Metallic fiber

Introduction:

The hallmark of all Indian festivities is the golden glitter of the sarees and similarly-adorned dresses worn on such occasions.There is a famous proverb that “All that glitters are not gold” in the same way the ‘Zari’ used in the sarees is not of pure gold but sometimes it may contain gold but not 100%.But while purchasing a saree you would have got nice description from vendor that this sarees zari is made of pure gold but it is not actually gold it is the “Metallic fibre”which is responsible for this lustrous appearance.Where with the advancement of technology this metallic fibre has wide range of application in apparel and technical field in Textiles.This article deals with the different types of metallic fibres, their production,properties and applications.

History of Metallic Fibres

Metallic threads in general ,have been known for more than 3000 years .Gold and silver were hammered into extremely thin sheets, then cut into ribbons and worked into fabrics of kings,leaders, nobility and people of status . Historically, the metallic thread was constructed by wrapping a metal strip around a fiber core (cotton or silk), often in such a way as to reveal the color of the fiber core to enhance visual quality of the decoration. These were the first man-made fibre which came thousands of years before nylon or rayon .The Persians made fabulous carpets with god thread and the Indians,ornamental sarees with it.Ancient textiles and clothing woven from wholly or partly gold threads is sometimes referred to as Cloth of Gold. They have been woven on Byzantine looms from the 7th to 9th Centuries The Dobeckmum Company produced the first modern metallic fiber in 1946.

In the past, aluminum was usually the base in a metallic fiber. More recently Stainless steel has become a base as well. It is more difficult to work with but provides properties to the yarn that allows it to be used in more high tech applications .

What Is Metallic Fibre ?

The term metallic fibre, in its general sense, means simply a fibre that is made from metal .In generic term it is defined as Metallic fibers are manufactured fibres composed

of metal, plastic-coated metal, metal-coated plastic, or a core completely covered by metal . Gold and silver have been used since ancient times as yarns for fabric decoration. More recently, aluminium yarns, aluminized plastic yarns, and aluminized nylon yarns have replaced gold and silver. Metallic filaments can be coated with transparent films to minimize tarnishing. A common film is polyester Lurex .

These metal filaments were made by beating soft metals and alloys, into thin sheets, and then cutting the sheets into thin sheets, and then cutting the thin sheets into narrow ribbon-like filaments .

Multicomponent Metallic Filaments

In recent years, the ribbon filament of metal has undergone a transformation, which has changed the commercial outlook, for this ancient product. The metal of the filament is now sandwiched between layers of plastic, which protect it from the atmosphere and from other corrosive influences. The multicomponent filaments produced by slitting sandwich materials of this type are stronger and more robust than the filaments cut from metal foil alone. They retain the glitter of the metal during prolonged periods of use, and have a soft, pleasant handle. Coloured pigments may be added to the adhesive used in sticking the plastic films to the metal foil or metallized film.

Types of Metallic Fibres

Production method

There are two basic processes that are used in manufacturing metallic fibers. The most common is the laminating process, this are mainly American made yarns described as ham sandwich which seals a roll of aluminum foil of 0.00045 inch thickness and 20 inch wide. To both sides of the sheet is applied a thermoplastic adhesive to which has already been added the required colouring matters. The adhesive-coated foil is heated to about 90-95oc, and a sheet of cellulose acetate-butyrate transparent flim is laminated to each side of the foil by passing through squeeze roller at a pressure of 2000 lb/in .

These fibers are then cut into lengthwise strips for yarns and wound onto bobbins. The metal can be colored and sealed in a clear film, the adhesive can be colored, or the film can be colored before laminating. There are many different variations of color and effect that can be made in metallic fibers, producing a wide range of looks.

Metallic fibers can also be made by using the metalizing process. This process involves heating the metal until it vaporizes then depositing it at a high pressure onto the polyester film . This process produces thinner, more flexible, more durable, and more comfortable fibers.

Methods of Metal coating:

There are 4 methods have been developed to coat fibres and textile materials by metals, they are

1. Sputter coating2. Coating metal powder with binders

3. Electroless coating

4. Vaccum deposition

Now let us see everything in brief

1. Sputter Coating:

The equipment consists of a vacuum chamber containing an inert gas, usually argon, at 10-3 to 10-1 torr. The chamber is equipped with a cathode (target), which is the source of the coating material, and an anode, which acts as a substrate holder. Application of an electrical potential of the order of 1000 VDC, between the two electrodes, produces a glow discharge. A flow of current occurs due to movement of electrons from cathode to anode. The electrons ionize the argon gas. The argon ions are accelerated toward the cathode at a high speed due to high electric potential. Considerable heat is generatedduring the sputtering process, and it is necessary to cool the target. The sputtered atoms and ions condense on the substrate to form a thin film of coating.But the

process is very expensive.

2.Coating with metal binders:

The process is similar to conventional polymer coating. High leafing aluminium pastes (65-70%) are incorporated into a polymeric carrier, like synthetic rubber, PVC, polyurethanes, silicones, acrylic emulsions, etc., and spread coated on the fabric.

3.Electroless plating:

It is a process to deposit metal film on a surface, without the use of electrical energy.Metal deposit is formed as a result of chemical reaction between a reducing agent and metal ions present in solution. If the deposited metal acts as a catalyst, autocatalysis occurs, and a smooth deposition is obtained. Such an autocatalytic process is the basis of electroless coatings.

4.Vaccum Deposition:

In this process, the substrate to be coated is placed in a chamber over a set of crucibles containing the metal to be coated in the form of a powder/wire. The chamber containing the whole assembly is evacuated to 0.5-1 torr. The crucible is heated by resistance heating to melt the metal. The temperature of heating is so adjusted that the vapour pressure of the metal exceeds that of the chamber pressure, so that substantial evaporation of the metal takes place. The temperature required for aluminium is about 1200ºC. The roll of web to be coated is passed over a cooled drum placed over the crucibles. The metal atoms coming out of the molten metal hit the surface of the web to be coated and condense in the form of solid metal as it passes over the crucible. The production speed is quite high, ranging from 150-500 m/min. The items to be coated should be pretreated for proper adhesion of the metal.

Fiber properties

Physical properties

Fine structure and appearance:

Metallic fibres are flat, ribbon like filaments, commonly 3.2-0.2 mm (1/8-1/128 in) width. They are smooth-surfaced and may be coloured or uncoloured.

Tenacity:

It varies with types of metallic fibre and the range is from 2.6 cN/tex to 11.0 cN/tex i.e (0.3 g/den to 1.25 g/den)

Elongation:

It varies from 30% to 140% with the types of metallic fibres .

Abrasion resistance:

It has good abrasion resistance .

Chemical Properties

Acids:

Generally good resistance

Alkalis:

Good resistance to weak alkalis but degraded by strong alkalis.

General:

Coated metallic filaments help to minimize tarnishing. When suitable adhesives and films are used, they are not affected by salt water, chlorinated water in swimming pools or climatic conditions.

Mechanical properties

As metallic yarns are used primarily for decorative purposes, they do not as a rule contribute significantly to the strength of fabrics or garments but they may be used as a warp or weft yarns and strong enough to withstand the weaving and knitting operations.

If possible anything made with metallic fibers should be dry-cleaned, if there is no care label. Ironing can be problematic because the heat from the iron, especially at high temperatures, can melt the fibers.

PROPERTIES/FIBRES Acetate Butyrate foil

Polyester foil Polyester metallized

Tenacity 2.6 cN/tex 6.2 cN/tex 11.0 cN/texElongation 30% 140% 140%Elastic Recovery 75% 50% 100%Flex resistance 1 18 70Abrasion Resistance fair good excellentMoisture Regain 0.1% 0.5% 0.25%

Table 1.Comparison of properties between type of metallic fibres

Table 1 Comparison of properties of Metallic fibres with major Textile fibres

Properties Natural fibres Manufactured Cellulosic Manufactured Noncellulosic

Cotton Flax Wool Silk Acetate Lyocell Viscose Rayon

Acrylic Polyester Metallic

Abrasion Resistance

Good Fair Fair Fair Poor Fair Fair Fair Good Good

Absorbency 8.5% 12% 13.5% 11% 6.5% 11.5% 11% 1.5% 0.4% 0.25%%Elongation at break

3-10 3 20-40 20 25-45 13-15 15-30 35-45 19-55 13-140

Elastic recovery%

75 65 95 90 48-65 - 95 92 81 75-100

Flexiblity Fair Poor Good Excel Excel Fair Good Good Fair GoodPilling Resistance

Good Good Fair Good Good Good Good Good Very Poor

Good

Static Resistance

Good Good Fair Fair Fair Good Good Poor Very Poor

Good

Producers

Currently metallic fibers are manufactured primarily in Europe with only three manufacturers still producing metallic yarn in the United States. Metlon Corporation is one of the remaining manufacturers in the U.S. that stocks a wide variety of laminated and non-laminated metallic yarns .

Trademarks

The Lurex Company has manufactured metallic fibers in Europe for over fifty years. They produce a wide variety of metallic fiber products including fibers used in apparel fabric, embroidery, braids, knitting, military regalia, trimmings, ropes, cords, and lace surface decoration. The majority of Lurex fibers have a polyamdie film covering the metal strand but polyester and viscose are also used. The fibers are also treated with a lubricant called P.W., a mineral based oil, which helps provide ease of use.

Metlon Corporation is a trademark of Metallic Yarns in the United States and has been producing metallic yarns for over sixty years. Metlon produces their metallic yarn by wrapping single slit yarns with two ends of nylon. One end of nylon is wrapped clockwise and the other end is wrapped counterclockwise around the metallic yarn. The most commonly used nylon is either 15 denier or 20 denier, but heavier deniers are used for special purposes.[8]

Uses

The most common uses for metallic fibers is upholstery fabric and textiles such as lame and brocade . Lames are most commonly made of a polyester jacket, overlain with a thin, interwoven metal usually steel or copper, which gives them a metallic grayish look . This apparel is popularly used in fencing . Brocade is the special fabric in which coloured silk is used woven with silver and gold threads which has a great demand in middle east and Asian regions . Many people also use metallic fibers in weaving and needlepoint.

Fig 7,8 Shows the upholstery manufactured from Metallic Fibres

Increasingly common today are metaillic fibers in clothing, anything from party and evening wear to club clothing, cold weather and survival clothing, and everyday wear. The shiny effect that the fibres create has become the symbol of new mellinium . Metallic yarns are woven, braided, and knit into many fashionable fabrics and trims. For additional variety, metallic yarns are twisted with other fibers such as wool, nylon, cotton, and synthetic blends to produce yarns which add novelty effects to the end cloth or trim.

FIG 9,10,11,12 Shows the apparel manufactured using Metallic fibres combined with various fibres in varying percentages

Stainless steel and other metal fibers are used in communication lines such as phonelines and cable television lines. Stainless steel fibers are also used in carpets. They are dispersed throughout the carpet with other fibers so they are not detected. The presence of the fibers helps

to conduct electricity so that the static shock is reduced. These types of carpets are often used in computer-use areas where the chance of producing static is much greater.

Composite Yarns

Multi-filament metal fibre yarns can be twisted or wrapped with textile yarns to produce composite yarns . These yarns are suitable for cut resistant apparel items, antistatic brushesfor machines, lightning strike protection and antistatic filter bags

Other uses include tire cord, missile nose cones, work clothing such as protective suits, space suits, and cut resistant gloves for butchers and other people working near bladed or dangerous machinery.

New developments

a) Multi-functional textilesb) Sensing yarn, woven/knitted into garments.

c) Inteligent textile applications.

d) Heatable textiles as the heating element

e) Weavable/knittable lead wires

f) Conductive seam ribbons for clean room garments

Sources

1. ̂ Federal Trade Commission Definition2. ^ a b Kadolph, Sara J. and Langford, Anna L. "Textiles Ninth Edition" pg. 129-130.

3. ^ a b c d e f g Textile Reference Manual: Metallic Fibers: Spinning Straw into Gold?

4. ̂ Smithsonian National Museum of Natural History

5. ̂ AllRefer.com - Cloth of Gold

6. ̂ Kim, Caroline "Humanities" The Treasures of Genghis Khan: Sept - Oct 2002 Vol. 23 #5

7. ̂ Fiber Source

8. ^ a b c http://www.metlon.com/metallic.htm www.metlon.com/metallic

External links

Lurex Metlon Corporation

Suncoco Metallic Yarn

Suncoco Lurex

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