ASTM D4974-04(2011)
(Test Method)Standard Test Method for Hot Air Thermal Shrinkage of Yarn and Cord Using a Thermal Shrinkage Oven
Standard Test Method for Hot Air Thermal Shrinkage of Yarn and Cord Using a Thermal Shrinkage Oven
SIGNIFICANCE AND USE
This test method may be used for the acceptance testing of commercial shipments of yarns and cords. Caution is advised because yarn and cord may contract in length over a period of time due to room temperature retraction. Thermal shrinkage values are reduced proportionately by the amount of room temperature retraction.
Note 1—Experience, especially with nylon, shows that yarn retraction, which may be observed directly as shortening of length (or indirectly as denier increase), will occur in unrestrained yarn or cord that is not at equilibrium (equilibrium in this case being defined as essentially zero thermal shrinkage yarn or fully relaxed yarn). Normally, retractive forces are present in most wound packages of yarn and cord; thus, unrestrained yarn near the surface is likely, with time, to undergo some retraction. After retraction, such yarns exhibit lower thermal shrinkage values than yarn or cord deeper within the package. The opposite condition of yarn on the surface exists with yarn or cord wound against or near a rigid package core, such as a metal or hardwood wind-up spool. Such core yarn or cord cannot move against this restraint, and thus, will exhibit thermal shrinkage values even several weeks later near to those which were measured immediately from the surface of the freshly wound package. Elevated humidity will accelerate retraction of unrestrained yarn, but moisture content in itself will have little influence on thermal shrinkage. Exposure of untensioned skeins of yarn or cord to 95 to 100 % relative humidity at room temperature for two days and reconditioning under standard laboratory conditions will cause most of the room temperature retraction that is possible within a sample to occur.
In case of differences of practical significance in reported test results from two or more laboratories conduct comparative tests to determine if there is a statistical bias between them. Competent statistical assistance is recommended for the investigation of ...
SCOPE
1.1 This test method covers the measurement of shrinkage of yarns and cords when exposed in a thermal shrinkage oven.
1.2 This test method is applicable to yarns and cords made of nylon, polyester, and other polymers not detrimentally affected by the temperature used and with linear densities in the range from 20 to 700 tex (180 to 6300 denier).
1.2.1 Yarns or cords for testing may be taken from yarn or cord 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 system of units known as the International System of Units. Inch-pound units is the technically correct name for the customary units used in the United States. The values stated in either acceptable metric units or other units shall be regarded separately as standard. The values expressed in each system may not be exact equivalents; therefore, each system must be used independently of each other, without combining values in any way. Referee decisions are to use SI units.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 8.
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Designation: D4974 − 04(Reapproved 2011)
Standard Test Method for
Hot Air Thermal Shrinkage of Yarn and Cord Using a
Thermal Shrinkage Oven
This standard is issued under the fixed designation D4974; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope D1776 Practice for Conditioning and Testing Textiles
D6477 Terminology Relating to Tire Cord, Bead Wire, Hose
1.1 This test method covers the measurement of shrinkage
Reinforcing Wire, and Fabrics
of yarns and cords when exposed in a thermal shrinkage oven.
1.2 This test method is applicable to yarns and cords made
3. Terminology
of nylon, polyester, and other polymers not detrimentally
3.1 Definitions:
affectedbythetemperatureusedandwithlineardensitiesinthe
3.2 For definitions of terms relating to tire cord, bead wire,
range from 20 to 700 tex (180 to 6300 denier).
1.2.1 Yarns or cords for testing may be taken from yarn or hose wire, and tire cord fabrics, refer to Terminology D6477.
3.2.1 The following terms are relevant to this standard:
cord packages or from fabrics.
greige cord, in tire cords, standard atmosphere for testing
1.3 This test method shows values in both SI and inch-
textiles, thermal shrinkage, tire cord.
pound units. SI is the technically correct name for the system
of units known as the International System of Units. Inch- 3.3 For definitions of other terms related to textiles, refer to
Terminology D123.
pound units is the technically correct name for the customary
units used in the United States. The values stated in either 3.3.1 The following terms are relevant to this standard:
yarn.
acceptable metric units or other units shall be regarded
separately as standard. The values expressed in each system
4. Summary of Test Method
may not be exact equivalents; therefore, each system must be
used independently of each other, without combining values in
4.1 A relaxed, conditioned specimen of yarn or cord is
any way. Referee decisions are to use SI units.
subjected to dry heat for a specified time while under a
1.4 This standard does not purport to address all of the specified tension. The percent shrinkage is read directly from a
safety concerns, if any, associated with its use. It is the scale or display on the instrument while the specimen is still
responsibility of the user of this standard to establish appro- under tension and exposed to heat.
priate safety and health practices and determine the applica-
5. Significance and Use
bility of regulatory limitations prior to use. Specific hazard
statements are given in Section 8.
5.1 This test method may be used for the acceptance testing
of commercial shipments of yarns and cords. Caution is
2. Referenced Documents
advised because yarn and cord may contract in length over a
2.1 ASTM Standards:
period of time due to room temperature retraction. Thermal
D123 Terminology Relating to Textiles
shrinkage values are reduced proportionately by the amount of
D885 Test Methods for Tire Cords, Tire Cord Fabrics, and
room temperature retraction.
Industrial Filament Yarns Made from Manufactured
NOTE 1—Experience, especially with nylon, shows that yarn retraction,
Organic-Base Fibers
which may be observed directly as shortening of length (or indirectly as
denier increase), will occur in unrestrained yarn or cord that is not at
equilibrium (equilibrium in this case being defined as essentially zero
This test method is under the jurisdiction ofASTM Committee D13 on Textiles
thermal shrinkage yarn or fully relaxed yarn). Normally, retractive forces
and is the direct responsibility of Subcommittee D13.19 on Industrial Fibers and
are present in most wound packages of yarn and cord; thus, unrestrained
Metallic Reinforcements.
yarnnearthesurfaceislikely,withtime,toundergosomeretraction.After
Current edition approved Jan. 1, 2011. Published March 2011. Originally
retraction, such yarns exhibit lower thermal shrinkage values than yarn or
approved in 1999. Last previous edition approved in 2004 as D4974–04. DOI:
cord deeper within the package. The opposite condition of yarn on the
10.1520/D4974-04R11.
surface exists with yarn or cord wound against or near a rigid package
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
core, such as a metal or hardwood wind-up spool. Such core yarn or cord
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on cannotmoveagainstthisrestraint,andthus,willexhibitthermalshrinkage
the ASTM website. values even several weeks later near to those which were measured
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4974 − 04 (2011)
immediately from the surface of the freshly wound package. Elevated
bias or determine the proper set point to give the specified
humidity will accelerate retraction of unrestrained yarn, but moisture
specimen temperature.
content in itself will have little influence on thermal shrinkage. Exposure
6.3 The degree of room temperature length retraction, (for
of untensioned skeins of yarn or cord to 95 to 100 % relative humidity at
room temperature for two days and reconditioning under standard
example, that which occurs in unrestrained skeins of yarn over
laboratory conditions will cause most of the room temperature retraction
time in the testing laboratory), of the laboratory sample or
that is possible within a sample to occur.
specimen affects the measurement of thermal shrinkage. Un-
5.1.1 In case of differences of practical significance in
relaxed nylon, for example, shrinks much more than relaxed
reported test results from two or more laboratories conduct
nylon. The amount of relaxation (retraction) occurring prior to
comparative tests to determine if there is a statistical bias
testing of thermal shrinkage can affect the result.
between them. Competent statistical assistance is recom-
6.4 Frictional forces against the pulley/indicator assembly
mendedfortheinvestigationofbias.Asaminimum,theparties
cause measurement errors. Ensure that the indicator needle
should take a group of test specimens that are as homogeneous
does not rub against the scale. Maintain the pulley bearings in
as possible and that are from a lot of material of the type in
good condition. The pulley wheel must be centered in the
question.Thetestspecimensthenshouldbeassignedrandomly
bearings. A force of 10 mN or less, applied to the tip of the
in equal numbers to each laboratory for testing. The average
indicatorneedle,shouldcausepulleyrotationwhenthetesteris
results from the two laboratories should be compared using
in proper operating condition.
Student’s t-testforunpaireddataandaprobabilitylevelchosen
6.5 Thermal shrinkage increases as the exposure time in-
by the parties before the testing is begun. If a bias is found,
creases. Check the exposure time with a stopwatch. Some
either its cause must be found and corrected, or future test
thermalovenmodelshaveatimerinstalled.Comparethistimer
results must be adjusted in consideration of the known bias.
to a stopwatch and calibrate as necessary.
5.2 Thermal shrinkage of nylon, polyester, and other fibers
6.6 Center the threadline between the heating plates of the
is related to the polymer of origin and its manipulation in
oven to obtain a correct measurement.
processing. Thermal shrinkage measurement can be used to
control product uniformity.
6.7 Specimens that are spun, textured, or crimped (as those
removed from a fabric) may allow filaments to come in contact
5.3 The level of thermal shrinkage is critical in the user’s
with interior surfaces of the thermal shrinkage oven. Such
subsequent operations. For example it can affect the drumset
physical contact will cause inaccurate readings of thermal
(original length of cord) required in tire building to produce a
shrinkage.
finished, final tire of a particular size.
6.8 Yarn or cords that are sufficiently sticky or tacky to
5.4 Thermal shrinkage is critical to final shape and size of
prevent their free release from the pulley surface as it rotates
fiberreinforcedarticles.Forexample,thermalshrinkageaffects
will cause inaccurate readings of thermal shrinkage.
final size of V-belts and their ability to maintain tension while
running.
7. Apparatus
5.5 This test method is similar to the procedures of Methods
7.1 Thermal Shrinkage Oven , consisting of a specimen
D885 for the determination of thermal shrinkage of yarns and
heatingcavitycapableofheatingupto250°C(480°F),ameans
cords. Shrinkage is measured while the specimen is within an
of accurately controlling the temperature of the cavity 6 2°C
oven and tensioned as specified in Methods D885;D885
(6 4°F), and a means for measuring and displaying the amount
however, there are enough vagaries among different units of
of specimen shrinkage to the nearest 0.1 %. Fig. 1 shows the
apparatusformeasurementofthermalshrinkagethatnumerical
principle of operation of commercial thermal shrinkage ovens.
equivalence between units of different design should not be
assumed, even under the same nominal conditions.
7.2 Stopwatch or Timer.
7.3 Clip-On Masses.
6. Interferences
7.4 Draft Shield, if the oven does not have one provided.
6.1 An effective draft shield on the thermal oven is critical.
Because the chamber in which the specimen is heated is open
8. Safety Hazards
on three sides, air drafts can effectively shorten the length of
specimen experiencing the prescribed temperature environ-
8.1 The oven portion of the tester can reach temperatures
ment. Results obtained without a shield generally are lower
over 200°C (390° F). Do not touch the oven.
than with a shield.
8.2 Do not leave oven unattended if a specimen is installed.
6.2 The accurate control of temperature at any prescribed
9. Sampling and Test Specimens
setting is of utmost importance. Bias between the set point
temperature and the temperature that the specimen sees is a
9.1 Primary Sampling Unit—Consider shipping containers
major cause of instrument bias. The temperature that the
of cords or rolls of fabric to be the primary sampling unit, as
specimen sees may be checked by attaching a small calibrated
applicable.
thermocouple to a piece of cord and suspending it in the
specimen position such that the tip of the thermocouple is in
the center of the oven cavity.The thermocouple must not touch
Commercial thermal shrinkage ovens are available. Clip-on masses also are
the oven walls. Either correct any set point/sample temperature available from the manufacturer.
D4974 − 04 (2011)
FIG. 1 Principle of Operation of a Thermal Shrinkage Oven
9.2 Laboratory Sampling Unit—As a laboratory sampling handling damage is available after conditioning (see 10.1). If
unit for acceptance testing, take material randomly from the the applicable material specification or other agreement be-
primary sampling unit as follows: tween the purchaser and the supplier specifies testing more
9.2.1 Forcords,takespoolsorpackagespercartonusingthe than one specimen per laboratory sampling unit, an additional
applicable procedure in Practice D2258. two specimens above the number to be tested should be taken
9.2.2 For fabric, take from rolls at least one full-width piece from the laboratory sampling unit and conditioned.
of fabric that is at least1m(1yd) along the selvage (machine
10. Conditioning Specimens and Preparation for Testing
direction), after first discarding all fabric from the outside of
the roll that contains creases, fold marks, disturbed weave, or 10.1 Conditioning:
contamination by foreign material. 10.1.1 Condition specimens as relaxed skeins or segments
of untensioned fabric as directed in Practice D1776 using the
9.3 Test Specimens:
atmosphere specified for industrial yarns (see Section 3).
9.3.1 For yarns and cords, strip at least 15 m (16 yd) from
Ensure that no change in yarn/cord twist occurs while carrying
the outside of each package in the laboratory sampling unit.
out this procedure.
Inspect the outside of the package after stripping off the yarn.
10.1.2 Condition and relax yarn and greige cord specimens
Ifthereisvisibledamage,continuetostripoffunitsof15m(16
12 to 28 h.
yd) and reinspect until there is no visible damage. Take one
10.1.3 Condition and relax adhesive-treated cord samples
specimen, 600 mm (24 in.) long, from each package in the
16 to 28 h, unless immediate testing (5 to 20 min after
laboratory sampling unit. Discard and replace specimens that
processing) is agreed upon between the buyer and the supplier.
are visibly damaged.
Immediate testing must be reported as an exception to this
9.3.2 For fabrics, remove a minimum of three lengths of
method (see Section 12).
warp yarn or cord 600 mm (24 in.) long from each swatch in
thelaboratorysamplingunit,withthespecimensbeingtakenat 10.2 Preparation for Testing:
least 75 mm (3 in.) from the selvage of the swatch. For fabrics
10.2.1 With the draft shield in place, preheat the oven until
other than tire cord fabric, such as square-woven tire fabrics, the chamber has attained the specified temperature for a
also take from each swatch in the laboratory sampling unit a minimum of 5 min.
minimum of three lengths of filling yarn or cord 600 mm (24 10.2.2 Test in standard atmosphere for testing industrial
in.)longafterdiscardingthoseportionswithin75mm(3in.)of yarns (see Section 3).
the selvage of the swatch. In all cases, take warp specimens 10.2.3 Adjust the oven temperature controller set point to
that are free of filling material and filling specimens that are give a specimen temperature of 177 6 2 °C (350 6 4° F). (See
free of warp material. 6.2).
9.3.2.1 Instructionsonthenumberoftestspecimensin9.3.2 10.2.4 One may consult with the instrument vendor if
assume that a single valid thermal shrinkage result will calibration of the oven temperature is suspected to be in error.
adequately characterize the thermal shrinkage of the laboratory
11. Procedure
sampling unit from which the specimens are taken. The extra
two specimens are taken to assure that a specimen free of 11.1 Test Conditions (Table 1):
D4974 − 04 (2011)
TABLE 1 Test Conditions indicator to a shrinkage level in 11.4 sufficient to prevent the indicator
from going below zero. Record positive shrinkage as the interval between
Time, s
the lowest and highest reading of the indicator during the test of that
Specimen with Linear Specimen with Linear
Temperature Tension
...
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