Syntactic foams are complex compounds produced by the incorporation of hollow spherical particles into a polymeric or ceramic matrix. The American Society for Testing and Materials (ASTM) states that synthetic foams have a resin matrix.

The properties of synthetic foam can be largely determined by changing some parameters during their production such as the material of the matrix and fillers, the size of the microspheres, the thickness of their wall and their number – meaning mostly the ratio of their volume with the total volume of foam. The easiness of production is another important advantage of synthetic foams.

Epoxy synthetic foams are preferred as a matrix material due to their good mechanical properties such as durability and stiffness, small creep and moisture resistance.
Structural polyamide foams have very good mechanical and electrical properties and their use is great in electronic devices. They are usually combined with silicon spheres.
Structural polyurethane foams have good compressive strength and high water resistance. They can be soaked in a humid environment for over 10 years and at a water temperature of up to 40oC without significantly degrading their properties.
Polyester synthetic foams in combination with hollow glass microspheres have found great application in the construction of marine vessels and underwater structures due to their buoyancy, non-adsorption of moisture and their low cost.
Polypropylene is used with hollow glass spheres to have low density, good mechanical and thermal insulation properties.

The main properties of synthetic foams that gave impetus to their production and growth include among others their reduced weight, increased rigidity, buoyancy and reduced cost. If we take into account their resistance to compression and hydrostatic loads, their relatively good response to impact and fatigue and their resistance to abrasion and chemicals, we understand why they have been widely applied in various types of constructions.