THE INDIA RUBBER WORLD 



[July 1, 1920. 



basket shall be so constructed with partitions, not less than 

 J4-inch apart, that the specimens may stand on edge. The speci- 



Table of Corrected Tensile Strengths of Fabric and Yarn at 

 Various Moisture Regains. 



Explanation. — \ sample of fabric in its natural state gave 

 an apparent tensile strength of 210 pounds. After drying its 

 moisture regain at the time of the test was found to have been 

 4.75 per cent of the dry weight. In the line opposite 210 and 

 under 4.75 regain in the table, will be found the figure 227.2, 

 the strength of the fabric corrected to a full regain of 6.5 per 

 cent. In the same manner a fabric with an apparent strength of 

 192 pounds and a regain of 5.25 per cent would have a corrected 

 streigth of 202.9 as determined by interpolation from the table. 



mens shall then be dried to bone dryness as described in Section 

 2. The combined weight of these specimens after drying repre- 

 sents the dry weight of 0.05 square yard of the fabric, and the 

 dry weight per square yard of the roll or piece is obtained by 

 multiplying the above quantity by 20. 



8. If by the first tests the fabric fails to meet the specifications 

 a second swatch shall be taken as follows : If the roll or piece 

 is a complete warp, the second swatch shall be cut from the center 

 of die roll or piece. If the roll or piece is a part warp, the second 

 swatch shall be taken not less than V/, yards from the other end. 



9. The difference between the normal weight of the fabric. Sec- 

 tion 6, and the dry weight, Section 7, is the amount of moisture 

 present. 



(a) When computed as percentage of the normal weight this is 

 the moisture content of the material. 



(6) When computed as percentage of the dry weight, this is the 

 moisture regain of the material. 



(D) NUMBER OF THREADS PER INCH. 



10 (a) The numl)er of threads per inch or count of the fabric 

 shall be determined by counting a space of not less than 1 inch 

 in at least five different places in the roll or piece. 



(b) The average of the five determinations shall be the count.' 



(E) THICKNESS, 



11. (a) The thickness shall be measured by an automatic 

 micrometer which presses upon at least 0.5 square inch of the 

 fabric with a uniform constant pressure, and which is so mounted 

 as to make measurements 6 inches from the selvage. 



(b) At least ten measurements at different portions of the roll 

 or piece shall be made, and the average shall be the thickness of 

 the fabric. 



(F) STRENGTH. 



12. Tensile strength tests shall be made by one of the four 

 methods described as follows in detail, and fabrics shall be tested 

 by the method shown for the classification under which they 

 fall. In each case the results shall be recorded separately for 

 warp and filling. 



For the determination of tensile strength a swatch of the 

 length specified in Table I shall be cut the entire width of the 

 cloth and test specimens shall be cut from this swatch according 

 to the respective diagrams shown at the bottom of Table I. 



Two methods of determining the tensile strength shall be 

 recognized : 



(o) Strip Test (Fig. 1). — Under this method a long narrow 

 strip of the fabric shall be clamped at each end by the jaws of 

 the testing machine and strained to the point of rupture. 



(6) Grab Test (Fig. 2). — Under this method the testing ma- 

 chine jaws, each of definite width, shall be made to reach into 

 the body of a rectangular piece of fabric and shall be clamped 

 a definite distance apart. Care shall be taken that the same set 

 of threads are embraced by both pairs of jaws. The specimen 

 shall then be strained to the point of rupture. 



13. Correction for Standard Moisture Regain. — When it is 

 desired to test tension specimens for tensile strength, in the 

 natural state in which they are cut from the roll or piece, the 

 following method shall be employed to reduce the tensile strength 

 found to the common basis of an assumed standard moisture 

 regain equal to 6.5 per cent of the bone-dry weight: 



(a) .\fter preparing the specimens for the testing machine, 

 those cut from the warp and those from the filling shall be 

 weighed each in a separate batch under the natural moisture 

 conditions which obtain at the time in the testing room. 



(b) The specimens shall then be tested immediately, in as 

 rapid succession as possible, by the method specified in Table II. 



(c) .\fter rupture the broken specimens (entire) shall be 

 placed in the basket of an oven and dried as defined in Section 2. 



^For tire fabric used for carcass building the nuinber of threads per inch 

 shall be determined. by counting a space of 10 inches in at lea.st five diflFerent 

 places in the roll or piece, and the average of the five determinations shall 



