Alkaline earth silicate wools – A new generation of high temperature insulation

Intensive study of the natural asbestiform minerals that cause human diseases, and the consequent understanding of their hazardous characteristics, has enabled the development of manufactured fibres whose physical and/or chemical properties, in particular as they relate to biopersistence, have been adjusted to minimize possible harm to health. A strong driver for the development of new high temperature insulation materials was the perception of the toxicity of refractory ceramic fibres (RCF) and their classification in the EU as a category 2 carcinogen under Directive 67/548/EEC. Such classification carries with it the requirement for substitution by less hazardous materials. This paper focuses on the development of alkaline earth silicate (AES) wools as a new class of high temperature insulation with the capability of such substitution in a number of applications. These wools have only a low potential to cause harm because they do not persist in lung tissue once deposited, and have produced minimal effects in experimental test systems. AES wools are increasingly being used in a wide range of high temperature applications.

► Short historical perspective on asbestos and man-made mineral fibre toxicology.
► Review of key properties that determine fibre toxicity with a focus on biopersistence.
► Overview of the regulatory approach to man-made mineral fibres.
► Description of the successful development of a new type of less hazardous man-made mineral fibre.