Rubber Coatings for Fiberglass Protection in an Alkaline Environment

31 Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 21, 2018 | https://pubs.acs.org Publication Date: October 14, 1986 | doi: 10.1021/bk-1986-0322.ch031

Rubber Coatings for Fiberglass Protection in an Alkaline Environment P. Dreyfuss , R. D . Vargo , R. S. Miller , and R. Bright 1

CEMCOM

2

3

Research Associates, Inc., 9901 George Palmer Highway, Lanham, MD 20706

Glass is known to be r e a d i l y attacked by strong alkali. This was reaffirmed in the present study when samples of s t y l e 3701 Ε - g l a s s f a b r i c l o s t 90% of t h e i r original tensile strength after immersion in aqueous alkali at pH 13 and 80°C for 7 days. The purposes of this study were to gain some understanding of the relative importance of the factors that influence the d e g r a d a t i o n of g l a s s and coated g l a s s in alkaline environments and to use t h a t knowledge to develop a p r o t e c t i v e c o a t i n g . F a c t o r s evaluated included the c o m p o s i t i o n , surface area and and nature of the sur face of the glass. The effects of the nature, uniform ity, thickness and degree of bonding of glass coatings as well as different methods of applying coatings were considered. I t was shown t h a t w e l l - b o n d e d rubber coatings can lead to good protection of glass i n alka line environments.

G l a s s i s known t o be r e a d i l y a t t a c k e d by s t r o n g a l k a l i Q_). T h i s was r e a f f i r m e d i n t h e p r e s e n t study when samples o f s t y l e 3701 E - g l a s s f a b r i c f r o m B u r l i n g t o n G l a s s F a b r i c s Co. l o s t 90% o f t h e i r o r i g i n a l t e n s i l e s t r e n g t h a f t e r immersion i n aqueous a l k a l i a t pH 13 and 80°C f o r 7 days. The purposes o f t h i s s t u d y were t o g a i n some u n d e r s t a n d ing o f t h e r e l a t i v e importance o f t h e factors that influence the d e g r a d a t i o n o f g l a s s and c o a t e d g l a s s i n a l k a l i n e environments and t o u s e t h e knowledge g a i n e d t o d e v e l o p a c o a t i n g t h a t would p r o t e c t g l a s s i n a l k a l i n e environments.

'Current address: Michigan Molecular Institute, 1910 W. St. Andrews Road, Midland, Ml 48640 ^Current address: Institute of Polymer Science, The University of Akron, Akron, OH 44325 ^Current address: 1749 Dana Street, Crofton, M D 21114 0097-6156/86/0322-0349S06.00/0 © 1986 American Chemical Society

Dickie and Floyd; Polymeric Materials for Corrosion Control ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

350

POLYMERIC MATERIALS FOR CORROSION CONTROL

Experimental Materials. T a b l e I l i s t s t h e k i n d s a n d sources o f g l a s s f i b e r s , b a r s and s l i d e s u s e d i n t h i s s t u d y . E - g l a s s f a b r i c s were from B u r l i n g t o n G l a s s F a b r i c s Co. G l a s s beads were from P e t r a r c h Systems, Inc. o r P o t t e r s I n d u s t r i e s , I n c . 3 - A m i n o p r o p y l t r i e t h o x y s i l a n e as was o b t a i n e d f r o m P e t r a r c h S y s t e m s , I n c . The b u l k p o l y b u t a d i e n e was F i r e s t o n e ' s Diene 35 NFA, a n o n c r y s t a l l i z y i n g a n i o n i c p o l y b u t a d i e n e o f M « 1 5 0 , 0 0 0 a n d cis:trans: v i n y l (%) * 36:54:10. N a t u r a l rubber l a t e x e s ( 4 5 a n d 5 5 % s o l i d s ) were f r o m K i l l i a n L a t e x I n c . and SBR l a t e x P o l y s a r XE-404 was from P o l y s a r R e s i n s I n c . Dicumyl p e r o x i d e (DICUP R) was f r o m H e r c u l e s , I n c . The aqueous a l k a l i s o l u t i o n was p r e p a r e d u s i n g 0.008g (0.022 m o l e s ) / l sodium h y d r o x i d e , 3.45g (0.062 m o l e s ) / l p o t a s s i u m h y d r o x i d e and 0.48g (0.006 m o l e s ) / l c a l c i u m h y droxide. A c e t a t e s p l i c i n g s o l u t i o n was o b t a i n e d from B u r l i n g t o n G l a s s F a b r i c s Co. Alumina a c i d (80-200) mesh and c a l c i u m o x i d e were from F i s h e r S c i e n t i f i c Co. Boron o x i d e (99%) was from A l f a P r o d u c t s , Thiokol/Venton D i v i s i o n . W e i g h t L o s s S t u d i e s . G l a s s samples were r i n s e d s u c c e s s i v e l y w i t h t o l u e n e a n d a c e t o n e a n d d r i e d i n an oven a t 80°C f o r 10 min. G l a s s s a m p l e s f o r t e s t i n g i n water were p l a c e d i n a l a r g e S o x h l e t e x t r a c t o r ( f r o m a 120 mm j o i n t ) and e x t r a c t e d w i t h d i s t i l l e d water f o r 24 h r s . b e f o r e d r y i n g and r e w e i g h i n g . The weight l o s s was the d i f f e r e n c e b e t w e e n t h e i n i t i a l weight and the f i n a l w e i g h t . S i n c e none o f t h e s a m p l e s l o s t a p p r e c i a b l e w e i g h t , t h i s method was a l s o u s e d f o r washing samples f o r weight l o s s s t u d i e s a f t e r immersion i n alkali. A f t e r c o o l i n g , weighed samples f o r t e s t i n g i n a l k a l i were p l a c e d i n p r e c l e a n e d 1000 m l p o l y p r o p y l e n e b o t t l e s f i t t e d w i t h d i v i d e r s from porous p o l y p r o p y l e n e when a p p r o p r i a t e . Beads, chopped f i b e r s a n d powders were p l a c e d i n T e f l o n e x t r a c t i o n t h i m b l e s b e f o r e p u t t i n g i n t o t h e b o t t l e s . Long f i b e r s were wrapped around s p e c i a l p o r o u s p o l y p r o p y l e n e h o l d e r s a s l o n g a s the b o t t l e s and then put i n t o the b o t t l e s . The b o t t l e s w e r e t h e n f i l l e d w i t h the aqueous a l k a l i s o l u t i o n , c l o s e d w i t h T e f l o n l i n e d caps and p l a c e d f o r 7 days i n a c i r c u l a t i n g w a t e r b a t h a t 80°C. The s a m p l e s were removed, t h o r o u g h l y r i n s e d w i t h w a t e r , d r i e d o v e r n i g h t i n an a i r oven a t 80°C, c o o l e d i n a d e s s i c a t o r and reweighed. Dumbbells from c u r e d rubber samples were s i m i l a r l y t e s t e d . A l k a l i D u r a b i l i t y T e s t s o f G l a s s F i b e r s and G l a s s F a b r i c s . These t e s t s were c a r r i e d o u t u s i n g a m o d i f i c a t i o n o f B u r l i n g t o n T e s t P r o c e d u r e FP-017. For d u r a b i l i t y t e s t s g l a s s f i b e r s were t r e a t e d i n t h e same way a s f o r w e i g h t l o s s s t u d i e s . C a r e was t a k e n t o run t e n s i l e t e s t s o n l y on t h o s e p o r t i o n s o f the f i b e r , which had not b e e n b e n t a r o u n d t h e edges o f the h o l d e r . Samples o f g l a s s f a b r i c 27.9 cm. ( 1 1 " ) l o n g ( i n the warp d i r e c t i o n ) and 15.2 cm. (6") wide ( i n t h e f i l l d i r e c t i o n ) were c u t from r o l l s o f f a b r i c and c o a t e d as d e s i r e d . The p r e p a r e d c l o t h specimens were p l a c e d i n heavy-duty 4.5 -mil t h i c k 24.13 χ 40.64 cm Kapak h e a t - s e a l a b l e pouches. Enough a l k a l i s o l u t i o n t o f i l l the bag was added, the pouch was h e a t - s e a l e d u s i n g a S c o t c h Pak Pouch S e a l e r and p l a c e d i n the c i r c u l a t i n g water b a t h a t 80°C f o r 7 d a y s . The f a b r i c was r e m o v e d from t h e a l k a l i s o l u t i o n , r i n s e d w i t h w a t e r , d r i e d o v e r n i g h t i n a vacuum oven a t 60°C, and p r e p a r e d f o r t e n s i l e t e s t i n g .

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n



2

Slides

Soda Lime

18.3 0.07 0.14 1.4 1.6 0.035 0.04 0.033 0.10 0.07 0.35

water; alkali: water: alkali: water: alkali: water: alkali: water: alkali: water: alkali:

% Wt. Loss

No change S l i g h t Fogging S t i f f , n o t much change S o f t and wooly No change No change No change Uniform fogging Fogged, e x t r e m e l y discolored Uniform fogging

Appearance

A f t e r immersion i n t h e medium shown i n column 4 a c c o r d i n g t o t h e procedure g i v e n i n t h e e x p e r i m e n t a l section. Ε-glass were random s i z e s u n s u i t a b l e f o r p e e l t e s t s . P y r e x and q u a r t z b a r s were 127 χ 25 χ 6.5mm. Alkali-resistant glass. Pre-cleaned microscope s l i d e s .

Kimble

F i v e P o i n t s G l a s s Co.

2

Bars

Quartz

4

F i v e P o i n t s G l a s s Co.

2

Cem-FIL Corp*

PPG I n d u s t r i e s * I n c .

B u r l i n g t o n G l a s s F a b r i c s Co.

Source

Bars

Fibers

Bars

Fibers

Form

Weight Loss Comparison f o r D i f f e r e n t G l a s s e s

Pyrex

Ε

Glass

Table I .


352


Tensile Testing. T e n s i l e t e s t s were run on an I n s t r o n 1000 u s i n g a 5.08 cm ( 2 i n c h ) guage l e n g t h a n d a s p e e d o f 12.7 cm ( 5 inches)/min. The p r o c e d u r e s i n B u r l i n g t o n Test Procedure FP-015 (ASTM-D-579) were f o l l o w e d . A t l e a s t 5 specimens o f each sample were tested. F a b r i c t e s t s r e s u l t s a r e q u o t e d f o r t h e warp d i r e c t i o n o n l y . The p e r c e n t r e t e n t i o n o f t e n s i l e s t r e n g t h was c a l c u l a t e d from t h e e q u a t i o n : % r e t e n t i o n « (PA^ NA^ 100 where F^ and FJJA s t r e n g t h a f t e r and b e f o r e a l k a l i immersion, r e s p e c t i v e l y . S i l a n e Treatment. G l a s s b a r s , f i b e r s o r f a b r i c were soaked 5 min i n s t i r r e d s o l u t i o n s ( 0 . 5 , 1.0, 1.5, o r 2.0%) o f 3-aminopropylt r i e t h o x y s i l a n e i n 95% e t h a n o l , then f o r 10 min. i n 95% e t h a n o l , and f i n a l l y f o r 1 min. i n a b s o l u t e e t h a n o l . The g l a s s was h e a t e d o v e r n i g h t i n a vacuum oven a t 110°C t o form a p o l y s i l o x a n e l a y e r bonded to the g l a s s ( 2 ) . Latex Treatment. A t y p i c a l procedure f o r l a t e x treatment i s shown s c h e m a t i c a l l y i n F i g u r e 1. D e t a i l s o f the procedure a r e g i v e n i n U.S. P a t e n t A p p l i c a t i o n S e r i a l No. 06/701,747, f i l e d 2/14/85. Blowers were used t o d i s l o d g e any l a t e x which might e x i s t as "window p a n e " l i k e f i l m s between b u n d l e s o f f i b r e s i n t h e f a b r i c . The tem p e r a t u r e i n the f i r s t two d r y e r s was m a i n t a i n e d a t 75-85°C, too l o w a t e m p e r a t u r e t o c u r e t h e l a t e x d u r i n g the d r y i n g t i m e . The temper a t u r e i n the t h i r d d r y e r was t y p i c a l l y 120°C and c u r i n g o f the r u b b e r was c o n t i n u e d a t t h a t t e m p e r a t u r e f o r 30 m i n u t e s . M i c r o s c o p y r e v e a l e d t h a t t h e f i r s t d i p r e s u l t s i n rubber p e n e t r a t i o n o f t h e f i b e r b u n d l e b u t d o e s n o t c o a t t h e b u n d l e . The second and t h i r d d i p s p r o d u c e c o a t i n g s o f about 10 micrometers each. F i g u r e 2 i s a schematic r e p r e s e n t a t i o n o f t h e manner i n which the c o a t i n g s d e p o s i t on t h e f i b e r s i n the f i b e r b u n d l e . P e e l T e s t s . Ε-glass p l a t e s (0.635 χ 20.32 χ 20.32 cm, 1/4 χ 8 χ 8") were c u t t o ~ 2 . 54 χ 7.62cm (1 χ 3") u s i n g a g l a s s saw. The b a r s w e r e c l e a n e d b y b o i l i n g i n 2% M i c r o s o l u t i o n ( a l a b o r a t o r y c l e a n e r from I n t e r n a t i o n a l P r o d u c t s C o r p . ) , washed f o r 48 h r s . w i t h d i s t i l l e d w a t e r i n a S o x h l e t e x t r a c t o r , d r i e d f o r 2 h r s . i n an a i r oven a t 150°C and s t o r e d i n a d e s s i c a t o r over P2O5 u n t i l used. P e e l t e s t s p e c i m e n s f o r t e s t i n g w i t h o u t immersion i n the aqueous a l k a l i were p r e p a r e d a n d t e s t e d a c c o r d i n g t o p r o c e d u r e s p r e v i o u s l y d e s c r i b e d ( 3-5) . T h u s , d i c u m y l p e r o x i d e was mixed i n t o p o l y b u t a d i e n e o n a n open m i l l . B e f o r e bonding, the e l a s t o m e r was p r e s s e d i n t o a t h i n l a y e r (-0.2 mm) b y p r e m o l d i n g f o r 1 h r . a t 65°C, then p r e s s e d i n t o a s h e e t o f c o t t o n c l o t h and a g a i n premolded f o r 1 h r . a t 65°C. The c l o t h b a c k e d l a y e r was t h e n p r e s s e d a g a i n s t t h e c l e a n e d g l a s s s l i d e s f o r 2 h r . a t 150°C i n a PHI p r e s s a t a p r e s s u r e o f -6 p s i / 5 i n ram i n o r d e r t o c u r e the e l a s t o m e r . The t h i c k n e s s o f the elastomer i n t e r l a y e r i n t h e r e s u l t i n g cloth-elastomer-glass s a n d w i c h was ~0.2mm. 180° P e e l i n g t e s t s were c a r r i e d out on s t r i p s o f c l o t h b a c k e d e l a s t o m e r l a y e r a f t e r t r i m m i n g them t o a u n i f o r m w i d t h on the g l a s s o f 2 cm. The e l a s t o m e r was p e e l e d o f f the g l a s s a t a c o n s t a n t r a t e , 0.5 cm/min (0.0083 cm/sec) u s i n g a t a b l e model I n s t r o n . The work o f a d h e s i o n , W^, was c a l c u l a t e d from the e q u a t i o n • 2P/w, where Ρ i s t h e time average p e e l f o r c e and w i s the w i d t h of t h e d e t a c h i n g l a y e r . Samples f o r t e s t i n g i n a l k a l i were c u r e d between a c l o t h backed r u b b e r s h e e t a n d a n u n b a c k e d r u b b e r s h e e t u s i n g t h e same c u r i n g c o n d i t i o n s and t h e n were trimmed i n two s t a g e s . I n t h e f i r s t s t a g e t h e s p e c i m e n s were c u t a p a r t so t h a t the g l a s s b a r s were c o m p l e t e l y


F

x

A


R

E

T

N

G

31.

Fiberglass Protection in an Alkaline Environment

DREYFUSS ET AL.

APPLY SILANE FINISH TO GLASS I . DIP INTO HIGH SOLIDS SBR L A T E X


•

I SQUEEZE TO REMOVE EXCESS AND IMPREGNATE

LATEX

GLASS

DRY IN FORCED AIR DRYER I DIP INTO HIGH NATURAL RUBBER

SOLIDS

»

SQUEEZE TO IMPREGNATE

,

I

DRY .

LATEX

FURTHER SCRIM

,

AGAIN

1 ' DIP IN THIRD RUBBER LATEX (NATURAL RUBBER)

»

DRY APPLY

F i g u r e 1.

AND

CURE

TALC OR STARCH (OPTIONAL)

Flow sheet showing s t e p s i n c o a t i n g p r o c e s s .

UNCOATED GLASS BUNDLE

F i g u r e 2.

COATED

GLASS

Schmatic v i e w o f g l a s s f i b e r

BUNDLE

bundles.


353


354


embedded i n the c u r e d e l a s t o m e r . Care was taken t o i n s u r e t h a t t h e r e were no h o l e s through the e l a s t o m e r t o the g l a s s , because a l k a l i can s e e p t h r o u g h h o l e s , degrade the g l a s s , and i n v a l i d a t e the measure ments. The t h i c k n e s s o f the e l a s t o m e r was 1 mm o r more on a l l s i d e s e x c e p t t h e one w i t h the c l o t h backed e l a s t o m e r , where t h e e l a s t o m e r t h i c k n e s s was 0.4-0.6 mm. The samples were t r e a t e d w i t h a l k a l i as d e s c r i b e d a b o v e , removed from the a l k a l i , and d r i e d o v e r n i g h t i n a vacuum o v e n a t 60°C. For p e e l t e s t s , s t r i p s o f c l o t h backed e l a s t o m e r were o b t a i n e d by t r i m m i n g as above. The s t r e n g t h o f the r u b b e r i m p r e g n a t e d c o t t o n c l o t h b a c k i n g was r e t a i n e d a f t e r a l k a l i t r e a t m e n t , even though u n t r e a t e d c l o t h d i s i n t e g r a t e d under t h e same c o n d i t i o n s . F i r e s t o n e ' s Diene 35 NFA was the rubber used f o r t h e s e s t u d i e s . 0.05% p a r t s per hundred o f rubber o f d i c u m y l p e r o x i d e was used f o r c u r i n g . C o a t i n g w i t h B u l k P o l y b u t a d i e n e . Ε-glass f a b r i c was embedded i n F i r e s t o n e ' s D i e n e 35 NFA u s i n g p r o c e d u r e s v e r y s i m i l a r t o those u s e d t o p r e p a r e p e e l t e s t specimens. Rubber, which had been m i l l m i x e d w i t h 0.05% d i c u m y l p e r o x i d e , was p r e m o l d e d b e t w e e n M y l a r s h e e t s t o the d e s i r e d t h i c k n e s s ( 0 . 3 0 8 , 0.151, o r 0.100 cm) and s i z e (- 30.5 χ 18 cm) b y m o l d i n g f o r 1 hour a t 60°C. and 40,000 l b s / 5 " ram. F a b r i c was c u t s o t h a t the f i n a l s i z e was a t l e a s t one i n c h s m a l l e r t h a n t h e r u b b e r s h e e t s i n a l l d i r e c t i o n s . A sandwich was made f r o m t h e f a b r i c a n d two p r e m o l d e d rubber s h e e t s o f the same t h i c k n e s s and about h a l f the t o t a l t h i c k n e s s o f the f i n a l sandwich. The s a n d w i c h was c u r e d i n a p r e s s f o r 2 h o u r s a t 150°C and 5000 l b s / 5 " ram. I n t h e c u r e d specimen the f a b r i c was embedded i n the c e n t e r o f t h e m o l d e d specimen (0.15 -0.40 i n t h i c k ) . Samples were immensed i n a l k a l i b e f o r e c u t t i n g t o s i z e f o r t e n s i l e t e s t s . T h i n n e r c o a t i n g s on f a b r i c s and f i b e r s were p r e p a r e d by d i p p i n g t h e f a b r i c o r f i b e r s i n t o a s o l u t i o n c o n t a i n i n g 500 ml hexane, 50 g p o l y b u t a d i e n e and 0.02 g d i c u m y l p e r o x i d e . Excess s o l u t i o n was s q u e e z e d o f f b y p a s s i n g t h e f a b r i c o r f i b e r s between r o l l e r s , t h e h e x a n e was removed b y e v a p o r a t i o n , and t h e rubber was c u r e d f o r 2 hours i n a vacuum oven a t 150°C. M i c r o s c o p y . A L e i t z O r t h o p l a n microscope f i t t e d w i t h a P o l a r o i d Land Camera was used t o examine samples a t low m a g n i f i c a tion. Scanning e l e c t r o n m i c r o g r a p h s were t a k e n w i t h an ISI-SS40. R e s u l t s and D i s c u s s i o n Many o f t h e f a c t o r s t h a t i n f l u e n c e the d e g r a d a t i o n o f g l a s s i n an a l k a l i n e e n v i r o n m e n t a r e o b v i o u s . They i n c l u d e the c o m p o s i t i o n o f t h e g l a s s , t h e s u r f a c e a r e a o f t h e g l a s s , a n d t h e n a t u r e o f the s u r f a c e o f the g l a s s . When c o a t i n g s are a p p l i e d t o the g l a s s , a d d i t i o n a l f a c t o r s need t o be c o n s i d e r e d a l s o . These a d d i t i o n a l f a c t o r s i n c l u d e t h e u n i f o r m i t y o f the c o a t i n g , the i n f l u e n c e o f the t h i c k n e s s o f t h e c o a t i n g , the degree o f bonding between the c o a t i n g and the g l a s s , and the e f f e c t o f d i f f e r e n t methods o f a p p l y i n g the c o a t ing. A comprehensive c o n s i d e r a t i o n o f each o f these f a c t o r s i s b e y o n d t h e s c o p e o f t h i s paper but each o f them was examined i n a t l e a s t a p r e l i m i n a r y way. The c o n c l u s i o n s o f t h i s study a r e based on w e i g h t l o s s s t u d i e s , m i c r o s c o p y , p e e l t e s t measurements and t e n s i l e p r o p e r t i e s b e f o r e and a f t e r immersion i n t h e aqueous a l k a l i solution.



31.

355


DREYFUSS ET AL.

S t u d i e s on G l a s s A l o n e . Weight l o s s comparisons f o r d i f f e r e n t k i n d s o f g l a s s a f t e r i m m e r s i o n i n w a t e r and a l k a l i a r e g i v e n i n T a b l e I . The d a t a showed t h a t a l l t h e g l a s s e s l i s t e d were r e a s o n a b l y s t a b l e i n w a t e r , t h a t f i b e r s were more s e v e r e l y degraded then b a r s , e s p e c i a l l y i n a l k a l i n e s o l u t i o n s and t h a t o f t h e g l a s s e s t e s t e d , Ε-glass and soda l i m e g l a s s were t h e most s e v e r e l y c o r r o d e d by t h e a l k a l i . The d i f f e r e n c e among t h e k i n d s o f g l a s s can be p a r t i a l l y e x p l a i n e d i n t e r m s o f t h e r e l a t i v e s t a b i l i t y i n water and a l k a l i o f t h e v a r i o u s m a t e r i a l s c o m p r i s i n g t h e g l a s s e s . Some t y p i c a l f o r m u l a t i o n s a r e g i v e n i n Table I I ( 6 - 8 ) . T a b l e I I . T y p i c a l Weight % C o m p o s i t i o n o f G l a s s e s ( 6 - 8 ) Oxide

Si0 Na 0 CaO A1 0 B 0 MgO K 0 Zr0 Li 0

Glass

2

2

3

3

2

Pyrex 80.5 3.8

2

Ε 54.5 1+ 17.0 14.5 8.5 4.5 4.0

2

2

1

AR 70.3 11.8

Quartz 100

2.2 12.9

Soda Lime 72 14 13 1

0.4 16.1 1

2

2

1

Only t h e major o x i d e s ( 1 % o r g r e a t e r ) are l i s t e d . Most g l a s s e s a l s o h a v e s m a l l amounts o f o t h e r m e t a l o x i d e s such as Fe 03» T i 0 , Mn Û3, e t c . A l k a l i - r e s i s t a n t glass. 2

2

2

2

A comparison o f the r e s u l t s i n Table I w i t h the compositions i n T a b l e I I s u g g e s t s t h a t h i g h c o n c e n t r a t i o n s o f CaO and A 1 0 l e a d t o decreased d u r a b i l i t y i n a l k a l i . T h i s i s n o t s u r p r i s i n g when t h e r e s u l t s o f % w e i g h t l o s s s t u d i e s on t h e s e m e t a l o x i d e s a l o n e and t h e i r known c h e m i s t r y a r e c o n s i d e r e d . A l 0 3 , when exposed t o t h e s t a n d a r d a l k a l i n e c o n d i t i o n s , l o s t 8.3% by w e i g h t . A 1 0 , when h y d r a t e d , i s a m p h o t e r i c , i s s o l u b l e i n s t r o n g a l k a l i s , and forms compounds l i k e N a A 1 0 o r C a ( A 1 0 ) . Thus t h e h i g h c o n c e n t r a t i o n o f A1 0 i n Ε-glass c a n a t l e a s t p a r t i a l l y account f o r t h e observed weight l o s s . ( B 0 was t o t a l l y s o l u b l e under t h e u s u a l a l k a l i n e c o n d i t i o n s and when h y d r a t e d , i n a c i d i c . However, t h e s t a b i l i t y o f P y r e x g l a s s suggests t h a t boron i s p r e s e n t i n g l a s s n o t as B 0 b u t i n some f o r m t h a t i s n o t r e a d i l y a t t a c k e d by a l k a l i . ) CaO, when exposed t o t h e s t a n d a r d a l k a l i n e c o n d i t i o n s , gained 13.3% by w e i g h t . T h i s i s u n d e r s t a n d a b l e b e c a u s e CaO c a n r e a c t w i t h water t o form Ca(0H) and w i t h d i s s o l v e d C 0 t o form CaC0 . Both p r o d u c t s have h i g h e r m o l e c u l a r w e i g h t s t h a n CaO. I n o r d e r t o account f o r t h e o b s e r v e d w e i g h t l o s s w i t h Ε-glass and even more so w i t h soda l i m e g l a s s , i t must be assumed t h a t e i t h e r t h e s e p r o d u c t s s l o w l y d i s s o l v e i n t h e a l k a l i o r e l s e they a r e washed o f f t h e s u r f a c e o f t h e g l a s s . ( A g a i n t h e N a 0 p r e s e n t i n s i g n i f i c a n t q u a n t i t i e s i n soda l i m e c a n not a c c o u n t f o r t h e s e v e r e w e i g h t l o s s o b s e r v e d w i t h soda lime 2

3

2

2

2

2

2

3

2

3

2

3

2

2

2

3

2


3

356


g l a s s , b e c a u s e AR ( a l k a l i - r e s i s t a n t ) g l a s s a l s o c o n t a i n s much N a 0 and i s e s p e c i a l l y f o r m u l a t e d t o be and indeed i s o b s e r v e d t o be more resistant to a l k a l i ) . T e n s i l e measurements o f t h e E - g l a s s and A R - g l a s s f i b e r s showed t h a t a l t h o u g h t h e Ε-glass f i b e r s w e r e s t r o n g e r i n i t a l l y than t h e A R - g l a s s f i b e r s , t h e A R - g l a s s retained i t s strength b e t t e r i n the a l k a l i . E - g l a s s f i b e r s were t o o weak t o t e s t a f t e r immersion i n t h e a l k a l i , w h e r e a s A R - g l a s s f i b e r s showed 1 9 % r e t e n t i o n o f i n i t i a l strength. The much g r e a t e r weight l o s s observed w i t h E - g l a s s f i b e r s r e l a t i v e t o Ε-glass b a r s s u g g e s t s t h a t exposed s u r f a c e area p l a y s an i m p o r t a n t r o l e i n d u r a b i l i t y i n a l k a l i n e s o l u t i o n s . The e f f e c t o f s u r f a c e a r e a was examined by d e t e r m i n i n g t h e p e r c e n t weight l o s s o f s o d a l i m e b e a d s o f d i f f e r e n t b u t known d i a m e t e r a f t e r immersion i n the a l k a l i . A s shown i n F i g u r e 3 t h e weight l o s s i n c r e a s e d l o g a r i t h m i c a l l y w i t h t h e square o f t h e beads' d i a m e t e r s , i . e . o f t h e i r surface area. We c o n c l u d e d t h a t t h e l a c k o f d u r a b i l i t y i n a l k a l i o f E - g l a s s i s r e l a t e d t o i t s c h e m i c a l c o m p o s i t i o n and t h a t a c o a t i n g was needed t o p r o t e c t t h e g l a s s . A s u i t a b l e c o a t i n g s h o u l d b o t h reduce t h e s u r f a c e a r e a e x p o s e d t o t h e a l k a l i and p r e v e n t c o n t a c t between t h e d e g r a d a b l e components i n t h e g l a s s and t h e a l k a l i . S t u d i e s on Coated G l a s s . G l a s s beads, f i b e r s , and f a b r i c s a r e c o m m e r c i a l l y a v a i l a b l e w i t h v a r i o u s p o l y s i l o x a n e c o a t i n g s , which a r e c h e m i c a l l y b o n d e d t o t h e g l a s s t h r o u g h t h e s i l a n o l g r o u p s (_2). U s u a l l y t h e p o l y s i l o x a n e c o a t i n g s c o n t a i n o t h e r f u n c t i o n a l groups, which can serve as bonding s i t e s f o r o t h e r c o a t i n g s . I t was o f i n t e r e s t t o compare t h e degree t o which t h e s e p o l y s i l o x a n e s r e n d e r e d the g l a s s c o r r o s i o n r e s i s t a n t t o a l k a l i n e s o l u t i o n . Weight l o s s d a t a g i v e n i n T a b l e I I I , showed s i g n i f i c a n t d i f f e r e n c e s . P o l y s i l o x a n e s w i t h a l o n g a l k y l group l i k e o c t a d e c y l gave c o a t i n g s t h a t r e s u l t e d i n a s i g n i f i c a n t i n c r e a s e i n t h e d u r a b i l i t y o f t h e coated g l a s s i n a l k a l i . S h o r t e r a l k y l s u b s t i t u e n t s l i k e e t h y l , d i m e t h y l and v i n y l w e r e d e l e t e r i o u s a n d most p o l a r s u b s t i t u e n t s t e s t e d ( g l y c i d o x y - , m e t h a c r y l o x y - ) seemed t o encourage w e i g h t l o s s . The b a s i c 3-aminop r o p y l g r o u p gave some p r o t e c t i o n . These d a t a suggest t h a t c o n t i nuous n o n p o l a r h y d r o c a r b o n c o a t i n g s might p r o t e c t t h e g l a s s and t h a t a p o l y s i l o x a n e c o a t i n g w i t h 3-aminopropyl-groups t o promote bonding w i t h t h e h y d r o c a r b o n l a y e r (2,3) s h o u l d n o t be d i s a d v a n t a g e o u s . S t u d i e s w i t h Rubber C o a t i n g s . The a b o v e s u g g e s t i o n s w e r e v e r i f i e d i n s t u d i e s w i t h rubber c o a t i n g s on g l a s s p l a t e s , f i b e r s and f a b r i c s . 180° p e e l t e s t s on E - g l a s s p l a t e s showed t h a t w i t h o r w i t h out p r i o r surface coating o f the p l a t e s with the aminopolysiloxane, t h e r e was no d e c r e a s e i n t h e a d h e s i o n between t h e g l a s s and p e r o x i d e - c u r e d p o l y b u t a d i e n e c o a t i n g s . The r e s u l t s a r e summarized i n F i g u r e 4. Most samples f a i l e d c o h e s i v e l y i n t h e r u b b e r l a y e r . The s t r e n g t h o f t h e s a m p l e s t h a t were n o t exposed t o a l k a l i i n c r e a s e d s t e a d i l y w i t h t h e percent o f 3-aminospropytriethoxysilane (AS) i n the s o l u t i o n used t o t r e a t t h e g l a s s . The s t r e n g t h s o f samples e x p o s e d t o a l k a l i were e s s e n t i a l l y c o n s t a n t a t c o n c e n t r a t i o n s o f 1% AS a n d a b o v e . B a r s t h a t were n o t c o a t e d w i t h t h e p o l y s i l o x a n e f a i l e d a d h e s i v e l y and t h e s c a t t e r i n t h e r e s u l t s (± ~ 35%) r e f l e c t e d t h e f a c t t h a t t h e s u r f a c e o f t h e b a r s was n o t as smooth as t h e s u r f a c e o f m i c r o s c o p e s l i d e s a n d o t h e r b a r s used i n p r e v i o u s s t u d i e s (3-5).


2


DREYFUSS ET AL.


θ


(%) wt. LOSS 4

1 Mill

1

1 1 1 1 1 III

I

I

1 1 1 M III

100 d

2

x

I0"

3

1

1000 (/im

2

1 11 Tm

)

F i g u r e 3. E f f e c t o f soda l i m e bead s i z e on p e r c e n t weight l o s s a f t e r immersion i n a l k a l i f o r 7 days a t 80°C.

1200

>

, No / Alkali Λ* Cohesive 800 W

A

Alkali χ Cohesive

X

(N/m)

A

400

/o

/

o Adhesive 0

i

%

AS

1

•

2.0

1.0 in

EtOH

F i g u r e 4. P e e l t e s t r e s u l t s on Ε-glass p l a t e s as a f u n c t i o n o f p e r c e n t o f 3 - a m i n o p r o p y l t r i e t h o x y s i l a n e i n s o l u t i o n used t o treat plates, x: r e s u l t s a f t e r immersion i n a l k a l i f o r 7 days a t 80°C. o: i n i t i a l r e s u l t s .


358


Table I I I .

S t u d i e s w i t h S i l a n e Coated Soda Lime G l a s s

F u n c t i o n a l Group on S i l i c o n CH (CH )i7 NH (CH ) Uncoated CH -CHCH CH CH ) Uncoated 0 3

1

Size Mesh 70-140 70-140 70-140 70-140 70-140 70-140 325

2

2

2

3

2


3

3

2

2

CH CHCH 0(CH ) 2

2

2

3

CH -C(CH )CO(CH ) 2

3

2

3

145 145 145 145 145 145 25

Beads

% Wt. Loss in A l k a l i 0.86 2.08 2.27 3.18 3.58 4.88 4.50

325

25

5.87

325

25

10.89

1

S i l a n e c o a t i n g s a r e c h e m i c a l l y bonded t o g l a s s t h r o u g h t h e s i l a n o l g r o u p s on t h e g l a s s s u r f a c e . The c o a t i n g s a r e o f t e n p r e p a r e d by r e a c t i n g a t r i a l k o x y a l k y l s i l a n e , ( R 0 ) S i R , w i t h t h e g l a s s and then h e a t i n g t o form a p o l y s i l o x a n e l a y e r w i t h t h e f u n c t i o n a l group from R', i f any, i n t h e s u r f a c e and a v a i l a b l e f o r f u r t h e r r e a c t i o n (2.). A d i a l k o x y d i a l k y l s i l a n e , ( R O ) S i R , can be used i n t h e same way. I f R i s C H and t h e s i l a n e i s ( R O ) S i R ' , e.g., the p o l y s i l o x a n e l a y e r w i l l have two C H groups and fewer bonds t o t h e g l a s s s u r f a c e . f

3

,

2

2

?

3

2

2

3

A R - f i b e r coated w i t h t h e same p o l y s i l o x a n e and passed through a hexane s o l u t i o n c o n t a i n i n g p o l y b u t a d i e n e and p e r o x i d e b e f o r e c u r i n g , showed 100% s t r e n g t h r e t e n t i o n i n a l k a l i n e s o l u t i o n . E - g l a s s f a b r i c embedded i n p e r o x i d e - c u r e d p o l y b u t a d i e n e showed n e a r l y 100% r e t e n t i o n o f o r i g i n a l strength f o r polybutadiene t h i c k n e s s e s o f 1 mm o r more. The s t r e n g t h t y p i c a l l y o b s e r v e d f o r #3701 g r e i g e goods as r e c e i v e d was 26.8-29.1 kN/m (153-166 l b s . p e r i n c h w i d t h ) . Strength r e t e n t i o n i n t h e a l k a l i was a t most 10%. P o l y b u t a d i e n e coated s p e c i m e n s h a d i n i t i a l s t r e n g t h s o f 16.6-19.8 kN/m (95-113 l b s p e r i n c h w i d t h ) , a n d s t r e n g t h r e t e n t i o n i n t h e a l k a l i was 80-100% f o r c o a t i n g s 1 mm t h i c k o r g r e a t e r . ( T h e s t r e n g t h o f t h e composite v a r i e d w i t h the t h i c k n e s s o f the polybutadiene. Thicker coatings gave weaker o v e r a l l composite s t r e n g t h s . ) From l a t e x e s , c o a t i n g s as t h i n a s 0.03 mm gave good p r o t e c t i o n . T y p i c a l d a t a i s shown i n F i g u r e 5. M u l t i p l e d i p p i n g s were n e c e s s a r y , s i n c e t h e f i r s t d i p gave o n l y p e n e t r a t i o n o f t h e f i b e r b u n d l e a n d no c o a t i n g . The f i r s t l a t e x d i p i s p r e f e r a b l y i n t o a l a t e x o t h e r than n a t u r a l rubber ( e . g . SBR l a t e x ) b e c a u s e good a d h e s i o n b e t w e e n t h e g l a s s and a c o a t i n g from n a t u r a l rubber l a t e x i s n o t o b t a i n e d . Acknowledgments S a m p l e s o f v a r i o u s E - g l a s s f a b r i c s and f i b e r s from B u r l i n g t o n G l a s s F a b r i c s Co., o f Diene 35 NFA from F i r e s t o n e T i r e and Rubber Co. and o f d i c u m y l p e r o x i d e , DICUP R, f r o m H e r c u l e s , I n c . a r e g r a t e f u l l y a c k n o w l e d g e d . Rubber l a t e x e s were k i n d l y s u p p l i e d by K i l l i a n L a t e x I n c . a n d P o l y s a r R e s i n s , I n c . Thanks a r e g i v e n t o J a n i n e R i z e r f o r h e l p w i t h t e n s i l e s t r e n g t h measurements.


31.

DREYFUSS ET AL.

Fiberglass Protection in an Alkaline Environment THICKNESS

(/im)

10

100

359

20


80

60h

UJ IU

a:

40h J //

/ /

20h

'/

i

Δ Pl*2, 70°C, 30min. O PI #2,150°C, 15 min. • P I * 4 , I 3 0 ° C , 10 min. ·

SBR, 100 °C, 30mln.

2 of DIPS F i g u r e 5. P e r c e n t r e t e n t i o n o f s t r e n g t h o f l a t e x c o a t e d #3701 f a b r i c w i t h 3 - a m i n o p r o p y l p o l y s i l o x a n e c o a t i n g , a f t e r immersion i n a l k a l i f o r 7 days a t 8 0 ° C , as a f u n c t i o n o f number o f d i p s i n l a t e x , k i n d o f l a t e x , and c u r i n g c o n d i t i o n s . PI#2 i s K i l l i a n 500 c l e a r p o l y i s o p r e n e l a t e x - Cure 2; PI M i s K i l l i a n 500 c l e a r p o l y i s o p r e n e l a t e x - Cure 4; PI#2 and PI//4 were r e c e i v e d from K i l l i a n as p a r t i a l l y c u r e d r e s i n s . SBR i s P o l y s a r XE-432 s t y r e n e - b u t a d i e n e l a t e x . The temperature and time o f c u r e a r e c i t e d a f t e r each l a t e x . I

NO.

Literature Cited 1. 2. 3. 4. 5. 6. 7. 8.

Boyd, D. C . ; Thompson, D. A. Encyclopedia Chem. Technol. 1980, 11, p. 843. Plueddemann, E. P. "Silane Coupling Agents"; Plenum Press:New York, 1982. Eckstein, Y . ; Dreyfuss, P. J . Adhesion 1983, 15, 193-202. Ahagon, Α . ; Gent, A. N. J. Polym. Sci.:Polym. Phys. Ed. 1975, 13, 1285-1300. Liang, F . ; Dreyfuss, P. J. Appl. Polym. Sci. 1984, 29, 31473159. Anledter, H. F. Encyclopedia Polym. Sci. and Technol. 1967, 6, p. 634. Mack, Jr., E.; Garrett, A. B.; Haskins, J . F.; Verhoek, F. H. "Textbook of Chemistry"; Ginn and Co.:New York, 1949; p. 760. Hannant, D. J. "Fibre Cements and Fibre Concretes"; John Wiley & Sons:New York, 1978; p. 100.


Rubber Coatings for Fiberglass Protection in an Alkaline Environment

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