NASA Technical Memorandum 106423

_.z)., ;

Infrared Analysis of Vapor Phase Deposited

Tricresylphosphate (TCP)

Wilfredo Morales

Lewis Research Center

Cleveland, Ohio

and

Bengi Hanyaloglu and Earl E. Graham

Cleveland State University

Cleveland, Ohio

January 1994

(NASA-TM-IO6423) INFRARED ANALYSIS

OF VAPOR PHASE DEPOSITED

TRIfiRESYLPHOSPHATE (TCP) (NASA)

20 p

G312T

N94-23371

Unclas

0203585

https://ntrs.nasa.gov/search.jsp?R=19940018898 2019-08-06T14:11:58+00:00Z
(
Infrared Analysis of Vapor Phase Deposited Tricresylphosphate (TCP)

Wilfredo Morales

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135

and

Bengi Hanyaloglu and Earl E. Graham

Cleveland State University

Cleveland, Ohio 44115

Abstract

Infrared transmission was employed to study the formation of a lubricating film deposited

on two different substrates at 700°C. The deposit was formed from tricresylphosphate

vapors and collected onto a NaC1 substrate and on an iron coated NaC1 substrate. Analysis

of the infrared data suggests that a metal phosphate is formed initially, followed by the

formation of organophosphorus polymeric compounds.

Introduction

Tricresylphosphate (TCP) has been used as an antiwear additive in base oils since

the early 1900s. It has been concluded (1) that the antiwear effectiveness of TCP results

from the formation of a phosphate group on a wearing surface. Recently, TCP has been

used in several studies involving the vapor phase lubrication of engineering surfaces at

temperatures in excess of 400°C (2-4). In these studies TCP is vaporized into a carrier gas

where the gas is directed at a hot surface (metal or ceramic). A deposit is formed on the

hot surface over a period of time. In many cases, the resulting deposit was found to be

highly lubricious.
Analysis of the resulting deposit has been attempted. Graham and Klaus (2) used

SEM to suggest that the deposit exists as a polymer. In a different study, Klaus et al. (5)

postulated that the deposit consisted of a bottom layer of Fe3C and a top layer of Fe2P,

Fe2Cs, and FePO4. In this present study, infrared analysis of the deposit was performed to

characterize more fully the nature of the deposit.

Experimental

The equipment used in this study has been described by Makld and Graham (4). It

is basically an oven (Figure 1) where TCP is vaporized into a carrier gas stream and the gas

stream is directed to a stationary substrate at a known temperature. Using a syringe pump,

liquid TCP is introduced into preheated N 2 carrier gas at a constant rate of 1.6 ml/hr. The

TCP concentration was maintained at 1 mole % in the N 2 gas stream flowing at a rate of

200 ml/min. Two different stationary substrates were used: one was a plain NaC1 window

that is typically used in infrared studies, and the other is a NaC1 window that had been

coated with approximately 800 * of iron. Figure 1 shows the dimensions of the substrate.

The substrates were maintained at 700 °C.

A time study was then conducted by first exposing a plain NaC1 substrate to the

TCP vapor stream for 1 minute. A second NaC1 substrate was then exposed to the TCP

vapor stream for 5 minutes, and finally a third NaC1 substrate was exposed to the TCP

vapor stream for 10 minutes. This procedure was then repeated for the iron coated NaC1

substrates. A transmission infrared analysis was then performed using a Nicolet fourier

transform infrared unit.
Resultsand Discussion

1. Plain NaC1Substrate

Figure 2 is the infrared (IR) spectrumof the 1 minutedepositon a plain NaC1

substrate. Analysis of this spectrumsuggeststhat the depositmay bea sodiumtriphosphate

compoundwith molecularformula NasP3010..In additionto the triphosphate,a small

quantity of an organic compound(or compounds)having a P-O-Ar group may be present.

Table 1 lists and comparesmanyof the depositIR peakswith the known IR peaksof the

triphosphate(6). Table 1 also lists the remainingIR peakswith the correspondinggroup

absorptions. Although the 569 cm"1depositpeakcould not be adequatelyassigned,the

presenceof a C1compoundis a possibility sincePC12absorbsin the 590 to 420 cmI range.

KBr powder, containingthe pure compoundNasP3010,waspressedinto a pellet and its

FTIR spectrum(Figure 3) was taken. Comparisonbetweenfigures 2 and 3 shows

agreementbetweennearly all the NasP3010 peaks.

Figure 4 is the IR spectrum of the 5 minute deposit on a plain NaC1 substrate.

Table 2 lists all the peaks present in three groups. Group I lists the sodium triphosphate

compound peaks where all the IR peaks have been diminished or masked by other peaks

(due to the apparent formation of a deposit film). Group II lists peaks corresponding to

CH, aromatic, and P-O-Ar groups.

to the 1 minute deposit spectrum.

Many of these peaks are more intense when compared

Group 3 lists new peaks that were not present in the 1

minute spectrum. Analysis suggests the presence of P-H, P=O, P-O-P, and P-O-Ar groups.

Peaks 1294 cm 1, 1266 cm _, 992 cm 1, and 693 cm "1 are assigned to a pyrophosphate. Only

the 640 cm "1 and 525 cm -i peaks could not be assigned.
The IR spectrumof the 10minute depositon the plain NaC1substrateis shownin

Figure 5. Nearly all the IR peaksfrom the spectrumof the 5 minute depositarepresentin

the spectrumof the 10minute deposit. The only major differencein thesepeaksis that the

10 minute depositespectrumexhibitsmuch strongerabsorptions(possiblydue to the growth

of the depositfilm). The major differencesbetweenthe 10and 5 minute depositsarethe

appearanceof the broadpeak at about2880cm-1,andthe sharppeakat 771 cm1. The

broad peak at 2880cm "1 can be attributed to P-O-H absorption and the peak at 771 cm "1 to

P-O-Ar or P-O-C absorption. The final difference between the 5 and 10 minute deposits is

the severe spectral overlap in the C-H region, prohibiting the detection of any C-H

absorption after the 10 minute deposit. These results indicate that the initial formation of

sodium triphosphate NasP3010 is followed by the appearance of an organophosphorus

compound (or compounds) containing P-O-Ar groups. As time progresses, the chemical

composition of the deposit apparently changes to include P-H, P=O, and P-O-P groups in

addition to the P-O-Ar groups.

2. Iron-Coated NaC1 Substrate

One will notice that the legends and format of the IR spectra shown in Figures 6, 7,

and 9 are different from previous IR spectra. Unfortunately, the FTIR unit that was being

used broke down and this necessitated the use of a different FTIR unit, thus the different

formats.

Figure 6 is the IR spectrum of the 1 minute deposit formed on the Fe coated

substrate. These peaks are not as well defined nor as sharp as the IR peaks found in the

4
plain NaC1substrates.

transmittedthroughthe Fe coatedsubstrate.

presenceof iron phosphate,FePO4o2H20(6).

This is most likely due to the reducedamountof IR radiation

Analysis of this IR spectrumsuggeststhe

Table 3 lists and comparesthe depositIR

peakswith the IR peaksof FePO4o2H20.In addition to the iron phosphatean organic

phosphorousmaterial may bepresent. Table 3 also lists thesepeaks. Peaks2957cm"1,

2911cm_, and 2846cm-1result from C-H absorptions.Peaks982 cm_ and 906 cm_ can

also beattributedto P-O, P-O-C, or P-O-Pabsorptions(ref. 7). Peak 1034cm_ canbe

attributedto P-O-C absorption. KBr powder, containing the pure compound FePO4*2H20,

was pressed into a pellet and its FTIR spectrum (Figure 7) was taken. Comparison between

figures 6 and 7 shows agreement between the major peak assignments of FePO4*2H20.

Figure 8 is the IR spectrum of the five minute deposit. Comparison with the one

minute deposit shows the presence of four new peaks: at 1266 cm _, 1089 cm _, 1017 cm "_,

and 770 cm _. The iron phosphate peaks are no longer detectable (due to the formation of a

deposit film). Peaks 1266 cm _ and 1089 cm 1 can be attributed to P=O absorption whereas

peak 1017 cm I can result from P-O-C absorption. Peak 770 cm _ can be attributed to P-OC or P-O-Ar absorption. The C-H peaks at 2957 cm _, 2911 cm _, and 2846 cm _ are still

present and appear to be stronger.

Figure 9 is the IR spectrum of the ten minute deposit on the iron coated substrate.

Comparison with the five minute deposit reveals no new peaks. The only difference is

stronger absorption of the peaks at 1089 cm "1, 1017 cm I and the doublet at 770 cm -1.

These results indicate that FePO4o2H20 is initially formed on the iron (iron oxide)

coated NaC1 substrate. This is followed by the appearance of a possible organophosphorus
compound(or compounds)having C-H, P-O-C,and possibleP-O-Pgroups. The deposit

grows, covering the suspected iron phosphate layer, and now may consist of C-H, P=O, PO-C, and P-O-P groups.

Conclusions

Analysis of the infrared spectra indicates that the initial product formed, from TCP,

on the stationary hot substrates is a metal phosphate (sodium triphosphate or iron

phosphate). The metal phosphate apparently then serves as an "active" surface for the

formation and growth of possible organophosphorus compounds. The growth of the deposit

could be polymeric in nature; thus, this work supports the suggestion made by Graham and

Klausl

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REFERENCES

Wheeler, D. R., Faut, O. D., "The Adsorption and Thermal Decomposition of

Tricresylphosphate (TCP) on Iron and Gold," Applications of Surface Science 18

(1984), p. 106-122.

Graham, E.E., Klaus, E. E., "Lubrication from the Vapor Phase at High

Temperatures," ASLE Preprint No. 85-AM-1B-1, 40th Annual Meeting in Las

Vegas, Nevada, 1985.

Makki, J. F., "Vapor Phase Lubrication of High Temperature Surfaces," Ph.D.

Thesis, Cleveland State University (1989).

Makki, J., and Graham, E. E., "Formation of Solid Films from the Vapor Phase on

High Temperature Surfaces," Lubrication Engineering, Vol. 47, No. 3, pp. 199-206

(1991).

Klaus, E. E., Phillips, J., Lin, S. C., Wu, N. L., and Duda, J. L., "Structure of Films

Formed During the Deposition of Lubrication Molecule on Iron and Silicon

Carbide," STLE Preprint 1-8 (1988).

Corbridge, D. E. C., Lowe, E. J., "The Infrared Spectra of Some Inorganic

Phosphorous Compounds," J. Chem. Soc., 1954.

Socrates, G., Infrared Characteristic Group Frequencies, John Wiley and Sons, Ltd.,

1980.
Table 1

1 Minme Deposit,PlainNaC1

Peaks Observed (cm 1) N___P__301oPeaks (cm -1)

~1656--->

1215

1149

1095

1031

990

909

754

733

712

1606 -1620w, vb

1265w

1215 s

1146 vs

1095 s

1022w

989 w

912 s,b

798vw,b

753m

731 w

708 s

Peaks Observed (cm "1)

Structural Group Assignment

To Observed Peaks (cm I)

_3356vb

3055

2919

1606

1483

1453

1407

1378

782

618

569

O-H

C-H

C-H

Aromatic str

Aromatic str

Aromatic str

Aromatic str

P-O-At

A-O-At

PC12

8
Table 2

5 Minute Deposit,PlainNaC1

I N__._P__sl01o Peaks Diminished (cm':)

~1656

1215

1152

1095

1031

9O9

782

733

II Peaks Observed (cm 1)

_3400

3053

2965

2919

2872

1606

1484

1454

1400

782

617

III New Peaks Observed (cm:)

2371

1640

1294

1266

1125

992

753

693

640

525

Structural Group Assignments

To Observed Peaks (cm 1)

OH

C-H

C-H

C-H

C-H

Aromatic

Aromatic

Aromatic

Aromatic

P-O-Ar

P-O-Ar

Structural Group Assignments

For Observed Peaks (cm _)

P-H

O-H

P=O

P=O

PH, P=O

P-O, P-O-P

P-O-Ar

P-O-P
Table 3

1 Minute Depositon Fe CoatedSubstrate

Peaks Observed (cm 1)

~3400 b

1625

1102

1064

1005

FePO*2H20 Peaks (cm l)

~3330 s,b

1600

1385

1255vw

1105

1068

1005

850

Peaks Observed (cm 1)

2957

2911

2846

1184

1034

982

9O6

Structural Group Assignment

To Observed Peaks (cm _)

C-H

C-H

C-H

P-O-C

P-O, P-O-C, P-O-P

P-O, P-O-C, P-O-P

10
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3500 3000 2500 2000 1750 1500 1250 1000 750 450

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Figure 2.--Infrared spectrum of I minute deposit. TCP on plain NaCI substrate.

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January 1994 Technical Memorandum

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Infrared Analysis of Vapor Phase Deposited Tricresylphosphate (TCP)

6. AUTHOR(S)

Wilfredo Morales, Bengi Hanyaloglu, and Earl E. Graham

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135-3191

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, D.C. 20546-0001

WU-505--63-5A

8. PERFORMING ORGANIZATION

REPORT NUMBER

E-8260

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

NASA TM-106423

11. SUPPLEMENTARY NOTES

Wilfredo Morales, NASA Lewis Research Center; Bengi Hanyaloglu and Earl E. Graham, Cleveland State University, Cleveland, Ohio 44115. Responsible person, Wilfredo Morales, (216) 433-6052.

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13. ABSTRACT (Maximum 200 words)

Infrared u'ansmission was employed to study the formation of a lubricating film deposited on two different substrates

at 700°C. The deposit was formed from tricresylphosphate vapors and collected onto a NaC1 substrate and on an iron

coated NaC1 substrate. Analysis of the infrared data suggests that a metal phosphate is formed initially, followed by

the formation of organophosphorus polymeric compounds.

14. SUBJECT TERMS

Tricresylphosphate; Vapor phase lubrication; Infrared analysis

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