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).
Analysis of the effects of ageing and storage conditions on Phenol-formaldehyde mouldings.
| Identifier | ExFiles\Box 61\1\ scan0130 | |
| Date | 12th September 1930 guessed | |
| -6- Ageing of Phenol-formaldehyde Mouldings. It has been stated that these materials improve with age. If stored in an "indoor" atmosphere the statement appears to be correct. Table II gives results on two sets of samples; A stored for 12 months in a works' office in a moulding factory; B stored in a dwelling house, subject to periodic dusting etc. TABLE II - AGEING DATA. Initial Test A B Appearance.................... Good Dull Good Diameter.................... 4.893 4.890 4.884 Electrical strength at 15ºC. volts/mm.................. 6,500 Track over 7,500 Electrical strength at 100ºC. volts/mm.................. 2,000 " " 5,600 Insulation resistance at 15ºC. megohms at gap.............>3,000 430 >3,000 Insulation resistance at 100ºC. megohms at gap............. 98 Small 680 Power loss (%).............. 3.9 High 1.95 S.I.C. ..................... 8.7 11 6.1 Stoving samples A for four hours at 110ºC. was sufficient to improve their electrical properties to B quality. Table II indicates that the properties of "bakelite" are affected by time, if conditions are good, then the material improves; if bad, then it deteriorates. It seems that mouldings when produced are really in a semi-finished condition, that means the resin has not been completely changed to the C form. To ensure the change being complete, several hours' stoving at 110ºC. are necessary, and the superlative finish is impaired. Only in extreme cases is the completion of the change necessary, so it is seldom effected. The existence of B resin in a moulding makes it slightly less resistant to the action of chemicals and atmospheric conditions; it absorbs moisture rather more readily; the softening point is high but definitely exists, so that deformation of the moulding is possible, though unlikely; and, lastly, the change from B to C can and is, always taking place, making a slight shrinkage of the moulding on all dimensions certain eventually. | ||