.K.: Ecofriendly titanium complex grease. NLGI

Spokesman 61(8), 2228 (1997)

15. Wagner, C.D., Riggs, W.M., Davis, L.E., Moulder, J.F., Mui-

lenberg, G.E.: Handbook of X-ray photoelectron spectroscopy.

Perkin-Elmer Corporation, London (1979)

Table 2 Relative atomic concentration on wear scar

Composition Based oil Sputter times t(s) Relative atomic concentration(%)

C1s O1s Fe2p Ti2p N1s

Benzoic acid/stearic acid Neopentyl polyol ester 0 61.61 30.97 1.59 4.32 1.51

120 28.33 47.05 10.41 12.48 1.73

Mixed oil (4.5:2.5:1) 0 81.21 14.82 1.37 0.67 1.92

120 66.45 23.41 8.35 1.79 0.00

Sebacic acid/stearic acid Neopentyl polyol ester 0 72.66 21.28 1.54 2.56 1.96

120 47.23 36.66 6.41 8.14 1.55

Mixed oil (4.5:2.5:1) 0 69.27 25.22 1.95 2.28 1.28

120 28.65 50.51 12.20 8.64 0.00

154 Tribol Lett (2010) 40:149154

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