Silicones for Surface Protection rEW people have heard of silicones.
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'They are probably the most interesting group of semi-plastics yet produced. Discovered some 50 years ago by an English chemist, Kipping, they were neglected for years, but developed during the war as a means for protecting aeroplanes and Tanks from the effects of moisture and corrosion. Made from sand and petroleum gas by the Dow Corning Corporation, they are now also being manufactured in England by Imperial Chemical Industries. Ltd.
Silicone fluid freezes at 99 degrees F. below zero. Silicone resins and varnishes will stand 400 degrees F. Silicones have low surface tension and are waterrepellent. They can be used for dampers in hydraulic brakes, hightemperature lubricants, bonding agents and protective coatings. Compounded with rubber, tubes made with this will remain flexible down to the freezing point mentioned and will not melt at 500 degrees F. Certain products made with them are used for gaskets and seals for highflying aeroplanes and for hot-air tubes to 'prevent icing. Electric motors, the armatures of which are wound with an insulation of glass fibre and-.silicones will run under water, and as they can be run hot without fear, small 'motors can develop much more power than normally.
They are being largely employed _now to prevent rubber sticking to its moulds, and even to replace grease in breadbaking pans. As a protective medium, they form fine films over metal or cellulosed surfaces, which never oxidize and stay put indefinitely.
Formed into material like putty. this can be rolled in the hands until dull, but at the end of a few minutes again develops its shine. A finger can be pushed into the putty and the hole will remain temporarily, but if bounced on the floor, the putty will rebound higher than would a rubber ball. It can be broken across, but if the parts be brought into contact they immediately rejoin and can then be pulled into almost a thread—in fact, silicones seem to refuse to obey most of the laws of nature.
When used as a polish containing 4 per cent. of silicones the silicones are left as a fine film which. after an hour or so. will not take finger-prints and %tin be cleaned with cold woei and a sponge, or merely by rain.
• Most of the people in this country will see silicones first in the form of a car polish, which is known as Autobrite and is marketed through garages, etc., by E. R. Howard, Ltd., "3-In-One" Works, Stowmarket, Suffolk, which has been given the sole Ilritish and Continental rights. Supplies are limited, but will steadily increase. Demonstrations Witnessed recently by "The Commercial Motor" showed that dirty and oxidized surfaces, such as the bonnet of an old vehicle, could be polished to brilliance in a few minutes. It is claimed that the surface will remain bright and prevent corrosion up to six months.
As an example of their lack of affinity for other materials, Scotch tape will not adhere to brown paper treated with silicones.
Another us $ for silicones is to prevent ignition troubles, for if the ignition leads, distributor and sparking-plug insulators be coated, they avoid difficulties caused by condensation from humid air or even the splashing of water,