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 properties and applications of sponge and cellular rubber, including potential uses in safety equipment and insulation.
| Identifier | ExFiles\Box 178\2\ img059 | |
| Date | 25th March 1940 guessed | |
| -4- Here is a sample of such a sponge. It is a useful material which finds application in a wide variety of products. More recently we have found that a very similar structure can be made by our methods involving the whipping of air into latex and the setting of this forth in a way which preserves the air bubbles. This development was discussed in considerable detail by Dr. Gibbons of the U.S. Rubber company before this Society about 3 years ago.(Published in ASTM Bulletin No. 86, April 1937 page 13). Since then the use of sponge made directly from latex has grown very rapidly and its use will be extended as its advantages become more widely known. Here are several examples of sponge made from frothed latex. This type and the older type previously mentioned have pores which are largely intercommunicating. There usefulness in many applications depends on this fact. For example, the porosity of latex sponge permits the free passage of air thru it providing the necessary ventilation and cooling when used as a mattress or cushion. Water penetrates such a sponge with ease so that it is effective in sopping up water, as I will demonstrate by squeezing both types under water then squeezing out what they have absorbed. Cellular: Another development along these lines differs from ordinary sponge by having the individual pores or cells insulated or walled off from each other. To distinguish this non communicating structure from the ordinary sponge it is called cellular rubber. New methods of making this material economically in large volume are now in operation. The material has a number of novel properties. If a piece is placed on water it floats, and it will continue to float in spite of repeated squeezings because the water is wetting only the exterior surface. This property combined with low density makes it suitable for life preservers or other flotation devices. Under a vacuum the volume increases sharply because of the expansion of the trapped air in individual cells. These closed air spaces give cellular rubber a very high resiliency. A steel ball dropped on it rebounds sharply. On ordinary sponge rubber the rebound is much lower. This immediately suggests that the material should have unique shock absorbing qualities and experiments fully confirm that idea. A relatively thin layer of cellular rubber will greatly reduce damage due to impacts. To show how effectively cellular rubber will reduce impacts we will break some glass flasks like the one I have here. To avoid flying glass I have some of these flasks covered with cloth and one is mounted in this apparatus. The flask is held back against a compressed spring so that when I release the trigger it is thrown against the test surface with considerable force. In the first impacts the iron surface is covered with a layer of cellular rubber an inch thick and you see that the flask can be thrown against it repeatedly, without breaking. A layer of this material should be useful in crash helmets, trench helmets, football helmets, skating caps and any other similar spots where skull fractures or concussions are not uncommon. It would also be useful as a packing for fragile materials. The low density and cellular structure of this material immediately suggests that it can be used for insulation against noise or heat. | ||