1、Designation: D 1445 05Standard Test Method forBreaking Strength and Elongation of Cotton Fibers (FlatBundle Method)1This standard is issued under the fixed designation D 1445; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe flat bundle test for cotton fiber strength gained immediate acceptance after its introduction in1953. The fi
3、rst 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. Resultswere expressed in Pressley Index (P.I.) calculated as the force-to-break in pounds divided by thebundle weight i
4、n 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 theChandler round bundle test (see former Method D 414) and the results expressed in pounds per squareinch (psi). The U.S. Department of Agriculture ob
5、tained results from both instruments on specimensfrom the same samples of a large number of cottons. From this study, an empirical equation to expressflat bundle test results in psi wasBreaking strength, 1000 psi = (10.81106 3 P.I.) 0.12When it was shown that a finite gauge length test was more high
6、ly correlated with yarn strengththan tests made at zero gage length, the clamp design was modified to accommodate a18 inch (3.2mm) spacer. Selection of an engineering unit for reporting of results from18 inch (3.2 mm) gauge testspresented a problem. However, the use of the tex for linear density and
7、 the introduction of a pendulumtype 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 ismounted across the clamp width and trimmed to the width. The bundle m
8、ass is mg/11.81 mm ormg/15.00 mm.The use of the flat bundle test in domestic and international commerce has had a long and successfulhistory. Correcting this error in the empirical relationship would have serious adverse affects in thetextile industry. Therefore, the empirical relationship is retain
9、ed to calculate zero gage cotton fibertensile strength designated as the Pressley strength in Eq 3 and 4 of D 1445.1. Scope1.1 This test method covers the determination of (1) thetensile strength or breaking tenacity of cotton fibers as a flatbundle using a nominal zero gage length, or (2) the tensi
10、lestrength or breaking tenacity and the elongation at the breakingload of cotton fibers as a flat bundle with18-in. (3.2-mm)clamp spacing. This test method is applicable to loose fibers ofuntreated cottons whether taken before processing or obtainedfrom a textile product.1.2 This test method is desi
11、gned primarily for use withspecial fiber bundle clamps and special strength testing instru-ments but may be used with other tensile strength andelongation testing machines when equipped with appropriateadapters to accommodate the fiber clamps.NOTE 1Other methods for measuring the breaking tenacity o
12、f fiberbundles include Test Method D 1294, Test for Breaking Strength of WoolFiber Bundles1 in gage Length;2and D 5867, Test Method for Mea-surement of Physical Properties of Cotton Fibers by High VolumeInstruments.1This method is under the jurisdiction ofASTM Committee D13 on Textiles andis the dir
13、ect responsibility of Subcommittee D13.11 on Cotton Fibers.Current edition approved March 1, 2005. Published April 2005. Originallyapproved in 1953. Last previous edition approved in 1995 as D 1445 95.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Servi
14、ce at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.1.3 The values stated in either acceptable me
15、tric units or inother units shall be regarded separately as standard. The valuesexpressed in each system may not be exact equivalents;therefore, each system must be used independently of eachother, without combining values in any way.1.4 This standard does not purport to address all of thesafety con
16、cerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 123 Terminology Relating to Textiles
17、D 1294 Test Method for Tensile Strength and BreakingTenacity of Wool Fiber Bundles 1-in. (25.4-mm) GageLengthD 1441 Practice for Sampling Cotton Fibers for TestingD 1447 Test Method for Length and Length Uniformity ofCotton Fibers by Fibrograph MeasurementD 1776 Practice for Conditioning and Testing
18、 TextilesD 3025 Practice for Standardizing Cotton Fiber Test Resultsby Use of Calibration Cotton StandardsD 5867 Test Methods for Measurement of Physical Proper-ties of Cotton Fibers by High Volume InstrumentsD 7139 Terminology for Cotton Fibers3. Terminology3.1 For all terminology related to D13.11
19、, see TerminologyD 71393.1.1 The following terms are relevant to this standard:breaking force, breaking tenacity, cotton, elongation at break-ing load, tenacity, tensile strength.3.2 For all other terminology related to textiles, refer toTerminology D 123.4. Summary of Test Method4.1 Abundle of fibe
20、rs is combed parallel, secured in clamps,cut to a known length, broken in the tensile testing machine,and weighed. Tensile strength or breaking tenacity is calculatedfrom the ratio of breaking load to bundle mass (weight).4.2 Elongation at the breaking force may be determined onthe specimens tested
21、for breaking strength with14-in. (3.2-mm)clamp spacing. The elongation is normally calculated as apercentage of the nominal gage length.5. Significance and Use5.1 When the level of results in the laboratory the purchaserand the supplier are both controlled by use of calibrationcottons, Test Method D
22、 1445 for the determination of thetensile strength and elongation is considered satisfactory foracceptance testing of commercial shipments of cotton and hasbeen used extensively in trade for acceptance testing.5.1.1 DiscussionTenacity is commonly expressed as cen-tinewtons per tex (cN/tex), grams-fo
23、rce per denier (gf/den) orpounds-force per denier (lbf/den). Tenacity in centinewtons/texis numercially equal to tenacity in grams-force/tex times 0.981.5.1.2 In case of a dispute arising from differences inreported test results when using Test Method D 1445 foracceptance testing of commercial shipm
24、ents, the purchaser andthe supplier should conduct comparative tests to determine ifthere is a statistical bias between their laboratories. Competentstatistical assistance is recommended for the investigation ofbias. As a minimum, the two parties should take a group of testspecimens that are as homo
25、geneous as possible and that arefrom a lot of material of the type in question. The testspecimens should then be randomly assigned in equal numbersto each laboratory for testing. The average results from the twolaboratories should be compared using Students t-test forunpaired data and an acceptable
26、probability level chosen by thetwo parties before the testing is begun. If a bias is found, eitherits cause must be found and corrected or the purchaser and thesupplier must agree to interpret future test results in the light ofthe known bias.5.2 This test method is useful in research studies to det
27、er-mine the influence of variety, environment, and processing onfiber strength and elongation; and in studies of the relationshipsbetween these fiber properties, processing performance, andquality of end-product.5.3 Values obtained for flat bundle tenacity and elongationshow a high correlation with
28、values measured on single fibersand require much less time and skill.5.4 Studies have shown that strength measurements ob-tained with different types of instruments are highly correlated,but the results are on different levels.35.5 By use of correction factors calculated from tests madeon standard c
29、alibration samples of known or established testvalues, the results obtained with different types of instrumentsat a specified gage length can be adjusted to comparable levels.Due to differences in cottons, strength test results for one gagelength cannot be reliably estimated from tests made at adiff
30、erent gage length.6. Apparatus and Materials6.1 Tensile Testing MachineEither of two commerciallyavailable fiber bundle tensile testing machines, one of thependulum type and one of the inclined-plane type, described inAppendix X1, or other machine from which comparable resultscan be obtained.6.2 Lab
31、oratory Balance:6.2.1 Balance, having a capacity of 3 or 5 mg and asensitivity of 60.01 mg for the zero gage length test.6.2.2 Balance, having a capacity of 5 or 10 mg and asensitivity of 0.01 mg for18-in. (3.2-mm) gage length test.6.3 Ancillary equipment from the instrument manufactur-ers.6.3.1 Cla
32、mp Vise (Pressley type or Stelometer type), with adevice to indicate approximately 8 lbfin. (9 kgfcm) torque.6.3.2 Fiber Clamps, having a total thickness of 0.465 60.001 in. (11.81 6 0.02 mm).6.3.3 Spacer, having a thickness of 0.125 6 0.001 in. (3.2 60.02 mm).6.3.4 Clamp Wrench or Torque Wrench.3Bu
33、rley, Jr., S. T., and Carpenter, F. “Evaluation of Results Obtained onAvailable Types of Fiber Strength Testers Using Various Gauge Spacings and TheirRelation to Yarn Strength,” AMS-71, U. S. Dept. of Agriculture (Sept. 1955).D14450526.3.5 Coarse Comb, approximately 8 teeth/in. (3 teeth/cm),or Fibro
34、graph comb.6.3.6 Fine Comb, approximately 52 teeth/in. (20 teeth/cm).6.3.7 Black Paper, to hold bundles.6.3.8 Shearing Knife.6.3.9 Tweezers.6.3.10 Standard Calibration Cotton, having specified fiberstrength.6.3.11 Fiber Clips or Sample Clips.7. Sampling7.1 Take the lot sample and laboratory sample a
35、s directed inPractice D 1441.8. Preparation, Calibration, and Verification ofApparatus8.1 Tensile Testing InstrumentBefore making fiberstrength tests, check the instrument and clamp vise for me-chanical adjustment as directed for the specific instrument inAppendix X1, or in accordance with the manuf
36、acturersinstructions.8.2 Laboratory BalanceCheck the zero setting of thelaboratory balance and make sure its sensitivity is within therange to be used.8.3 Clamp LeathersInspect the leathers in the clampsfrequently to ensure that they are in good condition. Keep theinner edges of the leathers trimmed
37、 flush with the metal surfaceand replace the leathers as soon as grooves become evident.9. Conditioning9.1 Bring the laboratory sample from the dry side tomoisture equilibrium for testing in the standard atmosphere fortesting textiles. See Practice D 1776.NOTE 2Cotton is normally received in the lab
38、oratory in a relatively“dry” condition, making special preconditioning procedures unnecessary.Samples that are obviously damp should be preconditioned before beingbrought into the laboratory for conditioning.9.2 Tufts prepared from the laboratory sample must beconditioned as required for the laborat
39、ory sample described in9.1.10. Preparation of Specimens10.1 Make the test specimens (flat bundles) from smallsubsamples (tufts or Fibrograph beards) which have beenprepared from the laboratory sample as directed in 10.1.1 or10.1.2.10.1.1 Prepare a tuft of fibers either (1) by taking two smallpinches
40、 at random from the unblended laboratory sample andplacing them one on top of the other near their mid-points, or(2) by taking a section from a blended laboratory sample. Holdthe tuft between the thumb and forefinger and comb with thecoarse comb to remove foreign matter and short fiber. Whenone end
41、of the tuft has been combed, reverse the tuft and combthe other end, taking care that the middle portion of the tuft iswell combed. Approximately 10 strokes are necessary forcombing each end of the tuft. Prepare two to six tufts, eachweighing 60 to 80 mg, from each sample to be tested. Beforetesting
42、, condition the tufts as directed in Section 9.10.1.2 Prepare a Fibrograph beard as directed in TestMethod D 1447. Prepare two to six Fibrograph beards for eachsample to be tested.10.2 Test a specimen from each tuft or Fibrograph beard,depending on the precision desired, and if possible, have twotec
43、hnicians participate with each one testing one half thenumber of specimens.10.3 Prepare the specimen as directed in either 10.3.1 or10.3.2.10.3.1 Grasp the prepared tuft near the midpoint betweenthe center and the end of the tuft, and pull out a portion of thefibers to form a specimen. Hold the spec
44、imen firmly by one endand pull the fibers through the fine comb on the vise two orthree times to remove loose fibers, neps, and trash. Comb theother end of the specimen in the same manner, keeping thefiber ends aligned while the middle portion is combed. Main-tain the width of the specimen at approx
45、imately14 in. (6 mm).If the specimen is too heavy, remove fibers from either side toobtain the correct weight. The specimen is now ready to beplaced in the clamps.10.3.2 Grasp a group of fibers on the Fibrograph comb,using the fiber clip or similar device to grip the fibers at a pointat least58 in.
46、(15 mm) from the teeth of the comb. Pull thesefibers, which constitute the specimen, through the Fibrographcomb teeth three or four times to straighten them and removeloose fibers. Use tweezers to remove any remaining neps orforeign matter. The specimen is now ready to be placed in theclamps.11. Pro
47、cedure11.1 Placing the Specimen in the ClampsPlace the testspecimen in the fiber clamps as directed in either 11.1.1 or11.1.2.11.1.1 Using a Pressley-type clamp vise, lock the fiberclamps in the vise, and then open the clamps. Hold both endsof the specimen, keeping it approximately14 in. (6 mm) wide
48、,and place it in the center of the open clamps. Apply sufficienttension to hold the fibers straight while the jaws of the clampsare lowered and tightened in place by applying an 8-lbfin.(9-kgtcm) torque. The torque is controlled by the clamp vise orby a torque wrench. Remove the fiber clamps from th
49、e vise.Shear off the protruding ends of the specimen with the shearingknife, shearing downward and away from the leather face ofthe clamps.11.1.2 Using the Stelometer-type clamp vise, lock the fiberclamps in the vise, and then open the clamps. Lift the fixedclamp on the vise and insert the loose ends of the flat-bundlespecimen held in the fiber clip. Draw the fiber clip forwarduntil it falls into place over the hook of the tension level.Applysufficient pressure on the fixed clamp to prevent fiber slippageand release the spring lever to apply tension on the spe
