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 hardness and heat tests of various insulating materials.
| Identifier | ExFiles\Box 24\2\ Scan192 | |
| Date | 10th April 1922 | |
| EFC. AD.44. 10th April, 1922. X.1192 - TESTS OF INSULATING MATERIALS. A series of tests has been carried out on a number of samples of insulating materials which have been received from various makers. The first test was for hardness by the brinell method, all samples being tested at 500 Kg. Siluminite stands highest at 40, the phenols coming next at about 30 and over, except Admiralty quality Paxolin, whose figure is 20. The rubbers are inferior being all less than 20. Beldalite could not be determined as it broke under the pressure and the same applies to Solidite. The second test consisted of heating the samples on an iron plate fitted with a thermometer, over a gas ring, and noting the effects. All the samples were tested together. The phenols mostly blistered at 250°C the fibres being comparable with them, though both grades of condensite celeron seemed to be unaffected at above 275°C. The rubbers became soft at about 75°C, Siluminite began to ooze out a tarry substance at 150°C and solidite was reduced to a soft mass at the same temperature. Following is a list giving the results of these two tests:- PHENOLS Material | Grade. | Test 1. | Test 2. | Remarks. Bakelite | Campbell. | 38 | Blisters 250° | Bent.throughout. Bak-dilecto | Black. | 35 | Small blisters at 250° Bak.Micarta | " | 29 | Blisters 250° Cont. Bak: | Brown. | 36 | " " | Canvas. | 34 | Small do. 250° " | Linen. | 32 | Blisters 250° Condensite celeron. | Canvas. | 35 | Unaffected. " | Paper. | 34 | " Paxolin. | Standard. | 32 | Blisters 250° " | Admiralty. | 20 | " RUBBERS Beldalite. | - | - | Soft, breaks 75° | Breaks on test 1. Ebonite. | Brit.Eb.Co. | 17 | Very flexible 75° " | Carson. | 14 | Soft, breaks 80° " | Hightensite. | 19 | Soft 75° Hightensite | Standard. | 18 | Fairly soft 75° " | Heat-resis. | 14 | Soft, breaks 75° Vulcanite. | 102. | - | Soft 75° | Rods not suitable for test 1. " | 110. | - | " FIBRES Diamond Fi. | Red. | 16 | Blisters 250° " | Natural. | 16 | " Contd. | ||