[Cir. 12S— BI 



■ THE STRENGTH OE TEXTILE PLANT FIBERS.^ 



By Lyster H. Dewey, Botanist in Charge, and Marie Goodloe, Laboratory Assistant, 



Fiber Investigations. 



INTRODUCTION. 



Tensile strength is the most important character of fibers used in 

 making yarn, twine, thread, and woven goods. This one character 

 must be combined with sufficient flexibility, fineness, length, uni- 

 formity of diameter, and smoothness to be suitable for spinnmg, 

 but strength must be regarded as a prime factor. 



In nearly all textile mills tests are made of yarns, twmes, ropes, 

 and also of woven goods made up of yarns, but very little has been 

 done heretofore to actually measure the strength of individual 

 raw fibers. A list of the '^strongest fiber known" would fill several 

 pages, and in the absence of accurate measurements superlative 

 claims are reasonably safe from authoritative contradiction. 



A paper ^ on the methods of testing fibers and givmg the results 

 of numerous tests of tensile strengths of smgle fibers was published 

 m Java in 1908, but this excellent treatise m the Dutch language is 

 little known in this country. 



Many different kinds of machines have been devised for testing 

 yarns, and some of these which are especially accurate in a low range 

 are suitable for single fibers. A machme for testmg cotton must be 

 accurate in a range from 2 to 20 grams and one for testing long, 

 hard fibers from 100 to 10,000 grams. 



STRENGTH OF COTTON FIBERS. 



More than a thousand samples of cotton fibers have been tested 

 in the Office of Fiber Investigations. The machine (fig. 1) used in 

 makmg these tests is based on the principle of balances, with a slid- 

 mg brass bar instead of weights. The operator moves the bar 

 steadily and without any jar by means of a thumbscrew which turns 

 a ratchet wheel touching teeth on the bar. A single fiber picked up 

 by the double forceps is placed in the jaws of the machme, the 

 rounded faces of which, pressed together with sprmgs, hold the fiber 

 firmly but do not cut it. The weight is added by turning the thumb- 



i Issued May 24, 1913. 



2 Havik, H. G. Laboratorium vor het onderzoek van vezelstoflen. Jaarboek, Departement van Land- 

 bcuw, Nederlandsch-Indie, 1908, p. 319-333, 2 pi., 1909. 



[Cir. 128] 17 



