Syntactic foams
Hollow Glass Microspheres?Syntactic foams

Syntactic foams are a family of cellular composite materials obtained by incorporating preformed cells into a base binder.

In practice, this is achieved by mixing a hollow spherical filler with an organic resin. The term syntactic is used by analogy with syntax, which refers to the arrangement of words making up a sentence. The term "syntactic foam" is therefore used to describe a material with an ordered arrangement, over short or long distances, of cavities called microbubbles.

A syntactic foam therefore has a different cellular structure to that found in conventional foams obtained by chemical or physical expansion of a gas during the polymerization or resin solidification process. The cavities formed in these materials...