Flammability Characteristics of Fiber-Reinforced Composite Materials

Chapter 32

Flammability Characteristics of Fiber-Reinforced Composite Materials 1

2

D. P. Macaione and A. Tewarson 1

U.S. Army Materials Technology Laboratory, Watertown, MA 02171-0001 Factory Mutual Research Corporation, Norwood, MA 02162

Downloaded by UNIV LAVAL on July 14, 2016 | http://pubs.acs.org Publication Date: May 9, 1990 | doi: 10.1021/bk-1990-0425.ch032

2

This paper describes the results of a joint study undertaken by the U.S. Army Materials Technology Laboratory (AMTL) and the Factory Mutual Research Corporation (FMRC) on fiber reinforced composite materials (FRC) for use in a composite combat vehicle. The objective of the study was to assess the flammability characteristics of FRC materials using small-scale experiments. In the study, five FRC samples, about 3 to 5 mm in thickness, were examined. The results from the study show that FRC materials have high resistance to ignition, high heat of gasification and high resistance to self-sustained fire propagation. These results suggest that a composite combat vehicle, by virtue of its construction, does not present an unusual fire hazard. F i b e r r e i n f o r c e d composite m a t e r i a l s are used e x t e n s i v e l y because o f t h e i r p h y s i c o c h e m i c a l p r o p e r t i e s and t h e i r high s t r e n g t h / w e i g h t ratio. The use o f composites i n Army v e h i c l e s as a means o f d e c r e a s i n g weight and enhancing s u r v i v a b i l i t y , w i t h o u t r e d u c i n g p e r s o n n e l s a f e t y , has been c o n s i d e r e d f o r some time. The U.S. Army M a t e r i a l s Technology L a b o r a t o r y (AMTL) has s u c c e s s f u l l y demonstrated, i n an e a r l i e r program, t h a t a ground v e h i c l e t u r r e t c o u l d be f a b r i c a t e d from FRC m a t e r i a l s ; now the t e c h n o l o g y has been a p p l i e d t o the f a b r i c a t i o n o f a composite v e h i c l e . The U.S. Navy i s a l s o c o n s i d e r i n g the use o f FRC m a t e r i a l s f o r numerous s h i p and submarine a p p l i c a t i o n s , i n c l u d i n g use as major s t r u c t u r a l components. FRC m a t e r i a l s are a l s o f i n d i n g a p p l i c a t i o n s i n the a e r o s p a c e , a u t o m o b i l e and o t h e r i n d u s tries. Although FRC m a t e r i a l s are very a t t r a c t i v e i n terms o f t h e i r p h y s i c a l p r o p e r t i e s , one o f the major o b s t a c l e s t o t h e i r a p p l i c a t i o n i s the concern f o r the hazards expected i n f i r e s . I n f i r e s , hazardous environments are c r e a t e d as a a r e s u l t o f g e n e r a t i o n o f heat ( t h e r m a l ) and g e n e r a t i o n o f smoke, t o x i c and c o r r o s i v e f i r e p r o d u c t s (nonthermal). For the assessment o f r e s i s t a n c e t o heat exposure and g e n e r a t i o n of hazardous environments by FRC m a t e r i a l s , the f o l l o w i n g p r o c e s s e s need t o be examined: 1) i g n i t i o n , 2) f i r e p r o p a g a t i o n , 3) g e n e r a t i o n 0097-6156/90/0425-0542$07.00/0 ©

1990 A m e r i c a n Chemical Society

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

32.

MACAIONE& TEWARSON

Fiber-Reinforced Composite Materials

of v a p o r s , h e a t , smoke, t o x i c and c o r r o s i v e f i r e p r o d u c t s , and f i r e extinguishment. The g e n e r a t i o n o f m a t e r i a l vapors can be q u a n t i f i e d i n terms o f : 1) r e l a t i o n s h i p between weight l o s s and sample t e m p e r a t u r e . AMTL used t h e r m o g r a v i m e t r i c t e c h n i q u e s f o r such q u a n t i f i c a t i o n (J_), and 2) the r e l a t i o n s h i p between t h e g e n e r a t i o n r a t e o f m a t e r i a l vapors and the heat f l u x . F a c t o r y Mutual Research C o r p o r a t i o n (FMRC) has dev e l o p e d a t e c h n i q u e u s i n g FMRC s S m a l l - S c a l e F l a m m a b i l i t y Apparatus ( 2 - 1 0 ) , which was used f o r t h e q u a n t i f i c a t i o n . The i g n i t i o n p r o c e s s f o r FRC m a t e r i a l s can be d e s c r i b e d i n terms of the r e l a t i o n s h i p between t i m e t o i g n i t i o n and heat f l u x . A t e c h nique developed by FMRC u s i n g i t s S m a l l - S c a l e F l a m m a b i l i t y Apparatus (2-6) was used f o r t h e q u a n t i f i c a t i o n . Techniques have been developed f o r t h e q u a n t i f i c a t i o n o f f i r e p r o p a g a t i o n u s i n g FMRC s S m a l l - S c a l e F l a m m a b i l i t y Apparatus (*J,6) and the N a t i o n a l I n s t i t u t e o f Standards and Technology (NIST) Flame Spread Apparatus ( . In t h i s s t u d y , t h e FMRC t e c h n i q u e was used. Oxygen Index and i t s dependency on temperature was used by AMTL t o examine t h e f i r e p r o p a g a t i o n b e h a v i o r o f s m a l l samples o f FRC m a t e r i als 0 2 ) . The heat g e n e r a t e d i n a f i r e i s due t o v a r i o u s c h e m i c a l r e a c t i o n s , t h e major c o n t r i b u t o r s b e i n g those r e a c t i o n s where CO and C 0 a r e g e n e r a t e d , and 0 i s consumed, and i s d e f i n e d as the c h e m i c a l heat r e l e a s e r a t e ( 3 ) . Techniques a r e a v a i l a b l e t o q u a n t i f y c h e m i c a l heat r e l e a s e r a t e u s i n g FMRC's F l a m m a b i l i t y Apparatus ( 2 - 6 ) , Ohio S t a t e U n i v e r s i t y (OSU) Heat R e l e a s e Rate Apparatus (J_3) and t h e NIST Cone C a l o r i m e t e r (J__U_). Techniques a r e a l s o a v a i l a b l e t o q u a n t i f y the c o n v e c t i v e heat r e l e a s e r a t e u s i n g t h e FMRC F l a m m a b i l i t y Apparatus (2,3) and t h e OSU Heat R e l e a s e Rate Apparatus (]_3). The r a d i a t i v e heat r e l e a s e r a t e i s the d i f f e r e n c e between t h e c h e m i c a l and convect i v e heat r e l e a s e r a t e s ( 2 , 3 ) . In t h e s t u d y , FMRC t e c h n i q u e s were used. Techniques a r e a v a i l a b l e t o q u a n t i f y t h e g e n e r a t i o n o f smoke, t o x i c and c o r r o s i v e f i r e p r o d u c t s u s i n g t h e NBS Smoke Chamber ( 1 5 ) , p y r o l y s i s - g a s chromatography/mass s p e c t r o m e t r y (PY-GC-MS) (J_6), FMRC F l a m m a b i l i t y Apparatus (2,3,5,17,18), OSU Heat R e l e a s e Rate Apparatus (13) and t h e NIST Cone C a l o r i m e t e r ( 1J0 . Techniques a r e a l s o a v a i l a b l e t o a s s e s s g e n e r a t i o n o f : 1) t o x i c compounds i n terms o f a n i m a l response 0 9), and 2) c o r r o s i v e compounds i n terms o f metal c o r r o s i o n 07). I n t h e s t u d y , FMRC t e c h n i q u e s and AMTL PY-GC-MS t e c h n i q u e s were used. The e x t i n g u i s h m e n t o f f i r e depends on the f i r e p r o p a g a t i o n r a t e , p h y s i c o - c h e m i c a l p r o p e r t i e s o f t h e m a t e r i a l s , r a t e o f a p p l i c a t i o n and the c o n c e n t r a t i o n o f e x t i n g u i s h i n g a g e n t s . Water a p p l i e d through s p r i n k l e r s i s t h e most w i d e l y used l i q u i d e x t i n g u i s h i n g agent, and Halon 1301 and C 0 a r e t h e most w i d e l y used gaseous a g e n t s . Techniques a r e a v a i l a b l e t o q u a n t i f y f i r e e x t i n g u i s h m e n t i n l a r g e - s c a l e f i r e s ( 2 0 ) ; r e c e n t l y attempts a r e b e i n g made t o d e v e l o p s m a l l - s c a l e t e c h n i q u e s f o r f i r e e x t i n g u i s h m e n t u s i n g FMRC's S m a l l - S c a l e Flammab i l i t y Apparatus (21_). The FMRC t e c h n i q u e f o r flame e x t i n g u i s h m e n t u s i n g Halon was used i n t h e s t u d y . AMTL and FMRC have been p e r f o r m i n g r e s e a r c h t o q u a n t i f y t h e f l a m m a b i l i t y c h a r a c t e r i s t i c s o f FRC m a t e r i a l s which a r e enumerated i n t h i s paper. 1


1

2

2

2


543

544

FIRE AND POLYMERS

Concepts G e n e r a t i o n o f M a t e r i a l Vapors. The magnitude o f heat r e q u i r e d t o generate vapors from a m a t e r i a l depends on t h e t h e r m a l s t a b i l i t y o f the m a t e r i a l . As the temperature o r heat f l u x i s i n c r e a s e d , genera t i o n r a t e o f v a p o r s , measured i n terms o f mass l o s s o f t h e m a t e r i a l , i n c r e a s e s and t h e f o l l o w i n g r e l a t i o n s h i p i s s a t i s f i e d ( 2 , 3 ) : m" = ( q " + q " - q" ) / L = q"/L, e τ >r n

(1)

M

where m" i s the mass l o s s r a t e (g/m s ) ; q" i s the e x t e r n a l heat f l u x (kW/m ); q" i s the flame heat f l u x (ÎiW/m ); q^ i s the s u r f a c e r e r a d i a t i o n l o s s (kW/m ); q" i s the n e t heat f l u x ^Cw/m ) and L i s the heat o f g a s i f i c a t i o n ( k 9 / g ) . I t has been shown t h a t i n s m a l l - s c a l e experiments w i t h t u r b u l e n t f i r e s , t h e flame heat f l u x approaches i t s a s y m p t o t i c v a l u e f o r oxygen c o n c e n t r a t i o n s g r e a t e r than about 30%; the a s y m p t o t i c v a l u e i s v e r y c l o s e t o t h e v a l u e e x p e c t e d ^ i n v e r y l a r g e f i r e s (]_). A c o n d i t i o n where q" + q" = q" , m" = 0 , and thus q" r e p r e s e n t s e f rr rr the minimum heat f l u x a t or below which t h e m a t e r i a l i s not expected to generate v a p o r s . 2


2

2

Mass Loss Rate as a F u n c t i o n o f Temperature. The most commonly used t e c h n i q u e i s t h e r m o g r a v i m e t r y (TG). The b a s i c components o f modern TG have e x i s t e d s i n c e t h e e a r l y p a r t o f t h i s c e n t u r y (22-2*0 . Thermal a n a l y s i s , i n t h e form o f TG, has been employed e x t e n s i v e l y i n the a r e a o f polymer f l a m m a b i l i t y t o c h a r a c t e r i z e polymer d e g r a d a t i o n . Mass Loss Rate as a F u n c t i o n o f E x t e r n a l Heat F l u x . The t e c h n i q u e f o r t h e measurement o f mass l o s s r a t e as a f u n c t i o n o f heat f l u x was developed i n 1976 a t FMRC u s i n g t h e S m a l l - S c a l e F l a m m a b i l i t y Appar a t u s ( 8_). S e v e r a l o t h e r f l a m m a b i l i t y a p p a r a t u s e s a r e now a v a i l a b l e f o r such measurements, such as OSU Heat R e l e a s e Rate Apparatus ( 1 3 ) and NIST Cone C a l o r i m e t e r (1*4). Ignition. For t h e r m a l l y t h i c k m a t e r i a l s , t i m e t o i g n i t i o n i s found t o f o l l o w t h e f o l l o w i n g r e l a t i o n s h i p as e x t e r n a l heat f l u x i s v a r i e d (1,6); t~g

/ 2

α

q» / ΔΤ (k ρ c )

1

/

2

,

(2)

where i s time t o i g n i t i o n ( s ) ; ΔΤ i s t h e t e m p e r a t u r e o f i g n i t i o n above ambient ( K ) ; k i s the t h e r m a l c o n d u c t i v i t y (kW/m Κ ) ; ρ i s t h e d e n s i t y ( g / r r r ^ a ^ d c i s the s p e c i f i c heat ( k J / g K ) . I n E q u a t i o n ( 2 ) , ΔT (kpc ) i s d e f i n e d as t h e Thermal Response Parameter (TRP) o f the materÇal and e x p r e s s e s i g n i t i o n and f i r e p r o p a g a t i o n r e s i s tance o f t h e m a t e r i a l . The minimum v a l u e o f q", a t o r below which e · t h e r e i s no i g n i t i o n , i s d e f i n e d as the c r i t i c a l heat f l u x , q£ , f o r ignition (1,6). E x p e r i m e n t a l l y , t i m e t o i g n i t i o n i s measured a t v a r i o u s heat f l u x v a l u e s and c r i t i c a l heat f l u x f o r i g n i t i o n and TRP a r e q u a n t i f i e d u s i n g t e c h n i q u e s such as the one used i n t h e FMRC S m a l l - S c a l e Flammab i l i t y Apparatus ( 1 , 6 ) . p


32.

545


MACAIONE& TEWARSON

Heat R e l e a s e R a t e . I t h a s b e e n shown t h a t t h e h e a t g e n e r a t e d i n c h e m i c a l r e a c t i o n s l e a d i n g t o t h e g e n e r a t i o n o f CO a n d C 0 a n d d e p l e t i o n o f C>2 c a n be u s e d t o c a l c u l a t e t h e c h e m i c a l h e a t r e l e a s e r a t e using the f o l l o w i n g r e l a t i o n s h i p s (2,3): 2

«ch

•

C A H

T

/ k

co

)

ô

2

co

+

[

(

2

Δ

Η

τ

A

-

H

co

)

/

k

co

]

6

( 3 )

co

and

2

where Q £ i s t h e c h e m i c a l h e a t r e l e a s e r a t e (kW/m ); Δ Η i s the net heat of complete combustion ( k J / g ) ; Δ Η ^ i s the heat o f combustion o f CO ( k J / g ) ; k and k a r e t h e maximum p o s s i b l e t h e o r e t i c a l y i e l d s h

Τ

c 0

C Q

o f CO a n d C 0 , r e s p e c t i v e l y ( g / g ) ;

kg


2

of

oxygen consumed

fuel

i s t h e maximum p o s s i b l e mass

p e r u n i t mass o f m a t e r i a l

s t o i c h i o m e t r i c r a t i o ) (g/g);

G£

vapors

a n d Ô£Q^

Q

(mass

2

tion rates

oxygen-to-

a r e t h e mass g e n e r a -

o f CO a n d C 0 , r e s p e c t i v e l y ( g / m s ) ; a n d ρ consumption r a t e of 0 (g/m s ) . I t h a s b e e n shown t h a t t h e c o n v e c t i v e h e a t r e l e a s e calculated using the f o l l o w i n g r e l a t i o n s h i p (2,3):

i s t h e mass

2

2

2

r a t e c a n be

Q" = M c ΔΤ /A , (5) Con p g . ρ where Q £ i s t h e c o n v e c t i v e h e a t r e l e a s e r a t e (kW/m ) ; M i s t h e t o t a l mass f l o w r a t e o f f i r e p r o d u c t s a n d a i r m i x t u r e ( g / s ) , ΔΤ i s t h e gas t e m p e r a t u r e above a m b i e n t (K) and A i s t h e t o t a l s u r f a c i a r e a of t h e m a t e r i a l i n v o l v e d i n f i r e (m ). I t has been shown t h a t h e a t r e l e a s e r a t e s a t i s f i e s t h e f o l l o w i n g r e l a t i o n s h i p (2,3): o n

2

Q»

= ΔΗ.ίη"

=

χ.

( A H / L ) q^ T

,

(6)

w h e r e i i s c h e m i c a l , c o n v e c t i v e o r r a d i a t i v e a n d ΔΗ i s the heat of c o m p l e t e c o m b u s t i o n ( k J / g ) , x i s t h e c o m b u s t i o n e f f i c i e n c y . ΔΗγ/L i s a fundamental physico-chemical property of the material. E x p e r i m e n t s c a n be p e r f o r m e d w h e r e c h e m i c a l , c o n v e c t i v e a n d r a d i a t i v e h e a t r e l e a s e r a t e s c a n be m e a s u r e d a t v a r i o u s e x t e r n a l h e a t flux values. L i n e a r r e l a t i o n s h i p s s h o u l d be f o u n d f o r t h e e x p e r i m e n t a l d a t a , w h e r e t h e s l o p e i s e q u a l t o χ.^ ( Δ Η γ / L ) . i

F i r e Propagation. I t has been shown t h a t t h e f i r e propagation b e h a v i o r c a n be q u a n t i f i e d u s i n g a F i r e P r o p a g a t i o n I n d e x ( F P I ) (1,6). FPI i s expressed as the r a t i o o f the r a d i a t i v e heat r e l e a s e r a t e t o t h e TRP, p

F I

α [(χ δ· )

π Lh η

1 / 3

/ TRP] χ 1000

,

(7)

where Q £ i s t h e c h e m i c a l heat r e l e a s e r a t e per u n i t w i d t h o r c i r c u m f e r e n c e o f t h e s a m p l e (kW/m), a n d x i s the r a d i a t i v e f r a c t i o n o f the c h e m i c a l h e a t r e l e a s e r a t e , a s s u m e d t o be c o n s t a n t a n d e q u a l t o 0.10. F P I i s q u a n t i f i e d by m e a s u r i n g Q£ as a f u n c t i o n o f time d u r i n g f i r e p r o p a g a t i o n a n d by m e a s u r i n g TRP i n s e p a r a t e i g n i t i o n e x p e r i m e n t s . h

R


546

FIRE AND POLYMERS


For s m a l l samples, t h e Oxygen Index (01) i s used t o c h a r a c t e r i z e f i r e p r o p a g a t i o n b e h a v i o r (25^. 01 i s d e f i n e d as t h e minimum concen t r a t i o n o f oxygen, i n an oxygen n i t r o g e n atmosphere, n e c e s s a r y t o s u s t a i n f l a m i n g combustion f o r a s p e c i f i e d p e r i o d o f time o r s p e c i f i e d sample l e n g t h . The 01 v a l u e i s a f f e c t e d by t h e temperature o f the environment ( 2 6 ) . W i t h i n c r e a s e i n t e m p e r a t u r e , t h e 01 v a l u e s d e c r e a s e , and thus i n many cases i n s t e a d o f 01 a Temperature Index (TI) i s used. TI o f a m a t e r i a l i s d e f i n e d as a temperature o f t h e environment a t which i t s 01 becomes equal t o t h e c o n c e n t r a t i o n o f oxygen i n normal a i r . TI and i t s p r o f i l e a r e found t o be more r e l i a b l e than 01 f o r t h e assessment o f t h e f l a m m a b i l i t y o f m a t e r i a l s ( 1 2 ) . G e n e r a t i o n o f Smoke, T o x i c and C o r r o s i v e F i r e P r o d u c t s . Smoke, t o x i c and c o r r o s i v e p r o d u c t s a r e g e n e r a t e d i n f i r e s as a r e s u l t o f v a p o r i z a t i o n , d e c o m p o s i t i o n and combustion o f m a t e r i a l s i n t h e presence o r absence of a i r . I t has been shown t h a t t h e g e n e r a t i o n r a t e o f f i r e p r o d u c t s s a t i s f i e s the f o l l o w i n g r e l a t i o n s h i p ( 2 , 3 ) : G»! = Y. m" = f. (k./L) q" J J J n 1

,

(8)

where G'! i s t h e g e n e r a t i o n r a t e o f product j (g/m s ) ; f j i s t h e g e n e r a t i o n e f f i c i e n c y o f the product and k j / L i s a fundamental physico-chemical property of the m a t e r i a l . G e n e r a t i o n r a t e o f smoke can be q u a n t i f i e d by measuring t h e mass of smoke and/or t h e o p t i c a l d e n s i t y o f smoke, D, d e f i n e d a s : D = (1/Jl) l o g

1 Q

(I /I) ,

(9)

0

where I i s t h e o p t i c a l path l e n g t h (m) and I / I i s t h e f r a c t i o n o f l i g h t t r a n s m i t t e d through smoke. D i s e x p r e s s e d as the^mass o p t i c a l d e n s i t y (MOD) i n m /g, where o n l y f u e l mass l o s s r a t e , m", i s taken i n t o c o n s i d e r a t i o n (17). Q

MOD =

(1/i) [ l o g

i n

ιυ

( I / I ) ] V/m" A , ο

(10)

where V i s the t o t a l v o l u m e t r i c f l o w r a t e o f the f i r e p r o d u c t - a i r m i x t u r e (m-Vs). I f the g e n e r a t i o n r a t e o f smoke i s c o n s i d e r e d , then from E q u a t i o n s ( 8 ) and ( 1 0 ) , s p e c i f i c mass o p t i c a l d e n s i t y (SM0D) i n m /g can be d e f i n e d a s : SM0D = where Y

s

(I/O [log

i n

10

( I / I ) ] V/m"Y A , o s

i s t h e y i e l d o f smoke ( g / g ) .

(11)

Thus SM0D = M0D/Y s

F i r e E x t i n g u i s h m e n t . The e f f i c i e n c y o f f i r e e x t i n g u i s h m e n t depends on t h e r a t e o f agent a p p l i c a t i o n and t h e a b i l i t y o f t h e agent t o i n t e r r u p t t h e c h e m i c a l r e a c t i o n s r e s p o n s i b l e f o r g e n e r a t i n g heat i n the gas phase o r removing heat from t h e s u r f a c e o f t h e b u r n i n g mate rial. No s m a l l - s c a l e t e c h n i q u e s a r e c u r r e n t l y a v a i l a b l e f o r q u a n t i f y i n g f i r e e x t i n g u i s h m e n t ; however, r e c e n t l y an attempt has been made t o d e v e l o p them u s i n g t h e FMRC S m a l l - S c a l e F l a m m a b i l i t y Apparatus (21),


32.

MACAIONE & TEWARSON


547

Experiments Thermal A n a l y s i s . The D u P o n t I n s t r u m e n t s M o d e l 9 9 0 0 , c o m p u t e r c o n t r o l l e d t h e r m a l a n a l y z e r a n d M o d e l 951 TGA m o d u l e w e r e u s e d i n t h e e x p e r i m e n t s , u s i n g a g a s f l o w r a t e o f 100 c c / m i n . E x p e r i m e n t s were p e r f o r m e d i n d y n a m i c a n d i s o t h e r m a l mode u s i n g a i r a n d a r g o n . Oxygen Index Oxygen Index t h e ASTM D 2 a m b i e n t and

and Temperature Index. A S t a n t o n - R e d c r o f t FTA/HFTA a p p a r a t u s was u s e d . E x p e r i m e n t s were p e r f o r m e d u s i n g 863-77 p r o c e d u r e s w i t h t e m p e r a t u r e v a r i a t i o n s between 300°C.


Smoke D e n s i t y . The smoke d e n s i t y was m e a s u r e d i n an NBS C h a m b e r f o l l o w i n g t h e p r o c e d u r e s o f ASTM Ε 6 6 2 .

Smoke

P y r o l y s i s - G a s Chromatography-Mass Spectrometry. In the experiments, a b o u t 2 mg o f s a m p l e was p y r o l y z e d a t 900°C i n f l o w i n g h e l i u m u s i n g a C h e m i c a l D a t a S y s t e m (CDS) P l a t i n u m C o i l P y r o l y s i s P r o b e c o n t r o l l e d by a CDS M o d e l 122 P y r o p r o b e i n n o r m a l mode. P r o d u c t s were s e p a r a t e d o n a 12 m e t e r f u s e d c a p i l l a r y c o l u m n w i t h a c r o s s - l i n k e d p o l y ( d i m e t h y l s i l i c o n e ) s t a t i o n a r y phase. The GC c o l u m n was t e m p e r a t u r e p r o g r a m m e d f r o m -50 t o 300°C. I n d i v i d u a l compounds were i d e n t i f i e d w i t h a H e w l e t t P a c k a r d (HP) M o d e l 5995C l o w r e s o l u t i o n q u a d r u p l e GC/MS S y s t e m . D a t a a c q u i s i t i o n and r e d u c t i o n w e r e p e r f o r m e d on t h e HP 100 Ε-series c o m p u t e r r u n n i n g r e v i s i o n E RTE-6/VM s o f t w a r e . I g n i t i o n , Mass L o s s R a t e , Heat R e l e a s e R a t e , G e n e r a t i o n R a t e s o f F i r e P r o d u c t s and F i r e E x t i n g u i s h m e n t . E x p e r i m e n t s were p e r f o r m e d i n the FMRC S m a l l - S c a l e ( 5 0 kW) F l a m m a b i l i t y A p p a r a t u s s h o w n i n F i g u r e 1. H o r i z o n t a l , 0.10 χ 0.10 m s a m p l e s w i t h e d g e s c o v e r e d t i g h t l y w i t h h e a v y d u t y a l u m i n u m f o i l w e r e e x p o s e d t o e x t e r n a l h e a t f l u x up t o a maximum o f 60 kW/m . A 0.01 m l o n g e t h y l e n e - a i r p r e m i x e d f l a m e l o c a t e d a b o u t 0.01 m f r o m t h e s u r f a c e , was u s e d a s a p i l o t f l a m e f o r ignition. I g n i t i o n e x p e r i m e n t s were p e r f o r m e d under n a t u r a l a i r f l o w ; a l l o t h e r e x p e r i m e n t s were p e r f o r m e d under f o r c e d a i r f l o w con ditions. The s a m p l e s u r f a c e was c o a t e d w i t h c a r b o n b l a c k t o e l i m i n a t e e r r o r s due t o d i f f e r e n c e s i n t h e s u r f a c e a b s o r p t i v i t y . In the e x p e r i m e n t s , t h e g e n e r a t i o n r a t e o f m a t e r i a l v a p o r s was m o n i t o r e d by m e a s u r i n g t h e mass l o s s r a t e u s i n g a l o a d c e l l . For the determina t i o n o f heat r e l e a s e r a t e , g e n e r a t i o n r a t e s o f f i r e p r o d u c t s and o p t i c a l d e n s i t y o f smoke, a l l t h e f i r e p r o d u c t s w e r e c a p t u r e d i n t h e sampling duct along with a i r . I n t h e d u c t , m e a s u r e m e n t s w e r e made f o r t h e t o t a l v o l u m e t r i c and mass f l o w r a t e o f t h e f i r e p r o d u c t - a i r mixture, concentrations of various f i r e products, o p t i c a l transmis s i o n t h r o u g h smoke and g a s t e m p e r a t u r e . F o r t h e q u a n t i f i c a t i o n o f f i r e p r o p a g a t i o n b e h a v i o r o f t h e FRC m a t e r i a l s , 0.10 m w i d e a n d 0.61 m l o n g v e r t i c a l s h e e t s w i t h t h i c k n e s s v a r y i n g f r o m 3 mm t o 5 mm w e r e u s e d . The b o t t o m 0.15 m o f t h e s h e e t was e x p o s e d t o 50 kW/m o f e x t e r n a l h e a t f l u x i n t h e p r e s e n c e o f a 0.01 m l o n g p i l o t f l a m e t o i n i t i a t e f i r e p r o p a g a t i o n . F o r t h e s i m u l a t i o n o f l a r g e - s c a l e f l a m e r a d i a t i o n , e x p e r i m e n t s were p e r f o r m e d i n 10/S o x y g e n c o n c e n t r a t i o n . 2

American Chemical Society Library 1155 16th St., N.W. Nelson; Fire Polymers Washington. O.C.and20036

ACS Symposium Series; American Chemical Society: Washington, DC, 1990.

548

FIRE AND POLYMERS

•

1 to 8 — Thermocouples

Exhaust

Orifice Plate


Coltimated Light Source

Insulation (0.045 m Thick)

0

2f

N , CO, C0 , etc. 2

2

Air Heater F i g u r e 1. Apparatus

F a c t o r y Mutual S m a l l - S c a l e

(50 kW-Scale) F l a m m a b i l i t y


32.

MACAIONE & TEWARSON


549

F i r e e x t i n g u i s h m e n t b e h a v i o r o f t h e FRC m a t e r i a l s u s i n g H a l o n 1301 was q u a n t i f i e d w i t h a h o r i z o n t a l 0.10 χ 0.10 m s a m p l e w i t h e d g e s covered t i g h t l y w i t h heavy duty aluminum f o i l . The s a m p l e s u r f a c e was e x p o s e d t o 60 kW/m o f e x t e r n a l h e a t f l u x . E x p e r i m e n t s were p e r f o r m e d u n d e r f o r c e d a i r f l o w c o n d i t i o n s , w h e r e H a l o n 1301 was a d d e d to the i n l e t a i r f l o w such t h a t f i r e remained w e l l v e n t i l a t e d . For the assessment of flame heat f l u x , expected i n l a r g e - s c a l e f i r e s , 0.10 χ 0.10 m s a m p l e s w i t h e d g e s c o v e r e d t i g h t l y w i t h h e a v y d u t y a l u m i n u m f o i l , w e r e b u r n e d i n k0% o x y g e n c o n c e n t r a t i o n w i t h o u t the e x t e r n a l heat f l u x . M a s s l o s s r a t e was m e a s u r e d a n d E q u a t i o n ( 1 ) was u s e d t o c a l c u l a t e f l a m e h e a t f l u x . The s a m p l e s u s e d i n t h e s t u d y a r e l i s t e d i n T a b l e I . T a b l e s I I t h r o u g h VI l i s t the e x p e r i m e n t a l d a t a .


2

Table

Sample MTL MTL MTL MTL MTL

No. in #2 #3 #1 #5

I.

F i b e r R e i n f o r c e d Composite Used i n the S t u d y

Materials

Fiber/Resin Components S2/Polyester S2/Polyester S2/Polyester Kevlar/Phenolic-PVB* S2/Phenolic

Thickness (mm) 1.8 1.8 1.8 1.8 3.2

Ratio 70/30 70/30 70/30 81/16 80/20

* R e s i n i s 50/50 P h e n o l i c - P V B .

Table I I

S a m p l e No. MTL #1 MTL #2 MTL #3 MTL #1 MTL #5

Table I I I .

Sample MTL MTL MTL MTL MTL

#1 #2 #3 #1 #5

No.

Isothermal for

Thermogravimetric Analysis FRC M a t e r i a l s

Temperature 300 100 0.73 29.8 2.0 21.1 3.1 25.1 3.1 28.9 0.0 3.1

25 23 28 52 28 53

Residue at 500°C {%) 60.1 70.5 67.1 10.1 82.1

(°C) 500 32. 9 29. 1 30.0 51. 0 9. 1

O x y g e n I n d e x f o r FRC

Data

M a t e r i a l s Versus

Temperature 100 23 28 95 30 98

Temperature

(°C) 200

300

Flammability Characteristics of Fiber-Reinforced Composite Materials

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