4 Silicone Amine Cured Fluoroepoxy Resins J. R. GRIFFITH and J. G. O'REAR P o l y m e r i c M a t e r i a l s B r a n c h , C h e m i s t r y D i v i s i o n , N a v a l Research L a b o r a t o r y ,
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Washington, DC 20375
Compounds which c o n t a i n l a r g e q u a n t i t i e s of f l u o r i n e are frequently incompatible w i t h those of a hydrocarbon n a t u r e , and liquid m a t e r i a l s of the two types form separate phases when mixed. This i n c o m p a t i b i l i t y presents a problem regarding the cure of the h e a v i l y f l u o r i n a t e d liquid epoxies p r e v i o u s l y synthesized at NRL (1) because h e a v i l y f l u o r i n a t e d aliphatic amines are not g e n e r a l l y e i t h e r s t a b l e nor r e a c t i v e . For higher temperature c u r e s , some fluoroanhydrides have been synthesized and work well ( 2 ) , but f o r cures near room temperature, compatible c u r i n g agents are not so plentiful. In many r e s p e c t s , silicone compounds are s i m i l a r in t h e i r p r o p e r t i e s to fluorocarbons and advantage can be taken of t h i s s i n c e polyamino silicones can be induced to become compatible w i t h fluoroepoxy r e s i n s q u i t e readily, and the polymers produced when these two types of m a t e r i a l s r e a c t are e x c e p t i o n a l in s e v e r a l important r e s p e c t s . Discussion The s e r i e s of f l u o r i n a t e d diglycidyl ethers represented by the f o l l o w i n g general formula are all clear, c o l o r l e s s liquids a t ambient temperatures:
(I)
This c h a p t e r n o t s u b j e c t t o U . S . c o p y r i g h t .
Published 1980 American Chemical Society May; Resins for Aerospace ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
36
RESINS F O R A E R O S P A C E
Amine-bearing s i l o x a n e s o f t h e f o l l o w i n g type a r e a l s o liquids: CH« CEL I 3 j 3 H N C H CH C H S i-O-S i C H C H C H N H I I 2 2j j 2 2 2 2 0
0
0
0
0
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C H
C H
3
0
0
(II)
0
3
I n t h e c o n v e n t i o n a l r e a c t i o n between g l y c i d y l e t h e r s and a m i n e s , t h e s e compounds a r e d i f u n c t i o n a l a n d t e t r a f u n c t i o n a l r e s p e c t i v e l y , w h i c h r e q u i r e s two m o l e s o f t h e f l u o r o e p o x y f o r e a c h of t h e s i l i c o n e amine i n a s t o i c h i o m e t r i c b l e n d . This composition produces a t i g h t l y c r o s s l i n k e d network, b u t t h e f o l l o w i n g m o d i f i c a t i o n o f t h e s i l i c o n e amine produces a n e l a s t o m e r i c c o m p o s i t i o n because o f t h e reduced f u n c t i o n a l i t y o f t h e amine. CH \3
CH« C H I I
0
3
CH«
n
3
/
3
^ICH CH CH Si-0-SiCH CH CH N 2
H
2
2
2
CH
3
CH
3
2
(III)
2
\
B l e n d s o f t h e s e two t y p e s o f a m i n e s g i v e c u r i n g a g e n t s c a p a b l e o f p r o d u c i n g p l a s t i c s upon r e a c t i o n w i t h t h e f l u o r o e p o x y w h i c h a r e i n t e r m e d i a t e i n p r o p e r t i e s b e t w e e n t h e e x t r e m e s . The m a t e r i a l produced from ( I ) and ( I I I ) a l o n e i s a n e a r l y l i n e a r polymer i n w h i c h f l u o r o c a r b o n and s i l i c o n e a l t e r n a t e a l o n g t h e p o l y m e r chains. Experimental
(R
f
A 25 X 150 mm t e s t t u b e was c h a r g e d w i t h 14.0 g o f ( I ) = C F ) and 2.0 g o f ( I I ) . C a r e was t a k e n t o e x p o s e t h e 6
1 3
amine t o t h e a t m o s p h e r e f o r a minimum t i m e i n o r d e r t o a v o i d carbon d i o x i d e absorption. A small Teflon-coated magnetic s t i r r i n g b a r was d r o p p e d i n t o t h e t e s t t u b e a n d i t was s e a l e d t i g h t l y w i t h a rubber stopper. The t e s t t u b e was t h e n c l a m p e d i n a v e r t i c a l p o s i t i o n w i t h t h e l o w e r o n e - h a l f immersed i n a s i l i c o n e o i l b a t h a t 50°C, and r a p i d s t i r r i n g was begun. A t f i r s t , t h e compos i t i o n was i n c o m p a t i b l e and a p p e a r e d " m i l k y " . A f t e r s t i r r i n g f o r 20 m i n u t e s , t h e i n c o m p a t i b i l i t y c l e a r e d t o p r o d u c e a c o l o r l e s s transparent syrup. A t t h i s time t h e syrup would c l o u d i f cooled to room t e m p e r a t u r e , b u t a f t e r a n a d d i t i o n a l 20 m i n u t e s s t i r r i n g a t 50°C, i t w o u l d r e m a i n c l e a r a t 25°C. T h i s p r e p o l y m e r s y r u p was d i v i d e d i n t o two p a r t s . One p o r t i o n was d i s s o l v e d i n t r i f l u o r o t r i c h l o r o e t h a n e a s a s o l v e n t a n d u s e d t o p r o d u c e p r o t e c t i v e c o a t i n g s o f h i g h h y d r o p h o b i c i t y . The o t h e r p o r t i o n was a l l o w e d t o c u r e f o r 24 h o u r s a t 25°C d u r i n g which g e l a t i o n occurred t o produce a c l e a r , n e a r l y c o l o r l e s s
May; Resins for Aerospace ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
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GRIFFITH
Fluoroepoxy Resins
A N D O'REAR
0.4
/
/
/ I
2
3
4
5
6
7
8
9
10
II
12
MONTHS OF IMMERSION
Figure I.
Water absorption of a silicone amine-cured fluoroepoxy during 1 yr of constant immersion
May; Resins for Aerospace ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
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RESINS F O R
plastic. The s t r e n g t h o f t h i s p l a s t i c was s u b s t a n t i a l l y by a p o s t c u r e a t 60°C f o r 5 h o u r s .
AEROSPACE
enhanced
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Conclusions The m a t e r i a l s p r e s e n t e d h e r e a r e e a s i l y p r o c e s s e d r e s i n s o f t h e epoxy c l a s s w h i c h a r e composed o f two o f t h e m o s t w a t e r r e s i s t a n t p o l y m e r t y p e s known. C o n s e q u e n t l y , i t i s n o t s u r p r i s i n g t h a t t h e water a b s o r p t i o n o f such r e s i n s i n t h e cured form would be m i n i m a l , a n d , i n d e e d , F i g u r e 1 i l l u s t r a t e s t h e v e r y l o w w a t e r a b s o r p t i o n o f such a r e s i n d u r i n g a year's c o n s t a n t immersion. I n t h e p r e c u r e d s t a t e t h e r e s i n components a r e l i q u i d s o f v e r y low s u r f a c e t e n s i o n and, as such, a r e e x c e l l e n t w e t t i n g f l u i d s . I t i s suggested, t h e r e f o r e , that composite s t r u c t u r e s which e n t a i l d i f f i c u l t s o a k - i n problems o r which encounter a s e r i o u s problem of water d e g r a d a t i o n i n s e r v i c e c o u l d p r o f i t a b l y u s e t h e s e systems. Literature 1. 2.
Cited
O'Rear, J. G.; Griffith, J. R.; O r g a n i c C o a t i n g s and Plastics Preprints, April 1973, 3 3 , No. 1, 657. Griffith, J. R.; O'Rear, J. G.; R e a r d o n , J. P.; A d h e s i o n S c i e n c e a n d T e c h n o l o g y , P l e n u m Press, New Y o r k , 1 9 7 5 , p . 4 2 9 .
RECEIVED
February
15,
1980.
May; Resins for Aerospace ACS Symposium Series; American Chemical Society: Washington, DC, 1980.
