Glass that is dimensionally stable during large heat fluctuations. Four types of heat-resistant glass are: borosilicate, alumina glass, alkaline-free silica and quartz. Borosilicate glass typically contains silica (81%), boric oxide (13%), soda (4%) with some alumina. It has a very low thermal expansion coefficient and a high softening point (>600C). Examples of borosilicate glass are Pyrex®, Duran and Kimax. Alkaline-free silica glass also has high thermal resistance. A normal glass mixture is softened then leached in an acid bath to remove alkalis followed by heating to 1100C to fill voids. This produces a hard glass, such as Vicor, that can be used up to 870C. Quartz glass, or pure fused silica, also provides excellent thermal stability.
Synonyms and Related Terms
heat resistant glass; verre résistant au chaud (Fr.); Duran; Kimex [Owens Illinois]; Pyrex [Corning Glass]; Vicor [Corning Glass]
Sources Checked for Data in Record
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 361
- Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993