ASTM D2256 uses Bollard Grips, which can be either Mechanical (shown above) or Pneumatic (shown below)
ASTM D2256: Tensile Properties of Yarns by the Single-Strand Method
Downloads: ASTM D2256 PDF (PDF)
Written by Chris Thomas, Universal Grip Company · Reviewed by Frank Bertini · Updated October 23, 2026
ASTM D2256/D2256M is the standard test method for tensile properties of yarns by the single-strand method. One end of yarn is held at a 250 mm (10 in) gauge length and pulled to break on a constant-rate-of-extension (CRE) tester. The force-elongation record gives breaking force, elongation at break, breaking tenacity, initial and chord modulus, and breaking toughness.
This guide covers the current edition, the A1 to C6 test options, the 20-second time-to-break rule, pretension, grip selection, conditioning, knot and loop testing, every calculation with a worked example, and the equipment Universal Grip supplies for the test.
Note: Current edition: ASTM D2256/D2256M-21 (ASTM Committee D13 on Textiles, Subcommittee D13.58 on Yarns and Fibers). Work from the edition named in your contract or material specification, and buy the current text from ASTM.
What ASTM D2256 measures and who uses it
D2256 covers monofilament, multifilament and spun yarns, whether single, plied or cabled, made from natural or man-made fibers. It is the routine single-end strength test for yarn spinners, filament producers, sewing-thread and cordage makers, weaving and knitting mills checking incoming yarn, technical-textile developers and independent test laboratories.
Breaking one strand at a time shows scatter and weak places that a skein break hides, which is why single-strand data is considered more informative.
From each force-elongation curve the method reports:
Breaking force: the maximum force the strand carries, in N, cN, gf or lbf.
Elongation at break: extension at break as a percentage of gauge length.
Breaking tenacity: breaking force divided by linear density (cN/tex or gf/den).
Initial modulus: stiffness of the steepest straight part at the start of the curve.
Chord modulus: average stiffness between two stated elongations.
Breaking toughness: work to break per unit mass of yarn in the gauge length (J/g).
What D2256 does not cover
Yarns that extend more than 5.0 % when the tension rises from 0.05 to 1.0 cN/tex (0.5 to 1.0 gf/tex) are excluded. In practice that rules out spandex and other elastomeric yarns, which have their own ASTM method. Glass, flax, hemp, ramie and kraft paper yarns, tire cords and rope need special handling under other methods such as ASTM D885 for tire cords and industrial filament yarns. Skein breaking force, where many ends break together, is ASTM D1578.
Acceptance testing versus development work
Option A1, straight specimens tested in the standard atmosphere, is considered satisfactory for acceptance testing of commercial shipments. Knot, loop, wet, oven-dry, hot and cold options are useful for development, troubleshooting and end-use studies, but treat them with caution as acceptance criteria. If buyer and seller results disagree, run comparative tests on homogeneous material with specimens randomly assigned to each lab.
ASTM D2256 at a glance
Standard: ASTM D2256/D2256M-21, Tensile Properties of Yarns by the Single-Strand Method
Machine: CRE tester preferred; CRT and CRL machines also recognized (machine types per ASTM D76/D76M)
Gauge length: 250 mm (10 in) nip to nip; 500 mm (20 in) by agreement
Speed: a rate that gives an average time-to-break of 20 ± 3 s
Alternate speed: 300 mm/min (12 in/min) at 250 mm gauge, only by agreement or where a material specification requires it
Pretension, straight specimens: typically 0.5 cN/tex (0.5 gf/tex); confirm in the current edition
Options: specimen form A (straight), B (knotted) or C (looped) combined with conditions 1 to 6, written A1 to C6
Conditioning: standard atmosphere for testing textiles, ASTM D1776/D1776M
Sampling and specimen count: material specification or ASTM D2258
Grips: flat rubber-faced jaws for fine yarns; bollard (snubbing) grips for strong or slippery yarns
Test options A1 to C6: specimen form and condition
D2256 does not have methods A through F. Each test option is a letter for the specimen form plus a number for the condition at test, which gives 18 combinations written A1 through C6. The option code belongs on every report, because a tenacity value without it is ambiguous.
Specimen form (the letter)
A, straight: a plain length of yarn clamped at both ends. This is the default form.
B, knotted: a single overhand knot tied in the gauge length before the test.
C, looped: two lengths of yarn interlooped at mid-gauge, with each length clamped in one grip.
Condition at test (the number)
1, conditioned: tested in the standard atmosphere for testing textiles.
2, wet, not immersed: soaked to saturation, then mounted and tested in air.
3, wet, immersed: tested while submerged in water.
4, oven-dried: dried to remove moisture and tested immediately.
5, elevated temperature: tested hot, at a temperature agreed in the contract.
6, low temperature: tested cold, at a temperature agreed in the contract.
Which option to use
A1 for acceptance testing, routine QC and certificates of analysis.
A2 or A3 when wet strength matters: regenerated cellulose, yarns for wet processing, outdoor and marine products.
A4 to compare yarns on a dry basis without moisture-regain effects, common for industrial filament yarns.
A5 or A6 for end-use temperatures such as automotive, filtration or cold-weather gear.
B and C options to measure sensitivity to sharp bending and shear, which matters for sewing threads, netting, fishing line and knotted or looped products.
Specimens, sampling, gauge length and pretension
Sampling
Lot samples, laboratory samples and the number of specimens come from the material specification or, where it is silent, from ASTM D2258 (sampling yarn for testing). D2256 does not set a universal count such as nine breaks per sample. Take specimens from several packages, strip off the outer layers, and unwind the yarn without adding or removing twist or stretching it.
Gauge length
The gauge length is 250 mm (10 in) measured nip to nip. A 500 mm (20 in) gauge may be used by agreement, for example to match long-gauge historical data. Hold the setting to a tight tolerance; check the current edition for the exact figure. A short jaw gap such as 100 mm (4 in) is not D2256 geometry, however long the cut specimen is.
With flat jaws the gauge length is simply the distance between the jaw nips. With bollard or capstan grips it is the free length between the points where the yarn leaves the curved snubbing surfaces, not the distance between the clamp blocks at the end of each wrap. Set the grip separation so that this free length is 250 mm, and cut specimens long enough to make the wraps and reach the clamp on both grips.
Pretension
Before the crosshead moves, the specimen is put under a small pretension to remove slack and crimp without stretching the yarn. For straight specimens the long-standing value is 0.5 cN/tex (0.5 gf/tex), held within a small tolerance. Confirm that value, and the values for knotted, looped and wet specimens, in the current edition before you write them into a procedure.
50 tex (450 denier) yarn: 50 × 0.5 = 25 cN, about 25.5 gf
150 denier yarn: 150 / 9 = 16.7 tex, so 16.7 × 0.5 = 8.3 cN, about 8.5 gf
Elongation is measured from the point where the curve reaches the pretension force. Too much pretension understates elongation and overstates initial modulus; too little leaves slack and inflates elongation.
Grips for yarn testing: flat jaws versus bollard grips
D2256 describes two families of clamps: flat-faced jaws for fine yarns, and capstan, drum or snubbing clamps for coarse or high-strength yarns, or whenever slippage or jaw breaks occur. The right choice is whichever one makes the yarn break in the gauge length, away from the jaws.
Flat-faced jaws
Flat jaws with rubber facings work well for fine spun yarns and low-strength filament yarns, and pneumatic grips close with the same force every time. The weak point is the jaw edge: a strong, smooth filament yarn is pinched hardest where it enters the jaw, so it tends to break or slip there.
Bollard (capstan or snubbing) grips
In a bollard grip the yarn wraps around a curved post before it reaches a small clamp. Friction along the wrap reduces the tension in the yarn according to the capstan relation T1 / T2 = e^(μθ), where μ is the friction coefficient and θ the wrap angle in radians, so by the time the yarn reaches the clamp it carries only a fraction of the test force. The yarn is no longer pinched at the highest stress, and the break moves into the gauge length. Bollard grips are the usual answer for high-tenacity filament yarns, sewing threads, monofilament and any yarn that breaks at flat jaws.
For filaments, cords and fine wire, 1 kN capstan rope grips work on the same principle.
Elongation with snubbing grips
As force builds, a little yarn can creep around each bollard, so crosshead-based elongation includes a small contribution from the wraps. For breaking force and routine elongation that is normally acceptable if the wrap count and setup stay the same from test to test. For modulus work or tight elongation specifications, a non-contact video extensometer measures strain directly on the free length without touching the yarn.
Testing machine, load cell and the 20-second rule
D2256 prefers a constant-rate-of-extension (CRE) tester, which is what a modern electromechanical universal testing machine is. Constant-rate-of-traverse (CRT) and constant-rate-of-load (CRL) machines are also recognized, but results from different machine types are not automatically interchangeable, so record the machine type in the report.
Load cell and data
Yarn breaking forces run from well under 1 N for fine filaments to a few hundred newtons for heavy industrial yarns. Pick a load cell and range so the breaks fall inside the range verified to ASTM E4, and report the full-scale range used. A 100 N cell suits most apparel yarns; 1 kN to 2.5 kN cells cover industrial filament yarns and threads. Sample fast enough to catch the true peak, because a yarn break is sudden.
The 20-second time-to-break rule
The rate of extension is set so that the average time-to-break is 20 ± 3 s. The speed is therefore not one fixed number; it depends on how far the yarn stretches before it breaks. At a 20 s target:
Crosshead speed (mm/min) = extension at break (mm) × 60 / 20 = extension at break (mm) × 3
At a 250 mm (10 in) gauge length that gives:
5 % elongation yarn (12.5 mm extension): 37.5 mm/min (1.5 in/min)
15 % elongation yarn (37.5 mm extension): 112.5 mm/min (4.4 in/min)
25 % elongation yarn (62.5 mm extension): 187.5 mm/min (7.4 in/min)
40 % elongation yarn (100 mm extension): 300 mm/min (11.8 in/min)
In practice, run a few trial specimens at an estimated speed, read the time-to-break, adjust, and confirm that the average for the full set falls between 17 and 23 s. The tolerance is not arbitrary: the current edition notes that breaking force at 17 s and at 23 s usually differs by no more than about 1.5 % of the higher value.
The 300 mm/min alternate
By agreement between the parties, or where a material specification requires it, a fixed rate of 300 mm/min (12 in/min) at a 250 mm gauge may be used. That is 120 % of the gauge length per minute. It only produces a 20 s break for a yarn that elongates about 40 %. A typical 15 % polyester yarn breaks in about 7.5 s at 300 mm/min, and its breaking force and elongation can differ from results at 20 s. Check the current edition on whether the alternate is acceptable for referee testing; when in doubt, use the 20 s rule.
Note: Common mistake: setting 300 mm/min and calling it the 20-second rate. It is only equivalent for yarns that stretch about 40 % before breaking.
Conditioning and wet, oven-dry, hot and cold testing
Yarn strength and elongation change with moisture content. Specimens are preconditioned so they approach equilibrium from the dry side, then conditioned to moisture equilibrium in the standard atmosphere for testing textiles defined in ASTM D1776/D1776M, nominally 21 °C (70 °F) and 65 % relative humidity. The tolerances have been revised over the years, so take them from the current D1776 rather than from an old procedure. Equilibrium is reached when successive weighings show no meaningful change in mass. For routine work many labs use a fixed minimum conditioning time, commonly 24 h, where the standard and specification allow it.
Wet testing (conditions 2 and 3)
Soak specimens in distilled or deionized water until saturated. A small amount of non-ionic wetting agent may be used for water-repellent yarns. For condition 2 the wet specimen is mounted and tested in air promptly after removal from the water; for condition 3 it is tested while immersed, which requires a water tank around the grips. Soak times and the time allowed between removal and test depend on fiber type; follow the current edition. Expect large wet-strength losses for viscose and other regenerated cellulose, smaller ones for nylon, and little change for polyester.
Oven-dried testing (condition 4)
Specimens are dried following the oven-dry procedure the standard references and tested immediately after removal, because a dry yarn starts regaining moisture within seconds. Have the machine set up and the grips open before the specimen leaves the oven.
Elevated and low temperature (conditions 5 and 6)
Test temperatures are set by contract or by the material specification. Fit an environmental chamber around the grips, let the grips and the specimen soak at temperature before the test, and make sure the grips are rated for the temperature. Pneumatic grips inside a chamber need seals and air lines suited to the range.
Knot and loop strength (options B and C)
Knot strength (form B)
A single overhand knot is tied in the yarn near the middle of the gauge length before the specimen is clamped. The direction of the knot relative to the yarn twist (Z or S) changes the result, and for plied yarns the final ply twist is the one that governs. Follow the current edition's instructions on knot direction and tie every knot the same way.
Loop strength (form C)
Two lengths of yarn from the same package are interlooped so the loop sits near the middle of the gauge length, and each length is clamped in one grip. The yarn fails where the two strands bear on each other, so loop strength measures resistance to the shear and bending found in netting, interlooped structures and sewn seams.
Knot efficiency
Knot and loop strengths are always lower than straight strength, because the yarn is bent sharply and loaded in shear and compression at the knot or loop. Knot efficiency puts the loss in one number:
Knot efficiency (%) = knot breaking force / straight breaking force × 100
Example: a yarn with a straight breaking force of 980 cN and a knot breaking force of 610 cN has a knot efficiency of 610 / 980 × 100 = 62.2 %. If you express loop strength as a ratio, state exactly how you calculated it, since the loop involves two strands.
Step-by-step ASTM D2256 procedure
Confirm the option code, gauge length, rate method (20 s rule or agreed alternate) and number of specimens from the material specification or ASTM D2258.
Precondition and condition the packages in the standard atmosphere per ASTM D1776/D1776M.
Install the grips, set the gauge length to 250 mm (nip to nip for flat jaws, tangent point to tangent point for bollard grips) and zero the load cell with the grips hanging free.
Select a load cell and range so the expected breaks fall within the verified range.
Run trial specimens and adjust the crosshead speed until the time-to-break is close to 20 s.
Clamp the specimen in the upper grip, thread it through the lower grip, apply the pretension and close the lower grip. For options B and C, tie the knot or form the loop first.
Start the test and record the full force-elongation curve to break.
Note where the break occurred: in the gauge length, at or near a jaw, or by slippage.
Repeat for the required number of specimens, replacing discarded specimens as the standard directs.
Check that the average time-to-break is within 20 ± 3 s.
Calculate results for each specimen, then report the average and the standard deviation or coefficient of variation together with the option code, machine type, clamp type, any jaw padding, full-scale force range and the rate or time-to-break used.
Calculations with a worked example
Linear density and unit conversions
Yarn strength is normalized by linear density (mass per unit length), not by cross-sectional area. Yarn has no well-defined cross-section, so 'tensile strength = force / area' does not apply.
tex = grams per 1,000 m; dtex = grams per 10,000 m; denier = grams per 9,000 m
tex = denier / 9; dtex = 10 × tex
1 gf/den = 8.826 cN/tex
1 cN/tex = 0.1133 gf/den = 0.1 cN/dtex
1 cN/tex of toughness = 10 J/g
Use measured linear density (for example by the skein method) where the specification requires it, and say in the report whether nominal or measured linear density was used.
Formulas
Breaking tenacity = breaking force / linear density
Elongation at break (%) = extension from the pretension point to break / gauge length × 100
Initial modulus = (force at a point on the tangent to the steepest initial straight part × 100) / (elongation % at that point × linear density), with elongation measured from where the tangent meets the zero-force axis
Chord modulus = ((F2 − F1) × 100) / ((E2 − E1) × linear density), commonly between 0 % and 10 % elongation unless the specification says otherwise
Breaking toughness = work to break / (linear density × gauge length), which is work per unit mass of yarn in the gauge length
Worked example: 50 tex polyester, option A1
A 50 tex (450 denier) polyester filament yarn is tested at a 250 mm gauge with a pretension of 50 × 0.5 = 25 cN. One specimen gives:
Breaking force: 980 cN (9.80 N, 2.20 lbf)
Extension at break, measured from the pretension point: 37.5 mm
Breaking tenacity: 980 / 50 = 19.6 cN/tex = 1.96 cN/dtex = 19.6 × 0.1133 = 2.22 gf/den
Elongation at break: 37.5 / 250 × 100 = 15.0 %
Initial modulus: the tangent line passes through 50 cN at 1.0 % elongation, so 50 × 100 / (1.0 × 50) = 100 cN/tex (11.3 gf/den)
Chord modulus, 0 to 10 %: force is 25 cN at 0 % (the pretension) and 430 cN at 10 %, so (430 − 25) × 100 / (10 × 50) = 81 cN/tex (9.2 gf/den)
Work to break, the area under the curve from the pretension point to break: 0.190 J
Mass of yarn in the gauge length: 50 g per 1,000 m × 0.250 m = 0.0125 g
Breaking toughness: 0.190 J / 0.0125 g = 15.2 J/g (1.52 cN/tex, 0.17 gf/den)
Sanity check on toughness: for a nearly linear curve, toughness is about ½ × tenacity × strain = 0.5 × 19.6 × 0.150 = 1.47 cN/tex, or 14.7 J/g. That is close to the 15.2 J/g measured, as expected for a curve that bows slightly above a straight line.
Speed check: 37.5 mm × 3 = 112.5 mm/min gives a 20 s break for this yarn. At the 300 mm/min alternate, the same yarn breaks in 37.5 / 300 × 60 = 7.5 s, well outside 20 ± 3 s.
Jaw breaks, slippage and common errors
Jaw breaks and slippage
The standard sets a rule for discarding a break at or very near a jaw when its breaking force falls well below the average of the other specimens, and for discarding specimens that slip or where the machine misbehaves. Discarded specimens are replaced. Check the current edition for the exact distance and threshold. A jaw break near the average is a valid result; discarding it biases the average upward.
If slippage or jaw breaks are frequent, the standard allows corrective measures such as padding the jaws, coating the yarn ends or modifying the jaw faces, and any change must be reported. Often the cleaner fix is to move from flat jaws to bollard grips.
Common errors
Running at a fixed 300 mm/min and calling it the 20-second rate.
Using a short jaw gap such as 100 mm (4 in) instead of the 250 mm (10 in) gauge length.
Measuring gauge length between bollard clamp blocks instead of between the points where the yarn leaves the bollards.
Reporting tensile strength as force per cross-sectional area instead of tenacity per linear density.
Guessing or skipping pretension, which shifts elongation and modulus.
Leaving the option code off the report, or mixing A1 and A4 data in one average.
Testing out of the conditioned atmosphere, or conditioning to an out-of-date tolerance.
Testing stretch yarns that fall outside the 5 % scope limit.
Citing the wrong designation: older pages list ASTM D2101 for single fibers, but the single-fiber method in current use is ASTM D3822.
ASTM D2256 vs ISO 2062 and related ASTM methods
ISO 2062
ISO 2062 is the international single-end method for breaking force and elongation of yarns taken from packages, also run on CRE testers. It is commonly run at a 500 mm gauge length and a constant rate of extension expressed as a percentage of gauge length per minute (typically 100 %/min) rather than a time-to-break target. It uses a similar 0.5 cN/tex pretension for dry yarn and conditions to the ISO 139 atmosphere (20 °C, 65 % RH). D2256 adds modulus, toughness and the knot, loop, wet and temperature options. Because gauge length, rate and atmosphere differ, the two give close but not interchangeable results; check the current ISO edition for exact settings.
Related ASTM methods
ASTM D885/D885M: tire cords, tire cord fabrics and industrial filament yarns made from man-made organic-base fibers.
ASTM D7269: tensile testing of aramid yarns.
ASTM D1578: breaking strength of yarn in skein form, many ends at once.
ASTM D3822: tensile properties of single textile fibers, one level down from yarn.
ASTM D4268: testing fiber ropes, one level up.
Supporting standards: ASTM D1907 (yarn linear density by skein), D2258 (sampling), D1776/D1776M (conditioning) and D76/D76M (textile tensile machines).
Equipment for ASTM D2256 from Universal Grip
Universal Grip designs and builds grips and fixtures for yarn, thread and cord testing and is the distributor for Galdabini universal testing machines. A complete D2256 setup usually includes:
Bollard grips: 200 N pneumatic for fine yarns and threads, 2 kN pneumatic for most filament yarns, and 5 kN mechanical and pneumatic versions for heavy industrial yarns and cords.
Capstan rope grips: 1 kN capstan grips for filaments, yarns, cords and fine wire, with larger rope grips for cord work under ASTM D885 and rope testing.
Pneumatic grips with rubber faces for fine spun yarns where flat jaws are acceptable.
Universal testing machines: Galdabini benchtop frames in 2.5 kN and 5 kN capacities cover nearly all yarn work, with load cells sized to your breaking forces.
Video extensometers for non-contact strain when modulus or elongation must be measured on the free length.
Environmental chambers for options 5 and 6, hot and cold testing.
See our textile testing page for fabric and fiber methods that run on the same frame. To get a quote, contact us with your yarn type, linear density, expected breaking force and the D2256 options you run, and we will recommend grips, a load cell and a frame.
ASTM D2256 FAQ
What is ASTM D2256?
ASTM D2256/D2256M is the ASTM standard test method for tensile properties of yarns by the single-strand method. One end of yarn is clamped at a 250 mm (10 in) gauge length and pulled to break on a constant-rate-of-extension tester. The test reports breaking force, elongation at break, breaking tenacity, initial modulus, chord modulus and breaking toughness. The current edition is D2256/D2256M-21.
What gauge length does ASTM D2256 use?
The gauge length is 250 mm (10 in) between the clamp nips. A 500 mm (20 in) gauge may be used by agreement between the parties. With bollard or capstan grips, the gauge length is the free length between the points where the yarn leaves the curved snubbing surfaces, not the distance between the clamp blocks at the end of each wrap.
What test speed does ASTM D2256 require?
The rate of extension is set so the average time-to-break is 20 ± 3 seconds. The speed depends on the yarn's elongation: crosshead speed in mm/min equals extension at break in mm times three. By agreement, or where a material specification requires it, a fixed alternate of 300 mm/min (12 in/min) at a 250 mm gauge may be used instead.
What do ASTM D2256 options A1, B1 and C1 mean?
The letter is the specimen form: A straight, B knotted, C looped. The number is the condition at test: 1 conditioned in the standard atmosphere, 2 wet not immersed, 3 wet immersed, 4 oven-dried, 5 elevated temperature and 6 low temperature. A1 means straight specimens in the standard atmosphere, the option considered satisfactory for acceptance testing of commercial shipments.
What pretension is used in ASTM D2256?
For straight specimens the long-standing pretension is 0.5 cN/tex (0.5 gf/tex); confirm the value in the current edition. Multiply by linear density to get the force: a 50 tex yarn takes 25 cN (about 25.5 gf) and a 150 denier yarn about 8.3 cN. Elongation is measured from the point where the curve reaches the pretension force.
How is breaking tenacity calculated?
Breaking tenacity is breaking force divided by linear density. For example, a 50 tex yarn that breaks at 980 cN has a tenacity of 980 / 50 = 19.6 cN/tex, which equals 1.96 cN/dtex or 2.22 gf/den. Yarn strength is normalized by linear density rather than cross-sectional area, because a yarn has no well-defined cross-section.
How do I convert gf/den to cN/tex?
Multiply gf/den by 8.826 to get cN/tex, or multiply cN/tex by 0.1133 to get gf/den. Divide cN/tex by 10 to get cN/dtex. For linear density, tex equals denier divided by 9, and dtex equals tex times 10. For toughness, 1 cN/tex equals 10 J/g.
What are knot strength and loop strength?
Knot strength (form B) is the breaking force of a yarn with a single overhand knot tied in the gauge length. Loop strength (form C) is the breaking force of two lengths interlooped at mid-gauge. Both are lower than straight strength because the yarn is bent and sheared at the knot or loop. Knot efficiency is knot breaking force divided by straight breaking force times 100.
Why does my yarn break at the jaws, and which grips should I use?
Flat jaws pinch the yarn hardest at the jaw edge, where the stress is highest, so strong or smooth yarns often break or slip there. Bollard (capstan or snubbing) grips wrap the yarn around a curved post so friction carries much of the load before the clamp, moving the break into the gauge length. D2256 names both flat jaws and snubbing clamps.
What is the difference between ASTM D2256 and ISO 2062?
D2256 sets the speed by a 20 ± 3 s time-to-break at a 250 mm gauge and adds modulus, toughness and knot, loop, wet and temperature options. ISO 2062 is commonly run at a 500 mm gauge at a constant rate expressed as a percentage of gauge length per minute, with conditioning at 20 °C and 65 % RH. Results are close but not interchangeable.
Can ASTM D2256 be used for spandex or other stretch yarns?
No. D2256 excludes yarns that extend more than 5.0 % when the tension is increased from 0.05 to 1.0 cN/tex (0.5 to 1.0 gf/tex). That covers spandex and other elastomeric yarns, which have their own ASTM test method with different pretension and handling. Textured or crimped yarns that pass the 5 % check can still be tested under D2256.
How does ASTM D2256 differ from D885 and D1578?
D2256 breaks one strand of yarn at a time. ASTM D885 covers tire cords, tire cord fabrics and industrial filament yarns made from man-made organic-base fibers, with procedures suited to heavy cords. ASTM D1578 breaks a skein, many ends of yarn at once, giving a single bulk strength value instead of the single-strand distribution D2256 provides.