ASTM D1445-95

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An American National Standard
Designation: D 1445 – 95
Standard Test Method for
Breaking Strength and Elongation of Cotton Fibers (Flat
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Bundle Method)
This standard is issued under the fixed designation D 1445; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
The flat bundle test for cotton fiber strength gained immediate acceptance after its introduction in
1953. The first successful instrument was an inclined plane device with the beam calibrated in pounds.
The specimen was clamped with no space between the jaws and was called zero-gage strength. Results
were expressed in Pressley Index (P.I.) calculated as the force-to-break in pounds divided by the
bundle weight in mg. Obviously, P.I. is not a standard engineering unit.
Before the introduction of the flat bundle test, cotton fiber strength had been measured by the
Chandler round bundle test (see former Method D 414) and the results expressed in pounds per square
inch (psi). The U.S. Department of Agriculture obtained results from both instruments on specimens
from the same samples of a large number of cottons. From this study, an empirical equation to express
flat bundle test results in psi was
Breaking strength, 1000 psi = (10.81106 3 P.I.) − 0.12
When it was shown that a finite gauge length test was more highly correlated with yarn strength
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than tests made at zero gage length, the clamp design was modified to accommodate a ⁄8 inch (3.2
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mm) spacer. Selection of an engineering unit for reporting of results from ⁄8 inch (3.2 mm) gauge tests
presented a problem. However, the use of the tex for linear density and the introduction of a pendulum
type instrument calibrated in kilograms led to the expression of results in grams-force per tex (gf/tex).
The clamp width without spacer is 11.81 mm and with spacer is 15.00 mm. The bundle of fibers is
mounted across the clamp width and trimmed to the width. The bundle mass is mg/11.81 mm or
mg/15.00 mm.
The use of the flat bundle test in domestic and international commerce has had a long and successful
history. Correcting this error in the empirical relationship would have serious adverse affects in the
textile industry. Therefore, the empirical relationship is retained to calculate zero gage cotton fiber
tensile strength designated as the Pressley strength in Eq 3 and 4 of D 1445.
1. Scope 1.2 This test method is designed primarily for use with
special fiber bundle clamps and special strength testing instru-
1.1 This test method covers the determination of (1) the
ments but may be used with other tensile strength and
tensile strength or breaking tenacity of cotton fibers as a flat
elongation testing machines when equipped with appropriate
bundle using a nominal zero gage length, or (2) the tensile
adapters to accommodate the fiber clamps.
strength or breaking tenacity and the elongation at the breaking
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load of cotton fibers as a flat bundle with ⁄8-in. (3.2-mm)
NOTE 1—Other methods for measuring the breaking tenacity of fiber
clamp spacing. This test method is applicable to loose fibers of
bundles include Test Method D 1294, Test for Breaking Strength of Wool
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Fiber Bundles—1 in gage Length; Test Methods D 4604, Measurement
untreated cottons whether taken before processing or obtained
of Cotton Fibers by High Volume Instruments (HVI) (Motion Control
from a textile product.
Fiber Information System); Test Methods D 4605, Measurement of Cotton
Fibers by High Volume Instruments (HVI) (Spinlab System of Zellweger
Uster, Inc.).
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This method is under the jurisdiction of ASTM Committee D13 on Textiles, and
is the direct responsibility of Subcommittee D13.11 on Cotton Fibers.
Current edition approved May 15, 1995. Published August 1995. Originally
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published as D1445 – 53 T. Last previous edition D1445 – 95. Annual Book of ASTM Standards, Vol 07.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D1445–95
1.3 The values stated in either acceptable metric units or in tenacity is force divided by linear density. In indirect yarn
other units shall be regarded separately as standard. The values numbering sytems, tenacity is force times the reciprocal linear
expressed in each system may not be exact equivalents; density.
therefore, each system must be used independently of each
3.1.6 tensile strength, n—the maximum resistance of mate-
other, without combining values in any way.
rial to deformation in a tensile test carried to rupture; that is,
1.4 This standard does not purport to address
...