Syntactic foam is foam made from polymers with micro balloons, that are essentially made of hollow glass beads. Some syntactic foam is also made from solid glass beads. Syntactic foam is primarily used for a unique combination of lightweight and fair compressive modulus and strength, and secondly for thermal or acoustic insulation. From all the foams, the main advantage syntactic ones offer is their lightweight coupled with other interesting features such as insulating or acoustic properties and others. Syntactic foam can withstand the pressure of very deep water including waters of the deep Antarctic and can be resistant to heat, low temperature, water and seawater, oil, gas, hydrocarbon, petroleum, chemicals. They are excellent in all different climatic conditions. These properties and features make syntactic foam ideal for a wide range of applications in offshore construction, exploration and production; and defense as buoys for flotation, thick coatings for thermal and acoustic insulation or protection. Syntactic foam is primarily used as buoyancy materials for industrial, military, and scientific oceanographic applications.

Syntactic foam can include macro spheres or/and fibers. Sometimes micro and macro sphere can be made out of polymer materials, such as phenolic resin instead of glass. Syntactic foam is never used alone but always in combination with other plastics or metals to make hybrid or composite material. All the polymers could be used as matrices but those with a low viscosity are preferred because of the low crush strength of hollow glass beads. The most used polymers are epoxy resins for buoys and tooling materials but polyurethane, phenolic, unsaturated polyesters, polyimide, polycyanate, silicones are also used. Certain grades have a density ranging from 0.3 g/cm3 up to 0.6 g/cm3 , nearer to that of balsa wood with a density ranging from 0.1 to 0.2 g/cm3 than that of glass reinforced composites and have significantly higher strength than balsa wood. Depending on the used resin system, syntactic foams can have controlled dielectric properties and high transition temperatures suitable for space use.