Other Synthetic Fibres.—Certain fibres have been made which combine viscose rayon (made with cellulose) with proteins or resins to form a viscose rayon fibre with wool dyeing characteris tics. One method is to combine viscose and casein in the spinning solution. Others are made by introducing nitrogenous groups or synthetic resins into the viscose spinning solution or incorporating them with the viscose yarn by treatment immediately after it is spun.
Mention should also be made of fibres spun from glass, which have application especially where fire-, heat-, and chemical-resist ing qualities are needed. Fireproof decorative fabrics are made from this material, which also has found wide industrial use in chemical filter cloth, dust filters, electrical insulation, insulation against heat or cold, and sound-proofing. The glass fibres are spun in both continuous filaments and short lengths.
Strands of spun or cut rubber are used in the production of elastic fabrics. These are usually in the form of a single con tinuous rubber filament around which is wrapped a covering fibre, making an elastic yarn suitable for weaving or knitting. A tex tile fibre has also been experimentally produced from chlorinated rubber.
Although the commercial production of rayon was begun only in 1891, the continuous technical improvements in the quality of the yarn and its versatility have made it one of the major textile fibres today. The world production of rayon in 1939 equalled that of wool and was more than 20 times greater than the pro duction of silk.
Historical Development.—The first person to visualize the pos sibility of making an artificial fibre by a process similar to the silk worm's spinning was Dr. Robert Hooke, an English scientist, who included a discussion of the subject in his book Micrographia, published in 1664. Again in 1734 the French scientist, Rene A.
F. Reaumur, predicted the manufacture of an artificial textile from gums or resins, similar to varnishes then being manufactured, which had the necessary qualities of resistance to heat and sol vents. No concrete developments along these lines occurred, how ever, until the middle of the 19th century. In 1842 an English silk weaver, Louis Schwabe, exhibited a machine for making arti ficial filaments. This machine used nozzles with fine holes through which the liquid was forced to form filaments, which is the principle of the spinnerets through which rayon is spun to day. Schwabe spun his filaments of glass, but he was not satis fied with the product and appealed to British scientists to dis cover a better material from which to manufacture filaments. A third development preparing the way for rayon was the discovery of nitrocellulose by Schoenbein, a Swiss chemist, in 1846.
The first known patent for the manufacture of rayon was issued to George Audemars in 1855. He prepared fibres from the inner bark of mulberry and other trees, which he nitrated and dissolved in a mixture of ether and alcohol and combined with a rubber solu tion to form his spinning mixture. The filaments were spun by dipping the point of a needle into the solution and drawing out a filament which was connected with a winding machine. Two years later a patent was issued to E. J. Hughes for an elastic sub stance made of starch, gelatine, resin, tannins, fats, etc., which could be spun into silk-like filaments.
A further advance was made by Sir Joseph W. Swan, who, searching for a better carbon filament for electric light bulbs, patented in 1883 a process for making a filament by squeezing a nitrocellulose solution into a coagulating medium and denitrating the filament. The fact that nitrocellulose could be denitrated by the use of reducing agents such as ammonium sulphide was known as early as 1863. In 1885 Swan exhibited a few articles made from these filaments, but he did not follow up the textile possi bilities of his invention.