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).
Notes on synthetic insulation materials for electrical engineering, their production, and moulding process.
| Identifier | ExFiles\Box 39\3\ Scan255 | |
| Date | 1st November 1925 | |
| SYNTHETIC INSULATION. (Notes by F.J. Allen, read at Derby Wireless Club Meeting, Nov.1925). Early electrical engineering was looked upon with some disdain by mechanical engineers because electrical machines depended upon fabrics, rubber, fibre, etc. for their operation. It has long been the aim of electrical engineers to find an insulating material possessing mechanical properties more nearly like those of metals. The discovery of synthetic resinous (phenol-formaldehyde) materials, attributed to Baekeland, a Belgian and Tomlinson, Edison's chemist, represents a considerable advance in the endeavour to meet the ideals of electrical engineers. The material is produced by a fairly complicated series of chemical processes resulting in various forms of the substance, chief of which is a powder which is naturally brown but which is modified in colour by the addition of black or red pigment. It is also mixed with a "filler", usually of wood-flour but sometimes of asbestos or other substances. This powder is delivered to moulders for direct use in their dies. Accurately cut, polished tool-steel dies of the piston type are employed and a precise quantity of powder is weighed out (the amount being found by experience) and put into the die. The die is placed in a hydraulic press and subjected to a pressure of some thousands of pounds per square inch and steam heated at the same time. The powder then liquefies and takes the shape of the mould. Eventually it solidifies and is ready to be removed from the die. It comes out as a practically finished article possessing the same polish as the steel; a thin "flash" only may have to be removed from the part of the moulding where the two halves of the die met. No buffing is required, metal parts may be moulded in, threads moulded, and final dimensions to close limits may be obtained without machining. Some of the names under which the substances are marketed are :- Bakelite; Redmanol; Condensite (American) Elo; Formite; Mouldensite (English.) The physical changes which occur in the die are accompanied by chemical changes which make the solidification permanent; cannot be ground up and used again except as a filler for other powder. These resinous compounds are quite distinct from ebonite and similar materials, which are rubbers, and from fibres. A comparison of fairly representative properties of the three classes of material follows. Contd. | ||