Saturday, June 6, 2015

Melt-Spun Fibers
Art Resource

Marie-Therese Wisniowski

Preamble
This is the fortieth 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
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
Textured Filament Yarns
Fabric Construction - Felt
Fabric Construction - Nonwoven fabrics
A Fashion Data Base
Fabric Construction - Leather
Fabric Construction - Films
Glossary of Colors, Dyes, Inks, Pigments and Resins
Fabric Construction – Foams and Poromeric Material
Knitting
Hosiery
Glossary of Fabrics, Fibers, Finishes, Garments and Yarns
Weaving and the Loom
Similarities and Differences in Woven Fabrics
The Three Basic Weaves - Plain Weave (Part I)
The Three Basic Weaves - Plain Weave (Part II)
The Three Basic Weaves - Twill Weave
The Three Basic Weaves - Satin Weave
Figured Weaves - Leno Weave
Figured Weaves – Piqué Weave
Figured Fabrics
Glossary of Art, Artists, Art Motifs and Art Movements
Crêpe Fabrics
Crêpe Effect Fabrics
Pile Fabrics - General

The Glossary of Terms, Timelines of Fabrics, Dyes and Other Stuff, A Fashion Data Base, Glossary of Colors, Dyes, Inks, Pigments and Resins, Glossary of Fabrics, Fibers, Finishes, Garments and Yarns and Glossary of Art, Artists, Art Motifs and Art Movements have been updated in order to better inform your art practice.

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Introduction
The major fibers spun by the melt-spinning method are the nylons, polyesters and olefins. Melt-spinning is the third spinning method. It is a simple and speedy procedure and the only one of the three methods that can be done by hand techniques. For example, all you need is a flame, a pair of tweezers, and a piece of nylon, polyester or olefin cloth. (An old nylon stocking will do the trick). Allow the fabric to burn until a little melt has been formed, and then quickly draw out a fiber as shown in the figure below.

Hand drawn nylon fiber.

Fibers in a factory are drawn through a spinneret, which is not to dissimilar in appearance to a shower head.

Nylon drawn through a spinneret.

The extrusion for all commercial melt spun fibers is basically the same, but some adjustments are made for the physical performance of individual fibers. Also the extrusion of the filament and staple fibers is essentially the same. As extruded, the filament fibers are of little textile value due to their amphorous state causing them to be of little strength. Drawing, the second part of the melting process, develops a high level of strength and elasticity in the fibers.


Melt-Spinning Process
The basic steps for the melt spinning process are given below.

Melt spinning process.

Properties Common to Melt-Spun Fibers
In the drawing part of the spinning process an interesting change takes place. The chain-like molecules of the undrawn fiber are in a helter-skelter alignment, like straws in a haystack. Drawing aligns the molecules into an orderly array, placing them parallel to one another and bringing them closer together. Fiber diameter is also reduced in size.

Molecules are represented by short black lines.

Drawing develops good mechanical properties, improves the hand of the cloth etc. As the molecular chains come closer together, the forces (hydrogen bonds etc.) that attract them to one another becomes stronger and the fiber develops a great deal of strength, pliability, toughness, and elasticity. The melt-spun fibers are some of the strongest fibers made.

Comparison of the tenacity of melt-spun fibers.

Fiber Shape
The melt-spun fibers are unique in that they will keep the shape of the spinneret hole through which they were spun. The fiber is normally smooth and round as spun. Trilobal fibers are spun through triangular holes, flat fibers through rectangular holes and so on. These fibers are made for specific end-uses in mind.

Moisture Absorption
The moisture absorption of the melt-spun fibers is low. Nylon has a moisture regain of 4%; polyester of 0.4% and olefin of 0%. This is both an advantage and disadvantage. Fibers lose very little strength when they are wet, they dry rapidly, waterborne stains are not absorbed, and there is no fabric shrinkage because of the effect of moisture. On the other hand, fabrics made of these fibers will be uncomfortable in humid weather unless the fabrics are especially engineered to permit moisture to pass through and evaporate. Another disadvantage is the build-up of static electricity since such a build-up attracts dust particles and so soils the fabric more rapidly.

Static Electricity
Static electricity is generated by the friction of a fabric rubbed against itself or other objects. If the electrical charge is not muted (i.e. conducted away from the fabric) it tends to build up on the surface of the fabric. When the fabric comes in contact with a good electrical conductor, a spark may occur causing an electrical shock to the wearer or a transfer may occur to the object that it has come in contact with. Such transfer may cause sparks and if they occur in a combustible environment can initiate explosions. It is always more hazardous in such places as dry cleaning places or operating rooms where cylinders of combustible gases are present. For example, nurses are forbidden to wear polyester or nylon fabrics since oxygen cylinders are present to pump oxygen into a patient who is under a general anaesthetic during surgical procedures.

Static electricity tends to build up more rapidly in dry, cold regions since in moist atmospheres water molecules dissipate their effect. Other problems with static electricity are:
(i) Soil and lint cling to the surface of a fabric and so dark colors become unsightly. Brushing simply increases the problem.
(ii) Dust and dirt are attracted to curtains.
(iii) Fabrics cling to machinery at the factory and make cutting and handling very difficult. Static electricity is responsible for increased defects and so generates a high percentage of seconds.
(iv) Clothes cling to the wearer and cause discomfort and an unsightly appearance. Temporary relief can be obtained by the wearer if a damp sponge or paper towel is wiped across the surface to drain away the static. More permanent relief can be obtained by the use of fabric softeners. These are quite effective if used in the last rinse of the laundry.

Antistatic finishes are applied to many of the fabrics at the factory, but they are frequently washed out or come out in dry cleaning.

Oily Stains
The synthetic fibers seem to have an affinity for oily stains such as skin oil and cooking oils. They may be absorbed into the fiber if not removed immediately, and for that reason frequent washing of clothing is desirable. However, laundry research has shown that many oils, including body oils, are not removed at low temperature; at high temperatures the oil penetrates the fibers. The following “cold-spotting” treatment is suggested by Du Pont for heavily soiled areas such as collars and cuffs.

Work a strong solution of detergent into the spot with a sponge or brush. This emulsifies the oil. Rinse in cold water. Be sure to manipulate the spotted areas thoroughly or until the water is clear. Then wash in a regular manner.

Pilling
Pilling is a fabric problem caused by the balling up of fiber ends on the surface of the fabric. Pilling occurs on napped fabrics of wool and cotton, but pills often break off before the garment becomes unsightly. With nylon and polyesters, the fibers are so strong that none of the pills break off and they accumulate on the garment. Pills are of two kinds; lint and fabric. Lint pills are more unsightly, because they contain not only fibers from the garment, but also fibres that are picked up in the wash water or through contact with other garments and even via static attraction.

Pilling. Sock made of Dracon on the left and a sock made of Dynel on the right. Both were worn one day a week for 14 months and washed after each wearing.

In the two socks above, the left has lint pill and the right has fabric pill. Clearly the lint pill sock appears more unsightly.

The best single treatment to prevent pilling is singeing. The construction of a fabric is a more important factor in the prevention of pilling than the fiber content. Close weave, high twist or plied yarns, and longer-staple fibers are recommended. Resin finishes of cotton and fulling of wool finishes also assists in the prevention of pilling.


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

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