Yarn Formation Method

Table of Contents

Yarn Formation Method

The Yarn Formation Method production stage has different process options depending on material type. Most fabrics share common yarn formation variables, which are described in the first part of this section. Unique process options are described afterward for their relevant materials.

Common Yarn Formation

Acetate Triacetate fabric, Acrylic fabric, Alpaca fabric, Cotton fabric, Glass fiber fabric, Hemp fiber fabric, Lyocell fabric, Modal fabric, Nylon fabric, Polyester fabric, Polylactic Acid (PLA) fabric, Polypropylene (PP) fabric, Polytrimethylene Terephthalate (PTT) fabric, Polyurethane (PU) fabric, Viscose/Rayon fabric, Wool fabric

For these fabric types, the process options are differentiated by common variables including:

  • Yarn Spinning Method (Filament and Staple Fiber spinning methods)
  • Material Type (Raw Material Content)
  • Textile Formation Type (Knit and Woven)
  • Yarn Size (DTEX/denier/Ne/Nm)

These factors are included in the naming of the Yarn Formation Method and knowing how to choose between these variables will enable you to select the most appropriate process option for your fabric. Not all combinations of variables exist; only applicable Yarn Formation Method process options will be shown for each fabric.

If the yarn details of a fabric are not known, then the default selection can be used. At minimum, it is recommended to align the Textile Formation type (Knit or Woven) with the Textile Formation Production Stage.

Yarn Spinning Method

For synthetic polymers, the following yarn spinning methods can be customized:

  • Extrusion and melt-spinning, continuous filament, with texturing is the default variable type and should be used whenever a textured continuous filament yarn is used. This includes yarns textured by air jet and false twist (ATY and DTY). If a synthetic yarn is a continuous filament but it is not known if it is textured or not, the default choice of “with texturing” should be used.
  • Extrusion and melt-spinning, continuous filament, no texturing should only be used for flat continuous filament yarns. The yarn filaments should appear flat and straight together.
  • Extrusion and staple fiber spinning, […], ring spun should be used when the polymer filaments have been cut into shorter staple fibers after being extruded and are then spun into yarn using the ring spinning technique. If a synthetic yarn is a staple fiber yarn but the specific spinning method is not known, the ring spinning option should be selected.
  • Extrusion and staple fiber spinning, […], open end (rotor)should only be used whenever the polymer filaments have been cut into shorter staple fibers after being extruded and are then spun into yarn using the rotor spinning technique.
  • Spinning, microfibers (yarn size<1 DTEX) should only be used for continuous filament yarn that is constructed of microfiber filaments (<1 DTEX).

For natural fibers, there is no extrusion step and the yarn spinning methods that can be customized are:

  • Spinning, […], ring spun should be used when the natural fibers are spun into a yarn using the ring spinning technique. If the specific spinning method is not known, the ring spinning option should be selected.
  • Spinning, […], open end (rotor) should be used when the natural fibers are spun into a yarn using the rotor spinning technique.

Material Type

The material type is listed for some fabric types in the yarn formation process name. This variable does not have to be customized, as only the material type applicable to the selected fabric type will be shown. For instance, “Spinning, cotton, […]” will be the only material type shown for cotton fabric spinning options while “Spinning, synthetics, […]” will be the only material type shown for polyester fabric spinning options. The different material types are used to differentiate impacts and yield loss within the spinning processes.

Textile Formation Type

The textile formation type influences the impacts of Yarn Formation Method, since woven fabrics generally require yarns with a higher degree of twist than do knit fabrics. This variable is only found within staple fiber yarn choices and where there is data to support separating processes. The following choices will be available:

  • Spinning, […], for knit should be used in conjunction with the selection of a knitting process in the Textile Formation.
  • Spinning, […], for woven should be used in conjunction with the selection of a weaving process in the Textile Formation.

If using a non-woven Textile Formation, keep the default selection “Extrusion and melt-spinning, continuous filament, no texturing” for synthetic polymers, even when staple fibers are used. This is the most appropriate proxy in the Higg MSI. For natural fibers, select “None” as the most appropriate proxy.

Yarn Count (Size)

Yarn count can have a significant influence on the impacts of the Yarn Formation Method. Yarn counts are listed in the following equivalent units: decitex (DTEX, grams per 10 kilometer), denier (grams per 9 kilometer), English Cotton Count (Ne, 840 yards per pound), and Numero Metric Count (kilometers per kilogram). Not every discrete yarn size is listed, so it is necessary to select the best proxy from available yarn sizes. In accordance with general LCA principles, when selecting the between two possible representative proxies, the more conservative choice should be used. The following table provides a guide to selecting yarn size process accordingly:

Actual Yarn Count (Range) Higg MSI Spinning Process
Yarns below 65DTEX – 58 denier – 91/1 Ne – 154 Nm Spinning […] (45 DTEX-41 denier-130/1 Ne-222 Nm)
66DTEX– 59 denier – 90/1 Ne – 153 Nm to 110DTEX – 99 denier – 54/1 Ne – 91 Nm Spinning […] (70 DTEX-63 denier-84/1 Ne-143 Nm)
111DTEX – 100 denier –53/1 Ne – 90 Nm to 144DTEX – 130 denier – 41/1 Ne – 69 Nm Spinning […]  (120 DTEX-108 denier-49/1 Ne-83 Nm)
145DTEX–131 denier –40/1 Ne – 68 Nm to 166DTEX–150 denier – 35/1 Ne – 60 Nm Spinning […] (150 DTEX-135 denier-40/1 Ne-67 Nm)
167DTEX–151 denier –34/1 Ne – 59 Nm to 194DTEX–175 denier –30/1 Ne – 51 Nm Spinning […] (170 DTEX-153 denier-34/1 Ne-59 Nm)
195DTEX–176 denier –29/1 Ne – 50 Nm to 240DTEX–216 denier –25/1 Ne – 42 Nm Spinning […] (200 DTEX-180 denier-30/1 Ne-50 Nm)
241DTEX–217 denier –24/1 Ne – 41 Nm to 290DTEX–261 denier –20/1 Ne – 34 Nm Spinning […] (250 DTEX-225 denier-24/1 Ne-40 Nm)
291DTEX–262 denier –20/1 Ne – 34Nm to 324DTEX–292 denier –18/1 Ne – 31 Nm Spinning […] (300 DTEX-270 denier-20/1 Ne-33 Nm)
325DTEX–293 denier –18/1 Ne – 31 Nm to 362DTEX–326 denier –16/1 Ne – 28 Nm Spinning […] (330 DTEX-297 denier-18/1 Ne-30 Nm)
363DTEX–327 denier –16/1 Ne – 28 Nm and above Spinning […] (370 DTEX-333 denier-16/1 Ne-27 Nm)

Once a group of single filaments or a group of staple fibers is twisted or spun into a yarn, it can be referred to as a single yarn. When two or more spun yarn strands are twisted together to construct a larger yarn, it is known as a plied yarn.

When using a plied yarn, the size of the individual yarn strand should be used to select the most appropriate Yarn Formation Method process.

Example:
A fabric is knit using a 72/2s (Ne) yarn, denoting a plied yarn of two strands with each strand having a yarn count of 72 Ne. In this case, the effective yarn count to be used (72 Ne) is in the middle of the range from the second row of the table above and the following MSI yarn size should be selected: Spinning […] (70 DTEX-63 denier-84/1 Ne-143 Nm)

For fabrics with multiple yarns of the same polymer type, it is possible to choose a single yarn size to represent them. The simplest way to do this is to take the average, by weight, of the yarns:

Example:
A fabric has the following yarn content:

45%Polyester (75D/36F)+ 30%Polyester (150D/48F)+ 25%Polyester (30D/01F)

Taking the weighted average of these yarns, the following single equivalent yarn size can be used:
(75D)*0.45 + (150D)*0.30 + (30D)*.25 = 86D

86D (denier) is in the middle of the range from the second row of the table above and the following MSI yarn size should be selected: Spinning […] (70 DTEX-63 denier-84/1 Ne-143 Nm)

Plied yarns should be accounted for before using this formula.

This approximation is acceptable for most yarn size combinations without introducing a difference in the closest MSI process. Because spinning impacts are not linear with regards to yarn size, a more representative equation is to use the inverse of yarn size. For the above example: (1/(1/75)*0.45+(1/150)*0.30+(1/30)*.25) = 61D. Even with this example, which has very different yarn sizes, the MSI yarn size that would be selected is Spinning […] (70 DTEX-63 denier-84/1 Ne-143 Nm).

For Continuous Filament Yarns, only one size range is available:

  • Extrusion and melt-spinning, continuous filament […] (80 to 500 DTEX- 72 to 450 den- 125 to 20 Nm)should be used for all yarn sizes. While the process impacts are generated from this size range, it is the best available proxy in the Higg MSI for the full range of continuous filament yarn sizes.

Aramid Fabric

When using Aramid fabric, the following default process is available:

  • Wet-spun continuous filament is the default process selection for Aramid fabrics. In wet-spinning, the polymer is dissolved in a solvent before the extrusion process rather than just using heat.

Bast Fiber Fabrics

(Flax fiber fabric, Hemp fiber fabric, Jute fiber fabric)

Bast fiber fabrics made from long fibers require additional processing that is not captured in the Raw Material Source. Instead the following process is the used and is the default for these fiber types:

Spinning, bast fiber (long fiber) contains further wet processing, including bleaching and pectin removal, that occurs after the scutching process. The fibers are then used in a wet spinning process.

Carbon Fiber Fabric

Carbon fiber fabrics require additional processing beyond the Raw Material Source. The Raw Material Source needs to be carbonized before it is carbon fiber. The following Yarn Formation Method process is the default:

  • Carbonization of fibers contains the impacts of oxidizing and stabilizing the raw material before carbonizing in an oxygen-free environment at high temperature (>1200°C).

Elastane/Spandex Fabric

The impacts of yarn formation for creating elastane/spandex yarns are currently included in the Raw Material Source impacts. The default Yarn Formation Method is:

  • Spinning, continuous filament (dry), The LYCRA Company (empty process, impacts contained in LYCRA raw material process)is a placeholder empty process that should be selected whenever the Raw Material Source is “Spandex fiber {The LYCRA Company}, contains data for yarn formation/spinning”.

Polyester Fabric

In addition to the common yarn spinning process options, there are the following special yarn spinning processes for polyester fabric:

  • Melt spinning with texturing, {The LYCRA Company} empty process, impacts contained in raw material process) should be selected whenever the Raw Material Source is “LYCRA® T400 EcoMade Fiber {The LYCRA Company}, (includes yarn formation)”.

Polyurethane (PU) Fabric

In addition to the common yarn spinning process options, there is the following special yarn spinning process for Polyurethane (PU) fabric:

  • Freeflex™ TPU melt spinning {BASF}, (15 to 100 DTEX- 14 to 90 den- 667 to 100 Nm)should be selected when using yarns made from Freeflex™ TPU resin {BASF}.

Silk Fabric

Silk fabric has a different yarn formation method than many other fabrics. For silk fabric, there is only one default process option:

  • Silk reeling (spinning) is the process of winding silk onto bobbins, cleaning it, doubling the silk, and spinning it into silk fibers.
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