Use of Nanoparticle Additives to Achieve Desirable Properties in Fluorine-Free Firefighting Foams

Graduation Year

2024

Document Type

Thesis

Degree

M.S.C.H.

Degree Name

MS in Chemical Engineering (M.S.C.H.)

Degree Granting Department

Chemical, Biological and Materials Engineering

Major Professor

David S. Simmons, Ph.D.

Committee Member

Ryan Toomey, Ph.D.

Committee Member

Weizhong Zou, Ph.D.

Keywords

Aqueous Foams, Cationic Surfactant, Laponite, Phase Behavior, Surfactant-Nanoparticle Systems

Abstract

Class B Firefighting foams play a crucial role in protecting equipment and people fromliquid fuel fires but concerns regarding the impacts of per- and poly-fluoroalkyl substances (PFAS) have resulted in bans on the use of aqueous film forming foam (AFFF). Fluorine-free replacements are yet to achieve the same level of performance. Nanoparticles including silica and clay have been used to improve foam stability, especially in environments where hydrocarbon fuels are present. These materials have also been used in solid composites to improve fire resistance. The stability of aqueous foams containing silica and Laponite RD nanoparticles along with surfactants of different charges was assessed using free drainage testing, and this resulted in a 1% Laponite RD/CTAB/Siloxane solution with greater stability performance than alcohol resistant (AR) AFFF and a comparable solution viscosity. Further analysis indicates these foams undergo a two-stage drainage process which extends the lifetime of the foams. The proposed mechanism is the creation of a network of clay particles within the lamellae of the foam which remains as a dry skeleton after the draining process. The platelet shape of the clay allows for effective stabilization and may improve the thermal stability and vapor barrier properties of the foam.

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