Document pBonpzvbexojKgeVkXrKx18m7
R226 -- [314
Overview of the Mechanics of Film Formation of AFFF
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Aqfluueorooucsarbfoinlms-ufroframcitnagntfsoaasmth(eAmFaFj)orgesnuerrfaalcleyaccotnitvaeicnosmmpioxnteunretssof hydrocarbon and
This class of fire-fighting uniform aqueous duplex
foams has film (10-30
the capability pm thick) on
to spread and forma thin, low-surface tension organic
liuids such as volatile hydrocarbons and fuels.
The fuel
formationof an vapor barrier in
aqueous addition
ltaoyetrhespcoroelaidngovaenrdtbhleafnukeeltsiunrgfeafcfeecptroofvitdheesfaoname.ffeTchtiisve
fuel vapor barrier also helps in the presenceofliquid fuel
to protect the and its vapor.
foam
matrix
from
excessive
degradation
= eItxitsinalgsuoiskhninogwnefftihcaitetnhcye osfpotnhetafnoeaomu.slTyhseprpreeasdeinncgeaoqfutehoeuasqluaeyoerusaufgilmmenitmpsrtohveesf.ire.
bmeucrhnabnaicskms.tability of the foam by its spontancous re-spreading and "repair"
.
The spontancousspreading property of AFFF is derived mainly from the high
surface activity (low surface tension)ofthe fluorocarbon surfactants at the
solution/air interface (15-20 dynes/cm).
+ Tthheissollouwtisounr/fsaucbestternastieoni.ntceorfuapcle,edalwliotwhs tthheelAoFwFiFntseorlfuatciioanl, taesnsaiornes(u1l-t5odfyaneposs/ictmiv)eat
spreading coefficient, to fucls (20-30 dynes/cm).
spread
spontaneously
on
many
liquid
hydrocarbons
and
By
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2 =
ifnltueorrfaocciaarlbtoennssuirofnactants, and therefore they are largely responsible for the low
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the based
on
,.
dtheipsevnadleunet)assutorftahceeeafnfedctiinvteernfeascsioaflttheensifiornesfainghdtihnegnfcoeamt.he "Ddyynnaammiicc"(tismper-eading
fcoielfmfifcoiremnattcioonncepphtenneoemdentoa baendustehde teofbfeectttievreunensdserosftfainred ftighhetirnegl,ationship between the
The turn
raaftfeeocftssptrheeaedxitinnggofutishhemeanqtueaonudsbfuirlnmbiascrkelpaetredfotromtahnecefiolfm
thickness, which an AFFF agent
in
*
The second most "fuel shedding,"
important role of fluorosurfactants in AFFF Because oftheir inherent olcophobicity (Lc.
is oil
the phenomena repellency).
of
pflruoobrloesmu.rfaIcntcaonnttsrarsetp,elhyfuderloc(oairlbothnussurpfraecvteannttisnagtotrrarcetd"ufcuienlgtthhues
"fuel pickup" turning the foam
aflnadmmtahbelper.eseDnucreinogf ftlhueofriorseufrifgahcttianngtaspipnlitchaetifoona,mfroeadmucgeetss pmriexveedntusp (wdietphenthdeinfgueoln
cFouneclecnotrnattaimoinn)attiheonfuoerl
contamination
fuel pickup is a
osfertihoeufsopamr,obwlheimcbheccaanu
sleeaitd
ctoom"pbruormniinsge"s
foam
not
.
only the speed of extinguishment but also burnback effectiveness.
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