Terpolymers of Tetrafluoroethylene, Perfluoro (Methyl Vinyl Ether), and

2

Terpolymers of Tetrafluoroethylene, Perfluoro (Methyl Vinyl Ether), and Certain Cure Site Monomers

Downloaded by MONASH UNIV on November 26, 2014 | http://pubs.acs.org Publication Date: June 1, 1973 | doi: 10.1021/ba-1973-0129.ch002

G. H . K A L B , A. A. K H A N , R. W. Q U A R L E S , and A. L . B A R N E Y Research Laboratory, Elastomer Chemicals Department, E . I. du Pont de Nemours and Co., Inc., Wilmington, Del. 19898

Copolymers

of tetrafluoroethylene,

perfluoro(methyl

ether), and a third monomer—selected perfluoro(4-cyanobutyl oxbutyl

vinyl

vinyl ether),

ether),

perfluoro(4-carbometh-

perfluoro(2-phenoxypropyl

ether), or perfluoro(3-phenoxypropyl

vinyl

vinyl ether)—give vul-

canizable, high performance elastomers. cyano and the carbomethoxy

vinyl

from the group of

Syntheses of the

compounds from

perfluoro-

glutaryl chloride and the phenoxy compounds from pentafluorophenol are presented. three copolymer

Vulcanization methods for the

types include

catalytic

condensation of

the nitrile, interchange of dibasic amines or esters with the methyl ester, and nucleophilic displacement

of a fluorine

atom on the phenoxy ring with a diamine or an aromatic bisnucleophile.

A brief description of vulcanizate

ties demonstrates the outstanding

solvent and

properchemical

resistance that may be obtained with these new elastomers.

A

n e w h i g h - p e r f o r m a n c e elastomer, p r e p a r e d f r o m tetrafluoroethylene ( T F E ) a n d p e r f l u o r o ( m e t h y l v i n y l ether) ( P M V E ) , a n d c h a r a c t e r i z e d

b y o u t s t a n d i n g resistance to c h e m i c a l attack a n d excellent t h e r m a l sta b i l i t y , w a s r e p o r t e d r e c e n t l y b y B a r n e y et al. ( 1 ) o f o u r l a b o r a t o r y . That paper described

a rubbery perfluorinated dipolymer that c o u l d

not b e c r o s s l i n k e d u s i n g o r d i n a r y techniques because of its c h e m i c a l inertness, a n d also a t e r p o l y m e r i n w h i c h a n u n s p e c i f i e d t h i r d

monomer

was u s e d to i n t r o d u c e a c t i v e c r o s s l i n k i n g sites. T h e d i p o l y m e r , w h i c h loses o n l y 5 to 1% o f its w e i g h t i n a n a i r c i r c u l a t i n g o v e n at 316° C i n seven days ( a n d o n l y a f e w p e r cent m o r e a m o n t h at these conditions) is, h o w e v e r , a t h e r m o p l a s t i c .

I t is a p p a r e n t ,

13 In Polymerization Reactions and New Polymers; Platzer, N.; Advances in Chemistry; American Chemical Society: Washington, DC, 1973.

14

POLYMERIZATION REACTIONS A N D N E W POYLMERS

therefore, that a c r o s s l i n k e d structure is necessary to g a i n t h e m e c h a n i c a l strength at elevated temperatures r e q u i r e d f o r a true h i g h - p e r f o r m a n c e elastomer.

T h i s p a p e r describes w o r k a i m e d at: d e v e l o p m e n t of a

s u i t a b l e crosslink s t r u c t u r e a n d various c a n d i d a t e t h i r d m o n o m e r s that copolymerize

with T F E and P M V E

to i n t r o d u c e t h e necessary

cross-

l i n k i n g sites; t h e i r p r e p a r a t i o n a n d c o p o l y m e r i z a t i o n ; c r o s s l i n k i n g reac tions i n v o l v e d w i t h some of t h e m o n o m e r s ;

and a f e w of the physical

properties of the c r o s s l i n k e d ( " v u l c a n i z e d " ) The

dipolymer

has m a n y

compositions.

d e s i r a b l e properties,

a n d , to m a i n t a i n

these properties, the r e q u i r e m e n t s f o r the t h i r d m o n o m e r a n d the cross-


l i n k i n g r e a c t i o n are q u i t e stringent.

T h e s e r e q u i r e m e n t s are:

( a ) T h e c u r e site m o n o m e r must c o p o l y m e r i z e r e a d i l y w i t h o u t a p p r e c i a b l e c h a i n transfer ( t h e p o l y m e r i z a t i o n is p a r t i c u l a r l y susceptible to c h a i n - t r a n s f e r r e a c t i o n s ) , a n d at a rate s u c h that reasonable a n d c o n t r o l l e d amounts of c r o s s l i n k i n g site are i n c o r p o r a t e d at a n adequate spacing. ( b ) T h e c r o s s l i n k i n g f u n c t i o n a l g r o u p m u s t not b e affected b y t h e p r e f e r r e d aqueous p o l y m e r i z a t i o n system. ( c ) T h e c r o s s l i n k i n g r e a c t i o n m u s t b e s u c h that t h e stock c a n b e f o r m e d i n t o d e s i r e d shapes at elevated temperatures ( b y m o l d i n g o r other m e a n s ) , t h e n b e c o n v e r t e d into a c r o s s l i n k e d structure. ( d ) T h e crosslink s h o u l d b e c o m p a r a b l e i n t h e r m a l , c h e m i c a l , a n d o x i d a t i o n resistance to t h e b a c k b o n e to m a i n t a i n t h e o u t s t a n d i n g p r o p erties of the d i p o l y m e r . CF

=CF - 0 -

2

where X = - C 0 0 R , and

(R )

Figure

f

1.

( R

f

) -

X

-CN,-0-C F 6

5

= PERFLUOROALKYL or P E R F L U 0 R 0 A L K Y L ETHER GROUP

Comonomer candidates—generalized structure

A survey o f a v a r i e t y o f p o l y m e r i z a b l e groups i n d i c a t e d that i n the preferred fluorovinyl

free-radical aqueous-emulsion

p o l y m e r i z a t i o n system, a p e r -

ether most n e a r l y fulfills these r e q u i r e m e n t s .

p e r f l u o r o v i n y l ethers c o p o l y m e r i z e

at a reasonable

I n general, the

rate.

T h e y change

l i t t l e i n rate w i t h variations i n c h a i n l e n g t h o r f u n c t i o n a l i t y i n the p e r fluoroalkyl

m o i e t y so l o n g as the t y p e of f u n c t i o n a l i t y o n the perfluoro-

a l k y l g r o u p is consistent w i t h requirements ( a ) a n d ( b ) .

I n addition,

s u c h ethers f u r n i s h t h e r m a l l y resistant structures i n t h e p o l y m e r . A

number

of m o n o m e r s

of t h e general

( 2 , 3 ) , w h e r e X is - C O O R , - C N , a n d - O C F 6

copolymerized with T F E and P M V E .

type 5

CF =CF-0-R X 2

f

( F i g u r e 1) have been

T h e i r c r o s s l i n k i n g reactions w i t h

d i f u n c t i o n a l v u l c a n i z a t i o n agents w e r e c a r r i e d o u t a n d t h e v u l c a n i z a t e

In Polymerization Reactions and New Polymers; Platzer, N.; Advances in Chemistry; American Chemical Society: Washington, DC, 1973.

2.

KALB E T AL.

15

Terpolymers

9 II

9 II

9 I

MnF

9 II

Cl-C-(CF ) -C-Cl ^ T ^ F - C - ( C F ) - C - F (89% YIELD) Perfluoroglutaryl Fluoride 1 n 2

3

2

9 II

HFPO

?3 F

'

F-C-(CF ) -CF 0-CF-CF0 (71% YIELD) 3-Oxa-perfluoro (2-methyl nonone dioyl) Fluoride (b.p.l06°C) ni

3

2

CsF

3

r

/

CH3OH

(near o°) 0

CF

0

3

0

K - 0- 8- (R )-0-CF-C-0" K • - g j g L (97,8% YIELD) Dipotassium 3-Oxa-perfluoro( 2-Methyl azelaoate )


o

r

2

4

f

3

H00C-(R)-0-CF=CF

2

f

21

2

(b.p.80°C/2mm)

22

-KF

/

jx

K*0 -C-(R )-0-CF=CF 2

0

3

CH 0-C-(CF ) VcF-C-0CH

f

^ —

CF

SK

CH 0H,H S0 3

NC-(CF ) -0-CF=CF -^NH -C-(R )-0-CF=CF 2 4

2

2

f

2

r

(b.p.90-93°C) (m.p. 89.5-91.5°C) (YIELD 90 - 95 %) (Yl ELD 75-80 %) Perfluoro (4-cyanobutyl ^ vinyl ether) 1

Figure 2.

4

f

2

(b.p.60°C/40mm) Perfluoro (4-carbomethoxybutyl vinyl ether) ™:

Synthesis of perfiuoro(4-cyanobutyl

properties i n v e s t i g a t e d .

2

0 CH 0-C-(R )-0-CF=CF

T h e simplest phenoxy

vinyl ether) compound

(perfluoro-

p h e n y l v i n y l ether) has b e e n r e p o r t e d b y W a l l a n d P l u m m e r to p o l y m e r i z e w i t h great difficulty ( 6 ) .

In general, ionically bonded

cross-

l i n k i n g agents a n d g r o u p i n g s that t e n d to i n t e r c h a n g e easily ( s u c h as ester g r o u p s ) g i v e g o o d c h e m i c a l - r e s i s t a n t p o l y m e r s , b u t d o not g i v e v u l canizates w i t h attractive h i g h - t e m p e r a t u r e properties b e c a u s e these r u b bers suffer h i g h r e l a x a t i o n u n d e r stress at e l e v a t e d temperatures. Among

the m o r e

a t t r a c t i v e v i n y l ether c a n d i d a t e m o n o m e r s

perfluoro ( 4 - c a r b o m e t h o x y b u t y l

vinyl

ether),

vinyl ether), perfluoro(2-phenoxypropyl phenoxypropyl vinyl ether).

are

perfluoro ( 4 - c y a n o b u t y l

vinyl ether), and perfluoro(3-

C o m p o s i t i o n s c o n t a i n i n g these

monomers

are discussed i n this report. P o l y m e r i z a t i o n is c a r r i e d out e x p e d i t i o u s l y i n aqueous m e d i a u s i n g either redox

or t h e r m a l l y generated

techniques m a y b e also u s e d . difference ethers.

f r e e - r a d i c a l systems;

anhydrous

I n g e n e r a l , there appears to b e no gross

i n r e a c t i v i t y rates w i t h different substituents o n the

vinyl

H o w e v e r , w h e r e s l i g h t differences w e r e n o t e d , i t is l i k e l y that

differences i n s o l u b i l i t y i n the m i c e l l e affect c o n c e n t r a t i o n at the p o l y m e r i z a t i o n site a n d thus m o d i f y the final content of the t h i r d m o n o m e r i n the p o l y m e r .

D i f f e r e n t c r o s s l i n k i n g reactions are u s e d w i t h various


16

POLYMERIZATION REACTIONS A N D N E W POLYMERS

s u b s t i t u t e d v i n y l ether structures. the appropriate copolymer

T h e s e reactions a r e d i s c u s s e d u n d e r

type.

Studies with Perfluoro(4-Cyanobutyl The

Vinyl Ether)

synthesis o f this m o n o m e r

i n v o l v e s n i n e steps s t a r t i n g w i t h

p e r f l u o r o g l u t a r y l c h l o r i d e , as i n d i c a t e d i n F i g u r e 2 ( 3 ) . M o s t o f t h e steps g i v e g o o d y i e l d s except f o r t h e selective p y r o l y s i s step ( F i g u r e 2, c o m p o u n d s V - V I ) , w h e r e t h e y i e l d s a r e o n l y 10-20%.


perfluoro(butenyl

vinyl

By-products are

a n d the hydrogen

fluoride

b o t h the desired a c i d a n d perfluoro ( b u t e n y l v i n y l

ether).

Polymerization. v i n y l ether)

ether)

adducts of

Copolymers of tetrafluoroethylene/perfluoro(methyl

a n d t h e n i t r i l e ( 1 - 4 m o l e %) h a v e b e e n p r e p a r e d b a t c h -

w i s e i n a s t i r r e d a u t o c l a v e u s i n g a n aqueous a m m o n i u m p e r s u l f a t e o r a m m o n i u m p e r s u l f a t e - s o d i u m sulfite redox c o u p l e system at 40°-100° C . The T F E / P M V E t h e pressure ethane.

gas m i x t u r e w a s p r e s s u r e d , as r e q u i r e d , t o m a i n t a i n

a n d the nitrile p u m p e d

i n solution i n trichlorotrifluoro-

After completion of t h e reaction, polymer was isolated

the latex

(25-30% s o l i d s )

from

b y c o a g u l a t i o n u s i n g e t h a n o l a n d aqueous

magnesium chloride solution.

It was washed w i t h alcohol/water solu

tions a n d d r i e d a t 7 0 ° C i n a n o v e n

under nitrogen.

Mass

balance

i n d i c a t e d that most o f t h e n i t r i l e h a d b e e n i n c o r p o r a t e d .

0-(CF ) CN 2

3--CF -CF-CF 2

4

-0-(CF )-C II 2

2

^C-(CF ) I 2

- 0 -

0 1 '— — 1

Figure 3. Crosslinking. action

Crosslinking

— -n

of polymer through the nitrile group

C r o s s l i n k i n g is b r o u g h t a b o u t b y t h e c a t a l y t i c i n t e r

of the pendant

n i t r i l e groups,

perhaps

to t h e t r i a z i n e , u s i n g

t e t r a p h e n y l t i n o r s i l v e r o x i d e ( F i g u r e 3 ) . T h e exact f o r m o f t h e cross l i n k has n o t b e e n e s t a b l i s h e d .

Henne ( 4 ) showed monomeric

perfluoro

c a r b o n i t r i l e s f o r m t r i a z i n e rings i n t h e presence o f t e t r a p h e n y l t i n o r other catalysts strongly

( 5 ) . T h e s e t r i a z i n e structures s o f o r m e d

a t 6.40-6.45/A

i n the infrared.

p a r e d f r o m t h e perfluoroelastomer

absorb

C r o s s l i n k e d g u m stocks

(polymer

a n d catalyst)

have

very pre been

e x a m i n e d i n t h e i n f r a r e d , a n d other u n a s s i g n e d b a n d s w e r e f o u n d , b u t the c h a r a c t e r i s t i c a b s o r p t i o n o f t h e t r i a z i n e s t r u c t u r e has n o t b e e n o b -


2.

KALB E T AL.

17

Terpolymers

RAW

TERPOLYMER

100 pts.

MED. T H E R M A L

BLACK

TETRAPHENYL

TIN

10 pts. 4.5 pts.

Cure Conditions:

18 hours 160°C ( 3 2 0 ° F )

~ 1000


Figure 4. Crosslinking for nitrite-containing served.

psi

formulation polymer

W h e n t h e viscous n a t u r e of t h e p o l y m e r stock is c o n s i d e r e d ,

c o u p l e d w i t h t h e f a c t t h a t t h e n i t r i l e is present i n t h e p o l y m e r to t h e extent o f o n l y 2 - 4 m o l e % o r less, i t appears u n l i k e l y t h a t c o m p l e t e

con

v e r s i o n t o a t r i a z i n e s t r u c t u r e is i n v o l v e d . I n p r a c t i c e , t h e c u r e i n g r e d i e n t s (see F i g u r e 4 ) a r e m i l l e d i n t o t h e p o l y m e r o n a r u b b e r m i l l ; c u r i n g is d o n e i n a press at 160° C a n d 1000 p s i f o r 18 h o u r s .

N o p o s t c u r i n g is r e q u i r e d .

Studies with Perfluoro(4'Carbomethoxybutyl S e v e r a l types

Vinyl Ether)

of c r o s s l i n k e d structures w e r e p r e p a r e d b y

m e r i z i n g v i n y l ethers c o n t a i n i n g 4 - c a r b o m e t h o x y p e r f l u o r o a l k y l

copolymoieties

i n t h e s t r u c t u r e a n d u s i n g v a r i o u s c r o s s l i n k i n g agents to b r i n g a b o u t vulcanization. Synthesis parent

of

Perfluoro(4-Carbomethoxybutyl

ester w a s p r e p a r e d f r o m

fluoropropylene

Vinyl

Ether).

The

fluoride

and hexa-

o x i d e b y t h e reactions s h o w n i n F i g u r e 2.

T h i s ester

h a d a b o i l i n g p o i n t o f 146°C,

perfluoroglutaryl

a n d showed

characteristic v i n y l

ether

i n f r a r e d absorptions a t 5.42/*, 5.55/A ( c a r b o n y l g r o u p ) , a n d 10.0/x ( - O C H

3

group). A c u t a l l y , b e t t e r y i e l d s of t h e m o n o c a r b o x y l i c

a c i d esters are o b

t a i n e d b y p y r o l y z i n g t h e h a l f - n e u t r a l i z e d a c i d i n s t e a d of t h e d i p o t a s s i u m salt.

E v e n so, t h e y i e l d of ester is o n l y a b o u t 25%.

Polymerization.

P o l y m e r i z a t i o n is c a r r i e d o u t i n t h e s a m e r e a c t o r

as i n d i c a t e d p r e v i o u s l y i n t h e s t a n d a r d persulfate-sulfite system.

The

presence o f t h e ester ( 1 m o l e % c h a r g e d ) i n t h e p o l y m e r is i n d i c a t e d b y t h e s t r o n g i n f r a r e d a b s o r p t i o n b a n d a t 5.55/x, a n d mass b a l a n c e i n d i c a t e s t h a t most o f t h e ester is i n c o r p o r a t e d . Crosslinking

the

Ester-Containing

b r o u g h t a b o u t easily u s i n g a c o n v e n t i o n a l

Polymer.

Crosslinking was

fluoroelastomer

hexamethyl-

enediamine carbamate cure, or b y using p-phenylenediamine. samples

tested, v u l c a n i z a t e p r o p e r t i e s

(hardness,

elongation)


I n the and re-

18


0 - C F - C F - 0 - C F = CF 2

2

F PERFLUORO (2-Phenoxypropyl Vinyl Ether)

F

F


F

Figure 5.

Monomers containing the phenoxy group

perfluoro-

sistance t o c h e m i c a l s a n d fluids i n d i c a t e d a d e q u a t e c u r i n g . less, c o m p r e s s i o n

set values

Neverthe

( 7 0 hours a t 121° C ) o n stocks v a r i e d

b e t w e e n 87 a n d 100%, i n d i c a t i n g t h e extreme m o b i l i t y o f the c r o s s l i n k i n g b o n d a t m o d e r a t e l y h i g h temperatures.

M e t a t h e t i c a l reactions o f t h e

ester groups, w i t h a m i n e s , a m m o n i a , a n d h y d r a z i n e g a v e m o d e l cross l i n k structures.

Heat-loss studies o n these,

along with

model

com

p o u n d s p r e p a r e d f r o m the free a c i d , i n d i c a t e d that c a r b o n y l functions are not t h e r m a l l y stable e n o u g h .

Studies with Monomers Containing the Perfluorophenoxy T w o monomers

containing the perfluorophenoxy

Group

group have been

synthesized a n d copolymerized w i t h T F E a n d P M V E . these m o n o m e r s are s h o w n i n F i g u r e 5. ing

Structures o f

P o l y m e r i z a t i o n a n d crosslink

reactions a r e s i m i l a r f o r p o l y m e r s c o n t a i n i n g these t w o i s o m e r i c

monomers a n d , a c c o r d i n g l y , these p o l y m e r s are discussed together. Synthesis of the P h e n o x y - C o n t a i n i n g M o n o m e r s .

Perfluoro (2-phe-

n o x p r o p y l v i n y l ether) is p r e p a r e d b y t h e route s h o w n i n F i g u r e 6 ( 3 ) . T h e 2-phenoxy

compound

various monomers. glass e q u i p m e n t .

requires t h e l e a s t - i n v o l v e d s y n t h e s i s o f t h e

T h e first t w o steps w e r e c a r r i e d o u t i n o r d i n a r y T h e last r e a c t i o n w a s c a r r i e d o u t u s i n g a b e d o f

d r i e d s o d i u m carbonate. P e r f l u o r o ( 3 - p h e n o x y p r o p y l v i n y l ether) six-step r o u t e s h o w n i n F i g u r e 7. out w i t h o u t i s o l a t i n g the p r o d u c t s .

( 7 ) is s y n t h e s i z e d b y t h e

T h e first three steps m a y b e c a r r i e d T h e a c i d c h l o r i d e p r o d u c t of step

3 is s e p a r a t e d b y f r a c t i o n a l d i s t i l l a t i o n , as is the a c i d fluoride p r o d u c t o f step 4.

I n step 5, the p r o d u c t is separated as the l o w e r o f a t w o - l a y e r

p r o d u G t a n d is p u r i f i e d b y d i s t i l l a t i o n .

T h e upper layer, a complex of


2.

Terpolymers

KALB ETAL.

C s F , the starting acid lyst.

19

fluoride,

a n d t e t r a g l y m e m a y b e r e u s e d as c a t a

B e t t e r p r o d u c t y i e l d s a r e o b t a i n e d w i t h reused catalyst t h a n w i t h

v i r g i n catalyst. fluidized

T h e last r e a c t i o n (step 6 ) is best c a r r i e d o u t u s i n g a

b e d of d r i e d s o d i u m c a r b o n a t e at 270°-300° C .

Polymerization. monomers

T e r p o l y m e r s of P M V E a n d T F E w i t h either of the

containing a phenoxy group have been prepared i n a pres

sure vessel u s i n g a n aqueous

redox p o l y m e r i z a t i o n system.

positional molar T F E / P M V E

ratio i n t h e p r e f e r r e d p o l y m e r is about

60/40.

T h e com

T h e t h i r d m o n o m e r p o l y m e r i z e s a t about t h e same rate as t h e

P M V E a n d is f e d either neat (as a l i q u i d ) o r i n F r e o n F - 1 1 3 s o l u t i o n . Downloaded by MONASH UNIV on November 26, 2014 | http://pubs.acs.org Publication Date: June 1, 1973 | doi: 10.1021/ba-1973-0129.ch002

I n f r a r e d analysis o f the b a n d at 10.0/x indicates 75-85% i n c o r p o r a t i o n o f the p h e n o x y

compound

over t h e 1-4 m o l e % m o n o m e r

change

range.

O n e t o 2 m o l e % of the crosslink m o n o m e r m u s t b e i n c o r p o r a t e d i n t h e elastomer to ensure g o o d v u l c a n i z a t e properties. 1. CcFc-OH + CsoC0 6

5

2

3

3

° » TETRAGLYME R

T

t 0

5 Q

0 / \ 2. C F - O C s + (n+1)CF -CF-CF 6

5

2

C

C F OCs + CsHCCU g

6

5

5

3

CF CF 0 I I II C F -0-(-CF-CF -0-KF-C-F 3

3

in-is°r ° ^ U

6

3

5

2

n= 1 BUT THERE MAY BE SOME n=2 CF

CF

3

3. C F - 0 - f C F - C F - 0 - ) t> o c 6

5

2

n

3

- C F - C 0 F r ^ ^ C F 0 - f C F - 0 + CF=CF 200-300°C B.R = 6 5 - 6 8 ° / 9 m m For n = 1 N 25°C = 1.3639 6

5

3

6

2

n

D

For n = 0

Figure

6.

Crosslinking

Synthesis

of perfluoro(2-phenoxypropyl

vinyl

Perfluorophenoxy-Containing Elastomers.

t i o n o f t h e perfluoroelastomer c a r r i e d o u t several w a y s . enediamine,

(Wall a Plummer, U.S. Patent 3,192,190, Unsatisfactory polymerization)

containing a phenoxy

ether) Vulcaniza

group

may be

O n e m e t h o d uses d i a m i n e s s u c h as p - p h e n y l -

tetraethylenepentamine,

or hexamethylenediamine

carba

m a t e ( D u P o n t D I A K N o . 1) (3). A t y p i c a l r e c i p e is s h o w n i n F i g u r e 8. T h e r u b b e r a n d t h e c o m p o u n d i n g ingredients a r e m i x e d o n a c o n ventional rubber

m i l l , a n d t h e d e s i r e d shape

molded

i n a press at

500-1000 p s i o n t h e s h a p e d p i e c e f o r 30 m i n u t e s at 160° C . T h e p i e c e is t h e n r e m o v e d f r o m t h e press a n d p o s t c u r e d stepwise o v e r five to s i x days t o c o m p l e t e v u l v a n i z a t i o n .

O u r present c o n c e p t o f this c r o s s l i n k

i n g r e a c t i o n i n v o l v e s r e a c t i o n of the d i a m i n e ( F i g u r e 9 ) w i t h the a c t i v e fluorine

a t o m p a r a t o the o x y g e n l i n k a g e o n the a r o m a t i c r i n g to l i b e r a t e

hydrogen

fluoride

(11).

T h i s , i n t u r n , reacts w i t h m a g n e s i u m o x i d e t o


20


1.

C F 0H + K C0 6

5

2

3

C

R

H

E

3

F

^

X

• C F -0K 6

+ KHC0

5

3

( 80% when isolated ) 0 2.

C F 0K + CF = CF +C0

3.

150 psig 0 II 3 C F - 0 - C F - C F - C - 0 K + POCI3

6

5

2

6

5

2

2

g

2

™ ' C F -0-CF -CF -C-0K

H

6

2

5

2

2

(95%) 0 II ^ • 3 C F - 0 - C F - C F - C - C l + K3PO4

c

6

5

2

(85%)


4-

0 II C F - 0 - C F C F - C - C l + NaF 6

5

2

2

T

M

S

6

0

5

2

2

5

2

(B.P. 49°/11mm)

^(2)

CF 0

C F - 0 - C F - C F - C - F + CF -CF-CF 6

5 mm )

0 II ' C F - 0 - C F - C F - C - F + NaCl (85%)

5.

2

(BP. 54°/

2

2

• C F -0-(CF

3

6

5

) ~CF -0-CF-C-F

2

2

2

(>70%) (B.P. 7 7 ° / l l m m ) CF 0 I II C F -0-(CF ) -CF -0-CF-C-F 3

6.

6

5

2

2

2

Z

7

N00CO7 ^ . Q

' C F - 0 - ( C F ) - C F - 0 - C F = CF

C

6

5

2

2

2

2

(>85%)

Figure

7.

Synthesis of perfluoro(3-phenoxypropyl

vinyl

ether)

PARTS by WEIGHT POLYMER MEDIUM

100

THERMAL

MAGNESIUM

BLACK

OXIDE

HEXAMETHYLENE

20.0 15.0

DIAMINE CARBAMATE

1.5

Figure 8. Diamine formulation for curing perfluorophenoxy-containing polymer form water and magnesium

fluoride.

U n d e r the c o n d i t i o n s r e q u i r e d to

complete the vulcanization, water must b e expelled from t h e m o l d e d p i e c e , a n d , because o f the l o w p e r m e a b i l i t y o f the r u b b e r to m o i s t u r e , the step postcure must b e c a r r i e d o u t s l o w l y to p r e v e n t s p o n g i n g . Alternately, aromatic bisnucleophiles m a y b e used to cure perfluorophenoxy-containing polymers. agents are s h o w n i n F i g u r e 10. salts are also effective. to f u n c t i o n w e l l . are

p o l y ethers 2

P o t a s s i u m salts are s h o w n , b u t c a l c i u m

T h e s e c r o s s l i n k i n g agents r e q u i r e a n accelerator

I n g e n e r a l , the accelerators f o u n d to b e most efficient (Figure

11) such

CH -0-(CH -CH ) -OH—of 3

these

E x a m p l e s of t y p i c a l c r o s s l i n k i n g

2

n

as p o l y e t h y l e n e

ether

glycols—

m o l e c u l a r w e i g h t a b o u t 350 ( C a r b o w a x


2.

KALB ET AL.

350)

21

Terpolymers

( 8 ) , or the cyclic polyether compounds of " c r o w n " structure ( 9 ) .

A t y p i c a l f o r m u l a t i o n is s h o w n i n F i g u r e 12. T h e r o l e of t h e accelerators is n o t k n o w n , b u t t h e y m a y serve as s o l u b i l i z i n g agents, c o m p l e x i n g agents, o r i o n i z a t i o n agents.

T h e com

p l e t e c u r i n g r e a c t i o n is q u i t e s l o w , a n d t h e content o f c r o s s l i n k i n g sites is l o w so that l o n g post c u r e s — u p t o five d a y s — a r e r e q u i r e d .

T h e last

24 hours o f t h e c u r e is c a r r i e d o u t at 290° C u n d e r n i t r o g e n t o o b t a i n t h e best h i g h - t e m p e r a t u r e p r o p e r t i e s .


CF

CF

3

&

2

;

+

2

CF CF I I 0-CF-CF -0-CF 3

CH

9.

*

2

2

\

2

2

Figure

. '/ Mg0

2

i

F

Raw Polymer

H N-CH I CH + 2

2

0-CF-CF -0-CF

Diamine

+

\

(MgF )

curing of polymer

2

+ V H 0 2

2

phenoxy-containing

Properties

T h e p h y s i c a l properties o f r a w t e r p o l y m e r are essentially i d e n t i c a l w i t h t h a t o f t h e d i p o l y m e r d e s c r i b e d b y B a r n e y et al. ( I ) , w i t h a f e w exceptions.

L o w - t e m p e r a t u r e characteristics a r e essentially u n c h a n g e d ,

b u t u n c u r e d p o l y m e r s s h o w s o m e loss i n t h e r m a l s t a b i l i t y a t t r i b u t a b l e t o the third monomer.

F o r example, a perfluorophenoxy-containing

poly

m e r lost a b o u t 12% o f its w e i g h t after heat a g i n g i n a n a i r c i r c u l a t i n g o v e n a t 316° C i n s i x d a y s , whereas t h e d i p o l y m e r c o n t r o l lost o n l y 6.5% u n d e r s i m i l a r c o n d i t i o n s . Because of the similarity of the t h i r d monomers polymer

density

is essentially

constant

from

investigated, r a w

polymer

to polymer:

2.04 ± 0.01. C u r e d a n d p o s t c u r e d g u m stock has a d e n s i t y o f 2.01 a n d b l a c k stock c o n t a i n i n g 10 p h r .

S A F b l a c k has a d e n s i t y o f 2.02.

R a w p o l y m e r is i n s o l u b l e i n most fluids, m a k i n g t h e d e t e r m i n a t i o n of s o l u t i o n v i s c o s i t y v e r y difficult. be

prepared

Solutions o f 0.2 g / 1 0 0 g solvent m a y

i n 2,2,3-trichloroheptafluorobutane

(Halocarbon


437, b y

22

POLYMERIZATION REACTIONS A N DN E W POLYMERS O'K*


DIPOTASSIUM SALT OF HYDROQUINONE

Figure

10.

DIPOTASSIUM SALT OF 2,2"BIS( 4-HYDROXYPHENYL) PROPANE ( BISPHENOL A )

Typical

CH3-O

0"K*

DIPOTASSIUM SALTOF 2,2-BIS(4-HYDROXYPHENYL) PERFLUOROPROPANE (BISPHENOL AF)

bisnucleophiles used in curing perfluoroelastomer

-(-CH -CH -0 2

2

phenoxy-containing

H

e.g."CARBOWAX

350"

DICYCLOHEXYL- 1 8 - C R 0 W N - 6 ( 2 , 5,8,15,18, 21 -HEXAOXATRICYCLO [ 2 0 . 4 . 0 . 0

Figure 11.

Accelerators

H a l o c a r b o n Products, Inc.)

9,18

j

for perfluoroelastomer

HEXACOSANE)

curing

o r i n a f e w other chlorofluorocarbons

con

t a i n i n g 2-3% b y w e i g h t of a p o l a r cosolvent s u c h as m e t h a n o l , t r i c h l o r o acetic a c i d , o r g l y m e .

I n these solvents, d e t e r m i n a t i o n s of s o l u t i o n v i s

cosity i n d i c a t e that i n h e r e n t viscosities

( 7 7 ^ ) o f 0.4 o r greater a r e

necessary to o b t a i n a d e q u a t e v u l c a n i z a t e properties.

Properties of the Cured Polymer Stocks E x p e r i m e n t a l studies to date i n d i c a t e that there is l i t t l e b a s i c differ ence i n the resistance to c h e m i c a l s o r s w e l l i n g b y fluids b e t w e e n c o m positions c o n t a i n i n g t h e different crosslink m o n o m e r s . T h i s is p r o b a b l y because t h e c u r e site m o n o m e r , a n d e v e n t h e c r o s s l i n k i n g agent i n the p o l y m e r , represent o n l y a s m a l l p a r t of the finished v u l c a n i z a t e . F u r t h e r m o r e , the i n h e r e n t resistance o f the p o l y m e r to various fluids a n d to c h e m i c a l attack, c o u p l e d w i t h its l o w p e r m e a b i l i t y , c o n t r i b u t e to the s i m i l a r i t y o f materials c u r e d w i t h various agents. O n l y the most d r a s t i c tests s h o w differences i n p e r f o r m a n c e .


2.

23

Terpolymers

KALB E TA L .

A b r i e f t a b u l a t i o n o f the v u l c a n i z a t e properties t o i n d i c a t e the l e v e l of p e r f o r m a n c e t h a t c a n b e a c h i e v e d w i t h these n e w perfluoroelastomers is i n o r d e r (10): F i g u r e 13 tabulates some o f t h e p h y s i c a l properties. T h e d a t a s h o w n are for b l a c k stocks. F i g u r e 14, illustrates t h e o u t s t a n d i n g resistance o f b l a c k v u l c a n i zates to heat a g i n g i n a i r ( t h e r m a l o x i d a t i o n ) .


POLYMER SUPER ABRASION FURNACE BLACK MAGNESIUM

BLACK STOCK

GUM STOCK

100

100

10

OXIDE

4

ACCELERATOR

3

BISPHENOL

3

4*

Cure 30 min at 177 ° C Oven Cure. ROOM TEMP to 290 ° C 5 DAY S T E P - N 2

Figure 12. Typical cure formulation for curing phenoxy-containing perfluoroelastomer with bisnucleophiles 90 DUROMETER STOCK Cure

30 mins. / 3 5 0 ° F

20phr SAF BLACK + CURATIVES

+ POSTCURE TO 4 0 0 ° F ( 5 0 0 ° F tor COMP. SET)

ORIGINAL PHYSICAL PROPERTIES STRESS / STRAIN at 7 5 ° F

Mioot Psi.

1350

T , psi.

2720

B

E

B

, %

160

HARDNESS (Durometer A )

89

COMPRESSION SET-METHOD B 70 hrs. at 121 °C

(250 °F )

23%

70 hrs. at 288 °C

(550 °F )

45%

CLASH -BERG STIFFNESS TEMP. (10,000 psi TORSIONAL MODULUS )

+28°F

BRITTLE TEMPERATURE

-38°F

TEMPERATURE T-IO T-50

RETRACTION

TEAR D-470 (pli)

Figure

13. Typical

+30 °F 46°F 13

physical properties of black vulcanizates

perfluoroelastomer


24



500 |

400

5 (3

300

TEMP. 2 8 8 ° C AIR

(550°F)

CIRCULATING OVEN

12 16 T I M E , DAYS

Figure

14. Effect of heat aging on perfluoroelastomer (10 phr SAF) vulcanizate tensile properties

black

3*

It—

200

"X

o z

S

100

232°C (450 F) 30mm Hg of MOIST AIR W

V

cJT 24 b ~ 20 / o. 16 m

S

,2

o

T7~ V

V V

I"

8 4• 20

Figure

40 60 WEEKS at

80 232°C

100

15. Effect of heat aging under conditions for high-performance aircraft

120

140

of operation

F i g u r e 15 shows heat a g i n g characteristics at 30 m m a i r pressure a n d 232° C — c o n d i t i o n s s i m i l a r to w h a t a h i g h - p e r f o r m a n c e a i r c r a f t m i g h t encounter i n flight. F i g u r e 16 illustrates t h e excellent resistance of b l a c k v u l c a n i z e d stocks to s w e l l i n g w i t h various fluids.


2.

KALB ET AL.

25

Terpolymers

I n a d d i t i o n to b l a c k , t h e elastomer m a y b e c o m p o u n d e d w i t h other common

fillers

s u c h as s i l i c a , c l a y , a n d asbestos.

H o w e v e r , i n general,

t h e i r r e i n f o r c i n g properties a r e i n f e r i o r t o c a r b o n . is advantageous t o c o m p o u n d the r u b b e r w i t h o u t

F o r c e r t a i n uses, i t fillers.

This gum vul

c a n i z a t e has p o o r e r p h y s i c a l properties t h a n l o a d e d stock b u t is better i n c h e m i c a l resistance. perfluoro greases

B o t h r e i n f o r c e d a n d g u m recipes m a y i n c l u d e

o r oils as plasticizers t o soften v u l c a n i z a t e s w i t h o u t

affecting a p p r e c i a b l y c h e m i c a l resistance. F i g u r e 17 tabulates t h e e l e c t r i c a l properties o f t h e g u m stock i n


c o m p a r i s o n w i t h those of T e f l o n

fluorocarbon

resin.

WT. INCREASED

TENSILE EL0N6. RETD..% RETD.,%

0

100

100

1.3

80

100

3.2

75

100

0

100

100

ACETONE

1.0

73

100

ETHYL

1.2

73

100

1.0

96

100

0.5

94

100

0

100

100

JP-5

JET-FUEL

BENZENE CARBON 2B

TETRACHLORIDE

ALCOHOL

ACETATE

PYRI DINE ACETIC

ANHYDRIDE

SODIUM

HYDROXIDE

(46%)

Figure 16. Resistance of black vulcanizate perfluoroelastomer (10 phr SAF black) to various fluids at 25° C and seven-day immersion

(i) ELASTOMER DIELECTRIC

CONSTANT " E "

2.8-3.2

DISSIPATION FACTOR "D" (50%RH, 7 3 ° F ) DC.

RESISTIVITY

"p"

DIELECTRIC STRENGTH ( BREAKDOWN )

1 x 10"

10

18

3

ohm-cm

> 2 0 0 0 volts/mil

TFE 2.1 3 x 10"

4

10

18

400

(1) GUM STOCK -VULCANIZED 2

Figure

PLASTICS

WORLD

17. Dielectric

(1965).

properties elastomer

of gum

perfluoro-


26


Safety Notes ( 1 ) M a n y of perfluoro c o m p o u n d s m e n t i o n e d a r e toxic a n d s h o u l d be h a n d l e d o n l y b y c o m p e t e n t investigators i n w e l l v e n t i l a t e d areas. ( 2 ) T h e p o l y m e r i z a t i o n w o r k r e p o r t e d h e r e i n requires c o m p r e s s i o n of tetrafluoroethylene-perfluoro ( m e t h y l v i n y l e t h e r ) mixtures. T h i s o p e r a tion must b e considered potentially hazardous a n d should b e carried out o n l y i n a d e q u a t e l y b a r r i c a d e d areas. Acknowledgments


T h e authors t h a n k A . F . B r e a z e a l e , D . F . B r i z z o l a r a , D . B . P a t t i s o n , a n d H . J . S t i n g e r for t h e i r c o n t r i b u t i o n s t o this study.

Literature

Cited

1. Barney, A. L . , Keller, W . J., van Gulick, N . M . , J. Polym. Sci., A-1 (1970) 8, 1091. 2. Gladding, E . K., Sullivan, R; U.S. Patent 3,546,186 (1970); Anderson, D. G . , Gladding, E . K., Sullivan, R.; French Patent 1,527,816 (1968). 3. Pattison, D. B.; U.S. Patent 3,467,638 (1969). 4. Henne, A., Pelley, R. L . , J. Amer. Chem. Soc. (1952) 74, 1426. 5. Graham, T. L . , Rubber Age (1960) 43; Fritz, C. G . ; U.S. Patent 3,317,484 (1967). 6. Wall, L . A., Plummer, W . J.; U.S. Patent 3,192,190 (1965). 7. Quarles, R. W., Jr., French Patent 71.09113 (1971); Brizzolara, D . F . , Quarles, R. W., Jr., French Patent 71.09114 (1971). 8. Barney, A. L . , Honsberg, W . U.S. Patent 3,524,836 (1970). 9. Barney, A. L . , Honsberg, W.; U.S. Patent 3,580,889 (1971). 10. Barney, A. L . , Kalb, G . H . , Khan, A. A., Rubber Chem. and Tech. (1971) 44, 660. 11. Brizzolara, D. F . ; this laboratory; unpublished results based on model compound studies indicate primarily para position attack. ;

R E C E I V E D April 13, 1972.


Terpolymers of Tetrafluoroethylene, Perfluoro (Methyl Vinyl Ether), and

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