Novel Triazine Schiff Base-Based Cationic Gemini Surfactants

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Novel Triazine Schiff Base-Based Cationic Gemini Surfactants: Synthesis and Their Evaluation as Antiwear, Antifriction and Anticorrosive Additive in Polyol Raj Kumar Singh, Aruna Kukrety, Rakesh C. Saxena, Gananath D. Thakre, Neeraj Atray, and Siddharth Sankar Ray Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.5b04242 • Publication Date (Web): 22 Feb 2016 Downloaded from http://pubs.acs.org on February 24, 2016

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Industrial & Engineering Chemistry Research

Increased lubricity property of polyol base oil by blending 14-MTR-14 159x121mm (96 x 96 DPI)

ACS Paragon Plus Environment


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Novel Triazine Schiff Base-Based Cationic Gemini Surfactants: Synthesis and Their Evaluation as Antiwear, Antifriction and Anticorrosive Additive in Polyol Raj K. Singh,*,† Aruna Kukrety,† Rakesh C. Saxena,† Gananath D. Thakre,‡ Neeraj Atray,§ and Siddharth S. Ray† Chemical Science Division, ‡Tribology Division, §Biofuels Division, CSIR-Indian Institute

†

of Petroleum, Dehradun 248005, India

ABSTRACT: Two novel triazine Schiff base-based cationic gemini surfactants namely N,N’-bis{(p-(N,N,N-tetradecyldimethylammonium bromide)benzylidene} 6-methyl-1,3,5triazine-2,4-diamine (14-MTR-14) and N,N’-bis{(p-(N,N,N-tetradecyldimethylammonium bromide)benzylidene} 6-phenyl-1,3,5-triazine-2,4-diamine (14-PTR-14) were synthesized following the two step reaction. First the intermediate adduct was synthesized by reaction of the 4-(dimethylamino)benzaldehyde with 1-bromotetradecane. In the second step, the germinal surfactants 14-MTR-14 and 14-PTR-14 were synthesized by imine coupling with this intermediate adduct with 6-methyl-1,3,5-triazine-2,4-diamine and 6-phenyl-1,3,5triazine-2,4-diamine respectively. Both were characterized using elemental analysis (CHN), infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and thermogravimetry (TG). The compounds were then evaluated as anticorrosive and lubricity improver additive in polyol lube base oil. Both the surfactants show the similar anticorrosive activities. The antiwear and antifriction characteristics were estimated in terms of average wear scar diameter (AWSD) and average friction coefficient using a four ball test following ASTM D4172B. It was found that the 14-MTR-14 is comparatively more effective than 14PTR-14. 14-MTR-14 reduces the AWSD of the polyol from 690 to 575.83 µm while the average friction coefficient decreases from 0.110 to 0.082 at 4000 ppm doping concentration. 1. INTRODUCTION In present scenario the concept of environmental friendly or green lubricants is increasing day by day due to the increasing environmental hazards caused by spillage, leakages and disposal of spent lubricants to the environment.1 For a lubricant to be environment benign, the additive must also be nontoxic along with the base oil. The conventional popular additives like ZDDP2 are usually environmentally unsafe due to their severe toxicity and low biodegradability.3,4 These are still in use because no alternative green technology with


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comparable performance is available so far. Thus it is a matter of great concern to develop novel efficient eco-friendly additives for the formulation of advanced environment friendly lubricants. Many efforts have been made in recent past5-8 but it has been found that nitrogen containing heterocyclic’s e.g. benzotriazole, benzimidazole, benzoxazole, thiazole and triazine derivatives with compact and stable structures possesses excellent extreme pressure, antiwear and friction-reducing properties, as well as good anticorrosion and antioxidation performances.9-12 Recently among these compounds, triazine derivatives are attaining considerable interest due to their tailorable chemical structure and its low toxicity as well as high thermal stability, oxidation and corrosion resistance characteristics e.g. some good antiwear and extreme pressure additives were developed from triazine by derivatization along with the incorporation of borate ester moiety. The evaluation was done by a four-ball test machine.13 The thermal stabilities, anticorrosive properties and tribological behaviors of three novel triazine derivatives, referred to as ZOO, ZOS and ZDION were evaluated as additive in rapeseed oil and found to have good thermal stability, corrosion inhibiting ability and excellent tribological behaviour.14 The synthesized triazine derivatives having 2,4-bi-alkoxy6-(O,O’-dialkyldithiophosphate)-s-1,3,5-triazine framework were evaluated as antiwear and friction-reducing additives in vegetable oil using a four-ball tester.15 The tribological evaluation of the novel synthetic triazine diester derivatives 2-tris(2-ethylhexyl)-3,3,3-(1,3,5triazine-2,4,6-triyl)-tris(sulfanediyl)tripropanoate dimercapto-1,3,5-triazin-2-ylthio)propanoate tribometer.16

Similarly

(TETST)

(EDTYP)

was

and

2-ethylhexyl-3-(4,6-

done

using

laurylamino-methylthio-1,3,5-triazine-2,4-dithiol

a

four-ball

(TRLA)

and

diisooctylamino-methylthio-1,3,5-triazine-2,4-dithiol (TREA), were found to have excellent tribological properties when evaluated using four-ball friction and wear tester as additive in rape seed oil and synthetic diester.17 Inspite of evaluating so many triazine compounds, it is hard to mention any one as a complete substitute for ZDDP. So more efforts are needed in to be made in this direction because we believe that triazine could be a good feedstock for synthesizing novel multifunctional additive of environment friendly nature. In the present work, the efficiency of novel triazine schiff base based germinal surfactants 14-MTR-14 and 14-PTR-14 as anticorrosive, antiwear and antifriction additive in polyol lube base is discussed on the basis of standard corrosion test and four ball test. The tribological mechanism of additives was also discussed on the basis of morphology and surface protective film analysis of the scar developed on specimen balls by scanning electron microscopy/energy-dispersive X-ray



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spectroscopy (SEM-EDX). Along with improved antiwear and antifriction properties due to the added polar ionic functionalities, the synthesized additives may have the improved anticorrosion property due to the incorporated Schiff functionalities and better solubility because of the long fatty alkyl chain. 2.

MATERIALS AND METHODS

2.1. Materials.

4-(dimethylamino)benzaldehyde,

1-bromotetradecane,

6-methyl-1,3,5-

triazine-2,4-diamine and 6-methyl-1,3,5-triazine-2,4-diamine were purchased from SigmaAldrich. Ethanol and tetrahydrofuran (THF) were purchased from Mark Millipore, Germany and used as received. The pentaerythritol tetra oleate (polyol) was purchased from Mohini Organics Pvt. Ltd. Mumbai, India. 2.2.

Synthesis

of

14-MTR-14

and

14-PTR-14.

4.50

g

(30

mmol)

4-

(dimethylamino)benzaldehyde and 8.40 g (30 mmol) 1-bromotetradecane were taken in a 100 mL round bottom flask along with 50 mL ethanol as solvent. The content was stirred at 100 o

C for 24 h. The intermediate adduct was obtained by removing the ethanol using the rota-

evaporator. The yellow coloured product was obtained with 9.45 g yield. In the next step, 0.65 g (5.2 mmol) 6-methyl-1,3,5-triazine-2,4-diamine was reacted with 4.43 g (10.4 mmol) synthesized intermediate with 20 mL ethanol and 5 mL THF as solvents. The content was stirred at 100 oC for 24 h and finally the dark yellow coloured product was obtained by removing the solvent using rota-evaporator. Washing was done with THF three times to obtain the pure compound. The yield obtained of the final product 14-MTR-14 was 1.52 g. Similarly for synthesizing the 14-PTR-14, 0.97 g (5.2 mmol) 6-phenyl-1,3,5-triazine-2,4diamine was taken in place of 6-methyl-1,3,5-triazine-2,4-diamine and the bluish green product 14-PTR-14 was obtained with 1.80 g yield. The purity was insured by the NMR as no impurities signals were observed. 2.3. Characterizations. The synthesized intermediate, 14-MTR-14 and 14-PTR-14 were characterized by using various analytical techniques. CHNS analysis was performed on the Perkin Elmer Series II CHNS/O 2400 analyzer. Fourier transform infrared (FTIR) spectra were recorded using a Thermo-Nicolet 8700 Research spectrophotometer by KBr pellet method with a 4 cm-1 resolution. NMR were also recorded on a Bruker Avance 500 spectrometer in the proton noise-decoupling mode with a standard 5-mm probe. Perkin Elmer EXSTAR TG/DTA 6300 was used for recording thermogravimetry curves using aluminum pans. The experiments were carried out under continuous nitrogen flow of 200 mL min-1. The temperature ramp was set at 10 °C min-1. The mass loss was recorded from 30 to 800 °C.


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2.4. Anticorrosion Test. The anticorrosion potential of the synthesized compounds 14-MTR14 and 14-PTR-14 were evaluated using the standard Corrosion Testing Procedure.18,19 At first the carbon steel metal was cut into small pieces of size 15 mm × 10 mm × 2 mm (area 0.6 sq. inches) by machining and milling. After machining and milling these metal pieces were hand polished using carborundum emery paper grade number C 201 AH extra fine. Afterwards, these metal pieces were degreased using xylene–isopropanol mixture (1:1). These coupons were weighed up to an accuracy of 0.1 mg before exposing in base oil and various blends of additive in the base oil. These degreased and pre-weighed metal specimens were suspended using Teflon thread separately in base oil and various blends of additive in the base oil contained in stopped measuring cylinders. These static immersion studies were carried out for a period of 25 days (600 h) at 110 °C maintained in an air oven. The test metal specimens were evaluated after 25 days for qualitative and quantitative estimation of corrosion. After the test duration the metals were derusted using derusting solution (36% HCl containing 5% Sb2O + 4% SnCl2) and finally weighed up to an accuracy of ±0.1 mg. The weight loss of each test metal was recorded and the corrosion rate was calculated according to the equation 1.

CorrosionRate=

Wt.Loss×15.5 = mg /(sq.dm)(day) or mdd ( Area)(Time)

(1)

By taking density of carbon steel (7.8 g/cm3) into account penetration rate was also calculated according to the equation 2.

Penetration Rate =

Wt.loss× 22.3 = mils/ yearor mpy ( Area)(time)(metal density)

(2)

Where wt. loss is taken in mg; area in sq. inches of metal surface exposed; time in days exposed; density in g/cm3; As far as the qualitative examination is concerned, visual surface inspection was carried out for corrosion product, tarnishing, pitting, cracking etc. Photograph of test metals were taken after washing with 50:50 (xylene + isopropyl alcohol).Total acid number (TAN), a measure of the extent of fuel oxidation as well as corrosion was also evaluated before and after corrosion test as per ASTM standard test method (D664-11a).20 2.5. Lubricity Test. The synthesized 14-MTR-14 and 14-PTR-14 were evaluated for antiwear and antifriction potential in terms of average wear scar diameter (AWSD and) average friction coefficient determined by four ball test machine from Ducom, India as per the standard test method ASTM D4172B.21 Samples were prepared by blending the varying



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concentration (1000, 2000, 3000, 4000 and 5000 ppm) of 14-MTR-14 and 14-PTR-14 in polyol. The typical four ball set up consists of a rotating 12.7 mm steel ball having the 392 N load in contact with three similar stationary balls kept in a bowl filled with the sample. Tests were performed at a rotating speed of 1200 rpm and 75 °C temperature for 60 min duration. 3. RESULTS AND DISCUSSION The triazine Schiff base cationic gemini surfactants 14-MTR-14 and 14-PTR-14 were synthesized following the reaction route as shown in Figure 1. The synthesized intermediate and final compounds were first characterized by CHN analysis. According to the results shown in Table 1, the observed values of the elemental analysis are in good agreement with the calculated ones.


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H2N

N N

Br

Intermediate

N+ Br-

O C H

N

+

N

O C H

+

+

N

N

NH2 H2N

N

Br-

NH2

14-PTR-14

14-MTR-14

+N

N

N N

C N H

N C H

N+ Br-

14-MTR-14

N +N Br-

C N H

N N

N C H

N+ Br-

14-PTR-14

Figure 1. Reaction Scheme and the chemical structure of the synthesized cationic gemini surfactants of triazine Schiff base.



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Table 1. The elemental analysis data for intermediate and additives 14-MTR-14 and 14PTR-14a.

Sample

% Content C

H

N

Intermediate

65.75 (64.77)

9.03 (9.45)

3.65 (3.28)

14-MTR-14

63.78 (64.80)

9.53 (8.70)

10.59 (10.08)

14-PTR-14

66.97 (65.79)

8.28 (8.53)

10.13 (9.76)

a

Values in parentheses are calculated.

3.1. FT-IR. The compounds were further characterized by using FT-IR spectroscopy. The FT-IR spectra of the intermediate and additive 14-MTR-14 is shown as Fig. 2 gives the clearcut evidences of the successful synthesis as per molecular strucutre shown in Fig. 1. In the spectrum of the addiive 14-MTR-14, dissappearance of the N-H stretching (primary amine) signal at 3433 cm-1 attributing to the triazine diamine and ˃C=O streching of the intermediate at 1690 cm‒1 (Fig. 2a), appearance of the prominent new peak at 1662.5 cm‒1 corresponding to C=N (imine) stretching along with the persisting characteristic C=N stretching peak at 1533 cm‒1 attributing to triazine backbone. The introduction of tetradecyl fatty chain along with N, N diemthyl groups in the triazine framework is also evidenced by the existence of strong peak at 2924 and 2853 cm‒1 attributing to the asymmetric and symmetric C-H stretching (CH2). Peak appeared at 3000 cm‒1 corresponds to the aromatic C-H stretching. C=C stretching (aromatic ring) were observed at 1601 and 1554 cm‒1. All other bands attributing to the asymmetric C-H bending, symmetric C-H bending, C-N stretching, C-H bending (aromatic) and CH2 rocking appears at 1466, 1372, 1166, 813 and 728 cm‒1 respectively (Fig. 2b).


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100

(a) 1690

% Transmittance

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1600

2853

80

1165

2922

60 813

40 1662.5 1533 1372 1166

3433

20

3000

(b)

4000

1601

2853 2924

3500

3000

2000

1500

1000

-1

Wavenumber (cm )

Figure 2. FT-IR spectra of (a) intermediate adduct (b) 14-MTR-14.

3.2. NMR. Apart from FT-IR, NMR also presents very good evidence in support of the successful synthesis of the 14-MTR-14 and 14-PTR-14. Figure 3 shows the 13C NMR of the additive 14-MTR-14. Signals corresponding to all the carbons present in its molecular structure were clearly observed e.g. signals, observed in the range of 10−50 ppm, correspond to the carbons of the tetradecyl chains of the germinal surfactant, dimethyl groups attached to amine along with methyl group attached with triazine moiety. Signals for aromatic carbons are observed between 110−155 ppm. The presence of C15 carbon signal at 165 ppm is a strong evidence of the imine coupling between intermediate adduct and 6-methyl-1,3,5triazine-2,4-diamine. The C16 and C17 signals appearing at 171 ppm and 190 respectively attribute to the triazine ring carbons.



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Figure 3. 13C NMR of additive 14-MTR-14 in CDCl3. 3.3. TG. TG curves were recorded in order to estimate the working temperature range of the compound as additive. As per thermo-gravimetric (TG) analysis, it was found that the compounds 14-MTR-14 and 14-PTR-14 possess good thermal stability and their decomposition temperature is 170 oC and 175 oC respectively. Figure 4 shows the TG curves of the intermediate adduct and 14-MTR-14. Addition of the trizaine moiety to the intermediate adduct provides some thermal stability to it as the decomposition temperature for the triazine reactants is high e.g. 6-methyl-1,3,5-triazine-2,4-diamine decomposition temperature is 220 oC. The lower thermal stability of the 14-MTR-14 may be due to the presence of the methyl group in place of phenyl in triazine moiety.


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100

Intermediate adduct 14-MTR-14 14-PTR-14

80

60

Weight %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


40

20

0 0

100

200

300

400

500

600

700

800

o

Temperature ( C)

Figure 4. The TG curves of the intermediate adduct, 14-MTR-14 and 14-PTR-14.

3.4. Anticorrosion Test. After characterization, both the compounds 14-MTR-14 and 14PTR-14 were blended in the polyol base oil. Both have solubility due to the presence of tetradecyl fatty chains in their molecular structure. 14-MTR-14 has comparatively high solubility. 14-PTR-14 was solubilising by sonication at 50 oC. As Schiff bases are well known to have the anticorrosion tendency particularly for steel-steel contact.22-25 In view of this, blends in different concentrations of the additives were prepared by sonication if required at 50 oC in polyol and tested first for the anticorrosion activity as per standard corrosion test procedures.18,19 Both the additives were found to be good anticorrosion additive but the performance of the 14-MTR-14 is far better than the 14-PTR-14. According to anti corrosion test results shown in Table 2 for the 14-MTR-14, it can be easily revealed that the anticorrosion activity increases with the increasing concentration and the optimum concentration is 4000 ppm at which the values for the weight loss, corrosion rate and penetration rate decrease to 0.09 mg, 0.09 mdd and 0.01 mpy from the original values of 0.80 mg, 0.83 mdd and 0.11 mpy for the polyol. The acid value difference also decreases from a value of 4.77 for polyol to 2.31 for 4000 ppm 14-MTR-14 blend. The concentration higher than the 4000 ppm shows the negative effect. Similar trends were observed for the 14-PTR-



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14 but it is less effective comparatively. The reason may the more aromatic content in the additive molecular structure as compared to the other.

Table 2. Corrosion behavior of carbon steel in base oil and various blends of additive vis a vis acid values. Samples

Weight Loss (mg)

Corrosion Rate, mdd

Penetration rate, mpy

Acid value mg/g KOH Before

After

Difference

Polyol base

0.80

0.83

0.11

08.62+0.23 13.39+0.64

4.77

1000 ppm 14-MTR-14 in polyol

0.45

0.47

0.06

11.47+0.82 15.55+0.47

4.08


0.20

0.21

0.03

10.74+0.88 13.28+0.49

2.54


0.15

0.16

0.02

13.09+0.76 15.52+0.38

2.43


0.09

0.09

0.01

11.99+0.49 14.30+0.10

2.31


0.14

0.15

0.05

12.42+0.62 15.66+0.33

3.24

3.5. Lubricity Properties. Both the synthesized additives 14-MTR-14 and 14-PTR-14 have the triazine moiety along with the imine and polar germinal quaternary amine groups. Triazine is well known to impart the antiwear and antiwear property13-17 to the molecules while some studies have also revealed that the organic Schiff compounds reacts with the metal surface to form a surface-complex film leading to the hindered metal contact thus providing the friction reducing and anti-wear properties.26 So we have tested the antiwear and antifriction properties too in terms of AWSD and average friction coefficient determined by four ball test machine following ASTMD4172B21 and both were found to have the lubricity characteristics. A graph is shown in Figure 5a having the average wear scar diameter as function of the additive concentration. It is revealed that the synthetic germinal surfactant molecule 14MTR-14 and 14-PTR-14 possess the concentration effect and at 4000 ppm 14-MTR-14 shows the best anti-wear property while 14-PTR-14 shows the best performance at 5000 ppm. For the 14-MTR-14 AWSD is reduced by 16.54 % viz. 575.83+17.03 µm compared with the AWSD lubricated by polyol alone the value for which is 690+12.07 µm. At higher concentration than 4000 ppm it shows the negative effect. Similarly for 14-PTR-14, the reduction in AWSD is observed only 15.43 % at 5000 ppm. The AWSD of the steel ball


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increases slightly when the concentration of the additive 14-PTR-14 is increases beyond the optimum concentration of 5000 ppm also. The antifriction property of the additives 14-MTR-14 and 14-PTR-14 was also evaluated in terms of average friction coefficient as shown in Figure 5b. Both the compounds have the excellent antifriction property. The 14-MTR-14 reduces the average friction coefficient of the blank polyol viz. 0.1109+0.0077 reduces to the value of 0.0823+0.0121 in 4000 ppm blend in polyol. This is a 25.79 % decrease in average friction coefficient. Similarly in 14-PTR-14, 23.15 % decrease is observed at 5000 ppm concentration. Figure 6 shows the relationship between contact time and friction coefficient in case of polyol and at 4000 ppm 14-MTR-14 blend in polyol. After an initial increase, as time of contact increases the friction coefficient also decreases and it becomes minimum in the last of the test revealing the quite stable film. The reason for slightly low antiwear and antifriction activity of 14-PTR-14 may be its low solubility although its thermal stability is slightly higher than the 14-MTR-14. Along with this, the phenyl group may hinder the effective interaction of the polar triazine framework with the metal surface as compared to the 14-MTR-14. However in both the additives, it is clearly evident from the SEM-EDX morphology analysis of the ball worn surface that there exist an interaction between the additive and the metal surface. Figure 7a and 7b shows the SEM micrographs of the worn out test specimens lubricated with blank polyol and 4000 ppm 14-MTR-14 respectively. Clear contour fluctuation and many deep wear furrows can be found after lubrication by polyol base oil. The rubbed surface lubricated by 4000 ppm 14MTR-14 had few deep wear furrows along with the smaller size scar. The EDX analysis shows that carbon, iron, chromium, and oxygen are prominent on the surface lubricated with only polyol owing to the steel surface (Fig. 7c, 7e) while on rubbed surface lubricated with 14-MTR-14, quite high percentage of nitrogen (5.28 wt %) was present (Fig. 7d, 7f) which is a strong evidence favouring contribution from the additive in film formation on the surface and a boundary lubrication function avoided direct contact of the frictional metal pairs. Comparative study of the synthesized germinal surfactant 14-MTR-14 and 14-PTR-14 with the traditional single chain surfactants i.e. sodium dodecyl sulphate (SDS) was also done. As far as the antiwear and antifriction properties are concerned, synthesized compounds are found to be far better than the SDS for which the values of the average wear scar diameter and average friction coefficient at 4000 ppm concentration were found to be 621.67+21.88 µm and 0.0974+0.0069 respectively. The introduced triazine moiety imparts surface complex forming abilities to the synthesized geminis surfactant molecules which



enables them to make a stable protective film and thus showing higher antiwear, antifriction. The sodium dodecyl sulphate (SDS) also forms a layer on the metal surface but may not be so stable to provide it the lubricity characteristics.

0.13

(a) Average Coefficient of Friction

700

Wear Scar Diameter, µm

650

600

(b) 0.12 0.11 0.10 0.09 0.08 0.07

550 0

1000

2000

3000

4000

5000

0

Cocentration of Additive, ppm

1000

2000

3000

4000

Cocentration of Additive 5, ppm

Figure 5. Reduction in (a) WSD and (b) average friction coefficient with increasing concentration of 14-MTR-14 in polyol base.

Polyol 4000 ppm Additive

0.14

0.12

Friction Coefficient

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0.10

0.08

0.06

0.04 0

10

20

30

40

50

60

Time (min.)

Figure 6. Friction coefficient vs. time graph for the polyol and a blend having 4000 ppm 14-MTR-14.


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(a)

(b)

(c)

(d)

Element

Wt %

At %

CK

14.33

37.47

OK

10.18

19.99

CrK

02.10

01.27

FeK

73.39

41.28

Element

Wt %

At %

CK

14.07

35.33

NK

05.28

11.36

OK

07.18

13.54

CrK

02.07

01.20

FeK

71.41

38.57

(e)

(f)

Figure 7. SEM micrographs of the worn out ball test specimens lubricated (a) polyol and (b) 4000 ppm blend of 14-MTR-14 in polyol; EDX results for the worn out ball test specimens lubricated with (c)(e) polyol and (d)(f) 4000 ppm blend of 14-MTR-14 in polyol.



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4. CONCLUSION Two triazine Schiff base germinal surfactants 14-MTR-14 and 14-PTR-14 were synthesized following a two step reaction route. Both molecules has the important triazine moiety along with the imine and the polar quaternary amine groups with the only difference that the 14PTR-14 has the phenyl group in place of methyl as exists in 14-MTR-14. These groups are capable of providing the lubricity and anticorrosion properties by surface film formation. So both the additives were evaluated as multifunctional lubricant additive in polyol (a biolubricant reference fluid) for antifriction, antiwear and anticorrosion properties using standard methods. Both the additives show the tested properties but the 14-MTR-14 is comparatively more effective. 4000 ppm 14-MTR-14 decreases the AWSD and average friction coefficient to 16.54 % and ~26 % respectively in comparison to the blank polyol. The 14-MTR-14 shows good anticorrosive activity at this concentration too. AUTHOR INFORMATION Corresponding Author *Phone: +91-135-2525708. Fax: +91-135-2660202. E-mail: [email protected]. Notes The authors declare no competing ﬁnancial interest. ACKNOWLEDGMENTS We kindly acknowledge Director IIP for his kind permission to publish these results. The Analytical Division of the Institute is kindly acknowledged for providing analysis of samples. REFERENCES (1) Nagendramma, P.; Kaul, S. Development of ecofriendly/biodegradable lubricants: An overview. Renew. Sust. Energ. Rev. 2012, 16, 764. (2) Barnes, A. M.; Bartle, K. D.; Thibon, V. R. A. A review of zinc dialkyldithiophosphates (ZDDPS): characterisation and role in the lubricating oil, Tribol. Int., 2001, 34(6), 389. (3) Hewstone, R. K. Environmental health aspects of additives for the petroleum industry,

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(19) Ailor, W. H. (Ed.), Handbook of Corrosion Testing and Evaluation, John Wiley & Sci, Inc., 1971, p. 119. (20) ASTM D664-11a, Standard test method for acid number products by potentiometric titration, In Annual Book of ASTM Standards, ASTM International: West Conshohocken, PA., 2011. (21) ASTM D4172, Standard test method for wear preventive characteristics of lubricating fluid (Four-Ball Method), In Annual Book of ASTM Standards, ASTM International: West Conshohocken, PA., 2010. (22) Agarwala, V. S.; Rajan, K. S.; Sen, P. K. Synthetic lubricating oil greases containing metal chelates of schiff bases. US patent no. 5,147,567, 1992. (23) Shokry, H.; Yuasa, M.; Sekine, I.; Issa, R. M.; El-baradie, H. Y.; Gomma, G. K. Corrosion inhibition of mild steel by schiff base compounds in various aqueous solutions: Part 1, Corros. Sci. 1998, 40, 2173. (24) Emregül, K. C.; Akay, A. A.; Atakol, O. The corrosion inhibition of steel with Schiff base compounds in 2 M HCl. Mater. Chem. Phys. 2005, 93, 325. (25) Gopi, D.; Govindaraju, K. M.; Kavitha, L. Investigation of triazole derived schiff bases as corrosion inhibitors for mild steel in hydrochloric acid medium. J. Appl. Electrochem. 2010, 40, 1349, (26) Wan, Y.; Liu, W.-M.; Xue, Q. The tribological properties and action mechanism of schiff base as a lubricating oil additive. Lubr. Sci. 1995, 7, 187.


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