Fire and Polymers - American Chemical Society

Chapter 27

Use of Highly Stabilized High-Expansion Foams in Fighting Forest Fires

Downloaded by UNIV OF MASSACHUSETTS AMHERST on June 4, 2017 | http://pubs.acs.org Publication Date: May 9, 1990 | doi: 10.1021/bk-1990-0425.ch027

Connie M. Hendrickson AR'KON Consultants, 2915 LBJ Freeway, Suite 161, Dallas, TX 75234

Foams for woodland and grass fire-fighting have been developed with low drainage (water loss from foam) and high expansion (volume of foam per volume of s t a r t i n g l i q u i d ) , two parameters traditionally considered to be inversely proportional. The stabi l i z i n g additive is poly (methyl vinyl ether/maleic anhydride), thought to cross-react with fatty a l c o h o l components of the foam base v i a the anhydride function.

Foam u s e i n r e g u l a r f i r e - f i g h t i n g , p a r t i c u l a r l y i n i n d u s t r i a l s i t u a t i o n s , h a s b e e n common f o r a n u m b e r o f y e a r s now. H o w e v e r , foam i s a r e l a t i v e newcomer a s a t o o l i n c o m b a t i n g f o r e s t a n d g r a s s land f i r e s . W e t t i n g a g e n t s have been a s t a n d a r d i n t h e f i e l d , used t o " s t r e t c h " t h e a v a i l a b l e w a t e r s u p p l i e s i n s i t u a t i o n s where w a t e r i s o f t e n a t a premium. I t i s i n d i s p u t a b l e t h a t f o a m g i v e s a f i r e - f i g h t e r more power f o r t h e w a t e r a v a i l a b l e , s t r e t c h i n g s u p p l i e s even f u r t h e r than use of a w e t t i n g agent. A h i g h e x p a n s i o n foam d e l i v e r s 4 0 0 t o 8 0 0 t i m e s t h e v o l u m e o f foam f o r t h e s t a r t i n g v o l u m e o f c o n c e n t r a t e a n d water ( c a l l e d the premix). A v o l u m e o f c o n c e n t r a t e , d i l u t e d 2% i n w a t e r , t h e n y i e l d s 20,000 t o 40,000 t i m e s i t s o r i g i n a l volume (Table I ) . Table

I.

A d v a n t a g e s o f Foam U s e

High Expansion: E f f i c i e n t use o f m a t e r i a l s Expansion: 400-800: 1 ( f o a m : l i q u i d volume) 1 gal concentrate 50 g a l p r e m i x

Ψ 2 0 , 0 0 0 g a l foam

0097-6156/90/0425-0450$06.00/0 © 1990 American Chemical Society

Nelson; Fire and Polymers ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

27.

this

HENDRICKSON

However, t h e r e a r e a number o f r e a s o n s p a r t i c u l a r segment o f t h e i n d u s t r y : 1. 2. 3. 4. 5.


Use of High-Expansion Foams in Fighting Forest Fires

6.

f o r foam u n d e r u s e i n

Foam c o n c e n t r a t e i s more e x p e n s i v e t h a n w a t e r o r w e t t i n g agents. S h e l f l i f e i s o f t e n l e s s than w e t t i n g a g e n t s . Foam u s e r e q u i r e s g e n e r a t o r s and more s o p h i s t i c a t e d e q u i p m e n t t h a n w e t t i n g a g e n t s , and t h u s A d d i t i o n a l t r a i n i n g of personnel i s also required. M a n y f o a m s on t h e m a r k e t c o n t a i n i n g r e d i e n t s w h i c h a r e n o t highly s u s c e p t i b l e t o b i o d é g r a d a t i o n , o r w h i c h may b e h a r m f u l t o t h e e n v i r o n m e n t on a l o n g - t e r m b a s i s . H i g h e x p a n s i o n foam, n e c e s s a r y f o r the coverage r e q u i r e d in a woodland or g r a s s l a n d s i t u a t i o n , usually loses i t s w a t e r c o n t e n t v e r y r a p i d l y ( r a t e of water loss i s c a l l e d drainage). T h e r e m a i n i n g f o a m i s t h e n e x t r e m e l y d r y and f r a g i l e , and s u s c e p t i b l e t o wind, water from o t h e r h o s e s , etc. (Table I I ) .

Table 1. 2. 3.

II.

Disadvantages

o f U s i n g Foam

Foam i s more e x p e n s i v e t h a n w a t e r or w e t t i n g a g e n t s Generators: more e q u i p m e n t n e e d e d and t r a i n i n g H i g h e x p a n s i o n t r a d i t i o n a l l y means a. fast drainage b. high f r a g i l i t y

T y p i c a l l y , h i g h e x p a n s i o n foams have c h a r a c t e r i s t i c s s i m i l a r to t h o s e i n T a b l e I I I . As e x p a n s i o n i n c r e a s e s , d r a i n a g e a l s o increases. A foam w i t h an e x p a n s i o n o f 400:1 l o s e s 3 5 % o f i t s w a t e r i n t h e f i r s t 15 m i n u t e s a f t e r f o r m a t i o n ; h o w e v e r , a f o a m w i t h an e x p a n s i o n o f 1 0 0 0 : 1 l o s e s 8 5 % o f i t s w a t e r i n i t s i n i t i a l f i f t e e n minutes.

Table

III.

Typical

Expansion

Parameters

Foams

Drainage (% l o s t i n 15 m i n ) *

400: 1 800: 1 1000: 1 ^percentage

of High Expansion

Fragility 1

of the t o t a l

85 ψ w a t e r l o s t i n 15 m i n .

Foam u s e d was M a c r o f o a m Β ( R o c k w o o d S y s t e m s ) : 2% p r e m i x , on a UL l a b o r a t o r y g e n e r a t o r

There a r e a number o f ways t o p r o d u c e h i g h e x p a n s i o n w h i l e r e t a i n i n g a r e a s o n a b l e d r a i n a g e , o r s t a b i l i z a t i o n o f t h e foam ( J _ ) .


451


452

FIRE AND POLYMERS

I n t h e c a s e o f f o a m s f o r m u l a t e d on t h e b a s i s o f a l k y l and e t h o x y l a t e d a l k y l s u l f a t e s , the s t a b i l i z i n g m a t e r i a l i s g e n e r a l l y the c o r r e s p o n d i n g f a t t y a l c o h o l (e.g., l a u r y l s u l f a t e , l a u r y l alcohol). The r e l a t i v e l y n o n - p o l a r h y d r o x y l group i s thought to i n s e r t between the charged s u l f a t e "heads" i n the m i c e l l e and then i n the bubble w a l l ; s t a b i l i z a t i o n i s a r e s u l t of a more c o m f o r t a b l e d i s t a n c e between the s u l f a t e g r o u p s t h a n w o u l d o t h e r w i s e be the case. I t i s a p a s s i v e p r o c e s s i n that no chemical r e a c t i o n takes p l a c e and no bonds are formed or broken. A complete d i s c u s s i o n of t h e s e s t a b i l i z a t i o n methods i s i n c l u d e d i n Rosen (J_). In a t y p i c a l f o r m u l a t i o n , h o w e v e r , as t h e p e r c e n t a g e o f f a t t y a l c o h o l i s i n c r e a s e d and d r a i n a g e d e c r e a s e s , the v i s c o s i t y and pour p o i n t are altered. V i s c o s i t y i n c r e a s e s s l i g h t l y at a normal use temperature (65 F o r a b o v e ) and i n c r e a s e s d r a s t i c a l l y as temperatures d e c r e a s e (40 or below). The pour p o i n t ( t e m p e r a t u r e a t w h i c h the c o n c e n t r a t e i s e a s i l y p o u r e d or e d u c t e d ) i s t h u s r a i s e d to l e v e l s w h i c h may r e n d e r the now " s t a b i l i z e d " foam c o n c e n t r a t e u n u s a b l e under r e l a t i v e l y moderate c o n d i t i o n s . A d d i t i o n of g l y c o l o r g l y c o l e t h e r s as a n t i - f r e e z e a m e l i o r a t e s the pour p o i n t s i t u a t i o n somewhat but i s l i m i t e d by the f a c t that these m a t e r i a l s a c t as foam b r e a k e r s i n h i g h c o n c e n t r a t i o n s . The g e n e r a l f e e l i n g i n f o r m u l a t i o n s of t h i s type has been that i n c r e a s e d v i s c o s i t y i n the c o n c e n t r a t e i s a n e c e s s i t y f o r d r a i n a g e c o n t r o l (JO · H i g h v i s c o s i t i e s and c o l d s u s c e p t i b i l i t y s i m p l y r e n d e r e d the p r o d u c t u n u s a b l e i n o u t d o o r s i t u a t i o n s where such c o n d i t i o n s might be encountered. A number of p o l y m e r s used f o r foam s t a b i l i z a t i o n a f f e c t the v i s c o s i t y i n much the same manner but may c o n t r i b u t e a h i g h e r d e g r e e of s t a b i l i z a t i o n f o r the p e r c e n t a g e o f the a d d i t i v e used t h a n t h e low m o l e c u l a r w e i g h t f a t t y a l c o h o l s . High m o l e c u l a r w e i g h t a d d i t i v e s of t h i s t y p e , l i s t e d i n Table IV, are a l s o thought t o be p a s s i v e p a r t i c i p a n t s i n that no c h e m i c a l r e a c t i o n takes p l a c e and no bond changes o c c u r . Table IV.

P o l y m e r i c A d d i t i v e s f o r Foam S t a b i l i z a t i o n

P o l y v i n y l a l c o h o l ( c o l d - w a t e r s o l u b l e ) (_3) P o l y s a c c h a r i d e s ( K e l z a n ) (3) L i g n i n s u l f o n a t e s (3) P r o t e i n (animal h y d r o l y s a t e s , z e i n , albumin) Methyl c e l l u l o s e d e r i v a t i v e s (3) P o l y a c r y l i c a c i d s ( C a r b o p o l s ) T4)

(3)

These p o l y m e r i c a d d i t i v e s g e n e r a l l y i n t r o d u c e a whole new set o f c o n s i d e r a t i o n s , l i s t e d i n Table V, which may l i m i t or o t h e r w i s e a f f e c t foam p r o d u c t i o n or use. Table V.

Problems w i t h P o l y m e r i c A d d i t i v e s

Dispersion during addition Use of a l c o h o l s o l v e n t s S t a b i l i t y and s h e l f l i f e ( g e l and p r e c i p i t a t e formation) High v i s c o s i t y at low temperatures (non-educting)


27.

HENDRICKSON

Use ofHigh-Expansion Foams in Fighting Forest Fires

We h a v e r e c e n t l y d e v e l o p e d and o b t a i n e d a p a t e n t f o r an u l t r a - s t ab i 1 i ze d h i g h e x p a n s i o n foam (_5) w i t h e x p a n s i o n and d r a i n a g e c h a r a c t e r i s t i c s as shown i n T a b l e V I , u s i n g a p o l y m e r i c a d d i t i v e f o r s t a b i l i z a t i o n w i t h o u t harming e x p a n s i o n . Table V I .

U l t r a s t a b i l i z e d High Expansion Foams


Expansion*

Drainage (% l o s t i n 15 m i n ) * *

400:1 ( f a n ) 750:1 ( s c r e e n ) 1000:1 ( s c r e e n )

3 12-18 23

*dependent on g e n e r a t o r fan=water-driven f a n screen=nozzle/screen s t a t i o n a r y **percentage of the t o t a l water l o s t i n 15 min Foam used was Macrofoam (Rockwood) i n a 2% premix. Gantrez AN139 (GAF) was used at a 3% c o n c e n t r a t i o n . A l t h o u g h expansion and d r a i n a g e a r e s t i l l i n c r e a s i n g t o g e t h e r , i t c a n be e a s i l y s e e n t h a t t h e p o l y m e r - s t a b i l i z e d foam has a d r a i n a g e f a r b e l o w t h a t o f t h e t y p i c a l foam ( e a c h w i t h the same b a s i c f o r m u l a t i o n ) s h o w n i n T a b l e I I I . The foam base i s an a l k o x y / 1 i n e a r a l k y l s u l f a t e , f a t t y a l c o h o l , and g l y c o l / g l y c o l e t h e r m i x t u r e , as o u t l i n e d i n Table V I I . Table V I I .

Foam I n g r e d i e n t s

A.

A l k y l and a l k o x y s u l f o n a t e s F a t t y a l c o h o l s and amides G l y c o l s and g l y c o l e t h e r s

Foamers Secondary s t a b i l i z e r s Cosolvent/antifreeze

B.

P o l y (methyl v i n y l e t h e r / m a l e i c a n h y d r i d e )

CH C-Ô-C

Ç

A

A

0

3

The d r a i n a g e - s t a b i l i z i n g a d d i t i v e i s a polymer: p o l y (methyl v i n y l e t h e r / m a l e i c anhydride (PMVEMA) (Gantrez AN, GAF C o r p . ) . The PMVEMA i s not a p a s s i v e a d d i t i v e b u t , v i a the anhydride f u n c t i o n , a r e a c t i v e s p e c i e s w h i c h w i l l undergo h y d r o l y s i s and bond f o r m a t i o n i n t h e p r e s e n c e o f an a l c o h o l o r w a t e r ( F i g u r e 1 ) . Percentages added t o the foam c o n c e n t r a t e g i v i n g s a t i s f a c t o r y performance range


453

454

FIRE AND POLYMERS


f r o m 1-3%. The p o l y m e r m u s t be a d d e d p r i o r to the glycol a n t i f r e e z e c o m p o n e n t i n o r d e r t o a v o i d e x t e n s i v e c r o s s - l i n k a g e s and gel formation. We h a v e v i s u a l i z e d the mechanism of s t a b i l i z a t i o n i n the following steps: In

the

1.

The p o l y m e r i s a d d e d t o t h e o t h e r c o m p o n e n t s o f t h e c o n c e n t r a t e p r i o r to m i c e l l e f o r m a t i o n . Effective stabilization d o e s n o t o c c u r i f t h e p o l y m e r i s added a f t e r the c o n c e n t r a t e i s a l l o w e d t o age f o r s e v e r a l h o u r s . The anhydride f u n c t i o n s r e a c t w i t h the f a t t y a l c o h o l molecules p r e s e n t i n t h e m i x t u r e ( a s w e l l as w i t h w a t e r ) . G l y c o l s are not added u n t i l after the anhydride is c o m p l e t e l y h y d r o l y z e d (24 h o u r s o r m o r e ) ( F i g u r e 1 ) . The fatty a l c o h o l hydrophobic " t a i l s " are incorporated i n t o t h e m i c e l l e s as t h e c o n c e n t r a t e i s aged ( F i g u r e 1 ) , s h o w n by t h e i n c r e a s i n g v i s c o s i t y a s t h e f o a m a g e s b u t a f t e r the a n h y d r i d e h y d r o l y s i s r e a c t i o n i s c o m p l e t e . the premix ( 2 % c o n c e n t r a t e i n w a t e r ) : As t h e c o n c e n t r a t e i s d i l u t e d i n t o p r e m i x and foam i s generated, the h y d r o p h o b i c " t a i l s " become p a r t of the bubble w a l l (Figure 2). T h e w i d t h o f t h e b u b b l e w a l l d e c r e a s e s as t h e i n n e r w a t e r l a y e r d r a i n s downward under the i n f l u e n c e of g r a v i t y (Figure 2). The p o l y m e r s t r a n d s p r e v e n t t h e n a r r o w i n g o f t h e b u b b l e w a l l and c a u s e s l o w i n g o f t h e w a t e r d r a i n a g e , t h u s d e c r e a s i n g d r a i n a g e t i m e a n d s t a b i l i z i n g t h e foam ( s e e B i k e r m a n (6) f o r a d i s c u s s i o n of the mechanism of d r a i n a g e ) .

2.

3.

In 4.

5.

6.

concentrate:

The f o a m h a s b e e n s u c c e s s f u l l y u s e d i n a g r a s s l a n d f i r e by R o c k w o o d S y s t e m s and i n a f o r e s t f i r e s i t u a t i o n (Bureau of I n d i a n A f f a i r s ) ( L a t h a m , Α., R o c k w o o d S y s t e m s , p e r s o n a l c o m m u n i c a t i o n , 1988). The l a y o u t u s e d t o c o m b a t t h e f i r e i s shown i n F i g u r e 3. The f o a m c h e m i c a l s w e r e s u p p l i e d as a p r e m i x ( 2 . 5 % c o n c e n t r a t e / w a t e r ) f r o m a t a n k e r , and t h e foam was p r o d u c e d f r o m two d i f f e r e n t portable generators. The w a t e r - d r i v e n f a n g e n e r a t o r ( M a c r o g e n 5 0 , R o c k w o o d S y s t e m s ) was u s e d t o l a y a " b a r r i e r w a l l " o f foam f i v e f e e t f r o m t h e f a n ; t h e s c r e e n e d n o z z l e t y p e ( S u p e r j e t X, R o c k w o o d ) was t h e n u s e d t o t h r o w a l a r g e q u a n t i t y o f foam o v e r t h a t b a r r i e r (15-20 f t . range). The b a r r i e r w a l l c r e a t e d by t h e w a t e r - d r i v e n fan a c t e d t o r e t a i n t h e l o o s e r foam p r o d u c e d by t h e s c r e e n e d n o z z l e and c r e a t e a t h r e e - d i m e n s i o n a l s i t u a t i o n to f u l l y u t i l i z e the power o f t h e f o a m a g a i n s t the oncoming f i r e . Figure 4 i s a schematic f o r t h e s e t - u p b o t h f o r a p r e m i x t a n k e r , and f o r a w a t e r t a n k e r u t i l i z i n g c o n c e n t r a t e and an e d u c t o r s y s t e m . The f o r m u l a t i o n i s n o n - t o x i c , n o n - h a z a r d o u s , and biodegradable (.L> Ζ.» !ί) t h a t i t may be s a f e l y u s e d i n s i t u a t i o n s w h e r e an a d v e r s e c o n t a m i n a n t m i g h t have a l a r g e e n v i r o n m e n t a l i m p a c t . It h a s a l s o b e e n s u c c e s s f u l l y u s e d i n t h r e e - d i m e n s i o n a l f i r e s , s u c h as w a r e h o u s e p r o t e c t i o n a n d a i r p l a n e h a n g e r s y s t e m s , and as a s p i l l fume s u p p r e s s a n t on h y d r o c a r b o n s and on o l e u m (9^). s

o


HENDRICKSON


\

Use of High-Expansion Foams in Fighting Forest Fires

R-OH

OH

F i g u r e 1. I n t e r a c t i o n of polymer and foam: an a l c o h o l group i n the foam r e a c t s w i t h an a n h y d r i d e f u n c t i o n on the polymer c h a i n and i s t h u s l i n k e d t o the p o l y m e r c h a i n . The h y d r o p h o b i c R g r o u p i s s u b s e q u e n t l y i n c o r p o r a t e d i n t o the m i c e l l a r structure.

F i g u r e 2. Foam d r a i n a g e and water l o s s from the bubble w a l l : c o n c e n t r a t e i s d i l u t e d i n t o a p r e m i x , and t h e foam i s g e n e r a t e d f r o m the premix. When foam i s g e n e r a t e d , hydrophob i c R g r o u p s become p a r t o f the b u b b l e w a l l (X = w i d t h o f bubble w a l l ) . X d e c r e a s e s as water d r a i n s downward under the i n f l u e n c e of g r a v i t y . The p o l y m e r s t r a n d s prevent n a r r o w i n g o f b u b b l e w a l l , d e c r e a s i n g d r a i n a g e time and s t a b i l i z i n g the foam.



FIRE AND POLYMERS

F i g u r e 3. Foam g e n e r a t o r s and placement f o r a f o r e s t , l a n d , or o t h e r outdoor s c e n a r i o .

grass-

Concentrate

Premix (1-2Va%)

= ^

A or B

F i g u r e 4. S c h e m a t i c of foam p r o d u c t i o n : T a n k e r - s t o r e d water u s i n g an e d u c t i o n s y s t e m ( I ) o r a p r e m i x s t o r e d i n a t a n k e r ( I I ) may be used f o r foam g e n e r a t i o n u s i n g a w a t e r - d r i v e n fan (A) or a screened n o z z l e ( B ) .


27.

HENDRICKSON

Use ofHigh-Expansion Foams in Fighting Forest Fires

The d e v e l o p m e n t o f u l t r as t ab i 1 i z e d h i g h expansion foams must c o n t i n u e i n o r d e r f o r foam use i n f o r e s t and g r a s s l a n d s c e n a r i o s to g a i n w i d e r a c c e p t a n c e and p o p u l a r i t y . The long-term p o t e n t i a l of foams o f t h i s t y p e i s an e x c i t i n g c h a l l e n g e f o r t h e s u r f a c t a n t chemist as w e l l as the f i r e - f i g h t i n g p r o f e s s i o n a l . Acknowledgments T h i s work was done f o r Rockwood Systems Corp., L a n c a s t e r , Texas.


Literature 1. 2. 3.

4. 5. 6. 7. 8. 9.

Cited

Rosen, M. S u r f a c t a n t s and I n t e r f a c i a l Phenomena; Wiley and Sons: New York, 1989; pp 297-299. Bikerman, J . J . Foams; Springer-Ver1ag: New York, 1973; pp 173-174. Perri, J . M. " F i r e - F i g h t i n g Foams" i n Foams: Theory and I n d u s t r i a l Use, Bikerman, J . J . , Ed.; Rheinhold: New York, 1953; pp 189-242. Rand, P. U.S. Patent No. 4 442 018, 1984. Hendrickson, C. M. U.S. Patent No. 4 836 939, 1989. Bikerman, J . J . Foams; S p r i n g e r - V e r l a g : New York, 1973; pp 159-183. Longman, G. F. The A n a l y s i s of Detergents and Detergent Products; Wiley and Sons: New York, 1978; pp 494-539. Rosen, M. S u r f a c t a n t s and I n t e r f a c i a l Phenomena; Wiley and Sons: New York, 1989; pp 7-16. Hendrickson, C. M. Proc. 42nd Southwest Regional Meeting of the ACS, 1986, p 106.

RECEIVED November 1,

1989


457

Fire and Polymers - American Chemical Society

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