1、Designation: D4974 04 (Reapproved 2016)Standard Test Method forHot Air Thermal Shrinkage of Yarn and Cord Using aThermal Shrinkage Oven1This standard is issued under the fixed designation D4974; the number immediately following the designation indicates the year oforiginal adoption or, in the case o
2、f revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of shrinkageof yarns and cords when exposed in a therm
3、al shrinkage oven.1.2 This test method is applicable to yarns and cords madeof nylon, polyester, and other polymers not detrimentallyaffected by the temperature used and with linear densities in therange from 20 to 700 tex (180 to 6300 denier).1.2.1 Yarns or cords for testing may be taken from yarn
4、orcord packages or from fabrics.1.3 This test method shows values in both SI and inch-pound units. SI is the technically correct name for the systemof units known as the International System of Units. Inch-pound units is the technically correct name for the customaryunits used in the United States.
5、The values stated in eitheracceptable metric units or other units shall be regardedseparately as standard. The values expressed in each systemmay not be exact equivalents; therefore, each system must beused independently of each other, without combining values inany way. Referee decisions are to use
6、 SI units.1.4 This standard does not purport to address all of thesafety concerns, 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. Spec
7、ific hazardstatements are given in Section 8.2. Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD885 Test Methods for Tire Cords, Tire Cord Fabrics, andIndustrial Filament Yarns Made from ManufacturedOrganic-Base FibersD1776 Practice for Conditioning and Testing Textiles
8、D6477 Terminology Relating to Tire Cord, Bead Wire, HoseReinforcing Wire, and Fabrics3. Terminology3.1 Definitions:3.2 For definitions of terms relating to tire cord, bead wire,hose wire, and tire cord fabrics, refer to Terminology D6477.3.2.1 The following terms are relevant to this standard:greige
9、 cord, in tire cords, standard atmosphere for testingtextiles, thermal shrinkage, tire cord.3.3 For definitions of other terms related to textiles, refer toTerminology D123.3.3.1 The following terms are relevant to this standard:yarn.4. Summary of Test Method4.1 A relaxed, conditioned specimen of ya
10、rn or cord issubjected to dry heat for a specified time while under aspecified tension. The percent shrinkage is read directly from ascale or display on the instrument while the specimen is stillunder tension and exposed to heat.5. Significance and Use5.1 This test method may be used for the accepta
11、nce testingof commercial shipments of yarns and cords. Caution isadvised because yarn and cord may contract in length over aperiod of time due to room temperature retraction. Thermalshrinkage values are reduced proportionately by the amount ofroom temperature retraction.NOTE 1Experience, especially
12、with nylon, shows that yarn retraction,which may be observed directly as shortening of length (or indirectly asdenier increase), will occur in unrestrained yarn or cord that is not atequilibrium (equilibrium in this case being defined as essentially zerothermal shrinkage yarn or fully relaxed yarn).
13、 Normally, retractive forcesare present in most wound packages of yarn and cord; thus, unrestrainedyarn near the surface is likely, with time, to undergo some retraction.Afterretraction, such yarns exhibit lower thermal shrinkage values than yarn orcord deeper within the package. The opposite condit
14、ion of yarn on thesurface exists with yarn or cord wound against or near a rigid packagecore, such as a metal or hardwood wind-up spool. Such core yarn or cordcannot move against this restraint, and thus, will exhibit thermal shrinkagevalues even several weeks later near to those which were measured
15、1This test method is under the jurisdiction of ASTM Committee D13 on Textilesand is the direct responsibility of Subcommittee D13.19 on Industrial Fibers andMetallic Reinforcements.Current edition approved July 1, 2016. Published August 2016. Originallyapproved in 1999. Last previous edition approve
16、d in 2011 as D497404(2011). DOI:10.1520/D4974-04R16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright
17、 ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1immediately from the surface of the freshly wound package. Elevatedhumidity will accelerate retraction of unrestrained yarn, but moisturecontent in itself will have little influence on thermal sh
18、rinkage. Exposureof untensioned skeins of yarn or cord to 95 to 100 % relative humidity atroom temperature for two days and reconditioning under standardlaboratory conditions will cause most of the room temperature retractionthat is possible within a sample to occur.5.1.1 In case of differences of p
19、ractical significance inreported test results from two or more laboratories conductcomparative tests to determine if there is a statistical biasbetween them. Competent statistical assistance is recom-mended for the investigation of bias.As a minimum, the partiesshould take a group of test specimens
20、that are as homogeneousas possible and that are from a lot of material of the type inquestion. The test specimens then should be assigned randomlyin equal numbers to each laboratory for testing. The averageresults from the two laboratories should be compared usingStudents t-test for unpaired data an
21、d a probability level chosenby the parties before the testing is begun. If a bias is found,either its cause must be found and corrected, or future testresults must be adjusted in consideration of the known bias.5.2 Thermal shrinkage of nylon, polyester, and other fibersis related to the polymer of o
22、rigin and its manipulation inprocessing. Thermal shrinkage measurement can be used tocontrol product uniformity.5.3 The level of thermal shrinkage is critical in the userssubsequent operations. For example it can affect the drumset(original length of cord) required in tire building to produce afinis
23、hed, final tire of a particular size.5.4 Thermal shrinkage is critical to final shape and size offiber reinforced articles. For example, thermal shrinkage affectsfinal size of V-belts and their ability to maintain tension whilerunning.5.5 This test method is similar to the procedures of MethodsD885
24、for the determination of thermal shrinkage of yarns andcords. Shrinkage is measured while the specimen is within anoven and tensioned as specified in Methods D885;D885however, there are enough vagaries among different units ofapparatus for measurement of thermal shrinkage that numericalequivalence b
25、etween units of different design should not beassumed, even under the same nominal conditions.6. Interferences6.1 An effective draft shield on the thermal oven is critical.Because the chamber in which the specimen is heated is openon three sides, air drafts can effectively shorten the length ofspeci
26、men experiencing the prescribed temperature environ-ment. Results obtained without a shield generally are lowerthan with a shield.6.2 The accurate control of temperature at any prescribedsetting is of utmost importance. Bias between the set pointtemperature and the temperature that the specimen sees
27、 is amajor cause of instrument bias. The temperature that thespecimen sees may be checked by attaching a small calibratedthermocouple to a piece of cord and suspending it in thespecimen position such that the tip of the thermocouple is inthe center of the oven cavity. The thermocouple must not touch
28、the oven walls. Either correct any set point/sample temperaturebias or determine the proper set point to give the specifiedspecimen temperature.6.3 The degree of room temperature length retraction, (forexample, that which occurs in unrestrained skeins of yarn overtime in the testing laboratory), of
29、the laboratory sample orspecimen affects the measurement of thermal shrinkage. Un-relaxed nylon, for example, shrinks much more than relaxednylon. The amount of relaxation (retraction) occurring prior totesting of thermal shrinkage can affect the result.6.4 Frictional forces against the pulley/indic
30、ator assemblycause measurement errors. Ensure that the indicator needledoes not rub against the scale. Maintain the pulley bearings ingood condition. The pulley wheel must be centered in thebearings. A force of 10 mN or less, applied to the tip of theindicator needle, should cause pulley rotation wh
31、en the tester isin proper operating condition.6.5 Thermal shrinkage increases as the exposure time in-creases. Check the exposure time with a stopwatch. Somethermal oven models have a timer installed. Compare this timerto a stopwatch and calibrate as necessary.6.6 Center the threadline between the h
32、eating plates of theoven to obtain a correct measurement.6.7 Specimens that are spun, textured, or crimped (as thoseremoved from a fabric) may allow filaments to come in contactwith interior surfaces of the thermal shrinkage oven. Suchphysical contact will cause inaccurate readings of thermalshrinka
33、ge.6.8 Yarn or cords that are sufficiently sticky or tacky toprevent their free release from the pulley surface as it rotateswill cause inaccurate readings of thermal shrinkage.7. Apparatus7.1 Thermal Shrinkage Oven3, consisting of a specimenheating cavity capable of heating up to 250C (480F), a mea
34、nsof accurately controlling the temperature of the cavity 6 2C(6 4F), and a means for measuring and displaying the amountof specimen shrinkage to the nearest 0.1 %. Fig. 1 shows theprinciple of operation of commercial thermal shrinkage ovens.7.2 Stopwatch or Timer.7.3 Clip-On Masses.7.4 Draft Shield
35、, if the oven does not have one provided.8. Safety Hazards8.1 The oven portion of the tester can reach temperaturesover 200C (390 F). Do not touch the oven.8.2 Do not leave oven unattended if a specimen is installed.9. Sampling and Test Specimens9.1 Primary Sampling UnitConsider shipping containerso
36、f cords or rolls of fabric to be the primary sampling unit, asapplicable.3Commercial thermal shrinkage ovens are available. Clip-on masses also areavailable from the manufacturer.D4974 04 (2016)29.2 Laboratory Sampling UnitAs a laboratory samplingunit for acceptance testing, take material randomly f
37、rom theprimary sampling unit as follows:9.2.1 For cords, take spools or packages per carton using theapplicable procedure in Practice D2258.9.2.2 For fabric, take from rolls at least one full-width pieceof fabric that is at least1m(1yd)along the selvage (machinedirection), after first discarding all
38、 fabric from the outside ofthe roll that contains creases, fold marks, disturbed weave, orcontamination by foreign material.9.3 Test Specimens:9.3.1 For yarns and cords, strip at least 15 m (16 yd) fromthe outside of each package in the laboratory sampling unit.Inspect the outside of the package aft
39、er stripping off the yarn.If there is visible damage, continue to strip off units of 15 m (16yd) and reinspect until there is no visible damage. Take onespecimen, 600 mm (24 in.) long, from each package in thelaboratory sampling unit. Discard and replace specimens thatare visibly damaged.9.3.2 For f
40、abrics, remove a minimum of three lengths ofwarp yarn or cord 600 mm (24 in.) long from each swatch inthe laboratory sampling unit, with the specimens being taken atleast 75 mm (3 in.) from the selvage of the swatch. For fabricsother than tire cord fabric, such as square-woven tire fabrics,also take
41、 from each swatch in the laboratory sampling unit aminimum of three lengths of filling yarn or cord 600 mm (24in.) long after discarding those portions within 75 mm (3 in.) ofthe selvage of the swatch. In all cases, take warp specimensthat are free of filling material and filling specimens that aref
42、ree of warp material.9.3.2.1 Instructions on the number of test specimens in 9.3.2assume that a single valid thermal shrinkage result willadequately characterize the thermal shrinkage of the laboratorysampling unit from which the specimens are taken. The extratwo specimens are taken to assure that a
43、 specimen free ofhandling damage is available after conditioning (see 10.1). Ifthe applicable material specification or other agreement be-tween the purchaser and the supplier specifies testing morethan one specimen per laboratory sampling unit, an additionaltwo specimens above the number to be test
44、ed should be takenfrom the laboratory sampling unit and conditioned.10. Conditioning Specimens and Preparation for Testing10.1 Conditioning:10.1.1 Condition specimens as relaxed skeins or segmentsof untensioned fabric as directed in Practice D1776 using theatmosphere specified for industrial yarns (
45、see Section 3).Ensure that no change in yarn/cord twist occurs while carryingout this procedure.10.1.2 Condition and relax yarn and greige cord specimens12 to 28 h.10.1.3 Condition and relax adhesive-treated cord samples16 to 28 h, unless immediate testing (5 to 20 min afterprocessing) is agreed upo
46、n between the buyer and the supplier.Immediate testing must be reported as an exception to thismethod (see Section 12).10.2 Preparation for Testing:10.2.1 With the draft shield in place, preheat the oven untilthe chamber has attained the specified temperature for aminimum of 5 min.10.2.2 Test in sta
47、ndard atmosphere for testing industrialyarns (see Section 3).10.2.3 Adjust the oven temperature controller set point togive a specimen temperature of 177 6 2 C (350 6 4 F). (See6.2).10.2.4 One may consult with the instrument vendor ifcalibration of the oven temperature is suspected to be in error.11
48、. Procedure11.1 Test Conditions (Table 1):FIG. 1 Principle of Operation of a Thermal Shrinkage OvenD4974 04 (2016)311.1.1 For yarns or cords possessing low levels of shrinkageforce, a tension loading of 1.0 6 0.2 mN/tex (0.010 6 0.002gf/den) may be used. Use of this lower tension load should benoted
49、 in the report.11.2 Install one end of the specimen in the fixed clamp.11.3 Bring the other end of the specimen over the pulley.11.4 Set the indicator to zero and hold it on zero whileperforming the next step.11.5 Attach a clip-on mass to the unclamped end of thespecimen so that twist is not lost. Use a mass that creates atension load as specified in 11.1. Table 2 shows the total massneeded to effect such tensions for typical yarns and cords.NOTE 2If the specimen is likely to untwist in the portion below thepulley, attach a toothpick or the equivalent (approximately 7
