ASTM D1578-93(2016)

5.1.1 In case of a dispute arising from differences in reported test results when using Test Method D1578 for acceptance testing of commercial shipments, the purchaser and the supplier should conduct comparative tests to determine if there is a statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test specimens which are as homogeneous as possible and which are from a lot of material of the type in question. The test specimens should then be randomly assigned in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using Student's 5.2 This test method is not suitable for yarns that stretch more than 5 % when the force is increased from 2.5 to 7.5 mN/tex or 0.03 to 0.08 gf/denier, because (a ) they require special precautions as to tension in reeling, and (b) users of such yarns are more interested in their elastic behavior at low forces than in their ultimate breaking strength.

5.3 For Option 1, it is advisable to use a tensile testing machine of the proper capacity to break skeins with 80 turns. If it is necessary to break skeins having only 40 or 20 turns, convert the observed results to an 80-turn basis by multiplying by factors of 2 or 4, respectively. (The available literature does not show that any significant error is introduced by the use of these factors.)

5.4 The circumference of the skeins used to determine the breaking load is not critical, and as a consequence, close control of the tension at which the skeins are wound is not necessary. If, however, the same skeins are to be used to determine yarn number for any purpose, the skeins must be reeled under controlled tension on a reel meeting the requirements given in Test Method D1907.

5.5 For some purposes it may be advisable to convert the skein breaking strength observed for yarn of one number to the estimated skein breaking strength of a different yarn number. Factors for making such a conversion for cotton yarns are given in 11.2. No corresponding factors have been developed for yarns spun from other fibers.

5.6 The results obtained from different options are not fully comparable because the breaking force per wrap increases slightly as the perimeter of the skein is reduced. The skein breaking tenacity observed for 1-m skeins may be as much as 4 % higher, and from 1-yd skeins 5 % higher, than that observed for 1.5-yd skeins. These relationships may vary with the type of yarn or with yarn unevenness and should not be used as conversion factors. With a reasonable number of specimens, this method provides a useful index that combines the effects of unevenness and single strand strength.

5.7 This method is rarely, if ever, used for filament yarns because their uniformity makes it possible to obtain reliable results economically by the single-strand method.

1.3.1 Option 1—Eighty, forty, or twenty turns on a 1.50-m or 1.5-yd reel, broken at 300 mm/min or 12 in./min.

1.3.2 Option 2—Fifty turns on a 1.00-m or 1-yd reel, broken at 300 mm/min or 12 in./min.

1.3.3 Option 3—Fifty turns on a 1-m reel, broken in 20 s.