DEVELOPMENT OF LUBRICATING OILS SUITABLE FOR USE WITH LIQUID OXIDIZERS

QUARTERLY PROGRESS REPORT NO. 3 1 June 1970 - 31 August 1970

Contract NAS8-25510 Control DCN l-X-50-20131(1F)

MRI Project No. 3380-C

For

National Aeronautics and Space Administration George C. Marshall Space Flight Center

Marshall Space Flight Center, Alabama 35812

Attn: A&TS-PR-M

https://ntrs.nasa.gov/search.jsp?R=19710001944 2018-08-29T13:33:15+00:00Z

WASHINGTON, D.C. 20005-1522 K STREET, N.W. AREA 202 293-3800

DEVELOPMENT OF LUBRICATING OILS SUITABLE FOR USE WITH L I Q U I D OXIDIZERS

L. W. Breed R. L. E l l i o t t

QUARTERLY PROGRESS REPORT NO, 3 1 June 1970 - 31 August 1970

Cont rac t NAS8-25510 Cont ro l DCN l-X-50-20131(1F)

MRI P r o j e c t No. 3380-C

For

Nat iona l Aeronaut ics and Space Adminis t ra t ion

Marshall Space F l i g h t Center , Alabama 35812 George C. Marshal l Space F l i g h t Center

Attn: AScTS-PR-M

MtDWEST RESEARCF! BWiTlTUTE 425 VOLKER BOULEVARD, KANSAS CITY, MISSOURI 6411 0 Q AREA 816 561-0202

PREFACE

This r e p o r t w a s prepared by Midwest Research I n s t i t u t e , 425 Volker Boulevard, Kansas Ci ty , Missouri 64110, under Contract NAS8-25510, "Development of Lubr i ca t ing O i l s S u i t a b l e f o r Use With Liquid Oxid izers , f o r t h e George C. Marshall Space F l i g h t Center o f t h e Nat ional Aeronaut ics and Space Adminis t ra t ion. The work was adminis te red under t h e t e c h n i c a l d i r e c t i o n of the Science and Engineer ing As t ronau t i c s Laboratory of the Marshal l Space F l i g h t Center w i t h M r . C. F. Key a c t i n g as t h e Cont rac t ing O f f i c e r ' s t e c h n i c a l r e p r e s e n t a t i v e .

This r e p o r t covers work conducted from 1 June 1970 t o 31 August 1970.

The work a t Midwest Research I n s t i t u t e w a s designated 3380-C and w a s c a r r i e d ou t by Mr. R. L. E l l i o t t and M r . L. W. Breed, who ac t ed as P r i n c i p a l I n v e s t i g a t o r , under t h e supe rv i s ion of D r . C. C. Chappelow, Jr., Head, Organic and Polymeric Materials Sect ion.

Approved f o r :

MIDWEST RESEARCH INSTITUTE

H. M. Hubbard, D i rec to r Phys ica l Sc iences Div is ion

14 September 1970

3 - i i

TABLE OF CONTENTS

Page

Abstract......................... . . . . 3-1

I. Introduction . . . . . . . . . . . . . . . . . . . . . . . 3-2

11. Properties of Modified Fluorine-Substituted Esters . e e . 3-3

. . . . . . . . . . . . A. jD-Alkoxyacetic Acid Esters 3-3 B. Unsymmetrical Esters. . . . . . . . . . . . . . . . 3-5 C. Ester Blends. . . . . . . . . . . . . . . . . . . . 3- 7 D. Water Corrosion . . . . . . . . . . . . . . . . . . 3-9 E. Samples.. 3-11 . . . . . . . . . . . . . . . . . . . .

111. Anticipated Work . . . . . . . . . . . . . . . . . . . . . 3-11

IV. Experimental Part. . . . . . . . . . . . . . . . . . . . . 3-11

A.

B.

Preparation and Characterization of &‘--Alkoxyacetic

Preparation and Characterization of Modified Acids . . . . . . . . . . . . . . . . . . . . . . 3-11

Fluorinated Esters from L-Alkyloxyacetic Acids

Preparation of Fluorinated Esters from tJ’--Alkanols and Various Polyols . . . . . . . . . . . . . . . 3-15

C. and Various Aliphatic Acids . . . . . . . . . . . 3-15

D. Determination of Lubricant Properties . . . . . . . 3-15 E. Water Corrosion Tests . . . . . . . . . . . . . . . 3-21

List of References. . . . . . . . . . . . . . . . . . . . . . . . 3-22

LIST OF TABLES

Table Title Page

I Pour Points, Evaporation Rates, Viscosities, and Viscosity Indexes for New Modified Fluorine- Substituted Esters. . * - . a e . * . . . * \. e . * 3-6

I11 Properties of Unsymmetrical Esters. . e e e . It 3-8 IV Pour Points and Evaporation Rates of Blends of

Fluorinated Ester Fluids. . . . . . . . . . . . . . . 3-8 V Water Corrosion Data. . . e e . . e . a e e e e 3-9 VI Preparation of $-Alkyloxyacetic Acids: First Method e 3-12

I1 Experimental Four-Ball Wear Test Data e . . a e e 3-7

3-iii

TABLE OF CONTENTS (Concluded)

LIST OF TABLES (Concluded)

Table Title

VI1 Preparation of x-Alkyloxyacetic Acids: Second Method. VI11 Properties of $--Alkyloxyacetic Acids a . . . IX Preparation of Modified Fluoro-Substituted Esters From

$--Alkyloxyacetic Acids and Various Polyols . . . e e

X Properties of Modified Fluoro-Substituted Esters. . e .

LIST OF FIGURES

Figure Title

1

6

7

8

9

10

11

12

Corrosion on 52-100 Steel Balls in the Presence of Fluorine-Containing Fluids and Water. e . . e e . . .

Infrared Spectrum of $--Propyloxyacetic Acid (Liquid) . Infrared Spectrum of &-Pentyloxyacetic Acid (Liquid) e

Infrared Spectrum of $--Heptyloxyacetic Acid (Liquid) e

Infrared Spectrum of l,l,l-Trimethylolethane Tris- ($--propyloxyacetate) (Liquid). . e . . . . . . . . .

Infrared Spectrum of l,l,l-Trimethylolpropane Tris- ($'--propyloxyacetate) (Liquid) e . . e e . . . . . . .

Infrared Spectrum of 2,2-Dimethylolpropane Bis-(L- propyloxyacetate) (Liquid). . . . . . . . e . . . . .

Infrared Spectrum of l,l,l-Trimethylolethane Tris- (i-pentyloxyacetate) (Liquid). e . e a . . . e

Infrared Spectrum of l,l,l-Trimethylolpropane Tris- (L-pentyloxyacetate) (Liquid). e e . . . e . . e

Infrared Spectrum of 2,2-Dimethylolpropane Bis($-- pentyloxyacetate) (Liquid). . e e . e . . . . e e e .

Infrared Spectrum of 2,2,3,3,4,4-Hexafluoropropanediol Bis($--pentyloxyacetate) (Liquid) a e . . e . .

Infrared Spectrum of 2,2-Dimethylolpropane Bis($-- heptyloxyacetate) (Liquid). . . e , e a e e

Page

3-13 3-13

3-16 3-17

Page

3- 10 3-14 3-14 3-14

3-18

3-18

3-18

3-19

3-19

3-19

3-20

3-20

3-iv

ABSTRACT

The sea rch has continued f o r f l u o r i n a t e d ester compositions, which have improved vacuum c o m p a t i b i l i t y b u t a t t h e same t i m e have s a t i s f a c t o r y pour p o i n t s and LOX-compatibility, A series of neopentyl polyol esters o f g - a l k o x y a c e t i c a c i d were prepared and screened as f l u i d s f o r use i n g r e a s e compositions du r ing t h e c u r r e n t r e p o r t period. Although t h e evaporat ion rates of t h e f l u i d s were cons ide rab ly lower than those of t h e c - a l k y l 3- me thy lg lu t a ra t e s , o i l s w i th much g r e a t e r v i s c o s i t i e s a t room temperature and h ighe r pour p o i n t s were obtained. Two of t h e experimental f l u i d s had pour p o i n t s as low as -40'F. Improved v i s c o s i t y indexes i n t h i s series seemed t o be r e l a t e d more t o t h e higher v i s c o s i t i e s than t o t h e s t r u c t u r e i t s e l f . When mixed wi th t r i c r e s y l phosphate, t h e f l u i d s performed sa t i s - f a c t o r i l y on the wear tests. Samples of two of t h e f l u i d s have been f o r - warded t o Marshall Space F l i g h t Center fo r LOX-compatibility t e s t i n g . f l u i d compositions based on unsymmetrical esters and on blends of s p e t r i - c a l e s t e r s showed no improvement over t he pure esters i n t h e i r u s e f u l t e m - pe ra tu re range. I n a d d i t i o n a l work, two samples of L - a l k y l S-methylgluta- rates con ta in ing 2 w t . % of t r i c r e s y l phosphate and thickened wi th Vydax 1000 have been prepared and forwarded f o r LOX-compatibility screening:. Also, c o r r o s i o n tests have shown t h a t b i s ( c - p e n t y l ) 3-methylglutarate has a marked e f f e c t on t h e r educ t ion o f r u s t i n g on 52-100 s t ee l b a l l s when t h e b a l l s are s t o r e d w i t h t h e f l u o r i n a t e d f l u i d i n t h e presence of water.

Other

3-1

I INTRODUCTION

The o b j e c t i v e of t h i s work i s p r imar i ly the opt imiza t ion o f the l u b r i c a t i o n p r o p e r t i e s and vacuum c o m p a t i b i l i t y o f s e l e c t e d f l u o r o e s t e r based g reases that were prepared and s tud ied under Contract NAS8-21269. The spe- c i f i c goa l s and t h e accomplishments under Cont rac t NAS8-21269 were reviewed i n Quar te r ly Progress Report No . 1. were presented and publ ished r e p o r t s were c i t e d t o show t h a t a d d i t i v e modi- f i c a t i o n of t h e f l u o r o e s t e r b a s e d g r e a s e s adequate ly improved the wear p r o p e r t i e s i n l u b r i c i t y t es t s and t h a t ox ida t ion-cor ros ion i n h i b i t o r s prob- a b l y were not necessary w i t h i n t h e p ro jec t ed s e r v i c e range of up t o 300'F. The c h i e f l i m i t a t i o n on t h e f l u o r o e s t e r compositions w a s t h e i r r e l a t i v e l y h igh evapora t ion ra te a t 300°F and consequent ly the i r poor vacuum compati- b i l i t y . S a t i s f a c t o r y p r o p e r t i e s of these l u b r i c a n t s inc lude low pour po in t , LOX-compatibility, h y d r o l y t i c s t a b i l i t y , noncorrosiveness , n o n r e a c t i v i t y w i t h aluminum under shear, and ease o f g e l a t i o n t o a grease.

I n that r e p o r t experimental r e s u l t s

A t a p r o j e c t conference a t Marshal l Space F l i g h t Center , 23 June 1970, i t w a s determined t h a t g rease requirements could be d i f f e r e n t i a t e d wi th r e s p e c t t o systems requirements: S ince LOX systems r e q u i r e 10% pour poin t performance, but can accept a compromise on the evapora t ion test , t h e g e l l e d L - a l k y l 3-methylg lu ta ra te g reases can be considered s a t i s f a c t o r y ; l u b r i c a n t requirements f o r GOX systems demand some a d d i t i o n a l s t r u c t u r a l mod i f i ca t ion of t h e esters t o achieve t h e evapora t ion requirement, bu t t h e requirements are s a t i s f i e d i n t h e low temperature range by esters having pour p o i n t s i n t h e range o f -45 t o -50°F. On t h e b a s i s of a survey o f t h e c u r r e n t l y manufactured l u b r i c a n t s and t h e experimental work so f a r com- p l e t ed under t h i s c o n t r a c t , i t i s improbable t h a t a s i n g l e l u b r i c a n t can m e e t t h e requirements f o r bo th systems.

The cont inued e f f o r t has l a r g e l y been d i r e c t e d toward achiev ing s t r u c t u r a l mod i f i ca t ion o f t h e esters i n o rde r t o s a t i s f y t h e requirement f o r the second c lass of l u b r i c a n t s , A decrease i n t h e v o l a t i l i t y of the o i l r e q u i r e s mod i f i ca t ion of the chemical s t r u c t u r e i n one of t h e fol lowing ways: A decrease i n the e x t e n t of f l u o r i n a t i o n ; an inc rease i n t h e formula weight; o r the i n t r o d u c t i o n of p o l a r groups i n t o the s t r u c t u r e . The spe- c i f i c mod i f i ca t ions r e q u i r e tha t the LOX-compatibility not be compromised and t h a t t h e low temperature v iscometr ic p r o p e r t i e s be maintained,

During t h e second q u a r t e r , a f i r s t series o f s t r u c t u r a l l y modi- f i e d f l u o r o e s t e r o i l s were prepared and some of their p r o p e r t i e s were de- termined. The p a r t i c u l a r s t r u c t u r a l mod i f i ca t ion s e l e c t e d m e t one o r more of t h e s t r u c t u r a l c r i te r ia f o r decreas ing the v o l a t i l i t y of t h e f l u i d w i t h - ou t being de t r imen ta l t o the low temperature v iscometr ic p rope r t i e s . The fol lowing i s the genera l ized s t r u c t u r e f o r t h i s new class of f l u i d s .

3-2

FF3 CH3CH C-O-CH2-CF-O-CH2 (CF2) .H] e 2

F lu id A n = 4 Flu id B n = 6

The s t r u c t u r e increased t h e formula weight through the a d d i t i o n of an ether l inkage and a f l u o r i n e - s u b s t i t u t e d a l i p h a t i c group, y e t maintained a h igh degree of f l u o r i n e conten t .

The pour po in t o f F lu id A w a s -65'F and of F lu id B -50°F, bo th h igher than t h e pour p o i n t s o f t h e unmodified esters. However, t h e e x t e n t of t h e i n c r e a s e was minimal cons ide r ing t h e i n c r e a s e i n t h e formula weight o f t h e f l u i d . B i s ( d - n o n y l ) 3-methylg lu ta ra te , t h e next h ighe r homologue i n t h e unmodified ester series r epor t ed t o f r e e z e a t +77"F.1/ I n select- i n g the modified s t r u c t u r e s , i t had been a n t i c i p a t e d tha t t h e presence o f the e t h e r l inkage i n the molecular s t r u c t u r e would a l low f r e e r cha in c o i l - i ng and consequent ly b e t t e r tempera ture-v iscos i ty p rope r t i e s . i n t h e inc rease i n v i s c o s i t y as t h e temperature i s lowered would r e s u l t i n a lower pour poin t . index improvement was observed i n F l u i d s A and B.

A lower ra te

Contrary t o expec ta t ions , no tendency toward v i s c o s i t y

V o l a t i l i t i e s w e r e reduced, bu t no t s o much as might b e expected from the formula weight i nc rease . A f t e r 1 hr. a t 300"F, F lu id A showed a 5% evapora t ion whereas b i s ( d - a m y l ) 3-methylg lu ta ra te showed a 23% evapora- t i o n ; F lu id B showed about a 1% evapora t ion as compared wi th 5% evapora t ion f o r bis(jr'--heptyl) 3 -methylg lu ta ra te . However, a n o v e r a l l comparison of pour p o i n t s and evapora t ion rates i n d i c a t e s t h a t the p r o p e r t i e s f o r F lu id A and b i s ( L - h e p t y l ) 3 -methylg lu ta ra te are much t h e same and tha t no sub- s t a n t i a l improvement w a s e f f e c t e d i n t h e s t r u c t u r a l modi f ica t ion .

The chief e f f o r t dur ing t h i s q u a r t e r has involved t h e syn thes i s and screening of a second chemical ly modified series of esters, the s t r u c - t u r a l c lass favored f o r t h e LOX system l u b r i c a n t .

11. PROPERTIES OF MODIFIED FLUORINE-SUBSTITUTED ESTERS

A. L -Alkoxyace t i c Acid Esters

A series o f newly modified ester f l u i d s incorpora ted an e t h e r s t r u c t u r e and allowed a n i n c r e a s e i n the p ropor t ion of hydrogen and the formula weight of t h e molecular s t r u c t u r e . These f l u i d s , which a r e s t r u c - t u r a l l y s imilar t o the commercial neopentyl po lyol esters, were prepared by condensing neopentyl po lyo l s w i t h L - a l k o x y a c e t i c ac ids .

3-3

H(CF2) 4CH20Na + ClCH2C02H - H(CF2) 4CH20CH2C02H Structural variations included the products of the esterification of rlr)- propyloxyacetic acid, d-pentyloxyacetic acid, or J'--heptyloxyacetic acid with l,l,l-trimethylolethane, l,l,l-trimethylolpropane, 2,2-dimethylolpro- pane, or 2,2,3,3,4,4-hexafluoropentane-1,5-diol. Specific procedures for the preparation of the esters are described in the experimental portion of this report.

Compound No.

1

2

3

4

5

6

7

8

Structure

CH3C [CH202CCH20CH2 (CF2) 2H]3

CF2 [CF2CH202CCH20CH2 (CF2) qH]2

Name - l,l, 1-trimethylolethane bis(c-propyloxyacetate)

1,l,l-trimethylolpropane bis(JL1-propyloxyacecate)

2,2-dimethylolpropane bis(JL1-propyloxyacetate)

l,l,l-trimethylolethane bis(d-pentyloxyacetate)

l,l,l-trimethylolpropane bis(&-pentyloxyacetate)

2,2-dimethylolpropane his($--pentyloxyacetate)

2,2,3,3,4,4-hexafluoro- pentane-l95-diol bis(JL1- pentyloxyacetate)

2,2-dimethylolpropane bis(j'--heptyloxyacetate)

3-4

I n i t i a l l y , a smal l q u a n t i t y o f each of the f l u i d s w a s prepared and screened f o r pour po in t , evapora t ion ra te , and v i s c o s i t y . Subsequently, l a r g e r samples of F lu ids 5 and 6 were prepared and submitted f o r LOX-com- p a t i b i l i t y screening.

The r e s u l t s o f t he de te rmina t ions o f f l u i d p r o p e r t i e s are sum- marized i n Table I. I n t h e de te rmina t ion of evapora t ion rates, some prob- l e m s i n r e p e a t a b i l i t y r equ i r ed ref inements i n the procedure; t he re fo re , new va lues f o r s e v e r a l commercial materials and previous ly prepared f l u i d s a r e provided f o r comparison. Some previous ly determined pour po in t s and vis- c o s i t i e s f o r t h e same f l u i d s a r e a l s o included.

Only t h e pour po in t s o f t h e dimethylolpropane d e r i v a t i v e s were s a t i s f a c t o r y , va lues of -40 and -45" being obta ined , and evapora t ion rates were lower than t h e evapora t ion r a t e s f o r $'--alkyl 3-methylglutarate . I n t h e new series, somewhat h ighe r v i s c o s i t y indexes were observed, bu t the improvment appeared t o be r e l a t e d t o the h igher v i s c o s i t i e s of these o i l s a t 100 and 210°F r a t h e r than t o changes i n t h e v iscometr ic p r o p e r t i e s inher - e n t i n the s t r u c t u r a l modi f ica t ion . Four-ba l l wear tests on two of the f l u i d s , w i t h and wi thout added t r i c r e s y l phosphate are summarized i n Table 11. T r i c r e s y l phosphate a f forded adequate wear p r o t e c t i o n t o these two f l u i d s .

I f t h e o v e r a l l p r o p e r t i e s of the f l u i d s i n Table I are compared, t h e pour po in t s , evapora t ion ra tes , and v i s c o s i t i e s of 2,2-dimethylolpro- pane bis(tJ'--pentyloxyacetate) (Compound 6 ) , tris($'--amyl) t r i c a r b a l l y l a t e , and Krytox 143AA are roughly equiva len t . now appears thattris($--amyl) t r i c a r b a l l y l a t e and bis(hydroxymethy1)propane bis(tf--pentyloxyacetate) as pure substances are t h e b e s t candida tes as GOX system l u b r i c a n t s . There i s cons iderable advantage i n materials c o s t s i n t h e second compound, b u t r e s u l t s have not y e t been obtained on i t s LOX- compa t ib i l i t y .

On the b a s i s of t h e s e da t a , i t

I n t h e ear l ie r work, t he t r i c a r b a l l y l a t e ester showed 0/20 re- a c t i o n s i n t h e LOX c o m p a t i b i l i t y test. The evapora t ion rates of n e i t h e r o f t hese compounds approach the requirement of less than 1% a t 300°F and less than 5% a t 400"F, y e t t he i r evapora t ion rates are not g r e a t e r t han those of t h e b e s t commercially a v a i l a b l e materials.

B. Unsymmetrical Esters

It i s r epor t ed that lower pour p o i n t s and evapora t ion rates a t no s a c r i f i c e i n the v i s c o s i t y o r v i s c o s i t y index can be achieved i n the a l i p h a t i c d i e s t e r series t h r o u g h - t h e use of esters w i t h mixed l igands . This improvement was observed by Cohen and o t h e r s i n comparing the p r o p e r t i e s

3-5

TABLE I

POUR POINTS, EVAPORATION RATES, VISCOSITIES, AND VISCOSITY INDEXES FOR NEW MODIFIED FLUORINE-SUBSTITUTED ESTERS

Wt. % Evaporation C omp o u nd 300 * 2°F Pour Point Viscosity cSt. ASTM Viscosity

Index No e 1 Hr. 6 Hr. OF 210°F 100°F

1 -- 3.0 -5 14.41 339.4 - 18 I- -- -- 2 -" 1.4 -5

m.p. 33-37°C

3 -- 13.7 -40 4.92 50.89 -31

4 -- 0.7 - 10 16.32 374.3 5

5 -- 1.4 - 10 16.12 349.6 13

6 -I 5.4 -45 6.03 74.17 - '+9 -- .".m -I -e -- -- 7

m.p. 66-70°C

8 -- 5.9 -35 7.02 91.03 -12

Bis (L-amyl) 3-methylglutarate 10.5 < -90 2.78 16.27 -59

Bis (L-heptyl) 3-methylglutarate 2.4 14,6 - 75 3.57 26.11 -80

Tris (L-amyl) tricarballylate 0.9 4.8 -45 6.78 86.23 -25

-- -- -- Fomblin L 13.0 37.3 -80

-- -- -- Krytox 143AA 1.8 6.1 -50

-- -- _ I Krytox 143AZ 9*4 32.0 - 70

3-6

TABLE I1

EXPERIMENTAL FOUR-BALL WEAR TEST DAT&

Add i t i v e Wear Scar Diameter

(mm.) a t 50 Kg.

2,2-Dimethylolpropane bis(jr'--pentyloxyacetate)

F lu id

No ne 2 w t . % T r i c r e s y l phosphate

l , l , l -T r ime thy lo le thane t r i s ( d - p e n t y l o x y a c e t a t e

F lu id

None 2 w t . % T r i c r e s y l phosphate

0.75 0.56

0.69 0.38

- a / Two hours a t 147", 600 rpm, 52-100 s teel b a l l s .

of t h e unsymmetrical esters w i t h b lends of pure esters con ta in ing t h e same propor t ions o f a l coho l and a c i d l i g a n d s . l /

The p r o p e r t i e s of two unsymmetrical f l u o r a t e d esters are r epor t ed i n Table 111. A comparison o f the pour p o i n t s and evapora t ion rates of the esters i n Table I11 w i t h the corresponding v a l u e s f o r s i m i l a r symmetrical esters i n Table I i n d i c a t e the va lues f o r t h e unsymmetrical esters are not s i g n i f i c a n t l y d i f f e r e n t from the va lues f o r the symmetrical esters, pro- v ided t h e formula weights are about the same,

C. Ester Blends

The p o s s i b i l i t y o f achiev ing a wider u s e f u l f l u i d range through t h e u s e o f b lends of f l u o r i n e - s u b s t i t u t e d esters was a l s o considered. Be- cause o f t h e s i m i l a r i t y i n chemical composition, such b lends should be compatible i n a l l proport ions. It w a s o f p a r t i c u l a r i n t e r e s t t o determine i f t h e -10'F pour po in t of l , l , l - t r i m e t h y l o l e t h a n e tris($--pentyloxyacetate) could b e e f f e c t i v e l y lowered by a small p ropor t ion of a low pour poin t f l u i d wi thout s e r i o u s l y i n c r e a s i n g i t ' s low evapora t ion rate (0.7% i n 6 h r e ) . I n some mixtures t h a t were i n v e s t i g a t e d and are r epor t ed i n Table I V , changes i n pour p o i n t s and evapora t ion rates were both roughly p ropor t iona l t o the percentage of each component i n t h e blends. produced compositions w i t h p r o p e r t i e s as f avorab le as t r i s ( g - a m y l ) t r i- c a r b a l l y l a t e o r 2,2-dimethylolpropane bis(jll-pentyloxyacetate),

3-7

None of the combinations

TABLE I11

PROPERTIES OF UNSYMMETRICAL ESTERS

Pour Point Evaporation Rate Components in Ester Preparation (OF) (6 Hr. at 300 f2OF)

Tricarballylic acid (0.085 mole) g-Pentyl alcohol (0.17 mole) f--Heptyl alcohol (0.099 mole)

2,2-Dimethylolpropane (0.10 mole) -Jrl.-Pentyloxyacetic acid (0.10 mole) L-Heptyloxyacetic acid (0.10 mole)

-40 3.8

-45 7.3

TABLE IV

POUR POINTS AND EVAPORATION RATES OF BLENDS OF FLUORINATED ESTER FLUIDS

Fluids A. l,l,l-Trimethylolethane tris(d-pentyloxyacetate) B. Bis($--amyl) 3-methylglutarate C. Bis(L-hepty1) 3-methylglutarate D. 2,2-Dimethylolpropane bis(j'--pentyloxyacetate)

Blend Composition (wt. X ) Wt. % Evaporation at Pour Point - A - B - C - D 300°F, 6 Hr. (OF)

-- I-

-_ 10 25 50 100 -- 10

25 50 100

0.7 5.5 14.0 26.6 10.5 (1 hr.) 2.2 4.8 9.8 14.6 1.2 1.9 3.2 5,4

- 10 - 15 -35 -50

< -90 - 15 -25 -45 - 75 - 15 -25 -30 -45

3-8

D. Water Corrosion

An additional property of $--alkyl 3-methylglutarate fluids was examined during this report period. When small quantities of water were mixed with the commercial and many of the experimental fluids and a ball bearing was stored in the mixture at 60"F, rusting occurred as if water alone were present, showed no rusting, although some pitting was observed. The results of a series of tests run for 91 hr. are summarized in Table V. In a second series of experiments, the water corrosion tests were run for much longer periods. The appearances of the bearings after the tests are shown in Figure 1.

A similar test with &!-pentyl 3-methylglutarate fluid

Fluid

Tris (g-amyl) tricarballylate

Bis(L-heptyl) 3-methylglutarate

Bis(d-amy1) 3-methylglutarate

TABLE V

WATER CORROSION DAT&

Fir st Sample

Loose rust

Loose rust

Slight staining

2,2-Dimethylolpropane bis(d- pentyloxyacetate

Krytox 143AA

Fomblin L

Mineral oil

Heavy staining

Loose rust

Loose rust

Loose rust

Second Sample

Loose rust

Loose rust

Slight pitting

Slight staining

Loose rust

Loose rust

Slight staining and pitting

- a/ 52-100 Steel balls in the presence of water and the test fluid for 91 hr. at 60°F.

3-9

C

D

F i g u r e 1 - Corrosion on 52-100 S t e e l Balls i n the Presence of Fluorine- Containing F l u i d s and Water: A. Water o n l y (14 days a t 6OOC); B. PR 143AA ( 4 days a t room temperature) ; C. hep ty l ) 3-Methylglutarate (22 days a t 60O); E. Bis(#--pentyloxytetrafluoro- propyl) 3-Methylglutarate (22 days a t 6 0 " ) .

Fomblin L (22 days a t 60"); D. B i s ( 2 -

3- 10

E. Samples

During this report period, the following lubricant samples were forwarded t o Marshall Space Flight Center for LOX-compatibility screening.

Bis(tf--pentyloxytetrafluoropropyl) 3-methylglutarate9 24 g.

Bis (2 -hep ty loxy te t r a f luo ropropy l ) 3-methylglutarate, 24 g.

Bis(tf--pentyl) 3-methylglutarate (containing 2% tricresyl phosphate) thickened with 16% Vydax 1000, 194 g.

Bis($'-heptyl) 3-methylglutarate (containing 2% tricresyl phosphate) thizened with 16% Vydax 1000, 219 g.

2,2-Dimethylolpropane bis(f--pentyloxyacetate), 181 g.

l,l,l-Trimethylolethane bis(c-pentyloxyacetate), 142 g.

None of the results of these tests has been received,

111. ANTICIPATED WORK

After the work on characterizing the fluids discussed in this report is complete, the final report covering the work under the entire program will be prepared. When the results of LOX-compatibility testing is complete, recommendations can be made concerning the fluid which most nearly meets the specified requirements.

IV. EXPERIMENTAL PART

A. Preparation and Characterization of d--Alkoxyacetic Acids

Two procedures were employed for preparing these acids. The results of preparations in which the 1]LL-alkanol was first treated with sodium hydride and subsequently with chloroacetic acid are reported in Table VI, The following summarizes the conditions for the two larger preparations, The sodium hydride dispersion in mineral oil, mixed with 800 ml. of ether, was treated with the tJ'--alkanol over a 2 hr, period, and then the chloro- acetic acid was added over a 1.5 hr. period. After the mixture cooled to room temperature and was stored overnight, 400 ml. of 25% hydrochloric acid was added and the ether layer was separated and dried over sodium sulfate,

3-11

TABLE V I

PREPARATION OF d-ALKYLOXYACETIC ACIDS : FIRST METHOD

Compound &-Propyl $'--Pentyl Chloroac e t i c No e Alcohol Alcohol Acid

1 232.0 g, (1.76 moles)

2

2

94.5 g. (0.80 mole)

102.1 g. 18.9 g. (0.44 mole) (0.20 mole)

408.3 g. 75.6 g. (1.76 moles) (0.81 mole)

Sod i d / Y i e l d Hydride (%)

38.4 g. 89 (1.60 moles) (136 g.)

9.6 g. 83 (0.40 mole) (96 g.1

38.4 g. 84 (1.60 moles) (196 g.)

a / Used a s a 55% d i s p e r s i o n i n mineral o i l . - When t h e e t h e r was evaporated, a f i r s t vacuum d i s t i l l a t i o n gave t h e a c i d contaminated wi th mine ra l o i l . A f t e r t h e mine ra l o i l w a s e x t r a c t e d wi th petroleum e t h e r , b.p. 35-60', t h e ac id w a s p u r i f i e d by f r a c t i o n a l d i s t i l - l a t i o n under vacuum.

I n t h e second method, the &'--alkanol, c h l o r o a c e t i c a c i d , and aqueous sodium hydroxide were heated t o g e t h e r i n one s tep. The r e s u l t s of t hese p r e p a r a t i o n s are summarized i n Table VII. The following i s a repre- s e n t a t i v e procedure. a c e t i c a c i d w a s added t o a mixture of t h e $--alkanol and sodium hydroxide dur- i ng 1.5 h r . an exothermic r e a c t i o n occurred. The mixture was r e f luxed over- n igh t , cooled, and n e u t r a l i z e d w i t h 20% aqueous hydroch lo r i c ac id . A f t e r t he lower l a y e r w a s s epa ra t ed , washed w i t h two p o r t i o n s of 20% aqueous hy- d r o c h l o r i c ac id , and two p o r t i o n s of water, t he a c i d w a s p u r i f i e d by f r a c - t i o n a l d i s t i l l a t i o n .

When an aqueous s o l u t i o n of t h e sodium s a l t of chloro-

The p r o p e r t i e s and t h e r e s u l t s o f t h e c h a r a c t e r i z a t i o n of t h e s e a c i d s a r e summarized i n Table V I I I .

3-12

TABLE V I 1

PREPARATION OF I~'-ALKYLOXYACETIC ACIDS: SECOND METHOD

Alcohol Compound C h l o r o a c e t i c g - P e n t y l X - H e p t y l Water Y ie ld Recovered

No. Acid Alcohol A l c o ho 1 NaOH (ml.) (7,) (7,)

2 18.9 g. 51.0 g. (0.20 mole) (0 .22 mole)

2 378 g. 1 ,020 g. (4 .00 moles) (4 .40 moles)

3 189 g. (2.00 moles)

88 g. 44 27 42 (0.22 mole) (16 9.1

176 g. 1,000 50 45 (4.40 moles) (585 g . )

730 g. 88 g. 500 20 64 (2.20 moles) (2.20 moles) (154 8.1

TABLE V I 1 1

PROPERTIES OF h'-ALKYLOXYACETIC ACIDS

Compound B o i l i n g P o i n t 20 Analyses LFound/(calcd) I I n f r a r e d F Calcd. fo r A n a l y s i s

F igu re 2

n - H - C - D roc (m.)i - No.- a /

'gHgF4'3 llr/ 92-93 (0.90) 1.3697 31.48 3.05 40.98 134-136 (9) (31.59) (3 ,18 ) (39.98)

2 134-135 (10) 1.3565 29.08 2.03 52.23 7H6F803 F i g u r e 3 (28.98) (2.09) (52.39)

3 128-130 (0.3) 1.3471 27.73 1.62 58,56 CgH6F1203 F i g u r e 4 (27.71) (1 .55) (58.44)

- a / - b /

For i d e n t i f i c a t i o n of Compound Nos., see Tab les V I and V I I . Reported, b.p. 109-114" (24 mm.), ng6 1.3632. (Ref. 2 ) .

3- 13

4300 3000 2000 1500 1200 1000 900 800 700 C M ’

Figure 2 - I n f r a r e d Spectrum of $‘--Propyloxyacetic Acid (Liquid) I

100

- 80

tif 5

a

Z 60

5 2 40

20 ai I-

0 3000 3000 2000 1500 1200 1000 900 800 700

CM ‘

Figure 3 - I n f r a r e d Spectrum o f $--Pentyloxyacetic Acid (Liquid)

I

WAVELENGTH (MICRYIS) 3 ‘ 4 5 6 7 8 9 11 12 13 14 15

100 100

- 80 80 * ! 60 60 4

9 40 40

20 20

-

5 d I-

0 0

C M ‘ 4000 3000 2000 1500 1200 1000 900 800 700

Figure 4 - I n f r a r e d Spectrum of f--Heptyloxyacetic Acid (Liquid)

3-14

B. Preparation and Characterization of Modified Fluorinated Esters From L-Alkyloxyacetic Acids and Various Polyols

The quantities, described in Table IX, of tf--propyloxyacetic acid or &-pentyloxyacetic acid and l,l,l-trimethylolethane, 12191-tri=- methylolpropane, 2,2-dimethylolpropane9 or 2,2,3,3,4,4-hexafluoropentane- 195-diol were dissolved in toluene to which was added sulfuric acid. The mixtures were heated from 4-17 hr. until the specified quantity of water had been collected in a Dean-Stark trap. After cooled mixtures were washed sequentially with water, aqueous potassium carbonate, and water, the toluene was distilled off and the esters were purified by fractional distillation. The characterization and properties of these fluids are reported in Table X.

C. Preparation of Fluorinated Esters from $--Alkanols and Various Aliphatic Acids

1. Bis($--amyl) 3-methylglutarate: A mixture of 114.0 g. (0.78 mole) of 3-methylglutaric acid, 408.0 g. (1.76 moles) of g-amyl alcohol, 600 ml. of toluene and 4 g, of sulfuric acid was refluxed for 21 hr. A total of 31.6 ml. of water (calcd,, 28.1 ml.) was collected in a Dear-Stark trap. When the cooled mixture was added dropwise to 200 ml, of water, the lower phase separated and was added dropwise successively to 200 ml, of 5% potassium carbonate and 200 ml. of water. After the solvent and traces of water were removed on a rotary evaporator, fractional distillation of the residue gave 411.4 g. (92%) of bis(&-amyl) 3-methylglutarate9 b,p. 123" (0.07 mm.), n6' 1.3605 [reported b.p. 130-132O (0.03 me), ng0 1.3606],2/

2. Mixed &-pentyl, g-heptyl ester of tricarballylic acid: When the procedure in the preceding paragraph was followed, 15.0 g. (0.085 mole) of tricarballylic acid, 40.1 g, (0.17 mole--2% excess) of $'--pentyl alcohol, and 32.8 g. (0.099 mole--14% excess) of J@--heptyl alcohol, heated in 50 ml. of toluene with 0.2 g. of sulfuric acid for 20 hr, gave 4,6 ml. (calcd., 4.6 ml.) of water. Purification and fractional distillation of the product gave 41 . (53%) of the mixed ester, b,p, 176-184' (0.07 mm,), pour point -40"F, n$ 1,3580.

D. Determination of Lubricant Properties

Fluid viscosities were determined by ASTM method D 445-65 and viscosity indexes were calculated by method D 2270-64, pour points followed ASTM method D 97-57. mined on the four-ball wear test at a load of 50 kg. after 2 hr, at 146" with 52-100 steel balls at 600 rpm,

The method for Wear scar diameters were deter-

3- 15

TABLE IX

PREPARATION

OF MODIFIED FLUORO-SUBSTITUTED ESTERS FROM ~'-ALKYLOXYACETIC ACIDS AND VARIOUS POLYOLS

Water

[MI. Fo

und

(Calcd) 1

3.3

(3.2

)

3.5

(3.2

)

3.5

(3.6

)

3.0

(2- 7

)

11.5

(10.8)

6.0

(5.4

)

(2.7

) 3.

0

3.1

(2.7

)

19.9

(1

9.8)

3.0

(2.7

)

4.0

(3.6

)

3.9

(3.6

)

Toluene

(ml . )

50

50

50

50

50

50

50

50

3 00 50

50

50

Yield

2-Pr

opyl

oxy-

acetic Acid

38.0

g.

(0

.20

mole)

38.0

g

. (0.20 mole)

38.0

g.

(0.2

0 mole)

d- Pent yloxy-

acetic Acid

46.4

g.

(0

.16

mole)

190 g.

(0.6

6 mole)

95 g

. (0

.33 mole)

46.4

g

. (0

.16

mole)

46.4

g

. (0.16 mole)

351

g.

(1.21

moles)

46.4

g.

(0.16

mole)

d-He

ptyl

oxy-

Trimethylol-

Trimethylol-

Dimethylol-

Hexafluoro-

Sulfuric

propane

pentanediol

Acid (a)

acetic Acid

ethane

propane

Compound

No. 1 2 3 4 4 4 5 6 6 7 8 9

7.2

g.

(0.0

59 mole)

0.25

- al

8.0

g.

(0.0

60 mole)

0.25

10.4

g.

(0.10 mole)

0.25

52

(2

3 9

.)

6.0

g.

(0.0

49 mole)

24.0

g.

(0

.20 mole)

0.25

84

(3

9 g

.)

1.0

91

(171 9.)

12.0

g

. (0.10 mole)

0.25

0.25

6.

7 g.

(0.5

0 mole)

7.8

g.

(0.0

75 mole)

0.25

57.2

g.

(0.5

5 mole)

1.5

94

(337

9.)

15.9

g.

0.

25

(0,0

75 mole)

0.25

86

(49

9.)

85.8

g

. (0

.22 mole)

39.0

g.

(0.10 mole)

10.4

g.

(0.10 mole)

10.4

g.

(0.10 mole)

0.25

29.0 g.

(0.10

mole)

86

(6

4 8

.)

- a/ After

a portion of the product was lost through spillage,

18.1

g.

of the fluid was obtained.

TABL

E X

PRO

PER

TIES

OF

MO

DIF

IED

FLU

ORO

-SU

BSTI

TUTE

D

ESTE

RS

Pou

r E

vapo

rati

on

An

aly

sis

[Fou

nd/(

calc

d) ]

F C

alcd

fo

r -

H -

C n2

6 n2

0 C

ompo

und

Bo

ilin

g P

oin

t P

oin

t (%

a

fte

r 6

-

No .a

/ La

c (mm

. ) 1

("P

I h

r. a

t 30

0°F

) 26

D

1

212-

222

(0.0

8)

-5

3.00

1.

463

1,40

36

37.9

7 3.

84

35.3

8 C

20H

24F1

20g

(37.

74)

(3,8

0)

(35.

83)

2 22

3-22

4 (0

.09)

m

.p.

33-

1.40

1.

450

1.40

48

38.7

3 3.

94

35.4

7 C

21H

26F1

20g

37 "C

(3

8.78

) (4

.03)

(3

5.05

)

3 15

4-15

6 (0

.10)

-4

0 13

.69

1.36

7 1.

3962

40

.16

4.54

33

.71

C15

H20

F806

(4

0.18

) (4

.50)

(3

3.91

)

4 23

3-23

6 (0

.07

)bl

-10

0.67

1.

606

1.38

15

32.8

7 2,

62

48.5

2 C

2@24

l?24

0g

(33.

35)

(2.5

8)

(48.

69)

c*, I r

5

230-

240

(0.1

0)

-10

1.44

1.

582

1.38

22

33.6

4 2.

89

48.4

4 C

27H

26F2

40g

4

(34.

12)

(2.7

5)

(47.

98)

6 17

1-17

4 (O

.O8)

C/

-45

5.44

1.

514

1.37

60

35.2

4 2.

91

46.6

7 C

1gH

20F1

606

(35.

19)

(3.1

1)

(46.

89)

7 16

8-17

8 (0

.07)

m

.p.

66-

-- --

1.36

01

29.6

7 1.

96

55.1

5 C

lgH

14F2

206

70°C

(3

0.17

) (1

.87)

(5

5.27

)

8 17

9-18

5 (0

.06)

-3

5 5.

92

1.63

9 1.

3642

32

.80

2.51

34

.66

C23

H20

F240

6 (3

2.56

) (2

.38)

(5

3.75

)

, -

a/

For

id

enti

fica

tio

n o

f C

ompo

und

Nos

., se

e T

able

IX

.

-

b/ -

c/

B.p

. 35

9°C

(d.

t.a.

1.

Dec

ompo

siti

on p

rece

ds

bo

ilin

g a

t 38

5°C

.

Infr

ared

A

na 1

ys i

s

Fig

ure

5

Fig

ure

6

Fig

ure

7

Fig

ure

8

Fig

ure

9

Fig

ure

10

Fig

ure

11

Fig

ure

12

" 4500 3000 2000 1500 1200 1000 900 aoo 700

CM' Figure 6 - Infrared Spectrum of l,l,l-Trimethylolpropane Tris-

(g-pr opyloxyac eta te) (Liquid)

I

WAVELENGTH (MICRONS) 3 ' 4 5 6 7 8 9 10 11 12 13 14 15

100 100

- a0 a0 &

3 Z 60 4 t i m40 Z 4

- 60

40 cd I-

20 20

0 0

CM ' 4000 3000 2000 1500 1200 1000 900 800 700

Figure 7 - Infrared Spectrum of 2,2-Dimethylolpropane B i s - , (L-propyloxyacetate) (Liquid)

3-18

4500 3000 2000 1500 1200 1000 900 800 CM'

" 700

Figure 8 - Infrared Spectrum of l,l,l-Trimethylolethane , Tris($--pentyloxyacetate) (Liquid)

WAVELENGTH (MlCRq#S) 11 12 13 14 15 3 ' 4 5 6 7 8 9

Figure 9 - Infrared Spectrum of l,l,l-Trimethylolpropane Tris(L-pentyloxyacetate) (Liquid)

I

WAVELENGTH (MICRONS) 3 ' 4 5 6 7 8 9 10 11 12 13 14 15

100 100

- 80 80

60 5

- E

2

Z 60 6

r 2 40 40

I-

20 20

0 0

CM ' 4000 3000 2000 1500 1200 1000 900 800 700

Figure 10 - Infrared Spectrum of 2,2-Dimethylolpropane Bis($'--pentyloxyacetate) (Liquid)

3-19

I

WAVELENGTH I '

100

- 80 E P 60 i? 3

d 2 40

20 c

0 4000 3000 2000 1500 1200 1000 900 aoo 700

CM'

Figure 11 - Infrared Spectrum of 2,2,3,3,4,4-Hexafluoropropanedi Bis($--pentyloxyacetate) (Liquid)

I

WAVELENGTH (MICR$$lS) 11

100 100 3 i 4 5 6 7 8 9 12 13 14 15

- 80 a0 %

P 60 60 Q

I

I-

2 2 40 46 Q D: t

20 20

G 0

CM' 4000 3000 2000 1500 1200 1000 900 800 700

Figure 12 - Infrared Spectrum of 2,Z-Dimethylolpropane Bis- (d-heptyloxyacetate) (Liquid)

01

3-20

Evaporation rates represent the value obtained when about 2.5 g.

The temperature was de- of a fluid weighed in a 24 mm, diameter and 7 mm, deep aluminum dish was heated on a hot plate at 300 -f 2°F for 1 or 6 hr. termined with a thermocouple just touching the bottom of the pan.

E. Water Corrosion Tests

In a series of tests a mixture of 3.0 g. of a fluid and 0.15 g. of water was placed in a jar in contact with a 52-100 steel ball. steel balls used were not new and had been previously used on various four- ball wear tests, but all were corrosion free at the beginning of the tests. The following fluids were examined: PR 143AA; Fomblin L; bis(L-heptyl) 3-methylglutarate; and bis(2-~-pentyloxytetrafluoropropyl) 3-methylglutarate. The samples were stored at 60°C for at least 14 days, except for the PR 143AA fluid, which was stored for 4 days, All of the balls, except the ball in the bis(f--heptyl) 3-methylglutarate showed rusting during the storage period. Rusting was particularly heavy with water alone and with the PR 143AA fluid. Photographs of the steel balls are shown in Figure 1. The dark mark at the center of each ball is a reflection of the camera lens. A light reflection also shows on each ball.

The

A second series of tests is summarized in Table V. In duplicate experiments 52-100 steel ball bearings were contacted thoroughly with each of the following fluids and three drops of water were added. The samples were stored at 60" for a total of 91 hr. At the end of the test period, the ball bearings were examined for loose rust, staining and pitting.

3-21

LIST OF REFERENCES

1. G. Cohen, C. M. Murphy, J. G. O ' R e a r , J. G. Ravner, and W. A. Zisman, NRL Report 4066 (1952).

2 . Bucham Research Labora to r i e s , Ltd. , B r i t . P a t e n t , 873,244 (1962) C.A. Ih, 780 (1962).

3. L. W. Breed, J, C. Wiley, Jr., and C. F. Key, Ind. Eng. Chem. Prod. R e s . Develop., L, 53 (1970).

3-22

PROG

RAM

PLA

NN

ING

CH

ART

Lit

era

ture

Sur

vey

and

Pla

nn

ing

To

tal

Dec

. Ja

n.

Feb

. M

arch

A

pri

l M

ay

3une

July

&

S

ept.

Oct.

Nz

Man

-Hou

rs

---

2 00

Tes

tin

g a

nd

Ev

alu

atio

n

6

c

of

Mat

eria

ls

1,0

00

Lu

bri

can

t O

pt im

i za

t io

n

4

c

500

Dev

elop

men

t S

tud

ies

4

d

5 00

b

152

Rep

ort

s

Est

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DISTRIBUTION LIST

Q u a r t e r l y Proqress Reports , Con t rac t NAS8-25510

No. of Copies Rec i p i e n t

1

1

1

2

10

National Aeronaut ics and Space Admin i s t r a t ion George C . Marshal l Space F l i g h t Center Marshal l Space F l i g h t Center , Alabama 35812 At tn : A&TS-PR-M

Contract NAS8 -255 10 DCN l-X-50-20131(1F)

Nat iona l Aeronaut ics and Space Admin i s t r a t ion George C . Marshal l Space F l i g h t Center Marsha l l Space F l i g h t Center , Alabama 35812 At tn : A&TS-MS-IL

Contract NAS8-255 10

DCN l-X-50-20131(1F)

Nat iona l Aeronaut ics and Space Admin i s t r a t ion George C . Marshal l Space F l i g h t Center Marsha l l Space F l i g h t Center , Alabama 35812 A t t n : A&TS-MS-TU

Contract NAS8-2 5510 DCN 1 -X- 50-2 013 1 (1F)

Na t iona l Aeronaut ics and Space Admin i s t r a t ion George C. Marshal l Space F l i g h t Center Marshal l Space F l i g h t Center, Alabama 35812 A t t n : A&TS -MS-IP

Con t rac t NAS8-25510 DCN 1-X-50-2 013 1 (1F)

Nat ional Aeronaut ics and Space Adminis t ra t ion George C. Marshal l Space F l i g h t Center Marshal l Space F l i g h t Center , Alabama 35812 A t t n : Sm-ASTN-RRI

Con t rac t NAS 8 -2 5 5 10 DCN 1-X-50-2013 1 (1F)