: 706 CREATIVE CHEMISTRY makes it possible, according to the most accepted modern theories, to link one molecule to another using sulfur as the bonding agent, thus producing tough, strong, and even very hard products, depending upon the amounts of sulfur used. When the storms of Charles Goodyear's failures gave way in 1839 to the sunshine of success, he found at the end of his rainbow, not a pot of gold, but a strip of vulcanized rubber that was the forerunner of to-day's billion-dollar rubber industry. The discovery was one of those "accidents" that come to those who strive to observe. It happened when the difficulties of the experiment, financial worries, and even ill-health were at their worst. Ironically enough, Goodyear's success resulted from a condition previously considered a hindrance — heat. Thoroughly familiar — to his financial loss and chagrin — with the effect of heat on rubber, Goodyear was defeated time after time in his effort to find how rubber could be made heat-resistant. That he was ultimately successful is a tribute to his perseverance, his thoroughly scientific mind, his resourcefulness, and his keen powers of observation.^ Of Goodyear's accidental discovery that rubber could be made heatresistant by heating it with sulfur, Goodyear said That which is hidden and unknown and has not been revealed by direct methods will most likely be discovered by an accident, by the man who applies himself perseveringly to the subject and is most observing of everything related thereto. In 1844 Goodyear was granted a patent for his discovery, which was often and bitterly contested. He was represented in one legal battle by the eloquent Daniel Webster, who said in the course of the trial, "This discovery will work important changes. It introduces a new material into manufacture, nothing less than elastic metal." The rubber industry is very important today. One American manufacturer advertises over thirty-two thousand different items made from rubber, while several hundred thousand patents dealing with rubber have been granted. Some of the more important newer developments in the utilization of rubber are: i. The Electrodeposition of Rubber. The particles of a rubber emulsion have a negative charge and may be attracted to a positive electrode, which may be in the form of a human hand made of metal on which true-fitting rubber gloves are thus deposited. Or, a metal plate may be covered with a textile fabric in which the rubber is deposited to make a waterproof material containing very little rubber. ' The Laboratory, Fisher Scientific Company, Vol. X, No. 5.
NATURAL AND SYNTHETIC RUBBERS 707 2. Sponge Rubber. Sponge rubber made by vulcanization of foamed-latex compositions is now used for mattresses and upholstering furniture and automobile seats. 3. Chlorinated Rubber. Chlorine will combine with rubber to form tough and horny resins which contain about 65 per cent chlorine. These resins are very resistant to water, acids, bases, salts, and many organic solvents and are finding wide application in the preparation of corrosion-resistant paints, lacquers, and floor coverings and in flameproofing textiles. "Paratex," "Parlon," and "Tornesite" are typical chlorinated rubber products. 4. Rubber Hydrochloride. Hydrogen chloride combines with rubber to form a moisture-resistant, flexible, shock-resisting material of many uses. Under the name of "Pliofilm" it is now found in shower curtains, raincoats, and protective covers for foods and other merchandise, wherever low moisture and oxygen permeability, with a high degree of flexibility and toughness, are desired. together 5. Pliolite. "Pliolite" is a resin prepared by the cyclization of rubber with stannic chloride or other similar compounds as catalysts. It finds useful applications in the paint, lacquer, and moistureproofing industry. 6. Rubber-metal Bonding Cement. Sulfonic acid or sulfonyl chlorides react with rubber to form isomers of a lower degree of unsaturation than rubber. Certain of these have been found to bond rubber firmly to metal. A solution of the isomer is applied to the clean metal surface, and the rubber is vulcanized in contact with it. This process is known as the "Vulcalock" process. This is one method by which tank cars, stationary tanks, and pipe are lined with rubber. 7. Kolok Fabrics. "Kolok" is the name of a fabric in which minute bind the particles of latex have been deposited in such a way as to fibers together. These fabrics are said to wear twice as long, fit better, appear neater, and resist shrinkage better than untreated fabrics. Millions of pairs of silk hosiery have been given the Kolok treatment. Some of the newer developments in the use of rubber are airplane armor plate of laminated rubber and steel, self-sealing (and therefore bulletproof) fuel tanks for airplanes, rubber printing plates which save 25 per cent on ink and a considerable amount of time in printing. The time saved through the use of rubber printing plates is in the so-called "make ready." When printing from metal type, all parts of the surface have to be carefully adjusted so that in printing none of the type causes depressions in the paper. Because of its flexibility, rubber will not cause depressions in the paper and "make ready" time is greatly reduced.