ASTM D1422-99(2008)
(Test Method)Standard Test Method for Twist in Single Spun Yarns by the Untwist-Retwist Method
Standard Test Method for Twist in Single Spun Yarns by the Untwist-Retwist Method
SIGNIFICANCE AND USE
This test method is used for acceptance testing in the trade for economic reasons even though it is less accurate than the direct method, Test Method D 1423.
If there are differences or practical significance between reported test results for two laboratories (or more), comparative tests should be performed to determine if their is a statistical bias between them, using competent statistical assistance. As a minimum, the test samples should be used that are as homogeneous as possible, that are drawn from the material from which the disparate test results are obtained, and that are assigned randomly in equal numbers to each laboratory for testing. Other materials with established test values may be used for this purpose. The test results from the two laboratories should be compared using a statistical test for unpaired data, at a probability level chosen prior to the testing series. 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.
The “setting” of twist in some fibers causes excessive contraction when the yarn is retwisted in the reverse direction. Therefore, the number of turns required to bring the specimen back to its original length may be less than the number of turns removed in untwisting. This effect may be partially offset by the use of higher pretensioning loads; but this increases the danger of stretching the yarn. Little information is available on the correct tensions to use for yarns made from different fibers or with different amounts of twist.
In addition to being less tedious, this test method requires fewer specimens than the direct-counting method and the results may be sufficiently accurate for certain purposes. This test method can be useful in those cases where the main objective is to measure variations from an average value. Another possible application is where a large amount of twist testing is required on yarns of similar type and twist. In thi...
SCOPE
1.1 This test method describes the determination of twist in single spun yarns when only an approximation of the true twist is required.
Note 1—For a more accurate method see Test Method D 1423.
1.2 This test method is applicable to spun single yarns in continuous lengths, and also to spun yarns raveled from fabrics, provided specimens at least 200 mm (8 in.) long can be obtained.
1.3 The values stated in either inch-pound or SI units are to be regarded separately as standard. Within the text, the SI units are shown in parentheses. The values stated in each system are not exact equivalents; therefore each system shall be used independently of the other. Combining values from the two systems may result in nonconformance within this test method.
1.4 This test method has been found satisfactory for use in determining twist in all single ring spun yarns and 100% cotton open-end yarns. For all open-end spun yarns that are not 100 % cotton this test method has not been found to be satisfactory for determining twist but may be used to measure deviation from an average value.
1.5 This specification shows the values in both inch-pound units and SI units. The “inch-pound” units is the technically correct name for the customary units used in the United States. The “SI” units is the technically corrected name for the system of metric units known as the International System of Units. The values stated in either acceptable metric units or in 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 the other, without combining in any way.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: D1422 − 99(Reapproved 2008)
Standard Test Method for
Twist in Single Spun Yarns by the Untwist-Retwist Method
This standard is issued under the fixed designation D1422; 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 and health practices and determine the applicability of regu-
latory limitations prior to use.
1.1 Thistestmethod describesthedeterminationoftwistin
single spun yarns when only an approximation of the true twist
2. Referenced Documents
is required.
2.1 ASTM Standards:
NOTE 1—For a more accurate method see Test Method D1423.
D123 Terminology Relating to Textiles
1.2 This test method is applicable to spun single yarns in
D1059 Test Method for Yarn Number Based on Short-
continuous lengths, and also to spun yarns raveled from
Length Specimens (Withdrawn 2010)
fabrics,providedspecimensatleast200mm(8in.)longcanbe
D1423 Test Method for Twist in Yarns by Direct-Counting
obtained.
3. Terminology
1.3 The values stated in either inch-pound or SI units are to
3.1 Definitions:
be regarded separately as standard.Within the text, the SI units
3.1.1 direction of twist, n—the right or left direction of the
are shown in parentheses. The values stated in each system are
helix formed in a twisted strand as indicated by superimposi-
not exact equivalents; therefore each system shall be used
tion of the capital letter “S” or “Z.”
independently of the other. Combining values from the two
3.1.1.1 Discussion—Yarn has S twist if, when the yarn is
systems may result in nonconformance within this test method.
held in a vertical position, the visible spirals or helices around
1.4 This test method has been found satisfactory for use in
its central axis conform in direction of slope to the central
determiningtwistinallsingleringspunyarnsand100%cotton
portion of the letter“ S,” and Z twist if the visible spirals or
open-endyarns.Forallopen-endspunyarnsthatarenot100 %
helices conform in direction of slope to the central portion of
cottonthistestmethodhasnotbeenfoundtobesatisfactoryfor
the letter “Z.” When two or more yarns, either single or plied,
determining twist but may be used to measure deviation from
are twisted together, the letters “S” and “Z” are used in a
an average value.
similar manner to indicate the direction of the last twist
1.5 This specification shows the values in both inch-pound
inserted.
units and SI units. The “inch-pound” units is the technically
3.1.2 single yarn, n—the simplest strand of textile material
correct name for the customary units used in the United States.
suitable for operations such as weaving, knitting, etc.
The “SI” units is the technically corrected name for the system
3.1.2.1 Discussion—A single yarn may be formed from
ofmetricunitsknownastheInternationalSystemofUnits.The
fibers with more or less twist; from filaments with or without
values stated in either acceptable metric units or in other units
twist; from narrow strips of materials such as paper,
shall be regarded separately as standard. The values expressed
cellophane,ormetalfoil;orfrommonofilaments.Ayarnwhich
in each system may not be exact equivalents; therefore, each
is either twistless or can be rendered twistless in a single
system must be used independently of the other, without
untwisting operation. When twist is present, it is usually all in
combining in any way.
the same direction.
1.6 This standard does not purport to address all of the
3.1.3 spun yarn, n—in a staple system, a continuous strand
safety concerns, if any, associated with its use. It is the
of fibers held together by some binding mechanism.
responsibility of this standard to establish appropriate safety
3.1.3.1 Discussion—The binding mechanism most com-
monly used in spun yarns is twist. Other useful mechanisms
This test method is under the jurisdiction ofASTM Committee D13 on Textiles
and is the direct responsibility of Subcommittee D13.58 on Yarns and Fibers. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Aug. 1, 2008. Published October 2008. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1956. Last previous edition approved in 1999 as D1422 – 99. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D1422-99R08. the ASTM website.
2 4
This test method is commonly designated by the less precise term“ Untwist- The last approved version of this historical standard is referenced on
Twist Method.” www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D1422 − 99 (2008)
that are used are chemical additives, wrapping, entanglement, originally present. Twist, as turns per unit length, is calculated
or some combination of these. Test Method D1422 is appli- ashalfthenumberofturnsregisteredonthecounterdividedby
cable only to yarns which have twist. the specimen length.
3.1.4 twist, n—in textile strands, the helical or spiral con-
5. Significance and Use
figurations induced by turning a strand about its longitudinal
axis.
5.1 This test method is used for acceptance testing in the
3.1.4.1 Discussion—Twist is usually expressed as the num-
trade for economic reasons even though it is less accurate than
ber of turns about the axis that are observed in a specified
the direct method, Test Method D1423.
length either metres (tpm) or inches (tpi).
5.1.1 If there are differences or practical significance be-
3.1.5 twist factor, TF,n—the product obtained when the
tween reported test results for two laboratories (or more),
twist expressed in turns per centimetre is multiplied by the
comparative tests should be performed to determine if their is
square root of the yarn number expressed in tex:
a statistical bias between them, using competent statistical
assistance.As a minimum, the test samples should be used that
Twist factor ~TF! 5 tpcm 3=T (1)
are as homogeneous as possible, that are drawn from the
where:
material from which the disparate test results are obtained, and
thatareassignedrandomlyinequalnumberstoeachlaboratory
T = yarn number expressed in tex.
for testing. Other materials with established test values may be
3.1.5.1 Discussion—Twist multiplier and twist factor are a
used for this purpose.The test results from the two laboratories
measure of the “twist hardness” of yarn because they are
should be compared using a statistical test for unpaired data, at
approximately proportional to the tangent of the angle between
a probability level chosen prior to the testing series. If a bias is
fibers on the outer yarn surface and the axis of the yarn; the
found, either its cause must be found and corrected, or future
larger this angle, the harder the twist. Furthermore, this angle
test results must be adjusted in consideration of the known
is a function of both the twist content (turns per unit length)
bias.
and the number of fibers per yarn cross section (yarn number).
5.2 The “setting” of twist in some fibers causes excessive
Hence, twist content alone cannot provide a measure of the
contraction when the yarn is retwisted in the reverse direction.
twist hardness of a yarn. Twist multiplier and twist factor are
Therefore, the number of turns required to bring the specimen
proportional to each other and differ only in the units used.
back to its original length may be less than the number of turns
The two are related by Eq 2 and Eq 3:
removed in untwisting. This effect may be partially offset by
TF 5 k 3TM (2)
the use of higher pretensioning loads; but this increases the
k 5 277.29/=L (3) danger of stretching the yarn. Little information is available on
the correct tensions to use for yarns made from different fibers
where:
or with different amounts of twist.
L = length in yards of the hank used to define the indirect
5.3 In addition to being less tedious, this test method
yarn number of the type,
requires fewer specimens than the direct-counting method and
N = hanks/lb. In particular for cotton count,
the results may be sufficiently accurate for certain purposes.
k = 9.567 so that Eq 2 becomes Eq 4:
This test method can be useful in those cases where the main
TF 5 9.567 3TM (4)
objective is to measure variations from an average value.
3.1.6 twist multiplier, TM,n—the quotient of the twist
Another possible application is where a large amount of twist
expressed in turns per inch and the square root of the yarn
testing is required on yarns of similar type and twist. In this
number in an indirect system.
case preliminary tests comparing this method and the direct
method could be used to determine the correct pretension.
Twist multiplier TM 5 tpi/=N (5)
~ !
5.4 Twist has important effects on the physical properties of
where:
yarn. Low-twist yarn is lofty and is usually preferred for
N = yarn number in an indirect system, the cotton system
knitting because of its softness, covering power, and warmth.
unless otherwise specified.
Increasing the amount of twist causes an increase in yarn
3.1.7 yarn, n—a generic term for a continuous strand of
strength by increasing fiber cohesion, but as the twist angle
textile fibers, filaments, or material in a form suitable for
increases beyond an optimum point, strength decreases due to
knitting, weaving, or otherwise intertwining to form a textile
a loss in effective fiber contribution. Maximum yarn strength is
fabric.
obtained by inserting a medium amount of twist to obtain an
optimum balance between these two opposing forces. High
3.2 For definitions of other textile terms used in this test
twist produces yarns of high density (“hard” or “wiry”) and
method, refer to Terminology D123.
high elongation and may improve the abrasion and impact
resistance of fabrics.
4. Summary of Test Method
4.1 A specimen is untwisted and then retwisted in the 5.5 The optimum twist for either manufacturing efficiency
opposite direction until it contracts to its original length. It is or physical properties usually increases as staple length de-
assumedthatthesameamountoftwisthasbeeninsertedaswas creases.
D1422 − 99 (2008)
5.6 The twist in a yarn before it is packaged may be at random intervals greater than1m(1yd) along the yarn.
different from that of the yarn after it has been withdrawn from Withdraw the yarn from the package in the direction of normal
the package because of changes in tension and the effect of the use, either from the side or over-end, if known. If the direction
method of withdrawal. If the yarn is withdrawn over-end, a is not known, withdraw the yarn from the side (Note 2). When
slight increase or decrease in twist will take place, depending more than five specimens are taken from an individual
upon the direction of the twist in the yarn, the direction of package, take groups of five or less at intervals of several
windingonthepackage,andthelengthoftheturn(orwrap)on yards. Do not cut the specimen free from the package or from
the package. the yarn to be discarded until after the yarn is secured in the
clamps of the twist tester. When possible, take the specimen
NOTE 2—The difference in twist between unwinding from the side and
from near the center of the traverse and not at the traverse
over-end is 1/πd, where d is the diameter of the package. Thus, for a
reversals.
25-mm (1-in.) diameter package, the difference would be about 13 tpm or
about one third tpi.
7.3.3 For woven fabric, take warp specimens from separate
ends, since each represents a separate package. Because the
5.7 When a yarn is taken from a more complex yarn
fabric may have been woven on any of a variety of looms
structure or from a fabric, the resultant twist should be
which are random quilling, sequential quilling or shuttleless,
consideredonlyanapproximationoftheoriginalvaluebecause
take filling specimens at random through the whole laboratory
of alterations that may have occurred as a result of the effects
sample to obtain as representative data as possible. If a strip
ofunwinding,handling,andmechanicalstrainsmetinprocess-
about2m(2yd) long is used as a source of specimens.
ing.
7.3.4 For weft-knit fabric known to be multi-feed, take
6. Apparatus
specimensfromsuccessivecoursesinoneportionoflaboratory
sample. For weft-knit fabric known to be single-feed or for
6.1 Twist Tester,consistingofapairofclamps,oneofwhich
which the type of feed is not known, take specimens at random
is rotatable in either direction and positively connected to a
from the whole sample.
revolution counter. The tester may be hand- or power-driven.
7.3.5 For warp-knit fabrics, cut a walewise strip from which
The position of one clamp (or both clamps) shall be adjustable
specimens can be raveled for testing as needed (Note 3). Cut
to accommodate specimens having the length prescribed in
strips from which the test specimens can be raveled for testing
10.2. The tester shall be provided with a variable tensioning
as needed (Note 4). Cut these strips to provide yarn specimens
devicesoconstructedthataspecificforcemaybeappliedtothe
at least 75 mm (3 in.) longer than the specimen length and to
specimen at the beginning and end of the test and removed
contain more than the required number of specimens for test. If
completely during the intervening untwisting and twisting
several strips are cut, divide the number of specimens among
operations.
the strips as nearly equally as possible. Use care to avoid loss
6.2 Dissecting needle or stylus.
of twist prior to testing.
6.3 Metal ruler to verify gage length (accurate to 2 mm or
NOTE 3—In order to minimize changes in twist, specimens should not
0.1 in.).
be unraveled from the strips until they are to be placed in the twist tester.
7. Sampling
7.4 Number of Specimens:
7.4.1 Spun Yarn Singles—Take 25 specimens from each
7.1 Lot Sample—Select one or more shipping units taken at
laboratory sampling unit of spun yarn singles.
random to represent an acceptance sampling lot and used as a
source of laboratory samples.
8. Conditioning
7.2 Laboratory Sample—For packaged yarns, take a mini-
8.1 Conditioning is not required for this test method.
mum of five packages for the laboratory sample unless
otherwise agreed upon between purchaser and seller. For yarns
9. Procedure
from woven or knitted fabrics, the sample must be large
enough to furnish specimens of the length and number speci-
9.1 To Determine Twist:
fied in 7.3.3.
9.1.1 Check the twist tester to be sure that the longitudinal
7.3 Selection of Specimens: play and radial play of the clamp
...
This document is not anASTM standard and is intended only to provide the user of anASTM 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:D1422–99 Designation: D 1422 – 99 (Reapproved 2008)
Standard Test Method for
Twist in Single Spun Yarns by the Untwist-Retwist Method
This standard is issued under the fixed designation D 1422; 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 describes the determination of twist in single spun yarns when only an approximation of the true twist
is required.
NOTE 1—For a more accurate method see Test Method D 1423.
1.2 This test method is applicable to spun single yarns in continuous lengths, and also to spun yarns raveled from fabrics,
provided specimens at least 200 mm (8 in.) long can be obtained.
1.3 The values stated in either inch-pound or SI units are to be regarded separately as standard. Within the text, the SI units are
shown in parentheses. The values stated in each system are not exact equivalents; therefore each system shall be used
independently of the other. Combining values from the two systems may result in nonconformance within this test method.
1.4 This test method has been found satisfactory for use in determining twist in all single ring spun yarns and 100% cotton
open-end yarns. For all open-end spun yarns that are not 100 % cotton this test method has not been found to be satisfactory for
determining twist but may be used to measure deviation from an average value.
1.5 This specification shows the values in both inch-pound units and SI units. The “inch-pound” units is the technically correct
name for the customary units used in the United States. The “SI” units is the technically corrected name for the system of metric
units known as the International System of Units. The values stated in either acceptable metric units or in 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 the other, without combining in any way.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior
to use.
2. Referenced Documents
2.1 ASTM Standards:
D 123 Terminology Relating to Textiles
D 1059 Test Method for Yarn Number Based on Short-Length Specimens
D 1423Test Method for Twist in Yarns by the Direct-Counting Method
D2258Practice for Sampling Yarn for Testing Test Method for Twist in Yarns by Direct-Counting
3. Terminology
3.1 Definitions:
3.1.1 direction of twist, n—the right or left direction of the helix formed in a twisted strand as indicated by superimposition of
the capital letter “S” or “Z.”
3.1.1.1 Discussion—Yarn has S twist if, when the yarn is held in a vertical position, the visible spirals or helices around its
centralaxisconformindirectionofslopetothecentralportionoftheletter“S,”and Ztwistifthevisiblespiralsorhelicesconform
in direction of slope to the central portion of the letter “Z.” When two or more yarns, either single or plied, are twisted together,
the letters “S” and “Z” are used in a similar manner to indicate the direction of the last twist inserted.
3.1.2 single yarn, n—the simplest strand of textile material suitable for operations such as weaving, knitting, etc.
3.1.2.1 Discussion—Asingleyarnmaybeformedfromfiberswithmoreorlesstwist;fromfilamentswithorwithouttwist;from
This test method is under the jurisdiction ofASTM Committee D13 onTextiles, and is the direct responsibility of Subcommittee D13.58 onYarnTest Methods, General.
Current edition approved Nov. 10, 1999. Published January 2000. Originally published as D1422–56 T. Last previous edition D1422–92.
This test method is under the jurisdiction of ASTM Committee D13 on Textiles and is the direct responsibility of Subcommittee D13.58 on Yarns and Fibers.
Current edition approved Aug. 1, 2008. Published October 2008. Originally approved in 1956. Last previous edition approved in 1999 as D 1422 – 99.
This test method is commonly designated by the less precise term“ Untwist-Twist Method.”
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
, Vol 07.01.volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 1422 – 99 (2008)
narrow strips of materials such as paper, cellophane, or metal foil; or from monofilaments.Ayarn which is either twistless or can
be rendered twistless in a single untwisting operation. When twist is present, it is usually all in the same direction.
3.1.3 spun yarn, n—in a staple system, a continuous strand of fibers held together by some binding mechanism.
3.1.3.1 Discussion—The binding mechanism most commonly used in spun yarns is twist. Other useful mechanisms that are
used are chemical additives, wrapping, entanglement, or some combination of these. Test Method D 1422 is applicable only to
yarns which have twist.
3.1.4 twist, n—in textile strands, the helical or spiral configurations induced by turning a strand about its longitudinal axis.
3.1.4.1 Discussion—Twist is usually expressed as the number of turns about the axis that are observed in a specified length
either metres (tpm) or inches (tpi).
3.1.5 twist factor, TF, n—the product obtained when the twist expressed in turns per centimetre is multiplied by the square root
of the yarn number expressed in tex:
Twist factor ~TF!5 tpcm 3 T (1)
=
where:
T = yarn number expressed in tex.
3.1.5.1 Discussion—Twist multiplier and twist factor are a measure of the “twist hardness” of yarn because they are
approximately proportional to the tangent of the angle between fibers on the outer yarn surface and the axis of the yarn; the larger
thisangle,theharderthetwist.Furthermore,thisangleisafunctionofboththetwistcontent(turnsperunitlength)andthenumber
of fibers per yarn cross section (yarn number). Hence, twist content alone cannot provide a measure of the twist hardness of a yarn.
Twist multiplier and twist factor are proportional to each other and differ only in the units used.
The two are related by Eq 2 and Eq 3:
TF 5 k 3 TM (2)
k 5 277.29/ L (3)
=
where:
L = length in yards of the hank used to define the indirect yarn number of the type,
N = hanks/lb. In particular for cotton count,
k = 9.567 so that Eq 2 becomes Eq 4:
TF 5 9.567 3 TM (4)
3.1.6 twist multiplier, TM, n—the quotient of the twist expressed in turns per inch and the square root of the yarn number in
an indirect system.
Twist multiplier ~TM!5 tpi/ =N (5)
where:
N = yarn number in an indirect system, the cotton system unless otherwise specified.
3.1.7 yarn, n—a generic term for a continuous strand of textile fibers, filaments, or material in a form suitable for knitting,
weaving, or otherwise intertwining to form a textile fabric.
3.2 For definitions of other textile terms used in this test method, refer to Terminology D 123.
4. Summary of Test Method
4.1 A specimen is untwisted and then retwisted in the opposite direction until it contracts to its original length. It is assumed
that the same amount of twist has been inserted as was originally present. Twist, as turns per unit length, is calculated as half the
number of turns registered on the counter divided by the specimen length.
5. Significance and Use
5.1 This test method is used for acceptance testing in the trade for economic reasons even though it is less accurate than the
direct method, Test Method D 1423.
5.1.1 If there are differences or practical significance between reported test results for two laboratories (or more), comparative
tests should be performed to determine if their is a statistical bias between them, using competent statistical assistance. As a
minimum, the test samples should be used that are as homogeneous as possible, that are drawn from the material from which the
disparate test results are obtained, and that are assigned randomly in equal numbers to each laboratory for testing. Other materials
with established test values may be used for this purpose. The test results from the two laboratories should be compared using a
statistical test for unpaired data, at a probability level chosen prior to the testing series. 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 The “setting” of twist in some fibers causes excessive contraction when the yarn is retwisted in the reverse direction.
Therefore, the number of turns required to bring the specimen back to its original length may be less than the number of turns
removed in untwisting. This effect may be partially offset by the use of higher pretensioning loads; but this increases the danger
D 1422 – 99 (2008)
of stretching the yarn. Little information is available on the correct tensions to use for yarns made from different fibers or with
different amounts of twist.
5.3 In addition to being less tedious, this test method requires fewer specimens than the direct-counting method and the results
may be sufficiently accurate for certain purposes. This test method can be useful in those cases where the main objective is to
measurevariationsfromanaveragevalue.Anotherpossibleapplicationiswherealargeamountoftwisttestingisrequiredonyarns
of similar type and twist. In this case preliminary tests comparing this method and the direct method could be used to determine
the correct pretension.
5.4 Twist has important effects on the physical properties of yarn. Low-twist yarn is lofty and is usually preferred for knitting
because of its softness, covering power, and warmth. Increasing the amount of twist causes an increase in yarn strength by
increasing fiber cohesion, but as the twist angle increases beyond an optimum point, strength decreases due to a loss in effective
fiber contribution. Maximum yarn strength is obtained by inserting a medium amount of twist to obtain an optimum balance
between these two opposing forces. High twist produces yarns of high density (“hard” or “wiry”) and high elongation and may
improve the abrasion and impact resistance of fabrics.
5.5 The optimum twist for either manufacturing efficiency or physical properties usually increases as staple length decreases.
5.6 The twist in a yarn before it is packaged may be different from that of the yarn after it has been withdrawn from the package
because of changes in tension and the effect of the method of withdrawal. If the yarn is withdrawn over-end, a slight increase or
decrease in twist will take place, depending upon the direction of the twist in the yarn, the direction of winding on the package,
and the length of the turn (or wrap) on the package.
NOTE 2—The difference in twist between unwinding from the side and over-end is 1/pd, where d is the diameter of the package. Thus, for a 25-mm
(1-in.) diameter package, the difference would be about 13 tpm or about one third tpi.
5.7 When a yarn is taken from a more complex yarn structure or from a fabric, the resultant twist should be considered only
an approximation of the original value because of alterations that may have occurred as a result of the effects of unwinding,
handling, and mechanical strains met in processing.
6. Apparatus
6.1 Twist Tester, consisting of a pair of clamps, one of which is rotatable in either direction and positively connected to a
revolution counter. The tester may be hand- or power-driven. The position of one clamp (or both clamps) shall be adjustable to
accommodate specimens having the length prescribed in 10.2. The tester shall be provided with a variable tensioning device so
constructedthataspecificforcemaybeappliedtothespecimenatthebeginningandendofthetestandremovedcompletelyduring
the intervening untwisting and twisting operations.
6.2 Dissecting needle or stylus.
6.3 Metal ruler to verify gage length (accurate to 2 mm or 0.1 in.).
7. Sampling
7.1 Lot Sample—Selectoneormoreshippingunitstakenatrandomtorepresentanacceptancesamplinglotandusedasasource
of laboratory samples.
7.2 Laboratory Sample—For packaged yarns, take a minimum of five packages for the laboratory sample unless otherwise
agreed upon between purchaser and seller. For yarns from woven or knitted fabrics, the sample must be large enough to furnish
specimens of the length and number specified in 7.3.3.
7.3 Selection of Specimens:
7.3.1 As nearly as possible take an equal number of specimens from each package or unit of the laboratory sample. Take the
specimens from each package in a random manner to minimize the effect of cyclic variations introduced during manufacturing
processes. When preparing specimens, conditioning them, or inserting them in the tester, take care to avoid any change in twist.
7.3.2 For packaged yarns, remove and discard the first 25 m (25 yd) of yarn. Using a minimum of tension, take specimens at
random intervals greater than1m(1yd) along the yarn.Withdraw the yarn from the package in the direction of normal use, either
from the side or over-end, if known. If the direction is not known, withdraw the yarn from the side (Note 2). When more than five
specimens are taken from an individual package, take groups of five or less at intervals of several yards. Do not cut the specimen
free from the package or from the yarn to be discarded until after the yarn is secured in the clamps of the twist tester. When
possible, take the specimen from near the center of the traverse and not at the traverse reversals.
7.3.3 For woven fabric, take warp specimens from separate ends, since each represents a separate package. Because the fabric
may have been woven on any of a variety of looms which are random quilling, sequential quilling or shuttleless, take filling
specimens at random through the whole laboratory sample to obtain as representative data as possible. If a strip about2m(2yd)
long is used as a source of specimens.
7.3.4 For weft-knit fabric known to be multi-feed, take specimens from successive courses in one portion of laboratory sample.
For weft-knit fabric known to be single-
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