Page:The American Cyclopædia (1879) Volume III.djvu/747

CAOUTCHOUC 737 to the pound. In April, 1831, George H. Richards of Washington, D. C., received a pat- ent for a fluid caoutchouc ; and soon after- ward Edwin M. Chaffee of Roxbury, Mass., and others established the Roxbury India-rub- ber company, which was chartered in 1833, and was the first company organized in the United States to manufacture caoutchouc into water-proof clothing. They made shoes, coats, life-preservers, and carriage traces, covering them with caoutchouc dissolved in some essen- tial oil, spirits of turpentine being principally used. Considerable excitement grew out of this enterprise,. and shares in the company's stock, which at first sold for $100, went up to $300 and $400. Active competition soon sprung up, and during that year six companies were chartered in Massachusetts for making India- rubber goods; and these were soon followed by others in Troy, Providence, and elsewhere. In 1834 Mr. Chaffee obtained a patent for manufacturing India-rubber hose, and another for making boots and shoes. In the same year Dr. Alexander Jones of Mobile, Ala., produced a kind of carpet by means of India- rubber varnish applied to canvas which had been covered with wall paper. In September, 1835, Charles Goodyear, after devoting much time to experiments, took out his first patent, which was for an India-rubber cement. In the following year he used nitric acid to deprive the surface of India rubber of its adhesiveness, enabling manufacturers to expose an India-rub- ber surface on their goods ; and this improve- ment was used till the production of vulcan- ized rubber. In the summer of 1838 Mr. Goodyear became acquainted with Nathaniel Hayward, who had been employed as foreman of the Eagle company at Woburn, Mass., where he had made use of sulphur by impregnating the solvent with it, and it was from him that he received his first knowledge of the use of this material. Mr. Goodyear soon afterward occupied the factory at Woburn, and employed Mr. Hayward in manufacturing life-preservers and other articles, by the sulphurous acid gas and solarizing process ; he purchased the sulphur- ing process of him and took out a patent for it as his assignee, Feb. 24, 1839. The sulphur process, however, would not have been of much value but for subsequent improvements made by Mr. Goodyear. The sulphur imparted an offensive odor, and did not prevent the rubber from hardening in cold weather. Continued experiments revealed to him the fact that the application of considerable heat would cause the sulphured article to become pliant in cold weather, to have its elasticity increased at all temperatures, and its offensive odor much di- minished. The new product of vulcanized rub- ber was the result of these experiments, and a patent was obtained for it, June 15, 1844. This patent was reissued in 1849, extended in 1858, and again reissued hi 1860. Mr. Nelson Good- year's subsequent improvements, and the pro- duction of hard rubber or ebonite by him, have left little room for further improvement in the vulcanization of caoutchouc. (See GOODYEAR.) Many of Mr. Goodyear's patents are for the mixing of white lead and other mineral sub- stances with caoutchouc, partially dissolved in some essential oil, grinding them together, and subjecting them to heat ; and many such sub- stances are still used for the manufacture of various articles. But most of the physical prop- erties for which vulcanized rubber is remark- able are obtained by a simple mixture of caou- tchouc and sulphur, the latter being added in quantities varying from 5 to 50 per cent., the larger quantities of sulphur being used, with an increase of heat, for the production of hard rubber, or ebonite. With the use of a moderate quantity of sulphur and a degree of heat vary- ing from 220 to 275 F., the compound is remarkable for possessing a much higher degree of elasticity than pure caoutchouc, and for retaining this at temperatures even below the freezing point of water ; neither is this prop- erty lost by frequent stretching. It also hears a considerable degree of heat without change, depending on the amount of sulphur with which it has been combined, and the degree of heat to which it has been subjected during the process of manufacture. Its elasticity is so much increased by vulcanization, that the ori- ginal article will scarcely hear a comparison. To test its power of enduring heavy blows, Mr. Brockedon subjected a piece of it an inch and a half thick and two inches square to one of Nasmyth's steam hammers of five tons' weight. When resting upon it, the caoutchouc was compressed to about half its thickness. The hammer was then lifted two feet and dropped upon it without injury. When dropped through a space of four feet the cake was torn, but its elasticity was not destroyed. The method of vulcanization of caoutchouc has undergone im- portant changes since its invention, both in the preparation of the crude material and in the process of adding the sulphur. At first the caoutchouc was cut up into small bits and shreds by knives placed on strong iron cylin- ders, revolving in hollow cylinders armed with teeth, after which it was immersed in melted sulphur and subjected to pressure; or it was partially dissolved in oil of turpentine and ground with sulphur and other materials; or in some cases dissolved in sulphide of carbon, and this process is still sometimes employed. The most approved method, however, and the one in general use in this country, is the fol- lowing : The crude caoutchouc is placed in a large vat of water, which is kept boiling by the introduction of jets of steam. In a vat which will contain about three hogsheads, 200 or 300 Ibs. of the crude material may be immersed. The clay and dirt are softened as well as the caoutchouc, which also slightly swells and in- creases in elasticity and pliability. A mass of it, say from 10 to 20 Ibs., is then taken and thrown upon a pair of strong fluted cast-iron cylinders, between which it is masticated into