From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Continued list of insulating materials, detailing their properties and applications.
| Identifier | ExFiles\Box 24\2\ Scan085 | |
| Date | 11th August 1920 | |
| S.G. 238A. 100 T) (S.H. 159. 11-8-20) G.{Mr Griffiths - Chief Accountant / Mr Gnapp} 2800 Contd. -2- Insulating material should be mechanically strong, impervious to moisture and oil. Easily machined & able to withstand heat. For switchboard work and supports ("burning match" test. No cracking, softening, etc. should occur. Where material varnished, holes drilled should be treated. Marble.& Slate poor mechanical qualities. Mica. - stand 40,000 volts per mm. or more. Small absorption. "Micanite" very nearly as good. Wood may be used under oil only. Vulcanite. Form of rubber. Unaffected by water, alkali or acids, but alters much with temperature. Melts at 120°C Swells in hot water and volatile oils, etc. Good machining, moulding, polishing. Sulphur separates out under light. Sulphuric acid formed of metals near. Mixed with fibres forms "Vulcan-asbestos". Inferior%. Gutta-percha. Can be moulded at 50°C. Treated as rubber, forms "ebonite". Galalith. Made from milk treated with "rennet" or dilute acid. Moulded, hardened with "formeldehyde". Easily machined. Limited use. Cellulose. Base of wood and paper insulations. Textiles can be made which carry insulating varnishes etc. Presspan. Dielectric strength 20,000 volts/mm. Contd. | ||