posted on 2023-10-10, 16:06authored byRandall
T. Snipes, Mauricio Melara, Andrii Tiiara, Jeffery Owens, Igor Luzinov
The current most efficient solution to extinguish liquid
hydrocarbon
(class B) pool fires involves fire-fighting foams containing fluorinated
surfactants. However, fluorocarbon surfactants are unsafe due to their
environmental persistence and negative toxicological/bioaccumulative
impact. To this end, we show that fluorine-free aqueous suspensions
of Glass Bubbles (GB) modified with hydrophilic polymer grafted layers
can efficiently extinguish hydrocarbon pool fires. Namely, GB grafted
with poly(oligo (ethylene glycol) methyl ether methacrylate) (POEGMA),
GB-G was fabricated employing “grafting-through” and
“grafting-from” methods and used to obtain the suspensions.
It was found that the GB suspension, with a grafted layer of higher
molecular weight and lower grafting density (GB-GL), proved superior
to the more densely grafted GB-GH and nongrafted GB-0 system. The
GB-GL suspensions displayed less negative spreading coefficients and
viscosities lower than those of GB-GH/GB-0 compositions. When siloxane–polyoxyethylene
surfactant was added to all GB suspensions, the interfacial properties
were dominated by the surfactant, with all suspensions having the
same positive spreading coefficient. However, the GB-GL-surfactant
composition had the lowest viscosity among the suspensions studied
in this work. Specifically, the viscosity of GB-GH and GB-0 suspensions
at a shear rate of 77 s–1 was ∼110% and 70%
higher than that of GB-GL. Due to the lower viscosity, the GB-GL suspension
demonstrated the most efficient spreading over model hydrocarbon solid
(polyethylene) and liquid (hexadecane) surfaces when the surfactant
was added. The suspension also showed the best performance in the
retardation of hexane evaporation when placed over the heated hexane
pool. After 50 min, the amount of hexane that evaporated through GB-GH
and GB-0 suspensions was ∼8 and 11 times higher, respectively,
compared to the GB-GL suspension. We found that the GB-GL-surfactant
system was the most efficient GB suspension in extinguishing the fire
due to its superior spreading and sealing ability. It was within 10%
of fluorine-containing foam’s fire extinguishment performance.
The GB suspensions are much safer in terms of burnback resistance
as a torch applied directly to the suspension after extinguishment
could not reignite the fire. The GB material is recyclable, since
it can be collected and reused after application to a fire.