Hollow glass microspheres (HGMs) have potential as components of a fluorine-free firefighting suspension or foam, as they exhibit low thermal conductivity, low density, and their surface can be easily modified to alter their behavior within an aqueous suspension. In this study, we used several polymer grafting methods to modify the surface of HGMs with hydrophilic polymers to tailor HGM surface properties. Poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) with various polyethylene glycol side chain lengths was tethered to the surface of the HGMs with a range of graft densities. The HGMs were first characterized using thermogravimetric analysis (TGA) to determine the amount of polymer grafted and scanning electron microscopy (SEM) to ensure uniform surface modification. The molecular weight of each polymer was found through static light scattering (SLS) to determine the graft density on the surface of the HGMs. With the HGM suspensions, shear viscosity, surface tension, interfacial tension with hexadecane, and spreading on liquid and solid hydrocarbon surfaces were investigated. These properties are critical for firefighting applications, as they impact the ability of a suspension to spread across and seal a liquid fuel surface efficiently.

Tailoring surface behavior of hollow glass microspheres with poly(ethylene glycol methacrylate) polymer brushes

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