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).
Technical document describing the three-stage manufacturing process and properties of a resin, likely Bakelite.
| Identifier | ExFiles\Box 61\1\ scan0126 | |
| Date | 12th September 1930 guessed | |
| -2- and remains associated with the resin until the completion of the moulding process, when it is liberated and remains trapped in the moulding itself. Dr. Baekeland, the greatest researcher into these compounds, has suggested that in the process of manufacture the resin goes through three distinct chemical and physical changes, which he calls the "A", "B" and "C" stages. Stage "A" is the product formed first by the action of the formaldehyde on the phenol. It is easily soluble in alcohol, acetone etc. and melts easily to a thin treacly liquid at fairly low temperatures, or it may exist in the liquid state at normal temperatures. On prolonged heating resin "A" changes to resin "B" which is solid and with difficulty soluble in acetone and practically insoluble in all other solvents; it does not melt, but becomes rubbery when heated to about 60°C. Further heating changes resin "B" into "C" which is insoluble in all solvents and infusible. In this final change any water not previously got rid of is thrown out of solution and appears either as froth or in the form of an emulsion, giving the resin a boney white appearance. A resin of this type heated for several days, or even weeks, will gradually clear at the surface, showing that the trapped water can escape through the material when hot, possibly due to the solution of a small amount of water into the hot resin "C", dispersion of this throughout the bulk, and elimination at the surface. Electrical tests show that resins which contain much water are poor insulators and that they are much improved by prolonged baking to remove as much water as possible. Tests show that it is not possible yet to make a resin with no contained water in it, as it is impossible to separate completely the two reactions of condensation and polimerisation, which go on simultaneously. Vacuum drying at low temperatures (below 50°C.) promotes condensation without materially affecting polymerisation and is consequently resorted to for the production of "electrical" mouldings. | ||