Abstract

The foams stabilized by nanoparticles (NPs), water-soluble polymers, and surfactants have potential application prospects in the development of new, environmentally friendly firefighting foams. In the present study, a gel foam containing a water-soluble polymer (xanthan gum, XG), hydrophilic silica NPs, hydrocarbon surfactant (SDS), and fluorocarbon surfactant (FS-50) were prepared. The surface activity, conductivity, viscosity, and foaming ability of foam dispersions were characterized. The gel foam stability under a radiation heat source and temperature distribution in the vertical foam layer were evaluated systematically. The results show that the addition of NPs and XG has a significant effect on the foaming ability, viscosity and foam thermal stability, but has a very subtle effect on the conductivity and surface activity. The foaming ability of the FS-50/SDS solution was enhanced by the addition of NPs, but decreased with increasing the XG concentration. The thermal stability of the foams stabilized by SDS/FS-50/NPs/XG increased with the addition of NPs and increasing XG concentration. Foam drainage and coarsening were significantly decelerated by the addition of NPs and XG. The slower foam drainage and coarsening are the main reason for the intensified foam thermal stability. The results obtained from this study can provide guidance for developing new firefighting foams.

Highlights

  • Foam is the assemblage of gas bubbles dispersed in a continuous liquid phase, where the gas phase may be of air or other gas, and the liquid phase consists of mostly surfactant solutions

  • The addition of xanthan gum (XG) led to further enhancement of the thermal stability of foams stabilized by SDS/FS-50/NPs dispersions

  • The thermal stability of foams stabilized by SDS/FS-50/NPs/XG kept increasing with increasing XG concentration

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Summary

Introduction

Foam is the assemblage of gas bubbles dispersed in a continuous liquid phase, where the gas phase may be of air or other gas, and the liquid phase consists of mostly surfactant solutions. Hydrocarbon surfactants are good foaming agents, and fluorocarbon surfactants are used to improve the surface activity of AFFF solutions [8], which are very important for AFFF to fight liquid fires. The addition of polymers and nanoparticles to a surfactant system can further help to improve the foam stability [32]. Abro et al reported the addition of xanthan gum (XG) to carbon foam for its heat absorption and retardation properties [36] It is unclear whether XG can improve the thermal stability of nanoparticle-stabilized firefighting foams. A gel foam stabilized by NPs, xanthan gum, and surfactants was prepared. The synergistic effect of xanthan gum and NPs to improve the gel foam thermal stability was analyzed systematically. The results obtained from this study provide a basis for the application of the new prepared gel foams in firefighting

Properties of Foam Dispersions
For theconductivity
Foaming Ability
Foam Drainage and Decay Process
Foam Thermal Stability
Variation in Foam Thickness and Drainage Height Versus Time
Variation
Temperature
Temperature distribution insidefoam foam layer different positions under 200
Conclusions
Preparation of Foam Dispersions
Characterization of Foam
Testing
10. Experimental
Fluorinated
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