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).
Description of insulating materials including Gutta Percha, Galalith, rubber and vulkan-asbestos.
| Identifier | ExFiles\Box 24\2\ Scan097 | |
| Date | 25th January 1921 guessed | |
| - 10 - This trouble may be completely removed by the simple means of washing the surface vigorously with distilled water, after which the previous insulation will be restored. Rubber is used in electrical processes in the most varied manner. Cables and wires are covered with it. It is used to cover textiles that are to act as insulators and in all conceivable formes and plates, in some cases with embedded metal parts. If it is pressed with an admixture of asbestos fibre, a product is formed that is known as vulkan-asbestos, a substance which is greatly inferior to vulcanite but may be used for many special purposes. Gutta Percha is very similar to rubber. It is obtained from the sap of large trees which are found principally in Borneo, Sumatra and the Malay Pensinsula. Formerly the whole tree was felled to obtain the sap, but the Government prevented this destruction and the sap is now obtained by tapping. It is to be found between the bark and the wooden structure. The gutta percha is suspended in this sap in spherical particles which coalesce into a solid mass after flowing out and collect on the surface of the liquid. A thick lump can be formed by kneading it with the hands. Cleaned fibrous gutta percha is pliable at 25 degrees, gets soft at about 50, and can be moulded into any form, such as tubes, strips, etc, in this condition. At 100 it becomes a sticky mass. Light and air have the effect of making it brittle. If gutta percha is treated with sulphur in a similar way as rubber, ebonite is formed. It is not equal to vulcanite in its power of withstanding temperature rise. Gutta percha has its particular use in the manufacture of submarine cables. Galalith is, as its name indicates, a material made of milk. If rennet is used instead of dilute acid to deposit this case-in material out of skimmed milk, a deposit is formed that may be finely ground and further treated after 10 to 12 hours. The damp mass, treated if desired with colored solutions, should be kneaded with a sliding pressure in order to cause the greatest plasticity and it may be pressed into moulds. The greatest difficulty in manufacture consists in hardening the material with formaldehyde, which is a tedious process. The product is then dried in a current of warm air. The insulation of galalith when dried is fairly good. It is, however, very sensitive to dampness and very hygroscopic, and softens in hot water. It is not combustible and withstands the action of oils, fats, benzine, ether etc., Its use in electrical manufacture is fairly limited in spite of its property of being easily machined. It may be successfully used under special circumstances. contd. | ||