ASTM D4974/D4974M-22

Standard Test Method for Hot Air Thermal Shrinkage of Yarn and Cord Using a Thermal Shrinkage Oven

SIGNIFICANCE AND USE
5.1 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.  
5.1.1 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 invest...
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 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 8.  
1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-May-2022
• ICS: 59.080.20 - Yarns
• ICS: 59.080.50 - Ropes
• Technical Committee: D13 - Textiles
• Drafting Committee: D13.19 - Industrial Fibers and Metallic Reinforcements

Relations

• Refers: ASTM D1776/D1776M-20 - Standard Practice for Conditioning and Testing Textiles
• Effective Date: 01-Feb-2020
• Refers: ASTM D123-17 - Standard Terminology Relating to Textiles
• Effective Date: 01-Mar-2017
• Refers: ASTM D1776/D1776M-16 - Standard Practice for Conditioning and Testing Textiles
• Effective Date: 01-Jan-2016
• Refers: ASTM D123-15b - Standard Terminology Relating to Textiles
• Effective Date: 15-Sep-2015
• Refers: ASTM D123-15a - Standard Terminology Relating to Textiles
• Effective Date: 01-Sep-2015
• Refers: ASTM D123-15 - Standard Terminology Relating to Textiles
• Effective Date: 01-Apr-2015
• Refers: ASTM D1776/D1776M-15 - Standard Practice for Conditioning and Testing Textiles
• Effective Date: 01-Feb-2015
• Refers: ASTM D885/D885M-10a(2014) - Standard Test Methods for Tire Cords, Tire Cord Fabrics, and Industrial Filament Yarns Made from Manufactured Organic-Base Fibers
• Effective Date: 15-May-2014
• Refers: ASTM D123-13a - Standard Terminology Relating to Textiles
• Effective Date: 15-Jun-2013
• Refers: ASTM D123-13ae1 - Standard Terminology Relating to Textiles
• Effective Date: 15-Jun-2013
• Refers: ASTM D123-13 - Standard Terminology Relating to Textiles
• Effective Date: 15-May-2013
• Refers: ASTM D6477-13 - Standard Terminology Relating to Tire Cord, Bead Wire, Hose Reinforcing Wire, and Fabrics
• Effective Date: 01-Jan-2013
• Refers: ASTM D123-12 - Standard Terminology Relating to Textiles
• Effective Date: 01-Feb-2012
• Refers: ASTM D123-12e1 - Standard Terminology Relating to Textiles
• Effective Date: 01-Feb-2012
• Refers: ASTM D6477-11 - Standard Terminology Relating to Tire Cord, Bead Wire, Hose Reinforcing Wire, and Fabrics
• Effective Date: 01-Jan-2011

Overview

ASTM D4974/D4974M-22: Standard Test Method for Hot Air Thermal Shrinkage of Yarn and Cord Using a Thermal Shrinkage Oven outlines a precise method for determining the thermal shrinkage of yarns and cords when exposed to heat in a thermal shrinkage oven. This ASTM International standard is essential for industries that rely on synthetic fibers such as nylon and polyester, establishing a reliable procedure to measure dimensional changes under controlled conditions.

The standard is applicable to yarns and cords with linear densities from 20 to 700 tex (180 to 6300 denier) made from polymers not detrimentally affected by test temperatures. The method is recognized internationally and supports trade and quality assurance by promoting uniformity in test results.

Key Topics

• Measurement Scope: The test method evaluates shrinkage in yarns and cords when heated under specific tension and time in a thermal oven. It supports both SI and inch-pound units, though test results must not combine values from both measurement systems.
• Specimen Preparation: Detailed guidelines are provided for sampling, conditioning, and preparing yarn or cord specimens, emphasizing the importance of relaxing material before testing to prevent inaccuracies due to pre-existing tension or damage.
• Testing Procedure: The process involves exposing a relaxed specimen to a set temperature (generally 177°C / 350°F) under controlled tension and measuring the reduction in length, reported as percent shrinkage.
• Factors Affecting Results: The standard highlights influences such as room temperature retraction, humidity, oven temperature precision, apparatus calibration, and specimen placement. Draft shields and precise temperature control are critical for valid results.
• Significance and Use: Results assist in product quality control, acceptance of commercial shipments, and process development related to thermal shrinkage behavior of yarns and cords. They have a direct impact on the dimensional stability of finished textile products.

Applications

The ASTM D4974/D4974M-22 standard is widely used in sectors where the thermal stability of industrial yarns and cords is critical:

• Tire and Automotive Industry: Ensures predictable performance and dimensional stability of tire cords, which influences final tire shape and assembly specifications.
• Reinforced Rubber Goods: Applied in manufacturing V-belts and hoses, where fiber shrinkage could affect performance, fit, and longevity.
• Textile Manufacturing: Used for acceptance testing and quality control in commercial shipments of synthetic yarns and cords to ensure compliance with contractual and regulatory requirements.
• Material Research and Development: Supports evaluation of new polymeric fibers by providing standardized shrinkage data crucial for product optimization.

Related Standards

• ASTM D885/D885M: Test Methods for Tire Cords, Tire Cord Fabrics, and Industrial Filament Yarns Made from Manufactured Organic-Base Fibers-offers similar procedures relevant to industrial filament yarns.
• ASTM D123: Terminology Relating to Textiles-provides definitions for key textile concepts used throughout ASTM D4974/D4974M-22.
• ASTM D1776/D1776M: Standard Practice for Conditioning and Testing Textiles-outlines conditioning requirements referenced in specimen preparation procedures.

By adhering to ASTM D4974/D4974M-22, manufacturers, researchers, and quality control personnel can ensure consistency, reliability, and compliance in the measurement of hot air thermal shrinkage of yarns and cords. This standard supports international trade and enhances product performance throughout the textile and polymer industries.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D4974/D4974M − 22
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/D4974M; 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 D885/D885M Test Methods for Tire Cords, Tire Cord
Fabrics, and Industrial Filament Yarns Made from Manu-
1.1 This test method covers the measurement of shrinkage
factured Organic-Base Fibers
of yarns and cords when exposed in a thermal shrinkage oven.
D1776/D1776M Practice for Conditioning and Testing Tex-
1.2 This test method is applicable to yarns and cords made
tiles
of nylon, polyester, and other polymers not detrimentally
D6477 Terminology Relating to Tire Cord, Bead Wire, Hose
affectedbythetemperatureusedandwithlineardensitiesinthe 3
Reinforcing Wire, and Fabrics (Withdrawn 2022)
range from 20 to 700 tex [180 to 6300 denier].
1.2.1 Yarns or cords for testing may be taken from yarn or
3. Terminology
cord packages or from fabrics.
3.1 Definitions:
1.3 The values stated in either SI units or inch-pound units
3.2 For definitions of terms relating to tire cord, bead wire,
are to be regarded separately as standard. The values stated in
hose wire, and tire cord fabrics, refer to Terminology D6477.
each system are not necessarily exact equivalents; therefore, to
3.2.1 The following terms are relevant to this standard:
ensure conformance with the standard, each system shall be
greige cord, in tire cords; standard atmosphere for testing
used independently of the other, and values from the two
textiles; thermal shrinkage; tire cord.
systems shall not be combined. Referee decisions are to use SI
3.3 For definitions of other terms related to textiles, refer to
units.
Terminology D123.
1.4 This standard does not purport to address all of the
3.3.1 The following terms are relevant to this standard:
safety concerns, if any, associated with its use. It is the
yarn.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter-
4. Summary of Test Method
mine the applicability of regulatory limitations prior to use.
4.1 A relaxed, conditioned specimen of yarn or cord is
Specific hazard statements are given in Section 8.
subjected to dry heat for a specified time while under a
1.5 This international standard was developed in accor-
specified tension. The percent shrinkage is read directly from a
dance with internationally recognized principles on standard-
scale or display on the instrument while the specimen is still
ization established in the Decision on Principles for the
under tension and exposed to heat.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
5. Significance and Use
Barriers to Trade (TBT) Committee.
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
room temperature retraction.
This test method is under the jurisdiction ofASTM Committee D13 on Textiles
NOTE 1—Experience, especially with nylon, shows that yarn retraction,
and is the direct responsibility of Subcommittee D13.19 on Industrial Fibers and
which may be observed directly as shortening of length (or indirectly as
Metallic Reinforcements.
denier increase), will occur in unrestrained yarn or cord that is not at
Current edition approved June 1, 2022. Published June 2022. Originally
equilibrium (equilibrium in this case being defined as essentially zero
approved in 1999. Last previous edition approved in 2016 as D4974–04(2016).
thermal shrinkage yarn or fully relaxed yarn). Normally, retractive forces
DOI: 10.1520/D4974_D4974M-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The last approved version of this historical standard is referenced on
the ASTM website. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4974/D4974M − 22
are present in most wound packages of yarn and cord; thus, unrestrained
temperature and the temperature that the specimen sees is a
yarn nearthesurfaceislikely,withtime,toundergosomeretraction.After
major cause of instrument bias. The temperature that the
retraction, such yarns exhibit lower thermal shrinkage values than yarn or
specimen sees may be checked by attaching a small calibrated
cord deeper within the package. The opposite condition of yarn on the
thermocouple to a piece of cord and suspending it in the
surface exists with yarn or cord wound against or near a rigid package
specimen position such that the tip of the thermocouple is in
core, such as a metal or hardwood wind-up spool. Such core yarn or cord
cannotmoveagainstthisrestraint,andthus,willexhibitthermalshrinkage
the center of the oven cavity.The thermocouple must not touch
values even several weeks later near to those which were measured
the oven walls. Either correct any set point/sample temperature
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
of untensioned skeins of yarn or cord to 95 to 100 % relative humidity at
6.3 The degree of room temperature length retraction, (for
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
that is possible within a sample to occur. time in the testing laboratory), of the laboratory sample or
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-
mendedfortheinvestigationofbias.Asaminimum,theparties
6.4 Frictional forces against the pulley/indicator assembly
should take a group of test specimens that are as homogeneous
cause measurement errors. Ensure that the indicator needle
as possible and that are from a lot of material of the type in
does not rub against the scale. Maintain the pulley bearings in
question.Thetestspecimensthenshouldbeassignedrandomly
good condition. The pulley wheel must be centered in the
in equal numbers to each laboratory for testing. The average
bearings. A force of 10 mN or less, applied to the tip of the
results from the two laboratories should be compared using
indicatorneedle,shouldcausepulleyrotationwhenthetesteris
Student’s t-testforunpaireddataandaprobabilitylevelchosen
in proper operating condition.
by the parties before the testing is begun. If a bias is found,
6.5 Thermal shrinkage increases as the exposure time in-
either its cause must be found and corrected, or future test
creases. Check the exposure time with a stopwatch. Some
results must be adjusted in consideration of the known bias.
thermalovenmodelshaveatimerinstalled.Comparethistimer
5.2 Thermal shrinkage of nylon, polyester, and other fibers
to a stopwatch and calibrate as necessary.
is related to the polymer of origin and its manipulation in
6.6 Center the threadline between the heating plates of the
processing. Thermal shrinkage measurement can be used to
oven to obtain a correct measurement.
control product uniformity.
5.3 The level of thermal shrinkage is critical in the user’s
6.7 Specimens that are spun, textured, or crimped (as those
subsequent operations. For example it can affect the drumset
removed from a fabric) may allow filaments to come in contact
(original length of cord) required in tire building to produce a with interior surfaces of the thermal shrinkage oven. Such
finished, final tire of a particular size.
physical contact will cause inaccurate readings of thermal
shrinkage.
5.4 Thermal shrinkage is critical to final shape and size of
fiberreinforcedarticles.Forexample,thermalshrinkageaffects
6.8 Yarn or cords that are sufficiently sticky or tacky to
final size of V-belts and their ability to maintain tension while
prevent their free release from the pulley surface as it rotates
running.
will cause inaccurate readings of thermal shrinkage.
5.5 This test method is similar to the procedures of Test
Methods D885/D885M for the determination of thermal
7. Apparatus
shrinkage of yarns and cords. Shrinkage is measured while the
7.1 Thermal Shrinkage Oven , consisting of a specimen
specimen is within an oven and tensioned as specified in Test
heating cavity capable of heating up to 250 °C [480 °F], a
Methods D885/D885M; however, there are enough vagaries
meansofaccuratelycontrollingthetemperatureofthecavity 6
among different units of apparatus for measurement of thermal
2°C [64 °F], and a means for measuring and displaying the
shrinkagethatnumericalequivalencebetweenunitsofdifferent
amount of specimen shrinkage to the nearest 0.1 %. Fig. 1
design should not be assumed, even under the same nominal
showstheprincipleofoperationofcommercialthermalshrink-
conditions.
age ovens. (Specifications of heater dimensions are available
6. Interferences on commercial thermal shrinkage oven brochures.)
6.1 An effective draft shield on the thermal oven is critical.
7.2 Stopwatch or Timer.
Because the chamber in which the specimen is heated is open
7.3 Clip-On Masses.
on three sides, air drafts can effectively shorten the length of
specimen experiencing the prescribed temperature environ-
7.4 Draft Shield, if the oven does not have one provided.
ment. Results obtained without a shield generally are lower
than with a shield.
6.2 The accurate control of temperature at any prescribed
Commercial thermal shrinkage ovens are available. Clip-on masses also are
setting is of utmost importance. Bias between the set point available from the manufacturer.
D4974/D4974M − 22
FIG. 1 Principle of Operation of a Thermal Shrinkage Oven
8. Safety Hazards minimum of three lengths of filling yarn or cord 600 mm [24
in.]longafterdiscardingthoseportionswithin75mm[3in.]of
8.1 The oven portion of the tester can reach temperatures
the selvage of the swatch. In all cases, take warp specimens
over 200 °C [390 °F]. Do not touch the oven.
that are free of filling material and filling specimens that are
8.2 Do not leave oven unattended if a specimen is installed.
free of warp material.
9.3.2.1 Instructionsonthenumberoftestspecimensin9.3.2
9. Sampling and Test Specimens
assume that a single valid thermal shrinkage result will
9.1 Primary Sampling Unit—Consider shipping containers
adequately characterize the thermal shrinkage of the laboratory
of cords or rolls of fabric to be the primary sampling unit, as
sampling unit from which the specimens are taken. The extra
applicable.
two specimens are taken to assure that a specimen free of
handling damage is available after conditioning (see 10.1). If
9.2 Laboratory Sampling Unit—As a laboratory sampling
the applicable material specification or other agreement be-
unit for acceptance testing, take material randomly from the
tween the purchaser and the supplier specifies testing more
primary sampling unit as follows:
than one specimen per laboratory sampling unit, an additional
9.2.1 Forcords,takespoolsorpackagespercartonusingthe
two specimens above the number to be tested should be taken
applicable procedure in Practice D2258.
from the laboratory sampling unit and conditioned.
9.2.2 For fabric, take from rolls at least one full-width piece
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 Condit
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D4974 − 04 (Reapproved 2016) D4974/D4974M − 22
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;D4974/D4974M; 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
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[180 to 6300 denier).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 SI units or otherinch-pound units shall are to be regarded separately
as standard. The values expressedstated in each system mayare not benecessarily exact equivalents; therefore, to ensure
conformance with the standard, each system mustshall be used independently of eachthe other, without combining values in any
way. and values from the two systems shall not be combined. 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 8.
1.5 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D123 Terminology Relating to Textiles
D885D885/D885M Test Methods for Tire Cords, Tire Cord Fabrics, and Industrial Filament Yarns Made from Manufactured
Organic-Base Fibers
D1776D1776/D1776M Practice for Conditioning and Testing Textiles
D6477 Terminology Relating to Tire Cord, Bead Wire, Hose Reinforcing Wire, and Fabrics (Withdrawn 2022)
This test method is under the jurisdiction of ASTM Committee D13 on Textiles and is the direct responsibility of Subcommittee D13.19 on Industrial Fibers and Metallic
Reinforcements.
Current edition approved July 1, 2016June 1, 2022. Published August 2016June 2022. Originally approved in 1999. Last previous edition approved in 20112016 as
D4974–04(2011).D4974–04(2016). DOI: 10.1520/D4974-04R16.10.1520/D4974_D4974M-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4974/D4974M − 22
3. Terminology
3.1 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 cord, in tire cords,cords; standard atmosphere for testing
textiles,textiles; thermal shrinkage,shrinkage; tire cord.
3.3 For definitions of other terms related to textiles, refer to Terminology D123.
3.3.1 The following terms are relevant to this standard: yarn.
4. Summary of Test Method
4.1 A relaxed, conditioned specimen of yarn or cord is subjected to dry heat for a specified time while under a specified tension.
The percent shrinkage is read directly from a scale or display on the instrument while the specimen is still under tension and
exposed to heat.
5. Significance and Use
5.1 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.
5.1.1 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 bias. As a minimum, the parties should take a group of test specimens that are as homogeneous as possible and that are from
a lot of material of the type in question. The test specimens then should be assigned randomly in equal numbers to each laboratory
for testing. The average results from the two laboratories should be compared using Student’s t-test for unpaired data and a
probability level chosen by the parties before the testing is begun. If a bias is found, either its cause must be found and corrected,
or future test results must be adjusted in consideration of the known bias.
5.2 Thermal shrinkage of nylon, polyester, and other fibers is related to the polymer of origin and its manipulation in processing.
Thermal shrinkage measurement can be used to control product uniformity.
5.3 The level of thermal shrinkage is critical in the user’s subsequent operations. For example it can affect the drumset (original
length of cord) required in tire building to produce a finished, final tire of a particular size.
5.4 Thermal shrinkage is critical to final shape and size of fiber reinforced articles. For example, thermal shrinkage affects final
size of V-belts and their ability to maintain tension while running.
5.5 This test method is similar to the procedures of Test Methods D885D885/D885M for the determination of thermal shrinkage
of yarns and cords. Shrinkage is measured while the specimen is within an oven and tensioned as specified in Test Methods
D4974/D4974M − 22
D885D885/D885M;D885 however, there are enough vagaries among different units of apparatus for measurement of thermal
shrinkage that numerical equivalence between units of different design should not be assumed, even under the same nominal
conditions.
6. Interferences
6.1 An effective draft shield on the thermal oven is critical. Because the chamber in which the specimen is heated is open on three
sides, air drafts can effectively shorten the length of specimen experiencing the prescribed temperature environment. Results
obtained without a shield generally are lower than with a shield.
6.2 The accurate control of temperature at any prescribed setting is of utmost importance. Bias between the set point temperature
and the temperature that the specimen sees is a major cause of instrument bias. The temperature that the specimen sees may be
checked by attaching a small calibrated 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 the oven walls. Either correct any
set point/sample temperature bias or determine the proper set point to give the specified specimen temperature.
6.3 The degree of room temperature length retraction, (for example, that which occurs in unrestrained skeins of yarn over time
in the testing laboratory), of the laboratory sample or specimen affects the measurement of thermal shrinkage. Unrelaxed nylon,
for example, shrinks much more than relaxed nylon. The amount of relaxation (retraction) occurring prior to testing of thermal
shrinkage can affect the result.
6.4 Frictional forces against the pulley/indicator assembly cause measurement errors. Ensure that the indicator needle does not rub
against the scale. Maintain the pulley bearings in good condition. The pulley wheel must be centered in the bearings. A force of
10 mN or less, applied to the tip of the indicator needle, should cause pulley rotation when the tester is in proper operating
condition.
6.5 Thermal shrinkage increases as the exposure time increases. Check the exposure time with a stopwatch. Some thermal oven
models have a timer installed. Compare this timer to a stopwatch and calibrate as necessary.
6.6 Center the threadline between the heating plates of the oven to obtain a correct measurement.
6.7 Specimens that are spun, textured, or crimped (as those removed from a fabric) may allow filaments to come in contact with
interior surfaces of the thermal shrinkage oven. Such physical contact will cause inaccurate readings of thermal shrinkage.
6.8 Yarn or cords that are sufficiently sticky or tacky to prevent their free release from the pulley surface as it rotates will cause
inaccurate readings of thermal shrinkage.
7. Apparatus
7.1 Thermal Shrinkage Oven ,consisting of a specimen heating cavity capable of heating up to 250°C (480°F),250 °C [480 °F],
a means of accurately controlling the temperature of the cavity 6 2°C (6 4°F), 2 °C [64 °F], and a means for measuring and
displaying the amount of specimen shrinkage to the nearest 0.1 %. Fig. 1 shows the principle of operation of commercial thermal
shrinkage ovens. (Specifications of heater dimensions are available on commercial thermal shrinkage oven brochures.)
7.2 Stopwatch or Timer.
7.3 Clip-On Masses.
7.4 Draft Shield, if the oven does not have one provided.
8. Safety Hazards
8.1 The oven portion of the tester can reach temperatures over 200°C (390° F). 200 °C [390 °F]. Do not touch the oven.
Commercial thermal shrinkage ovens are available. Clip-on masses also are available from the manufacturer.
D4974/D4974M − 22
FIG. 1 Principle of Operation of a Thermal Shrinkage Oven
8.2 Do not leave oven unattended if a specimen is installed.
9. Sampling and Test Specimens
9.1 Primary Sampling Unit—Consider shipping containers of cords or rolls of fabric to be the primary sampling unit, as applicable.
9.2 Laboratory Sampling Unit—As a laboratory sampling unit for acceptance testing, take material randomly from the primary
sampling unit as follows:
9.2.1 For cords, take spools or packages per carton using the applicable procedure in Practice D2258.
9.2.2 For fabric, take from rolls at least one full-width piece of fabric that is at least 1 m (1 yd)[1 yd] along the selvage (machine
direction), after first discarding all fabric from the outside of the roll that contains creases, fold marks, disturbed weave, or
contamination by foreign material.
9.3 Test Specimens:
9.3.1 For yarns and cords, strip at least 15 m (16 yd)[16 yd] from the 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 (16
yd)[16 yd] and reinspect until there is no visible damage. Take one specimen, 600 mm (24 in.)[24 in.] long, from each package
in the laboratory sampling unit. Discard and replace specimens that are visibly damaged.
9.3.2 For fabrics, remove a minimum of three lengths of warp yarn or cord 600 mm (24 in.)[24 in.] long from each swatch in the
laboratory sampling unit, with the specimens being taken at least 75 mm (3 in.)[3 in.] from the selvage of the swatch. For fabrics
other than tire cord fabric, such as square-woven tire fabrics, also take from each swatch in the laboratory sampling unit a minimum
of three lengths of filling yarn or cord 600 mm (24 in.)[24 in.] long after discarding tho
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