Abstract
A SEVEN-PAGE article on “Recent Developments in Electrical Insulating Materials” by Dr. L. Hartshorn (J. Sci. Inst., July) will prove of great use to constructors of electrical apparatus and will serve as a base from which research on the properties of insulating materials advocated by the Radio Research Board may operate. The author describes the properties of ebonite, of 'loaded' ebonites, of synthetic resins which can be readily moulded or used to bond laminated material into insulating boards, and when of the hydrocarbon type have dielectric constants little more than 2 and power factors so low as 2 x 10-4. Ceramics provide insulators of the steatite group depending mainly on magnesium silicate, and of the rutile group, principally titanium dioxide, used in the construction of condensers. After shaping, both are fired and cannot afterwards be worked without difficulty. They are apt to absorb moisture which alters their properties. Certain waxes, for example, the chloronaphthalenes, have high dielectric constants and fairly low power factors. A table of dielectric constants, power factors, resistivities, mechanical and electrical strengths and softening temperatures for nearly thirty insulators is given.
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Insulators. Nature 142, 508 (1938). https://doi.org/10.1038/142508a0
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DOI: https://doi.org/10.1038/142508a0