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2= e3m2 S3 ZB3o5 =x 35 FLUORINATED SURFACTANTS IN FIRE FIGHTING FOAMS: ANY INPUT FOR WATER MIST TECHNOLOGY
Martial PABON, PhD
DuPont de Nemours (France)
Chantereine, Mantes le Ville F-78202 Mantes la Jolie Cedex
&
| Structure of a fluorinated surfactant
Hydrophilic head
|
L.A
nar perfluorinated chain Ex. CFppure Hydrophobic and oleophobic chain
[EE
x A\ /\ 7)
TV NL
\
Spacer
Ne
3
Particularity of the perfluorinated chain
Higher rigidity than a perhydrogenated chain :
(radius of covalently bonded fluorine, only 0,72 A
- no steric stress)
iN fee
( Tate)\
More hydrophobic than a perhydrogenated chain :
1CF, << 1.7 CH,
Solubility of CF, in water = S21uPilityoC f H inw, ater
7
MH
Element with the Highest electronegativity = the valence electron is strongly attracted by the fluorine atome
= Great thermal and chemical stability
g
Low CMC
80f
70}
60}
Surface tension _
(mN/m) 3)
{
40f
|
30f
ow
|
surface 20f
ension
NSS-wpe------a t
0
{es
0.01
0.1
1
10
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||
6
THERMAL STABILITY
Loss of Mass (Wt%)
FORAFAC| Anioni 1033 c
FORAFAC| Anioni
1176
c
FORAFAC| Ampho
1157
teric
FORAFAC| Ampho
1183
teric
100AC | 200AC| 300AC| 400AC | 500AC
(212AF)
(392AF)
(572AF)
(752AF)
(932AF)
56 94
50 85
87
95
100
65 92 100 100
J--
The maces science
7
PARTICULARITY OF THE PERFLUORINATED CHAIN/ consequences on the surfactant properties
Type of surfactant
[[Hydrocar[bSio liconn e |Fluorochemical
Effectiveness (mN/m)
16-20
Efficiency
05-5
01:05
0.01-:0.05
(weight percent)
--
Stability
Strong acid/alkaline
Poor
Medium
Excellent
Oxidising media
Poor
Poor
Excellent
Thermal
Medium
Medium
Excellent
Medium-Good
[Relativepriceindex [1 [About 10 About 100 |
Tp
Ne
g
FOAM used to :
- Stop thevapor emission
- Prevent flames from heating the solvent
REQUIRED PROPERTIES: - Thermal stability as high as possible
- Positive spreading coefficient on the solvent
FOAM CREATION:
--
vena
(>
LL
wm
RPS
The miraciesfscience
Composition of a foam concentrate
Hydrocarbon surfactant orprotein
FLUORINATED SURFACTANT
----* Foam formation
Foam formation * Spreading coefficient
Thermal stability
| Butylcarbytol
|
| 1,2 propane diol
* Foam stabilizer
cosolvent for surfactants
~
| Protection against freezing
Polysaccharide
Mw ~ 2,510
|
srs | * Foartmathteiosnolovfeantprseucrifpaicteate
|
| expan NE
[Tr
NE
10
:
|
Conditions for a water film formation at the hydrocarbon surface
= Spreading coefficient (SC) > 0
Hydrocarbon
surface tension
Diluted foam
suerfcaocentension
Interfacial tension
between diluted foam
cohnycdernotcraatreboannd
8G =%e - (Yass Wi)
|
Use of fluorinated surfactants in order to lower the surface tension of the diluted foam concentrate
Use of hydrocarbon surfactants in order to lower interfacial tension between diluted foam concentrate and hydrocarbon
[Tp
Ne
u
ve
12
1g/loffluorinated carboxybetain Cyclohexane alone
13
Effect of a film of water onto heptane's rate of evaporation: role of the surfactants
>
: Measurweamteenrt of the heptane vapours going through :
Aqueous solution of fluorinated carboxybetain
Aqueous solution of hydrocarbon surfactants.
Valve
2-- 5 mm C
J
i\
2-- 5 mm <
7
| (ee) Droplet
/
|
Droplet
Heptane -- J
~~
1H
Effect of a film of water onto heptane's
rate of evaporation: role of the surfactants
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Effect of a film of water onto heptane's
rate of evaporation: role of the surfactants Feu
Measurement at
t=3000s
oonne
cr
;
coo |
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8 o AEE----- per rm TremwexrTon eewe eSRTRe co mai ved nana
Cicoeran acis2p wCeeliol 5 ECDteR LLMPKnOeTENSD
6
Effect of a film of water onto heptane's rate of evaporation: role of the surfactants
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aceon +
[ET wn 0fatmemAOIwmLeeeLRxeI m0 mTeh Bwoe aBm rene me ww
17
Effect of a film of water onto heptane's rate of evaporation: role of the surfactants
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19
Effect of a film of water onto heptane's rate of evaporation: role of the surfactants
-The amount of heptane going through a water droplet is not detectable - The hydrocarbon surfactant has to be carefully chosen. -Fluorinated surfactants do not participate to the heptane transfer through the water droplet
[Tp
NE
19
GENERAL CONCLUSION
=Fluorinated surfactants have a high thermal and chemical
i stability
= They give some very low surface tension values in water:
Lower droplet diameter ;
|
Improved spreading of droplet also on
|
solid surfaces.
| An appropriate formulation prevents the burn back
.
Ves AON, be AL, 2522002
TN
20