Hollow glass microspheres (sometimes termed microballoons, or glass bubbles) have been used as low-density fillers for various kinds of polymeric compounds since the mid-1960s. They are gas-filled, spherical, borosilicate particles with diameters typically between 10 and 100 microns. The spheres are manufactured on an enormous scale by several companies worldwide and, despite their structure, they can have extremely high compressive strength. They are routinely used as fillers in concretes, syntactic foams and other structural components, particularly in the marine and aerospace sectors. The profile of weight saving materials has increased dramatically in recent years due to both rising oil prices and environmental awareness.

MTL has taken low density fillers to the next stage of development. By adding less than 100 nanometers of materials, such as metals and metal oxides to the surface of the hollow glass particles, hybrid materials can be generated which retain the functionality of the coating material itself, but with the benefits of significantly reduced density, better handling/recovery properties and improved particle/matrix interfacial strength. Using its expertise in particle coating, MTL has developed low density fillers coated with, amongst other materials, titanium dioxide and metallic silver. The aqueous-based processes used to make these materials readily lend themselves to large scale production.

The range of applications in which coated microspheres and microparticles can be used to enhance current composites, or provide new solutions, is extremely diverse and the size, density, surface chemistry and functionality required by end users tend to be application specific. There is significant scope, therefore, for the development of a wide range of new materials to meet these diverse market opportunities.