Hollow Glass Microspheres?Syntactic foams

The composite materials industry has a range of mineral raw materials available for incorporation into synthetic resins to impart certain properties to manufactured parts that the resins do not intrinsically possess, such as rigidity, weight reduction, impact strength, thermal resistance, etc. Glass microspheres are mainly used as fillers to lighten thermoplastic or thermoset resins. Hollow glass microspheres, with a very low real density (0.12 to 0.60 g/cm ³ ), are mainly used as fillers to lighten thermoplastic or thermosetting resins and certain elastomers, leading, among other things, to the production of syntactic foams.

Syntactic foam is a complex composite material made from hollow glass microspheres embedded in a specially selected resin matrix. This material provides high mechanical strength at the lowest possible density.

These syntactic foams, also known as buoyancy materials, are fitted to equipment intended for marine applications at depths of between 1,000 and 10,000 m. Their purpose is to neutralize the weight of equipment immersed at their working depth. As a result, syntactic foams have to withstand considerable pressures, which can exceed 1,000 bar. In particular, they must retain all their buoyancy properties, i.e. be neither deformable nor permeable to water.

Glass microspheres are often used in conjunction with other cellular fillers such as silica-alumina fly ash, synthetic resin microspheres and perlites, which are briefly described at the end of this article.

This article discusses the manufacturing process and physico-chemical properties of glass microspheres, followed by a detailed look at syntactic foam technology, for which glass microspheres are an essential component.