Saturday, October 3, 2015

Textured Filament Yarns[1]
Art Resource

Marie-Therese Wisniowski

This is the forty-fourth post in the "Art Resource" series, specifically aimed to construct an appropriate knowledge base in order to develop an artistic voice in ArtCloth.

Other posts in this series are:
Glossary of Terms and Fabrics
Units Used in Dyeing and Printing of Fabrics
Occupational, Health & Safety
A Brief History of Color
The Nature of Color
Psychology of Color
Color Schemes
The Naming of Colors
The Munsell Color Classification System
Methuen Color Index and Classification System
The CIE System
Pantone - A Modern Color Classification System
Optical Properties of Fiber Materials
General Properties of Fiber Polymers and Fibers - Part I
General Properties of Fiber Polymers and Fibers - Part II
General Properties of Fiber Polymers and Fibers - Part III
General Properties of Fiber Polymers and Fibers - Part IV
General Properties of Fiber Polymers and Fibers - Part V
Protein Fibers - Wool
Protein Fibers - Speciality Hair Fibers
Protein Fibers - Silk
Protein Fibers - Wool versus Silk
Timelines of Fabrics, Dyes and Other Stuff
Cellulosic Fibers (Natural) - Cotton
Cellulosic Fibers (Natural) - Linen
Other Natural Cellulosic Fibers
General Overview of Man-Made Fibers
Man-Made Cellulosic Fibers - Viscose
Man-Made Cellulosic Fibers - Esters
Man-Made Synthetic Fibers - Nylon
Man-Made Synthetic Fibers - Polyester
Man-Made Synthetic Fibers - Acrylic and Modacrylic
Man-Made Synthetic Fibers - Olefins
Man-Made Synthetic Fibers - Elastomers
Man-Made Synthetic Fibers - Mineral Fibers
Man Made Fibers - Other Textile Fibers
Fiber Blends
From Fiber to Yarn: Overview - Part I
From Fiber to Yarn: Overview - Part II
Melt-Spun Fibers
Characteristics of Filament Yarn
Yarn Classification
Direct Spun Yarns

The Glossary of Terms and Fabrics and Timelines have been updated. The Glossary and Timelines will be updated in the future to incorporate more definitions and timeline events that we should be aware of in our art practice.

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The long straight continuous nature of filament yarns has limited their use in utility garments and in garments for comfort and warmth. Early efforts to over come these limitations in the synthetic fibers consisted of collecting continuous filaments in large ropes called tows, as they came from the spinneret, then cutting them into staple lengths, baling them and spinning them into yarn on one of the mechanical spinning systems.

More recently methods have focussed on:
(i) Retaining the continuity of the filament tow strand while the fibers are “stapled” and made into yarn – the direct spun system.
(ii) Retaining the continuous nature of fibers while imparting spun-like characteristics – texturizing yarns.

Textured yarns are those in which the individual filaments are displaced from their natural and relatively closely packed position into various configurations.

Difference between a spun yarn and a staple fiber.

Man-made filaments have always been made to resemble silk, but they have neither the feel nor behave like silk. The thermoplastic filaments are superior to silk in resiliency, ability to heat set, easy care, and uniformity, but they have certain disadvantages; namely, static build-up, poor handle (dead feeling rather than a lively feel), poor cover (i.e. opaque) and low absorbency. Textured filament yarns are superior to regular filament yarns in that the individual filaments are no longer closely packed parallel arrangement, but have loops curls, coils or crimps to give bulk, stretch, and surface texture. The textured yarns are more absorbent, since they have more air spaces and do no cling to the surface skin as closely. They should not build up as much static, since there is a direct relationship between absorbency and static build-up. Filaments pill less than spun yarns and in carpets, they do not shed as the spun yarns do.

Air textured yarn.

Textured filament yarns are classed bulk-type, stretch-type and textured surface “set” yarns.

Filament textured yarns.

Bulk-Type Yarns (No-Torque
Bulk yarns are those in which filaments have been modified to give greater mass per unit length. There are of two types: loop and crimp. Note: A yarn has torque if when held by one end, the free end tends to rotate.

Loop-type bulk yarns are made by feeding regular filament yarn over an air jet at a faster rate than it is drawn off by the take-up rolls. The blast of air forces some of the filaments into tiny loops. The rate at which the yarn is fed into the nozzle determines the amount of yarn thrown into loops; the velocity of the air affects the size of the loops.

The volume increase is between 50 and 150%. The yarn maintains its size and bulkiness under tension, since the straight sections of the fiber bear the strain and allow the loops to remain relatively unaffected. The yarns have little or no stretch. This process can be used on any kind of filament, since heat setting is not necessary. The looped yarn does not look like a novelty yarn when viewed without magnification. Taslan, Skyloft and Lofted Acetate are some trade names for loop-type yarns.

Left: diagram shows the jet air process. Right: a Taslan textured yarn.

Crimp-type yarns are bulk yarns made by compressing regular filament yarns in a stuffing box, causing individual filaments to take on a saw-tooth crimp. The yarn is then heat-set. The bulked single yarns are usually plied to hold the filaments together and minimize snagging.

The apparent volume increase is approximately 200 to 300%. The yarns have the same elasticity, but not enough to be classified as stretch yarns. Registered trade marks are Textralized and Spunized.

Left: diagram of the “stuffing-box” process. Right: a Texturized yarn.

Stretch-Type Yarns (Torque or No-Torque)
Stretch yarns have both bulk and stretch. They are used in hosiery, underwear, sweaters, gloves and swim suits. They make possible the manufacture of a one-size item that fits several wearers. The retailer needs to stock fewer sizes and can stock more depth in each size. Stretch yarns are of two types: coil and curl.

Coil-Type stretch yarns are made in two ways:
(i) The conventional process is based on twisting, heat-setting, and untwisting in separate steps.
(ii) In the false-twist process, a single yarn is twisted, heat-set and untwisted very quickly.

The conventional or step-by-step process inserts twist comparable to a crepe twist (75 twists per inch). Bobbins of twisted yarn are heat-set to give the maximum “memory” of the twisted condition. Yarn is cooled and then twisted again but in the opposite direction so that the twisted unfinished yarn will have zero twist.

Left: diagram of the conventional stretch process. Right: a Helanca yarn.

The yarns may be used as singles with alternating S-twist and Z-twist yarns in the fabric or they may be plied by twisting singles of opposite twists together. When the yarn is in the relaxed state, the effect is that of a soft staple or spun yarn. The yarns have a bulk increase of 300%. They stretch 300% in heavy denier and 4090 to 500% in finer yarn. Helanca is the trade name of the process.

The false-twist coil-type yarns are made by a continuous process in which the twisting and un-twisting is done in a four-to-ten inch space and takes less than a second. The yarn is led from the supply package to the heating chamber, then to the false-twist spindle, which consists of a rapidly revolving tube with an electrically located guided or hook The yarn is twisted, heat-set and then untwisted as it travels through the tube.

Left: Diagram of the false twist coil-type texturizing process. Right: Fluflon yarn.

The false-twist process can be demonstrated by tying the ends of a string together in a loop, holding the loop over the thumb and fore-finger, inserting a pencil between the two strands, and twisting. As the pencil turns there will be a S-twist on one side of the pencil, and a Z-twist on the other. As the pencil is moved up between the fingers, the twist is removed; as the pencil turns, the twist is put in.

Diagram of the technique for demonstrating false-twist principle.

Variation in the yarn can be obtained by differences in the amount of false twist, differences in heat-setting temperatures, and difference in the degree of tension on the feed roll. The yarns can be given right or left twist or they can be given alternating right and left twist by reversing the false-twist spindle at controlled time intervals. The yarn can be used as a single, or yarns can be plied by combining singles of right and left twist.

Knit-de-knit is a no-torque stretch yarn. This was one of the older methods that was revived in the 1960s. A tube of nylon is knit at a rapid speed, heat set for 20 minutes at 215oF for 30 minutes or at 240oF depending on the product, dyed and unravelled, and wound on cones. Crimp size and frequency can be varied by difference in stitch size and tension.

Diagram showing the knit-de-knit crimp.

The knitting stitch for the garment must be of a different gauge than that of the knit-de-knit crimp or pin holes will form where the crimp gauge and knit gauge match.

Curl-type stretch yarns are made by drawing heated filaments over a knife-like edge, which flattens the filaments on one side and causes the yarn to curl with an effect similar to that obtained by pulling Christmas ribbon over scissors to curl it. The yarn is then cooled. This process can be used on monofilaments as well as multi-filaments yarns. The yarn is used primarily for hosiery. Agilon is one such trade name for this process.

Left: Diagram showing curl-type yarn. Right: An Agilon yarn.

Texture “Set” Yarns
In the 1960s interest swung to texturing yarns for aesthetic fabric properties such as hand, appearance, and drapability. These textured yarns are “set” yarns. To “set” the yarn, it is first false-twisted, heat-set, and wound loosely on the package just as for regular textured yarns. Then the loosely wound package is heat-set again by steaming. This takes the stretch out of the yarn and stabilizes it with bulk and texture. The yarn has only the stretch that exists in the crimp. The yarn loses most of its torque.

Textured Acetate is a large seller in the market. These fabrics, however, cannot be dyed in the piece without removing much of its crimp and garments must dry-cleaned to retain crimp during use. The knits look like Italian silks. They are wrinkle-free and retain their shape and appearance during wear.

Ladies suit - gold textured acetate.

Textured Polyesters are higher cost than acetates but they have the advantage of retaining crimp during use and can be washed as well as dry-cleaned.

Textured polyester fabric in gold ochre color.

[1] N. Hollen and J. Saddler, Textiles, 3rd Edition, MacMillan Company, London (1968).