1、Designation: D 4974 04Standard Test Method forHot Air Thermal Shrinkage of Yarn and Cord Using aThermal Shrinkage Oven1This standard is issued under the fixed designation D 4974; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the
2、year 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.1. Scope1.1 This test method covers the measurement of shrinkageof yarns and cords when exposed in a thermal shrinkage ov
3、en.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 orcord packages
4、 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. The values stat
5、ed 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 SI units.1.4 T
6、his 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. Specific hazardstat
7、ements are given in Section 8.2. Referenced Documents2.1 ASTM Standards:2D 123 Terminology Relating to TextilesD 885 Methods of Testing Tire Cords, Tire Cord Fabrics,and Industrial Filament Yarns Made from ManufacturedOrganic-Base FibersD 1776 Practice afor Conditioning Textiles for TestingD 6477 Co
8、nditioning Textiles for Testing3. Terminology3.1 Definitions:3.2 For definitions of terms relating to tire cord, bead wire,hose wire, and tire cord fabrics, refer to Terminology D 6477.3.2.1 The following terms are relevant to this standard:greige cord, in tire cords, standard atmosphere for testing
9、textiles, thermal shrinkage, tire cord.3.3 For definitions of other terms related to textiles, refer toTerminology D 123.3.3.1 The following terms are relevant to this standard:yarn.4. Summary of Test Method4.1 A relaxed, conditioned specimen of yarn or cord issubjected to dry heat for a specified t
10、ime 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 acceptance testingof commercial shipments of yarns and cord
11、s. 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 with nylon, shows that yarn retraction,which may be
12、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). Normally, retractive forcesare present in most woun
13、d 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 condition of yarn on thesurface exists with yarn or cord
14、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 measuredimmediately from the surface of the freshly wound p
15、ackage. Elevatedhumidity will accelerate retraction of unrestrained yarn, but moisturecontent in itself will have little influence on thermal shrinkage. Exposureof untensioned skeins of yarn or cord to 95 to 100 % relative humidity atroom temperature for two days and reconditioning under standard1Th
16、is test method is under the jurisdiction of ASTM Committee D13 on Textilesand is the direct responsibility of Subcommittee D13.19 on Tire Cord and Fabrics.Current edition approved Oct. 1, 2004. Published October 2004. Originallypublished as D497499. Last previous edition D497402.2For referenced ASTM
17、 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohoc
18、ken, PA 19428-2959, United States.laboratory conditions will cause most of the room temperature retractionthat is possible within a sample to occur.5.1.1 In case of differences of practical significance inreported test results from two or more laboratories conductcomparative tests to determine if th
19、ere 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 that are as homogeneousas possible and that are from a lot of material of the type inquestion. The test specimens then
20、 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 and a probability level chosenby the parties before the testing is begun. If a bias is found,either its cause must be fo
21、und 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 origin and its manipulation inprocessing. Thermal shrinkage measurement can be used tocontrol product uniformity.5.3 Th
22、e 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 afinished, final tire of a particular size.5.4 Thermal shrinkage is critical to final shape and size offiber reinforced arti
23、cles. 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 MethodsD 885 for the determination of thermal shrinkage of yarns andcords. Shrinkage is measured while the specimen is within anov
24、en and tensioned as specified in Methods D 885; however,there are enough vagaries among different units of apparatusfor measurement of thermal shrinkage that numerical equiva-lence between units of different design should not be assumed,even under the same nominal conditions.6. Interferences6.1 An e
25、ffective 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 ofspecimen experiencing the prescribed temperature environ-ment. Results obtained without a shield generally are lowerthan wi
26、th 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 is amajor cause of instrument bias. The temperature that thespecimen sees may be checked by attaching a small calibra
27、tedthermocouple 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 touchthe oven walls. Either correct any set point/sample temperaturebias or determine the proper set point to give the spec
28、ifiedspecimen 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 the laboratory sample orspecimen affects the measurement of thermal shrinkage. Un-relaxed nylon, for example, shrinks
29、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/indicator assemblycause measurement errors. Ensure that the indicator needledoes not rub against the scale. Maintain the pu
30、lley 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 when the tester isin proper operating condition.6.5 Thermal shrinkage increases as the exposure time in-creases. Check t
31、he 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 heating plates of theoven to obtain a correct measurement.6.7 Specimens that are spun, textured, or crimped (as thosere
32、moved from a fabric) may allow filaments to come in contactwith interior surfaces of the thermal shrinkage oven. Suchphysical contact will cause inaccurate readings of thermalshrinkage.6.8 Yarn or cords that are sufficiently sticky or tacky toprevent their free release from the pulley surface as it
33、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 meansof accurately controlling the temperature of the cavity 6 2C(6 4F), and a means for measuring and displaying the amo
34、untof 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, if the oven does not have one provided.8. Safety Hazards8.1 The oven portion of the tester can reach temperaturesove
35、r 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 containersof cords or rolls of fabric to be the primary sampling unit, asapplicable.9.2 Laboratory Sampling UnitAs a laboratory s
36、amplingunit for acceptance testing, take material randomly from theprimary sampling unit as follows:9.2.1 For cords, take spools or packages per carton using theapplicable procedure in Practice D 2258.9.2.2 For fabric, take from rolls at least one full-width pieceof fabric that is at least1m(1yd)alo
37、ng the selvage (machinedirection), after first discarding all fabric from the outside ofthe roll that contains creases, fold marks, disturbed weave, orcontamination by foreign material.3Commercial thermal shrinkage ovens are available. Clip-on masses also areavailable from the manufacturer.D49740429
38、.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 after stripping off the yarn.If there is visible damage, continue to strip off units of 15 m (16yd) and reinspect until there is
39、 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 fabrics, remove a minimum of three lengths ofwarp yarn or cord 600 mm (24 in.) long from each swatch inthe laboratory sampling
40、 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 from each swatch in the laboratory sampling unit aminimum of three lengths of filling yarn or cord 600 mm (24in.) long after
41、 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 arefree of warp material.9.3.2.1 Instructions on the number of test specimens in 9.3.2assume that a single valid thermal shrinkag
42、e 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 specimen free ofhandling damage is available after conditioning (see 10.1). Ifthe applicable material specification or other
43、 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 tested should be takenfrom the laboratory sampling unit and conditioned.10. Conditioning Specimens and Preparation for Testing10.
44、1 Conditioning:10.1.1 Condition specimens as relaxed skeins or segmentsof untensioned fabric as directed in Practice D 1776 using theatmosphere specified for industrial yarns (see Section 3).Ensure that no change in yarn/cord twist occurs while carryingout this procedure.10.1.2 Condition and relax y
45、arn 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 upon between the buyer and the supplier.Immediate testing must be reported as an exception to thismethod (see Section 12).10.2
46、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 standard atmosphere for testing industrialyarns (see Section 3).10.2.3 Adjust the oven temperature controller set point togive
47、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. Procedure11.1 Test Conditions (Table 1):11.1.1 For yarns or cords possessing low levels of shrinkageforce, a tension loadi
48、ng 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 in the report.FIG. 1 Principle of Operation of a Thermal Shrinkage OvenTABLE 1 Test ConditionsTemperature Tension LoadTime, sSpecimen with LinearMass up to 400 tex(3600 denier)Specimen with Linear
49、Mass Greater than400 tex (3600 denier)177 6 2C(350 6 4F)5.0 6 1.0 mN/tex(or 0.05 6 0.01gf/den)120 6 10 240 6 10D497404311.2 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
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