Comparative study of the rheology and stability of firefighting foams stabilized by different nanoparticle/polymer systems: Fire suppression performance of selected β-Al₂O₃ formulations

Nanoparticles (NPs) and polymers are frequently combined to improve firefighting foam performance, but whether the effect of polymer addition depends on NP type remains unclear. In this study, Al(OH)₃ and β-Al₂O₃ NPs were separately incorporated into an FS-50/APG-0810 surfactant system and further combined with xanthan gum (XG) or guar gum (GG). The foaming ability, rheology, and drainage resistance of the resulting foams were systematically compared, while crossover strain and modulus of cohesion (MOC) were used to characterize deformation tolerance and resistance to structural breakdown. Polymer addition produced opposite effects in the two NP systems: XG and GG generally weakened the rheological properties and drainage resistance of Al(OH)₃ NP-stabilized foams, but enhanced those of β-Al₂O₃ NP-stabilized foams. Selected β-Al₂O₃ formulations were further evaluated for fire suppression performance. Among the tested formulations, the β-Al₂O₃/XG foam achieved the shortest extinguishment time of 22 s, whereas the β-Al₂O₃/GG foam exhibited the longest burn-back time of 1243 s. Unlike previous studies focusing on individual NP or NP/polymer systems, this work demonstrates that polymer-induced foam regulation is strongly dependent on NP type and that nanoparticle/polymer combinations do not necessarily produce universal synergistic effects. These findings provide a basis for rational NP/polymer matching to balance rapid extinguishment and burn-back resistance in firefighting foam formulation. Download: Download high-res image (243KB) Download: Download full-size image