ASTM D4974-99
(Test Method)Standard Test Method for Thermal Shrinkage of Yarn and Cord Using a Thermal Shrinkage Oven
Standard Test Method for Thermal Shrinkage of Yarn and Cord Using a Thermal Shrinkage Oven
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: D 4974 – 99
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 D 4974; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope 3.1.2 standard atmosphere for testing textiles,
n—laboratory conditions for testing fibers, yarns, and fabrics in
1.1 This test method covers the measurement of shrinkage
which air temperature and relative humidity are maintained at
of yarns and cords when exposed in a thermal shrinkage oven.
specific levels with established tolerances.
1.2 This test method is applicable to yarns and cords made
3.1.2.1 Discussion—for tire cord and yarns, a relative
of nylon, polyester, and other polymers not detrimentally
humidity of 55 6 2 % and at a temperature of 24 6 1°C (75 6
affected by the temperature used and with linear densities in the
2°F).
range from 20 to 700 tex (180 to 6300 denier).
3.1.3 thermal shrinkage, n—of textile yarns and cords,
1.2.1 Yarns or cords for testing may be taken from yarn or
contraction in length caused by heat.
cord packages or from fabrics.
3.1.4 tire cord, n—a twisted or formed structure composed
1.3 This test method shows values in both SI and inch-
of two or more single or plied industrial yarn elements having
pound units. SI is the technically correct name for the system
the same nominal twist, direction of twist, length, and tension.
of units known as the International System of Units. Inch-
3.1.4.1 Discussion—The direction of twist used to combine
pound units is the technically correct name for the customary
the single or plied yarn elements into a cord construction is in
units used in the United States. The values stated in either
the direction opposite to that used in the yarns. Frequently, tire
acceptable metric units or other units shall be regarded
and other reinforcing cords consist of a single yarn strand
separately as standard. The values expressed in each system
having little or no twist. These cords are used synonymously
may not be exact equivalents; therefore, each system must be
with twisted and plied cords in this test method.
used independently of each other, without combining values in
3.1.5 yarn, n—a generic term for a continuous strand of
any way. Referee decisions are to use SI units.
textile fibers, filaments, or material in a form suitable for
1.4 This standard does not purport to address all of the
knitting, weaving, or otherwise intertwining to form a textile
safety concerns, if any, associated with its use. It is the
fabric.
responsibility of the user of this standard to establish appro-
3.2 Definitions—For the definitions of other textile terms
priate safety and health practices and determine the applica-
used in this test method, refer to Terminology D 123.
bility of regulatory limitations prior to use. Specific hazard
statements are given in Section 8.
4. Summary of Test Method
2. Referenced Documents 4.1 A relaxed, conditioned specimen of yarn or cord is
subjected to dry heat for a specified time while under a
2.1 ASTM Standards:
specified tension. The percent shrinkage is read directly from a
D 123 Terminology Relating to Textiles
scale or display on the instrument while the specimen is still
D 885 Methods of Testing Tire Cords, Tire Cord Fabrics,
under tension and exposed to heat.
and Industrial Filament Yarns Made from Manufactured
Organic-Base Fibers
5. Significance and Use
D 1776 Conditioning Textiles for Testing
5.1 This test method may be used for the acceptance testing
3. Terminology of commercial shipments of yarns and cords. Caution is
advised because yarn and cord may contract in length over a
3.1 Definitions of Terms Specific to This Standard:
period of time due to room temperature retraction. Thermal
3.1.1 greige cord, n—in tire cords, a cord that has been
shrinkage values are reduced proportionately by the amount of
adhesive-treated, heat-treated, or otherwise treated before use
room temperature retraction.
(see cord).
NOTE 1—Experience, especially with nylon, shows that yarn retraction,
1 which may be observed directly as shortening of length (or indirectly as
This test method is under the jurisdiction of ASTM Committee D-13 on Textiles
denier increase), will occur in unrestrained yarn or cord that is not at
and is the direct responsibility of Subcommittee D13.19 on Tire Cord and Fabrics.
equilibrium (equilibrium in this case being defined as essentially zero
Current edition approved Nov. 10, 1999. Published January 2000.
Annual Book of ASTM Standards, Vol 07.01. thermal shrinkage yarn or fully relaxed yarn). Normally, retractive forces
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 4974
are present in most wound packages of yarn and cord; thus, unrestrained
specimen sees may be checked by attaching a small calibrated
yarn near the surface is likely, with time, to undergo some retraction. After
thermocouple to a piece of cord and suspending it in the
retraction, such yarns exhibit lower thermal shrinkage values than yarn or
specimen position such that the tip of the thermocouple is in
cord deeper within the package. The opposite condition of yarn on the
the center of the oven cavity. The thermocouple must not touch
surface exists with yarn or cord wound against or near a rigid package
the oven walls. Either correct any set point/sample temperature
core, such as a metal or hardwood wind-up spool. Such core yarn or cord
bias or determine the proper set point to give the specified
cannot move against this restraint, and thus, will exhibit thermal shrinkage
values even several weeks later near to those which were measured specimen temperature.
immediately from the surface of the freshly wound package. Elevated
6.3 The degree of room temperature length retraction, (for
humidity will accelerate retraction of unrestrained yarn, but moisture
example, that which occurs in unrestrained skeins of yarn over
content in itself will have little influence on thermal shrinkage. Exposure
time in the testing laboratory), of the laboratory sample or
of untensioned skeins of yarn or cord to 95 to 100 % relative humidity at
specimen affects the measurement of thermal shrinkage. Un-
room temperature for two days and reconditioning under standard
relaxed nylon, for example, shrinks much more than relaxed
laboratory conditions will cause most of the room temperature retraction
nylon. The amount of relaxation (retraction) occurring prior to
that is possible within a sample to occur.
testing of thermal shrinkage can affect the result.
5.1.1 In case of differences of practical significance in
6.4 Frictional forces against the pulley/indicator assembly
reported test results from two or more laboratories conduct
cause measurement errors. Ensure that the indicator needle
comparative tests to determine if there is a statistical bias
does not rub against the scale. Maintain the pulley bearings in
between them. Competent statistical assistance is recom-
good condition. The pulley wheel must be centered in the
mended for the investigation of bias. As a minimum, the parties
bearings. A force of 10 mN or less, applied to the tip of the
should take a group of test specimens that are as homogeneous
indicator needle, should cause pulley rotation when the tester is
as possible and that are from a lot of material of the type in
in proper operating condition.
question. The test specimens then should be assigned randomly
6.5 Thermal shrinkage increases as the exposure time in-
in equal numbers to each laboratory for testing. The average
creases. Check the exposure time with a stopwatch. Some
results from the two laboratories should be compared using
thermal oven models have a timer installed. Compare this timer
Student’s t-test for unpaired data and a probability level chosen
to a stopwatch and calibrate as necessary.
by the parties before the testing is begun. If a bias is found,
6.6 Center the threadline between the heating plates of the
either its cause must be found and corrected, or future test
oven to obtain a correct measurement.
results must be adjusted in consideration of the known bias.
6.7 Specimens that are spun, textured, or crimped (as those
5.2 Thermal shrinkage of nylon, polyester, and other fibers
removed from a fabric) may allow filaments to come in contact
is related to the polymer of origin and its manipulation in
with interior surfaces of the thermal shrinkage oven. Such
processing. Thermal shrinkage measurement can be used to
physical contact will cause inaccurate readings of thermal
control product uniformity.
shrinkage.
5.3 The level of thermal shrinkage is critical in the user’s
6.8 Yarn or cords that are sufficiently sticky or tacky to
subsequent operations. For example it can affect the drumset
prevent their free release from the pulley surface as it rotates
(original length of cord) required in tire building to produce a
will cause inaccurate readings of thermal shrinkage.
finished, final tire of a particular size.
5.4 Thermal shrinkage is critical to final shape and size of
7. Apparatus
fiber reinforced articles. For example, thermal shrinkage affects
7.1 Thermal Shrinkage Oven , consisting of a specimen
final size of V-belts and their ability to maintain tension while
heating cavity capable of heating up to 250°C (480°F), a means
running.
of accurately controlling the temperature of the cavity 6 2°C
5.5 This test method is similar to the procedures of Methods
(6 4°F), and a means for measuring and displaying the amount
D 885 for the determination of thermal shrinkage of yarns and
of specimen shrinkage to the nearest 0.1 %. Fig. 1 shows the
cords. Shrinkage is measured while the specimen is within an
principle of operation of commercial thermal shrinkage ovens.
oven and tensioned as specified in Methods D 885; however,
7.2 Stopwatch or Timer.
there are enough vagaries among different units of apparatus
7.3 Clip-On Masses.
for measurement of thermal shrinkage that numerical equiva-
7.4 Draft Shield, if the oven does not have one provided.
lence between units of different design should not be assumed,
even under the same nominal conditions.
8. Safety Hazards
6. Interferences
8.1 The oven portion of the tester can reach temperatures
over 200°C (390° F). Do not touch the oven.
6.1 An effective draft shield on the thermal oven is critical.
8.2 Do not leave oven unattended if a specimen is installed.
Because the chamber in which the specimen is heated is open
on three sides, air drafts can effectively shorten the length of
9. Sampling and Test Specimens
specimen experiencing the prescribed temperature environ-
9.1 Primary Sampling Unit—Consider shipping containers
ment. Results obtained without a shield generally are lower
of cords or rolls of fabric to be the primary sampling unit, as
than with a shield.
applicable.
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
Commercial thermal shrinkage ovens are available. Clip-on masses also are
major cause of instrument bias. The temperature that the available from the manufacturer.
D 4974
FIG. 1 Principle of Operation of a Thermal Shrinkage Oven
9.2 Laboratory Sampling Unit—As a laboratory sampling tween the purchaser and the supplier specifies testing more
unit for acceptance testing, take material randomly from the than one specimen per laboratory sampling unit, an additional
primary sampling unit as follows: two specimens above the number to be tested should be taken
9.2.1 For cords, take spools or packages per carton using the from the laboratory sampling unit and conditioned.
applicable procedure in Practice D 2258.
10. Conditioning Specimens and Preparation for Testing
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 10.1 Conditioning:
10.1.1 Condition specimens as relaxed skeins or segments
direction), after first discarding all fabric from the outside of
the roll that contains creases, fold marks, disturbed weave, or of untensioned fabric as directed in Practice D 1776 using the
atmosphere specified for industrial yarns (see 3.1.2). Ensure
contamination by foreign material.
9.3 Test Specimens: that no change in yarn/cord twist occurs while carrying out this
9.3.1 For yarns and cords, strip at least 15 m (16 yd) from procedure.
the outside of each package in the laboratory sampling unit. 10.1.2 Condition and relax yarn and greige cord specimens
Inspect the outside of the package after stripping off the yarn. 12 to 28 h.
If there is visible damage, continue to strip off units of 15 m (16 10.1.3 Condition and relax adhesive-treated cord samples
yd) and reinspect until there is no visible damage. Take one 16 to 28 h, unless immediate testing (5 to 20 min after
specimen, 600 mm (24 in.) long, from each package in the processing) is agreed upon between the buyer and the supplier.
laboratory sampling unit. Discard and replace specimens that Immediate testing must be reported as an exception to this
are visibly damaged. method (see Section 12).
9.3.2 For fabrics, remove a minimum of three lengths of 10.2 Preparation for Testing:
warp yarn or cord 600 mm (24 in.) long from each swatch in 10.2.1 With the draft shield in place, preheat the oven until
the laboratory sampling unit, with the specimens being taken at the chamber has attained the specified temperature for a
least 75 mm (3 in.) from the selvage of the swatch. For fabrics minimum of 5 min.
other than tire cord fabric, such as square-woven tire fabrics, 10.2.2 Test in standard atmosphere for testing industrial
also take from each swatch in the laboratory sampling unit a yarns (see 3.1.2).
minimum of three lengths of filling yarn or cord 600 mm (24 10.2.3 Adjust the oven temperature controller set point to
give a specimen temperature of 177 6 2 °C (350 6 4° F). (See
in.) long after discarding those portions within 75 mm (3 in.) of
the selvage of the swatch. In all cases, take warp specimens 6.2).
10.2.4 One may consult with the instrument vendor if
that are free of filling material and filling specimens that are
free of warp material. calibration of the oven temperature is suspected to be in error.
9.3.2.1 Instructions on the number of test specimens in 9.3.2
11. Procedure
assume that a single valid thermal shrinkage result will
adequately characterize the thermal shrink
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