ASTM D1423-99
(Test Method)Standard Test Method for Twist in Yarns by Direct-Counting
Standard Test Method for Twist in Yarns by Direct-Counting
SCOPE
1.1 This test method covers the determination of the amount and direction of twist at the completion of any stage of twisting in single (spun or filament), plied, cabled, or novelty (exclusive of long-term repeat patterns) yarns. The procedures are designed primarily for yarns in packages, but, with special precautions, they are applicable to yarns taken from fabrics. The procedure for spun yarn in 9.2 is also applicable to rovings. For tire yarns/cords and industrial yarns/cords use conditions as specified in Methods D885 and D885M.
1.2 For plied yarns, this test method covers the determination of the twist of the plied yarns and the twist of the single yarn before plying. For cabled yarns, the test method covers the determination of the cable or hawser twist; the twist of the plied yarn after plying, but prior to the last twisting operation; and the twist of the single yarn before plying. Procedures are also included for the determination of the twists of the single and plied yarn components as they lie in the final structure.
1.3 This test method is not intended for yarns that extend more than 5.0% when tension is increased from 2.5 to 7.5 mN/tex (0.25 to 0.75 gf/tex). However, the method may be applied to such yarns when mutually agreed upon tensions are used.
1.4 This test method is being evaluated for use in determining twist in open-end yarns using short lengths. Note 1-For a more rapid but less accurate method of determining twist in single spun yarns, refer to Test Method D1422. Note 2-This test method is being evaluated for use in determining twist in open end yarns using short lengths.
1.5 This standard does not purport to address all of the safety problems, 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. >
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Designation: D 1423 – 99
Standard Test Method for
Twist in Yarns by Direct-Counting
This standard is issued under the fixed designation D 1423; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope bility of regulatory limitations prior to use.
1.1 This test method covers the determination of the amount
2. Referenced Documents
and direction of twist at the completion of any stage of twisting
2.1 ASTM Standards:
in single (spun or filament), plied, cabled, or novelty (exclusive
D 123 Terminology Relating to Textiles
of long-term repeat patterns) yarns. The procedures are de-
D 1059 Test Method for Yarn Number Based on Short-
signed primarily for yarns in packages, but, with special
Length Specimens
precautions, they are applicable to yarns taken from fabrics.
D 1422 Test Method for Twist in Single Spun Yarns by the
The procedure for spun yarn in 9.2 is also applicable to
Untwist-Retwist Method
rovings. For tire yarns/cords and industrial yarns/cords use
D 1425 Test Method for Unevenness of Textile Strands
conditions as specified in Methods D 885 and D 885M.
Using Capacitance Testing Equipment
1.2 For plied yarns, this test method covers the determina-
D 1776 Practice for Conditioning Textiles for Testing
tion of the twist of the plied yarns and the twist of the single
D 1907 Test Method for Yarn Number by the Skein
yarn before plying. For cabled yarns, the test method covers the
Method
determination of the cable or hawser twist; the twist of the
D 2258 Practice for Sampling Yarn for Testing
plied yarn after plying, but prior to the last twisting operation;
and the twist of the single yarn before plying. Procedures are
3. Terminology
also included for the determination of the twists of the single
3.1 Definitions:
and plied yarn components as they lie in the final structure.
3.1.1 cable twist, n—the construction of cabled yarn, cord,
1.3 This test method is not intended for yarns that extend
or rope in which each successive twist is in the opposite
more than 5.0 % when tension is increased from 2.5 to 7.5
direction to the preceding twist, an S/Z/S or Z/S/Z construc-
mN/tex (0.25 to 0.75 gf/tex). Following the procedures of this
tion.
test method for such yarns would be independent of the bias
3.1.2 direction of twist, n—the right or left direction of the
and precision determined for this test method. The report from
helix formed in a twisted strand as indicated by superimposi-
such testing should include the tension used for this testing.
tion of the capital letter “S” or “Z.”
1.4 The values stated in either inch-pound or SI units are to
3.1.2.1 Discussion—Yarn has S twist if, when the yarn is
be regarded separately as standard. Within the text, the SI units
held in a vertical position, the visible spirals or helices around
are shown in parentheses. The values stated in each system are
its central axis conform in direction of slope to the central
not exact equivalents; therefore, each system shall be used
portion of the letter“ S,” and Z twist if the visible spirals or
independently of the other. Combining values from the two
helices conform in direction of slope to the central portion of
systems may result in nonconformance within this test method.
the letter “Z.” When two or more yarns, either single or plied,
NOTE 1—For a more rapid but less accurate method of determining
are twisted together, the letters “S” and “Z” are used in a
twist in single spun yarns, refer to Test Method D 1422.
similar manner to indicate the direction of the last twist
NOTE 2—This test method has been evaluated for use in determining
inserted.
twist in open end yarns and is not recommended.
3.1.3 final twist, n—the number of turns per unit length in a
1.5 This standard does not purport to address all of the
single yarn component of a plied yarn or the plied yarn
safety concerns, if any, associated with its use. It is the
component of a cabled yarn as the component lies in the more
responsibility of the user of this standard to establish appro-
complex structure. (Syn. “as-is” twist)
priate safety and health practices and determine the applica-
3.1.4 hawser twist, n—the construction of cabled yarn, cord,
or rope in which the single and first-ply twist are in the same
direction and the second-ply twist is in the opposite direction,
This test method is under the jurisdiction of ASTM Committee D-13 on
an S/S/Z or Z/Z/S construction.
Textiles, and is the direct responsibility of Subcommittee D13.58 on Yarn Test
Methods, General.
Current edition approved Nov. 10, 1999. Published January 2000. Originally
published as D 1423 – 56 T. Last previous edition D 1423– 98. Annual Book of ASTM Standards, Vol 07.01.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 1423
3.1.5 original twist, n—the twist in a single or plied yarn
N 5 yarn number in an indirect system, the cotton system
component of a plied or cabled yarn as the component was
unless otherwise specified.
before incorporation into the more complex structure.
3.1.11 twist take-up, n—the change in length of a yarn or
3.1.6 single yarn, n—the simplest strand of textile material
other textile strand caused by twisting, expressed as a percent
suitable for operations such as weaving, knitting, etc.
of the original untwisted length.
3.1.6.1 Discussion—A single yarn may be formed from 3.1.12 yarn, n—a generic term for a continuous strand of
fibers with more or less twist; from filaments with or without
textile fibers, filaments, or material in a form suitable for
twist; from narrow strips of material such as paper, cellophane, knitting, weaving, or otherwise intertwining to form a textile
or metal foil; or from monofilaments. A yarn which is either
fabric.
twistless or can be rendered twistless in a single untwisting 3.2 For definitions of other terms used in this test method,
operation. When twist is present, it is usually all in the same refer to Terminology D 123.
direction.
4. Summary of Test Method
3.1.7 spun yarn, n—in a staple system, a continuous strand
4.1 A specified length of specimen is mounted in a twist
of fibers held together by some binding mechanism.
device. One end is rotated until all the elements are free of
3.1.7.1 Discussion—The binding mechanism most com-
twist. The number of turns is counted and the turns per unit
monly used in spun yarns is twist. Other mechanisms used are
length are calculated.
chemical additives, wrapping, entanglement, or some combi-
4.2 The amount of twist in the component elements of a
nation of these.
plied or cabled yarn is determined by either of two options.
3.1.8 twist, n—in textile strands, the helical or spiral con-
4.2.1 In the procedure for determining original twist, one
figuration induced by turning a strand about its longitudinal
end of the yarn is fixed while the other end is rotated until the
axis.
structural components are parallel. Any one or all of these
3.1.8.1 Discussion—Twist is usually expressed as the num-
components may then be used as test specimens.
ber of turns about the axis that are observed in a specified
4.2.2 In the procedure for determining final twist in com-
length, either turns per metre (tpm) or turns per inch (tpi).
ponents, both ends of one component of the yarn are held fixed
3.1.9 twist factor, TF, n—the product obtained when the
while all the other components are removed and discarded. The
twist expressed in turns per centimetre is multiplied by the
twist is then determined in the remaining component.
square root of the yarn number expressed in tex.
5. Significance and Use
Twist factor ~TF! 5 tpcm 3 T (1)
=
5.1 Test Method D 1423 for testing for twist in yarns by the
where:
direct-counting method is considered satisfactory for accep-
T 5 yarn number expressed in tex.
tance testing of commercial shipments because current esti-
3.1.9.1 Discussion—Twist multiplier and twist factor are a
mates of between-laboratory precision are acceptable and the
measure of the “twist hardness” of yarn because they are
method has been used extensively in the trade for acceptance
approximately proportional to the tangent of the angle between
testing.
fibers on the outer yarn surface and the axis of the yarn; the
5.1.1 If there are differences or practical significance be-
larger this angle, the harder the twist. Furthermore, this angle
tween reported test results for two laboratories (or more),
is a function of both the twist content (turns per unit length)
comparative tests should be performed to determine if there is
and the number of fibers per yarn cross section (yarn number).
a statistical bias between them, using competent statistical
Hence, twist content alone cannot provide a measure of the
assistance. As a minimum, the test samples should be used that
twist hardness of a yarn. Twist multiplier and twist factor are
are as homogeneous as possible, that are drawn from the
proportional to each other and differ only in the units used. The
material from which the disparate test results are obtained, and
two are related by Eq 2 and Eq 3:
that are assigned randomly in equal numbers to each laboratory
for testing. Other materials with established test values may be
TF 5 k 3 TM (2)
used for this purpose. The test results from the two laboratories
k 5 277.29/ L (3)
=
should be compared using a statistical test for unpaired data, at
where: a probability level chosen prior to the testing series. If a bias is
L 5 length in yards of the hank used to define the indirect found, either its cause must be found and corrected, or future
yarn number of the type,
test results must be adjusted in consideration of the known
N 5 hanks/lb. In particular for cotton system,
bias.
k 5 9.567 and Eq 2 becomes Eq 4:
5.2 The determination of twist in a straight section of a yarn
is not the simple straightforward operation it appears to be, for
TF 5 9.567 3 TM (4)
the test results may be greatly influenced by variations in test
3.1.10 twist multiplier, TM, n—the quotient of the twist
procedures and techniques. In all manipulations, extreme care
expressed in turns per inch and the square root of the yarn
is necessary to prevent specimen rotation altering the twist
number in an indirect system.
level before testing begins.
Twist multiplier ~TM! 5 tpi/ N (5)
= 5.3 The twist in a yarn before it is packaged may be
different from that of the yarn after it has been withdrawn from
where:
the package because of changes in tension and the effect of the
NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D 1423
method of withdrawal. If the yarn is withdrawn over-end, a 5.7 The same amount of twist in yarns of different sizes
slight increase or decrease in twist will take place, depending (diameter) will produce yarns with different degrees of com-
upon the direction of the twist in the yarn, the direction of pactness, twist character, and twist angles. The twist multiplier
winding on the package, and the length of the wrap on the or twist factor is approximately proportional to the tangent of
package. the angle that the surface fibers make with the axis of the yarn.
5.4 When a yarn is incorporated into or removed from a Therefore, the greater the angle, the greater the twist multiplier.
more complex structure, alterations may occur as a result of the A constant twist multiplier indicates comparable compactness
plying, untwisting, or raveling operation. For example, when and degree of liveliness in yarns of different sizes and
determining the twist in plied yarn by the procedure for conversely a difference in twist multiplier indicates a difference
determining original twist, as the plied yarn is untwisted, a in compactness in yarns of the same size. Yarns intended for
comparable amount of twist is reinserted in, or removed from, different uses are frequently made with different twist multi-
the single-yarn components. As a consequence, the single yarns pliers, for example, warp yarns and filling yarns.
have approximately the original twist prior to the plying
6. Apparatus
operation but not the twist they have when they are functioning
6.1 Twist Tester, consisting of a pair of clamps, one of which
as components of the plied yarn. The latter or final twist may
is rotatable in either direction and positively connected to a
be estimated by adding the ply twist to (or subtracting it from)
revolution counter. The tester may be hand- or power-driven.
the single-yarn twist depending on the directions of the ply and
The position of one clamp (or both clamps) shall be adjustable
singles twist. For a more precise determination, the test
to accommodate specimens of the lengths specified in 9.2 and
procedure must be modified. There are thus two different
procedures for preparing specimens of the component elements 9.3 and to permit measuring the change in length during
untwisting. Means shall be provided for applying the specified
of a plied or cabled yarn for twist determination. The procedure
for the original twist measures the twist in a component of a tensions to the specimen and for determining the specimen
length with an accuracy of 60.5 mm (0.02 in.). The movable
complex strand after the components have been untwisted. The
procedure for final twist measures the twist in a component as but nonrotatable clamp shall be capable of being traversed with
substantially no friction to permit determining the untwisted
it lies in the complex strand. Although the original twist
procedure is most often used, selection of a particular proce- length of the specimen under the specified tension. The
counting device shall be resettable to zero count and shall
dure will depend on the type of information needed.
indicate the total number of turns to the nearest 0.1 turn.
NOTE 3—The difference in twist between unwinding from the side and
6.2 Dissecting Needle or Stylus.
over-end is 1/pd, where d is the diameter of the package. Thus, for a
6.3 Gage or Calipers.
25-mm (1-in.) diameter package, the difference would be about 13 tpm or
6.4 Magnifying Glass with Stand.
about ⁄3 tpi.
6.5 Equipment for Reeling Laboratory Sample Skeins, op-
5.5 When a yarn is taken from a more com
...
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