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Illlllllllwl!ll!luulluNATIONAL ADVISORY COMMITI’EEFOR AERONAUTICS 00bLD45

TECHNICAL IVOTE3257

EFFECTS OF CIIEMICAGLYACTIVE ADDITIVES ON BOUNDARY

LUBRICJYCIONOF STEEL BY SILICONES

0

By S. F. Murray and Robert L. Johnson

A previous investigation showed that silicones, which in themselvesare poor lubricants, can be made to lubricate effectivelyby the additionof a solvent, such as a diester, which is believed to increase the ener~of adhesion between the molecule and the surface.

In the presentreport another method of improving the lubricatingquality of silicones was investigated, namely, that”of providing chemi-cally active additives. It has been hypothesized that silicones do notmaintain oxide or other reactive coatings on metal surfaces. Conventionalchemically active additives and more active compounds such as a peroxidewere investigated. It was found that conventional additives were noteffective, but that more active materials such as the peroxide did giveeffective lubrication. However, all the chemically active-type additivesinvestigatedwere inferior to the solvent-type additions such as thediesters previously studied.

INTRODUCTION

Wing the past few yesrs, the use offor specialized applications has increased

silicone fluids as lubricantssteadily. They have the best

viscosity-temperaturerelation of any known class of fluids and a high-temperature chemical stability which is at least as good as that of anysynthetic lubricant now being considered for use in aircraft turbineengines (ref. 1). They therefore merit consideration as lubricants forhigh-temperature applications. However, the silicones are extremely poorboundary lubricants for ferrous surfaces.

An NACA research program has been directed toward finding means ofimproving the boundary-lubrication characteristics of silicones for fer-rous surfaces. Previously reported studies (ref. 2) have indicated thatblends of silicones with 30 to 40 percent by volume of various solvents

.

n

_—— . —.— — .— .. ~ —.— --.—

2 NACA TN 3257P

such as diesters will provide effective lubrication for steel surfaces.This result maybe associatedwith the effect of the solvents on the ge-

.

ometry of the silicone molecule. Silicone-diesterblends appear to have“ considerablepromise as possible engine lubricants.

The lubrication deficiencies of silicones themselves have been as-sociated with failure to maintain an oxide film on steel surfaces (ref.2), where an oxide film is generally considered essential to effectivelubrication. The oxide by itself may prevent welding of metal surfaces(ref. 3) and is essential to the surface chemical reactions necessary b

for effective lubrication with many types of lubricating fluids and :

additives (refs. 4 and 5).

The role of oxygen availability for surfaces lubricated by siliconeshas not been experimentally established. Also, there are only scattereddata on the effectiveness of chemically active lubrication additives inimproving lubrication of steel surfaces by silicones. It has been con-sidered possible that chemically active additives, such as chlorine com-pounds, in silicones could react with steel surfaces and thus the oxidefilm might be replaced with a reaction product, as, for example, an ironchloride film.

Ayatent (ref. 6) has recently been issued describing the use of an .ester of thioglycollic acid and a chlorinated saturated aliphatic mono-hydric alcohol ester of a lower saturated aliphatic acid as an additiveblend for use with silicone fluids. The combination of a sulfur and achlorine containing compound has been found by previous investigation(ref. 7) to be considerablybetl%r than either compound used alone. Thisfinding is corroboratedby the beneficial results, as reported in refer-ence 6, of the couibinationof sulfur and chlorine in the additive ascompared with the results of using either a sulfur or a chlorine additivesingly in silicone.

The object of this report is to present some data indicating theinfluence of available active oxygen on lubricating effectiveness ofsilicones for steel surfaces and also to indicate the influence of con-ventional types of chemically active lubrication additives on lubricationof steel by silicones. The resesrch reported herein was conducted at theNACA Lewis laboratory. I!oundarylubrication experiments were made atroom temperature using a kinetic friction apparatus. Reactive additivesof different chemical structure were studied in various concentrations inthe silicone fluid.

WORKING HYPOTHESES .

The basic structure and the geometry of the silicone molecule arediscussed in a previous report (ref. 2). In this reference, the primary Rhypothesis advanced is that solvents can change the geometry of the sili-cone molecule and thus affect its lubricating ability by allowing close

— .

.NACA TN 3257 3

packing aridmaximum adhesion of the molecule to the surface. The second-ary hypothesis,which is also suggested in this previous report and whichwill be advanced herein, was concerned with the availability of oxygen orother active atoms for the maintenance of a protective film on steel sur-faces sliding in contact. This hypothesis suggests that silicones preventavailable oxygen or other atoms from reacting with steel surfaces to formprotective films, which couldbe explainedby the possibly impervious (tooxygen or other atoms) nature of the adsorbed surface films formed bysilicones.

EXPERIME%CALFLUIDS

The silicone fluid used inmost cases in these tests was a line=dimethyl siloxane polymer. This fluid had a viscosity of 20 centistokesat 25° C and was used as received. An organic peroxide, a series ofchlorine compounds, and two conventional lubricant additives were usedas listed in table I.

APPAR&!?USAND PROCEDURE

Friction app=atus. - The apparatus used was previously describedin reference 2 and is shown schematically in figure 1. The basic ele-ments are the rotating mild-steel disk specimen (RockwellA-50, ~ in.

diam.) and the cylindrical hardened (Rockwell C-60) SAE 1095 steel riderspecimen with a hemispherical (3/16 in. rad.) contact tip. The rotatingspecimen is driven through a belt system by an electric motor coupledwith a variable-speed power transmission unit. Loading is obtained by theuse of dead weights which apply a force throu& the pulley system shown.The friction force is measured by means of four strain gages mounted ona copper-berylliumdynamometer ring and the readings are obtained from anindicating-typepotentiometer calibrated as a strain indicator. The fric-tion coefficient p is the ratio of friction force to applied load andis reproducible to within iO.02.

The specimens were finished by rotating them in a drill press andrubbing the surface with successive grades of abrasive cloth. The diskswere finished with grade 1/2 polishing cloth which left uniform circum-ferential finishing marks with a surface roughness of approximately 30rms as measured with a profilometer. The rider specimens were finishedwith grade 3/0 emery cloth. Prior to use, the specimens were cleaned bythe following sequence of operations: sosking and wiping in naphtha,wiping with clean cloths saturated with an”acetone-benzenesolution,scrubbing with moist levigated alumina powder, rinsing with water to re-move the alumina, testing for cleanlinessby the ability of water to wetthe surface, and removing the water by successive immersion and rinsing “with distilled acetone.

——.———..-.—c ._ ___ ._ _ ——

4 NACA TN 3257.

For all runs with each additive,the procedure to show the effect ofadditive concentrationwas a successive seriesof friction runs using the “same sample of silicone fluid with the various concentrationsmade up bysupplying additional sdditive to this original fluid. The small amount ofwear debris which accumulated in the fluid had no effect on the results.A new set of specimens was used for each run. In order to obtain eachindividual datum point, the appsratus was started with the surfaces incontact at the desired load; as soon as the a~aratus was at the properspeed (120 ft/min) and the friction readings were stable, the data weretaken. The conditions of the experiment included a constant slidingvelocity of 120 feet per minute, loads from 400 to 20~ grams (110,000 to &

N188,000 psi initial Hertz stress), and the bulk fluid at room temperature. m

RESULTS

Preliminary wear tests, which are discussed briefly in reference 8,have shown that with this apparatti, either unstable friction values oran increase in the coefficient of friction is generally accompanied by a “sharp increase in the rate of wear. During the course of these experi-ments, the following observationswere used to evaluate lubricating .effectivenesss:

(1) Onset of instability and high (~ >0 .2) or increasing values for ‘the coefficient of fri-ction

(2) Surface failure (incipient or mass) of the sliding specimens ob-served after the run was concluded

In figure 2 are shown photomicrographs of rider surfaces which are con-sidered typical of those obtained with (a) effective lubrication, (b)incipient failure, and (c) mass failure. Effective boundary lubricationis defined as the condition of no visible surface damage or welding witha stable friction coefficient in the range found common to boundarylubrication.

The results of the experimentsdescribed herein are presented infigures 3 to 13 and also in table I, in which are sumar ized the pertinentobservations on each fluid with respect to optimum concentration, frictioncoefficient, and surface appearance. The optimum concentration of addi-tive is defined herein as the smallest amount which will provide effectivelubrication in these tests, since the use of additives has an adverseeffect on the viscosity index of the silicone and would result in increasedcorrosion. When friction values were unstable, the maximum and minimumpoints were plotted and a vertical arrow was placed between them. Anotherlabel on each curve indicates the maximum load at which effective boundarylubrication (EEL) was obtained.

NACA TN 3257

SILICONE WITHOUT ADDITIVES

Friction data for the 20-centistoke silicone fluid alone are pre-sented in figure 3. As evidenced by high friction and surface welding,the silicone did not provide effective lubrication under any conditionsof this experiment. Accumulation, in the straight silicone fluid, ofvery fine wear debris caused the fluid to be practically opaque beforethe experiment was concluded.

.

.

5

EFFIY2TOF PEROXIDES

Friction data, obtained by adding various amounts of-methyl-~-amylketone peroxide to the silicone fluid, are presented in figure 4(a). Themanufacturer’s data, which specify a minimum of 15.5 percent active oxygenin this compound, were used as the basis for computing the active oxygenpresent. A concentration of only 1.7 percent by volume of methyl-~-amylketone peroxide (0.25 percent active oxygen) was sufficient to lower thecoefficient of friction considerably apd to decrease the amount of weardebris in the fluid, but mass stiace damage continued to occur (at aload of 800 g). Raising the concentration of peroxide to 3.3 percent(O.5 percent active oxygen) brought further improvement by increasing theload at which unstable friction values occurred to a value of approxi-mately 1400 grams. A concentration of 6.7 percent peroxide (1.0 percentactive oxygen) provided adequate lubrication under all conditions used,with no surface damage or welding visible on the friction specimens toloads of 2000 grams. Photomicrographs of the wear spot on the rider andthe wear tracks on the disk are shown in figure 5. Figure 6 shows theriders and disks ~ified. The fine black wear debris characteristicof silicone alone is easily visible on the set of specimens at the left.

In order to show that this effect was due to the active oxygen pre-sent and not to the methyl-n-smyl ketone, a series of friction runs show-ing the effect of various c~ncentrations of methyl-n-amyl ketone in sili-cone are shown in figure 4(b). It is apparent that–at least 30 percentby volume of the ketone is necesssry to achieve the same result that 6.7percent of the ketone peroxide provides. In concentrations greater than30 percent, the methyl-n-amyl ketone is quite beneficial, as discussed indetail in reference 2. –

Daties (ref. 9) has shown that when.mineral oil is used as a lubri-cant for steel sliding against steel in a closed system under reduced airpressure, there is a marked increase in the rate of wear when the airpressure is reduced below 110 millimeters of mercury. The addition of 1percent by weight of benzoyl peroxide lower”sthis critical air pressureto about 1 millimeter of mercury. He concluded that the peroxide con-tinued to repair broken oxide films at an adequate rate for protection ofthe surfaces when the concentration of oxygen in the chaniberwas no longer

6’ NACA TN 3257 .

adequate for this purpose-. It is probable that a similar effect has.taken ~place in these silicone experiments,with the peroxide decomposing on thesurface and providing an oxide layer as a lubricating film..

EFFECT OF CHLORIDES

In the previous report of solvent effect on lubrication by silicones(ref. 2), it was found that the-addition of carbon tetrachloride to thesilicone oil resulted in effective lubrication where a concentration of &10 percent by volume of carbon tetrachloride in silicone was used. This

Nh-)

was in contrast to the 30 to 40 percent by volume of other solvents re-quired, and the difference was attributed to an “E.P.’leffect by thiscompound.

The carbon tetrachloride concentration effect is illustrated in fig-ure 7. These data show that 5 and 7 percent concentrations result inlubrication failure (as shown by instability of the coefficient of fric-tion) at loads of 800 and 1200 grsms, respectively. The 10 percent con-centration resulted in no lubrication failure at loads to 2000 grams.Because of the beneficial results with carbon tetrachloride, chlorine was -chosen as a suitable element to replace oxygen.

The first series, chosen because they differed only slightly in mole-cular weight and geometry and contained almost the same percentage ofchlorine, shows clearly the effect of the change in reactivity of thechlorine atom. Figure 8(a) is for propionyl chloride, a very reactiveacid chloride. A concentration of about 2 percent by volume was suffi-cient to provide effective lubrication oyer the entire range of loads.Figure 8(b) shows that 20 percent by volume of methallyl chloride (fairlyactive chlorine atom) was necessezy to provide effective ltirication overthe same range of loads, and n-butyl chloride, which contains a relativelyinactive chlorine atom, requi=ed more than 30 percent concentration foreffective lubrication over the entire range of loads (fig. 8(c)). Theactual concentration was not determined, but the amount of improvementobtained with 30 percent and previous experience with the use of solventsindicated that between 35 to 40 percent would be necessary.

For an aromatic series of chloride coqounds, figures 9(a) and (b) ‘show that benzyl chloride and benzotrichloride did not differ significantly,both being required in concentrations of about 10 percent by volume foreffective lubrication. In figure 9(c) the effect of the chlorine substi-tuted in the ring, where it is stabilized by resonance and therefore isnot chemically active, is shown by the fact that 35 to 40 percent of~-chloroethylbenzene is required. It is probable that this material,unlike most of the other chlorine compounds, was acting in accordancewith the solvent hypothesis as discussed in detail in reference 2.

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M

.

NACA TN 3257 7

In view of the results obtained with ~-chloroethylbenzene,which hasthe chlorine substituted in the ring, it is interesting to note (fig. 10)that a methylphenyl silicone fl’uid,in which the phenyl groups also havechlorine substituted in the ring, gave a slight decrease in friction butlubrication fad-lurestill occwred; the improvement is therefore not con-sidered significant. Varying the temperature of the bulk fluid from 75°to 300° F did not change the friction results. (These data are not shown.)It is probable that under these conditions the chlorine which is substi-tuted into the phenyl side groups attached to the silicone chain will notreact with the surface unless the bulk metal surfaces can reach a tempera-ture high enough to cause appreciable decomposition of the fluid. Thisdecomposition can occur and was probably responsible for the effectivenessof a chlorinated methylphenyl silicone in preventing-mass-failure at thevery high surface stresses encountered in”some unreported runs with amodified SAE machine.

In order to determine the effectiveness of benzyl chloride as anadditive in fluids other than silicones, runs were made with cetane, astraight-chain saturated hydrocarbon, to obtain some basis for comparingthe smount of additive needed in silicone with that required for a paraf-finic hydrocarbon base stock. A sample of cetane was purifiedby re-peated percolation through columns of silica gel and fuller’s earth. Theresults of adding various concentrations of benzyl chloride to this fluidare shown in figure 11. The concentration of additive necessary for ef-fective lubrication with cetane is very small when compared with the con-centration of the same additive needed with the silicone.

EFFEX2TOF VISCOSITY

An attempt was made to determine whether the viscosity of the sili-cone fluid would have an effect on the concentration of additive requiredfor effective lubrication. It was felt,that the use of a higher viscosityfluid might alter the rate at which the khloride compound could diffusethrough the bulk fluid and the adsorbed surface layer of silicone on thesteel, which was being removed during sliding, to repair the chloridefilm. Silicone fluids of various viscosities (10 cs and 100 cs at 25° C)were each used with carbon tetrachloride as the additive. The resultsshowed no significant variations in the required smount (table I).

EFFECT OF OTHER CONVENTIONAL ADDITIVES

Although fatty acids are not considered to be extreme pressure lubri-cating additives, the effect of stearic acid on the lubricating ability ofsilicone fluid was considered of interest because its behavior is in-fluencedby oxide films. Since stearic acid is insoluble and ineffective

—-- .— _ _ .. — —. -.—. .—

8

in the silicone fltid, a mutual solvent, methylethylduced. The results, sho~m in figures 12(b) and (c),stearic acid is ineffective under these conditions.of 1 percent stearic acid to the blend of 20 percent

NACATN 3257 -

ketone, was intro- *indicate that theWhile the additionmethylethyl ketone

and 80 Tercent silicone appreciably decreased the friction coefficient,lubrication failure still occurred. For the blend of 40 percent methyl-ethyl ketone and 60 percent silicone, the addition of 1 percent stearicacid showed no significant difference. For purposes of compaison, theeffect of adding 1 percent stearic acid to cetane and to methylethylketone is also shown (fig. 12(a)). ~ :

Nm

A typical antiwear compound, triethyl phosphate, which has been shownto be quite effective alone or as a petroleum oil additive (ref. 10), wasfound to be soluble in silicone up to a concentra*3-on of about 10 Percent,by volume. However, no improvement in lubrication was obtained with thiscombination of straight silicone plus 10 percent triethyl phosphate (fig.13(a)). A series of runs made with silicone-methylethylketone blendsusing triethyl phosphate in place of stearic acid also showed no ad-vantages t~ be gained by the use of an additive of this type (figs. 13(b)and (c)). .

DISCUSSION OF RESULTS

The mechanisms for the behavior of additives included in this in-vestigation me still obscured by a lack of knowledge of the surfacechetistry of silicones. However, if it is assumed that in some mannerthe silicone inhibits oxide or reaction film formation on ferrous surfaces,the necessity for using relatively large quantities of even highly reactivecompounds to obtain effective lubrication can be explained.

There are several possible ways by which oxidation of the lubricatedsurfaces might be inhibited:

(1) A S1OW rate of reaction which prevents complete repair of thefilm before the slider again passes over a given point. In this regard

it should be mentioned that the experiments reported herein were per-formed at low sliding velocities and therefore, with respect to reactionrate, were less severe than should be expected in practical lubricationapplications.

(2) The silicone molecule itself is preferentially oxidized at thelocal “hot spots.”

(3) The adsorbed surface film formed by the silicone is imperviousto all but the most active atoms.

.

NACA TN 3257 9

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w

The results show that for effective lubrication under the conditionsof these experiments, highly reactive compounds must be used as additivesif low concentrations of additives are desired. This leads to other dif-ficulties, especially corrosion. On the other hand, addition of largerquantities of less reactive compounds or changes in the chemical structureof the silicone molecule (such as chlorination of side groups) necessarilyinvoke a viscosity index penalty and may not improve lubrication exceptat high temperatures.

The use of solvents (such as diesters) in silicones as previouslyreported in reference 2 swears to be a more practical method of obtainingeffective lubrication by silicones than the use of chemically reactiveadditives of the types discussed herein. The data of table 29 of reference1 and unreported experience at the Lewis laboratory indicate that lubri-cation additives can be used with silicone-diesterblends (containingmore than 30 percent diester) more effectively than with silicone alone.

One silicone-solventblend that has indicated promise as an aircraftturbine lubricant is a silicone-diesterblend that has been designatedNACA SD-17 lubricant. This fluid contains one-third (by volume) of di-(2-ethylhexyl)sebacate (Rohm and Haas Plexol 201), two-thirds low phenylcontent methylphenyl polysiloxane (Dow-Corning510 fluid, 100 cs at25° C), and 0.5 weight percent of phenothiazine (Dow Chemical N.F. puri-fied grade).

SUMMARY W RXSULTS

The following results were observed from boundary lubrication studiesconducted with silicones containing chemically active additives to improvelubrication:

1. Boundary lubrication of steel surfaces by silicones can be im-proved by increasing the availability of o~gen through the use of aperoxide additive. Additives that could supply necessary oxygen introd-uce other problems and therefore cannot be considered practical atpresent. The effect of the peroxide additive is substantiatingevidencefor a hypothesis to explain the poor lubricating ability of silicones,which suggests that silicones prevent normally available oxygen from re-acting with ferrous surfaces to form the oxide films that are necessaryfor good boundary lubrication.

2. Conventional types of chemically reactive lubrication additivesmust be used in very high concentrations or be highly active compounds inorder to improve boundary lubrication by silicones. Such usage would re-sult in loss of’good viscometric properties or in increased corrosivity.

———— —

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10 NACA TN 3257 .

3. The use of solvents (such as diesters) in silicones,appears to be ,a more practical method of obtaining effective lubrication by siliconesthan the use of chemically reactive additives.

w,N

Lewis Flight Propulsion Laboratory a-1

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

National Advisory Committee for AeronauticsCleveland, Ohio June 11, 1954

REFERENCES.

hon. : Fluids, Lubricants, Fuels, and Related Materials. Rep. No. PRL5.6, Quarterly Prog. Rep. Jan.-Feb.-Mar., 1953, School of Chem. andPhy&., The Penn. State College, Apr.(038)18193.)

Murray, S. F., and Johnson, Robert L.:ing Boundary Lubrication of Steel by

Johnson, Robert L., Peterson, Marshall

27, 1953. (Contract AF 33

Effects of Solvents in Improv-Silicones. NACATN 2788, 1952.

B., and ’swikert,Max A.:.

Friction at High Sliding Velocities of Oxide Films on Steel SurfacesIh.ndary-Lubricatedwith Stearic-Acid Solutions. NACA TN 2366, 1951.

Dubrisay, R&e, et Goupil, Jean-Jacques: Action sur les m~taux decertains acides organiques en solution clansdes liquides nonComptes Rendus, T. 207, No. 23, Dec. 5, 1938, pp. 1101-1103.

Bowden, F. P., and Tabor, D.: The Friction and Lubrication ofClarendon FYess (Oxford), 1950, pp. 211-214.

Wilcock, Donald Frederick, and Sprung, Murray M.: LubricatingPatent No. 2,597,045, U.S. Patent Office, May 20, 1952.

aqueux.

Solids.

oils.

Prutton, C. F., Turnbull, David, and Dlouhy, George: Mechanism ofAction of Organic Chlorine and Sulfur Compounds in Extreme-PressureLubrication. Jour. Inst. Petroleum, vol. 32, no. 266, Feb. 1946,pp. 90-118.

Murray, S. F., Johnson, Robert L.j and Bisson, Edmond E.: Effect ofHigh Bulk Temperatmes on Boundary Lubrication of Steel Surfaces bySynthetic Fluids. NACA TN 2940 1953.

Davies, C. B.: Influence of Roug@ess and Oxidation on Wear of Lubri-cated Sliding Metal Surfaces. Ann. New York Acad. Sci., vol. 53, .

art. 4, June 27, 1951, pp. 919-935.

Anon.: Triethyl Phosphate. Tennessee Eastman Corp., fingsport (Term.). “(See also Patent Nos. 2,175,877, Oct. 10, 1939 and 2,392,530, Jan.8, 1946.)

, ,

TABLE 1. - SOMMARY OF 0RE23RVATIONS M EFFECT OF ADDITIVE2

Base etock Additive Optiuum Relative activity Coefficient of friction Cocdition of

concentration, of additive at 2CW g for optimam lubri C!3t.ed

yrcent concetiration surface after

running

Silicone (20 CB) None -------------- ----------------- 0.3 Maoe failure

Silicone (20 CS) Methyl-~-emyl ketane 6“.7 Very active 0.1(% EffectivO

~oxide ~en mu.rce

.5ilic0ne (20 CS) Methyl- n-aruyl ketone 40 k“ctive o.13 I&f ective

solvent----------- 0,170 Effective

---- -----

--

Carbon tetracbloride None ------------- -------

Silicone (20 CS) Carbon tetracbloride 10 IActive I U.L!J Iurrectlve

Silicone (100 cB) Carbon t.atrachlor ide 10 IActive 0.12 IEffectin

Silicone (10 ca) Car&Silicone (20 ce) Propi.. d- -------- .—

Silicone (20 cs ) hhthal..ly chloride 2; FairLy acmve I u . LU.3 l1511ecxLYe

Silicone (20 CS) Butyl chloride >30 Inactive Hot determined Illaas fe.ilwe

Silicone (20 CS) Eenzyl chloride 10 Act “-.A-

‘“”ectin

Silicone -(20 cs) Berraotrlchloride 10 Active 0.10s lEffective

Silicone (20 cs ) n-chloroathvlhanz ene 40 Inactive I 0.120 dBff ectivc

-—on t@.rachloride I ii IActive I 0.12 IEffective+onvl .hlr-,rffia ? IV-?y adive 0.103 lHfective

,.,–. ––L,—- , A,-. 1--–-4.-..

;lve I u .LUL Inrr

.—– —., . .. —--——---Ohlorinated ~ -------------- ---------- ------ -

methyl phenyl aIlicone

Cetane E-enzyl chloride 1 Active 0.143 Effective

chlorine source

Mthylethyl ketone 6teUiC acid 1 Strong tendency 0.130 Hfectiva

I for chend.sorption

Catane 8tearic acid 1 Stroog tendency O.lw Effective

for ChdBO@.iOU

Silicone + solvents Thie ie a “blank” reference run 0.230 - 0.349 M%9s failure

Silicone + solvents SLearic acid I~c IStrong tetiency 0.L20 - 0.170 Mass failure

Ifor chemiso~tion I

Silicone + eolventa !CYiethyl phoBplMte SC ]Antiwear agent 0.220 - 0.522 mes failure

Silicone + Solventb TIIia is a “blank” reference run 0.E3 Effective

Silicone + solventb Stearic acid 10 Chemiaorp+,iori 0.160 Effective

Silicone + ‘solventb Triethvl chosuhate ~c lAntiweer aaent 0.170 Hfective

aS1.end of 20 percent methylethyl ketone and SO percent eilicone (20 CE ) .

%.end of 40 percent imthylethyl ketone and 60 percent silicone (20 ce ).

cPercentage edditive ueed is reasonable quantity based on experience tith mineral oils.

12

ltcictionalforce~

cylindricalPw= * —

Lubricatingfluld—

-Drivepulley

\ Weight pan

- Rotating disk spoimen

p[ <.., .Wc.en

I?igln’a1. - Schematicdlagmm of friction apparatusfor etu&Lng boundary lubricationbybulk Mbrictults.

—— -.— ————. ————.-

.

1

NAC.ATN 32-57

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.

,.

(a) lHfective lubrication.

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.... ..

(b) Incipient surface failure.

c-35875

(c) Mass surface failure.

Figure 2. - Photomicrographs showing typical wear areas on rider specimens. XIOO.

————c —.——

1

I

4-Io

0 200 400 600 am 10W 1200 14CX3 1600 1803 Zm

Load, g

Figure 3. - B?fect of loed on friction of steel .sliding.against steel lubricated with silicone

f luia . Sliding velocity, 120 feet psr tinute. ~

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NACA TN 3257 15

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.

llethyl-~-amylketone.5 p-erofide (percent

by volume)

a 3.3

.4 ‘\ ——— Silicone alone

.3-

.2EEq

{

.1n Em’o:~

%@

; (a)Methyl-~-amyl ketoneperofi=

$ Methyl-n-an@ ketone”3!h

(perceEt by volume).o

*A 6.7

g .5d:$!%(alG —— Sillcone alone

.4

.3 I

1

.2— -

.1

n.400 64)0 80Q lcmo 12CX3 1400 1600 1800 2000 2200

L@, g

(b) Methyl-~-smyl ketone.

Figure 4. - Effect of concentration in silicone of methyl-~-anwl ketone perotide andmethyl-n-amyl ketone on coefficient of friction of steel against steel. Sllding

velocity, 120 feet per minute; EBL, effective bonndary lubrication.

—. .— —

16 NACA TN 3257.

.

Rider specimen

(b) Silicone(20cs ) +

Disk specimen

:a)Silicone(20CS).

1.7 percent methyl-~-amgl ketone peroxide.

(c) Silicone(20 CS) + 6.7 percent methyl-~-amyl ketine peroxide.

Figure 5. - Photomicrographs showing effect of peroxide addition on wearof riderand disk specimens. =5.

areas

.

..

.

——. .———..

CZ-3 3297

g

I

~,.=. — . . . . . . .. . .___ -— __

‘rWear debris on rider

\ ~ mar debri. on disk

SUlcone Addition of 1.7 Addition of 6.7percent peroxide percent peroxide

—- . ... ...—.. .,, ._. . .. . .______ _ C-3.W76

Eigure 6. - Photograph of rich? @ad disk qmim?.w sbxing hmvy w debris with81UOOM and im’p~ Obtatied by two .sddltiona of peroxide.

18 I?ACA m 3257

Q-10

——— Silicone (20 CS)

\ -- _

.3-—.

(

.2- y & e) t> c) c

f,h r+ A

(a) 100 percent carbon tetrachloride..4-

.3

.2 ~ .

(>\f

.1 +

(b) 5 perceot carbon tetmchloride.

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.3— —

.2 T.

A

& A A \ A 4

.1 1 A t

(c) 7 percent carbon tetracbloride.

.4-

.3

.

.?,

.1400 m &xl 10CKI 1200 1400 1600 1800 21XKJ

m, g

(d) 10 percent cartin tetrachlorlde

Figure 7. - Effect of concentration of carbou tetrachlorlde in sil.lcom (20 cs at 23° C)on coefficlent of friction. Sllding velocity, 1.20feet per minute~ EBL, effectivebmmiary lubrication.

(J!N

3

.

—

.

————.. . ..-— —_ ———..— _

NACA TN 3257 19

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1I

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(a) Propionyl chloride.

Additive, percentby VOhUE

~ 1:\ L J

20

——-silicone (20Cs)-.

‘1J— _-r +- . –

)7

— _—

— ._

(b) Methallyl chloride.

400 Eao e03 Km 1.2CKI 14m 1HX3 IBa3 mmbaa, g

(c) g-htyl chloride

Figo.re8. - Effect of concetiration o a series of chlorides of different%reactivity in silicone (20 m at 25 C) on coefficient of friction.

Sliding velocity, 120 feet ~r minute; EE., affective boundary lubrication.

. .—... .—.—-——.. . —. . . ..—

20 NACA TN 32~

.4

.s

.2

.1

Additive,percentby Volulne

\ \

$4

r- 8- .

I —A——siiC020(20CS)

r ~

-1! ~ - P !?

f 3

(a) Benzyl chloride.

(b) Benzotrichloride.I 4

Additive,percentby VOIUmS

15 .

: 2s.4 \

, I , , , I

A 40

\ _ ———silicone (20 Cs )

-.

3— ._

— —.3k

1 r h t 3 r1

.2 I 1 I

xv *A

TQ , )\ + T

.14043 600 em 1000 1200 14c0 16J2Q 18WI 20CUI 2200

Load,g

Figure 9. - Effect of concentration of a series of aromtic chlorldes of differentreactifltles in silicone (20 cs at 25° C) on coefficient of friction. Slidlngvelocity, 120 feet per tinute; K2L, effecttve boundary lubrication.

.

0

.

.

.5

.— —- ——.—— ——.— _

——— Silicone (20 CB at 25° C)

from fig. 3

.5 o Chlorinated methylphenyl

silicone (71.1 cs at 25° C)\ H\‘\

.4

*\ )

— —

.3 1c)

.2 ~ \w

.11200 400 600 800 Km 1200 1400 16W 1600 2CO0

Lad, g

Figure 10. - Effect of load on friction of steel

mathylphenyl silicone fluid with phenyl groups

feet per minute.

sliding against steel lubricated with

chlorinated. Sliding velocity, ,120

.8 -

.7

.6

.5

0 Cetane1

0 Cetane + 1 Mrcetrt

benzyl chloride

,40 Cetaue + 5 percent,

benzyl chlorlde

.3 /

(i 1

/

[H

Y

.#

A

4 k sf ? *mL-

-4

“km m Mm lom lza) 1400 Mm MOO 2(H3

Load, g

Figure 11. - EKCect of concentration of benzyl chlorldc in cetane. EL, effective

boundary lubrication.

NN

L . 1

L6Z’2. ,

.

NACA.TN 32V 23

+ 1 percent

stearic acidN

.L

(a) Methylethyl ketone and cetane.

O 20 Percent methylethyl ketone +80 percent silicone (20 cs)

.4 & 99 Percent blend [20 percent methyl-ethyl ketone + 80 percent silicone(20 cs~ +1 percent stearic acid

.3

.2’ 1

.1

(b) Blendof 20 percentmethylethylketone+80 percentsilicone(2oCS).

.3040 Percent methylethyl ketone +

50 percemt silicone (20 cs)099 Percent blend 140 percent methyl-

ethyl ketone + 60 percent silicone(20 CS] +1 percent stearic acid

.2 <v

3 r19

400 600 800 1000 1200 1408 1600 1800 20@3

Load, g

(c) Blend of 40 percent methylethyl ketone plus 80 percent silicone (20 CS).

Figure 12. - Effect of adding 1 percent by weight of stearic acid to variousblends of methylethyl ketone in silicone (20 cs at 25° C) on coefficientof friction. Sliding velocity, 120 feet per minute; E8L, effectiveboundary lubrication.

———.— —-——. — .—— _

24 NACA TN 3257

.5 ‘--- silicone (20 Cs)d Silicone(20cs) + 10 perceut

triethyl phoephste

(>b Methylethylketone+ 5 percexrt

, triethyl phosphate

..41+\ ~ ~

- 1c> \ - ~ ~- —. -_

.3&

~

.2~ * ~a

L r\ r\

.“’ (a) Effectof adding triethyl phosphate to sillcone (20 CS) snd methylethyl ketone.

tj$.

0 20 Percentmethylethylketone +* JXlpercentsilicone(20 cs)

~A 95 Percent blend PO percent methyl-

ethyl ketone + SO percent silicone

: .4(20 csfl + 5 percent trlethyl phosphate

*

A 1$

htJ

g

~ “3

r &

3s

— ..

8g .2v

.1

.

(b) Blend d 20 percent methylethyl ketone plus SO percent silicone (20 CS) .

.3

.2

.1400 ‘Em Soo 10CM) 1200 1400 16ixl 1800 2Cixl

Loea, g

(c) Blendof 40 percent methyletbyl ketone plus S0 percent silicone (20 CS).

- Figure13. - Effectof adding5 percent (by weight) of trietbyl phoephd.e to verioueblends of methylethyl ketone in silicone (20 cs at 25° C) on coefficietiof frlctiou.SIwd, lm feet per minute; IISL,effectiveboundsry lubrication.

NACA-La@ey - 8-20-S4 -1044

—. ——. -. —