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).
The properties and applications of various dielectric and insulating materials such as Bakelite, Faturans, and Eswelite.
| Identifier | ExFiles\Box 24\2\ Scan102 | |
| Date | 25th January 1921 guessed | |
| - 15 - Bakelite can be produced in various forms that are suitable for electrical engineering by treating it in various manners, for instance, it may be transformed into mechanically strong substances by admixture of fibrous matter and loading materials. It is also able to be formed into a good insulating and anti-rusting varnishers. For instance, among others, the Chemical Factory, Amoneburg, produces a resinous phenol that is soluble in oil and according to the process of Dr.Albert and Dr.Behrend can withstand a voltage of 5000 to 6000 volts in a thickness of 0.1.mm. according to the experiments of the Bavarian Institution. The firm of Dr.Heinrich Traun & Sons, of Hamburg, uses resinous phenol in the much used Faturans that have, after being surface ground, an insulation that generally exceeds 100,000 and are not changed by the action of sulphuric acid, and retain a good insulating resistance under its action. Plates of 3 mm. thickness withstand stresses of 25.000 to 30,000 volts alternating current; they can be machined with clean surfaces with the application of small power and take a good polish. They can, in many cases, be used as a perfect substitute for vulcanite which they excel in their property of not containing sulphur which causes their surface to remain free from acid and well insulating. Certain varities do not catch fire and are not affected by immersion in boiling water. Another dielectric that can be produced from phenol resins and is perfect substitute for vulcanite is Eswelite the specific gravity of which is 1.2. It has, after grinding an average surface resistance of 8 million which is maintained after 24 hours immersion in water, and even after five days immersion in a 24 per cent solution of sulphuric acid it can be machined with moderate application of power but is rather brittle. The wear of the tools is only moderate and the material takes a good polish. It is generally only used in formed pieces. On removal of a flame it continues to burn, gets soft and carbonises; it becomes flexible in boiling water. The firm has informed me that according to their own tests eswelite plates have a tensile strength of 4 to 5 kg. per sq.mm. and a dielectric strength of 15000 volts with a thickness of 1 mm. Hitherto, with the exception of the natural insulating materials, we have only discussed those with constituents of organic origin. We will now discuss inorganic dielectrics beginning with glass. Under the general name glass is usually understood a melted flux that is solidified in an amorphous form. It may be said that glass is a solid solution in which the components of the glass have dissolved each other. It is assumed that a single chemical compound is not formed but in the main a solution of several substances at the same time. contd. | ||