Shieldex’s Pure Silver coated yarn and fabrics are in demand in many fields from medical products, military equipment, defence industry to factories producing electronic parts. Thanks to its oligodynamic activity, Pure Silver coated products, which prevent the proliferation of 650 different types of bacteria and microbes by disintegrating their DNA, are also used in wound and burn treatment.
For more information, please visit texcraf.
Founded in , Teksel Tekstil A.Ş. is the Turkish representative of Europe’s leading machinery manufacturers and consumables suppliers. Teksel Tekstil, which serves with its expert staff of approximately 50 people, has an R&D department of 8 people in order to make the right investments that can provide its stakeholders with effective competitiveness in international markets. One of the companies represented by Teksel in Turkey is Shieldex (Statex).
Dursun Ferikel, General Manager of Teksel Tekstil A.Ş., which has been offering Shieldex’s Pure Silver coated (fibre, yarn and fabric) functional products to its customers for nearly 20 years, gave an interview to our ‘Yarn Technologies’ special issue. Ferikel gave information on many subjects from the usage areas of pure silver coated yarn to its benefits in the interview.
In , we met Shieldex (Statex) company at the Technical Textile exhibition in Germany, where we went with our consultants. Thanks to the technical support provided by Prof. Dr. Bülent Özipek, the founder of ITU’s Faculty of Textile Technologies and Design, we were able to better understand the importance of the product and interpret what could be done. As the representative of Shieldex in Turkey for nearly 20 years, we offer our customers functional products (fibre, yarn and fabric) coated with Pure Silver.
Thanks to its oligodynamic activity, 99.99% Pure Silver breaks down the DNA of 650 different types of bacteria and microbes and prevents them from multiplying. In this way, the product gains anti-bacterial feature. It is successfully used in many different projects by providing an advantage in terms of comfort with its effect of preventing sweat odour caused by bacteria.
Pure Silver, according to the proportions used; It provides anti-static, anti-bacterial and anti-fungal (fungal) properties. With the right usage technique, silver products can also be designed to shield against electromagnetic waves, which are considered to be today’s invisible vital danger. In addition to Defence Industry products that can be 100% shielded, products that can protect expectant mothers and especially babies from the harmful effects of mobile devices, wifi and similar wireless communication devices at 85-90% rates are also being developed.
Pure Silver coated products are in demand in many areas from the medical world to daily clothes used for different purposes (maternity and baby clothes, socks, underwear, sportswear, gloves, athletes, diabetic products, skin masks, etc.), military equipment, defence industry, factories producing electronic parts. We know that pure silver coated products are also used in the treatment of wounds and burns abroad. We are making great efforts to popularise this application in our country.
Of course… You can also mix yarns made of different fibres into the fabrics you knit/weave using Pure Silver yarn during production. Sock or glove manufacturers can use 3% or 10% Pure Silver yarn with cotton/polyester etc. yarns depending on their purpose. The important point here is, as always, what your goal is. Which benefit you want to provide. Do you only want to produce an anti-static and anti-bacterial product? Or do you also want to have anti-fungal properties? Will this sock be produced for diabetic patients or for athletes? Our R&D department offers the optimum solution recommendation with the appropriate combination according to your target.
In addition, you do not have to use Pure Silver on the entire product. For example, you can achieve your goal by using our product only in the armpit, collar area or the net area of the underwear where sweating will be intense. Therefore, you can achieve the desired benefit not only with different yarns, but also by combining different fabrics. As can be seen, it is possible to obtain functional products at an affordable cost with various combinations in accordance with the purpose.
Yes, it is possible… Pure Silver coated yarns can be used in combination with other yarns made of different fibres. Taking advantage of this superiority and with the guidance of our technical consultants who have spent many years on optimum blend combinations, we have collaborated with the producer of Umorfil fibre obtained from waste fish scales. We obtained a very special yarn by blending Umorfil fibre with cotton and pure silver fibre. We have also applied for a “Utility Model” for our yarn named Silverion Collagen. Since Pure Silver increases its effectiveness by releasing higher amounts of ions in a humid environment, Umorfil’s ability to retain high humidity like wool has further increased our strength for this purpose. Thus, Pure Silver and Umorfil fibres have achieved a perfect harmony.
Umorfil fibre, which we use in our Silverion Collagen yarn, is produced by Camangi Corperation in Taiwan. The fibre makes an important contribution to the philosophy of sustainability with its 100% biodegradability. Because fish processing factories bury waste fish scale residues in the soil, causing acidification of the soil and causing environmental damage. Camangi has produced a bionic fibre series containing collagen peptide amino acids from waste fish scales with supramolecular technology. Thanks to Pure Silver, we benefited from this fiber to the maximum extent.
We tested many different ratios for many years to obtain Silverion Collagen yarn. Finally, we were able to reach the optimum performance level with a blend ratio of 5% Pure Silver, 60% Umorphyl and 35% Cotton fibre.
Our yarn passed accredited tests and received Anti-Static, Anti-Bacterial and Anti-Fungal certificates from EKOTEKS institution. We have also seen that some fabrics knitted with our yarn have Anti-UV and Thermal properties. Thanks to Umorfil, our yarn is able to retain moisture at very high rates and directly supports the skin with Collagen Peptide Polymers from waste fish scales. This feature is of great importance for human health. Our yarn also successfully passed the Anti-Aging (anti-ageing effectiveness) test we had conducted in a special laboratory.
Thanks to all these features, Silverion Collagen yarn directly contributes to nature and ecological balance by reducing the washing frequency and water consumption of the product used.
We have never used nanotechnology and chemicals given with finishing in our yarn. In fact, we are against the use of nanotechnology in products that come into contact with the skin. In Europe, restrictions are gradually coming to the use of nanotechnology for products that come into contact with human skin.
Umorfil and Pure Silver fibres in our yarn have Oeko-Tex Standard 100 Class-I certification. As you know, the Oeko-Tex Standard 100 Class-I certificate provides assurance to consumers around the world that textile products are safe and do not harm human health. This certification indicates that the products are also suitable for use such as skin contact and oral contact. The most stringent class, Class-I, indicates that textile products are suitable even for babies and young children. We blended these two unique fibres with the most valuable cotton fibre of our country and obtained our Silverion Collagen yarn. For us, health is more important than anything else…
With this useful and smart yarn; underwear, undershirts, tights, baby clothes, maternity clothes, specially designed underwear for our soldiers, finger socks, recovery abdominal corsets, sportswear, underwear, special gloves to support those undergoing skin treatment and many other useful products are made.
“Our brands must now go beyond producing with ordinary yarns. It is not possible for us to compete with countries such as China, India, Pakistan and Egypt in the production lane and win this struggle. Therefore, we need to increase our share in world exports with value-added products…” I am sure you have heard these words hundreds of times. First of all, we need to accept this role and allocate a significant part of our budget to this work without wasting time, but we are always trying to save the day.
As you know, technology is developing in every field and this has benefits as well as harms us. Almost all household appliances have met with IOT technology and these items can be controlled even from our mobile phones. Today, we live in the comfort of these, but do we ever think about the damage they cause to those who are sensitive to electromagnetic waves and to our babies?
5G technology, which will affect us almost five times more than 4.5G, will soon be used everywhere in our country. It is stated that we will no longer have a 5G base station every 3-4km, but every 150-200mt! What will be the impact of these base stations on pregnant women and babies who are sensitive to electromagnetic waves? Will cancer cases, Alzheimer’s, thyroid diseases and immune system disorders increase? We don’t know… Many European countries have an attitude against 5G, but it seems that we will have to accept this technology due to the targeted projects.
For more silver plated yarnsinformation, please contact us. We will provide professional answers.
It is obvious that we cannot avoid the negative effects of technology while benefiting from it, but can we live together by protecting ourselves from it with textile products? We need to question all these today and develop new functional products together. Textile is the breath of Turkey, we should not forget this… As Teksel Tekstil A.Ş. expert team, we are always ready to provide technical consultancy, as long as we have manufacturers and brands that want to invest in this way.
ABSTRACT
The hallmark of all Indian festivities is the golden glitter of the sarees and similarly-adorned dresses worn on such occasions. All that glitters may not be gold and the ‘zari’ (metallic yarn), responsible for this lustrous appearance, may or may not contain any gold. This paper reviews the different types of metallic fibres and their production.
INTRODUCTION
Metallic yarns or threads, in general, have been known for more than years. Gold and silver were hammered into extremely thin sheets, then cut into ribbons and worked into fabrics. These were the first ‘man made’ fibres, which came thousands of years before nylon or rayon. The Persians made fabulous carpets with gold thread and the Indians, ornamental sarees with it. The metal threads were twisted, doubled or wrapped around some other thread such as cotton.
With the advancement of technology, metal/conductive textiles found extensive functional applications. These materials have high electrical conductivity and radar reflecting property, yet are lightweight and flexible. Various methods have been developed to coat fibers and textile materials by metals.
» sputter coating
» coating metal powder with binders
» electro less coating
» vacuum deposition
Many technical applications demand properties which cannot be obtained by simply processing common textile material into single textile fabric. However, combination of knitted structure, textile and metal yarn of wire make it possible to create innovative products for multipurpose technical application. Thus knitted fabrics are flexible and extensible and metal wire possess properties which are advantageous in technical textile with regard to their permanent antistatic behavior, known conductivity, shielding from electro magnetic field & resistance to cutting.
METALLIC FIBRE
The term metallic fibre, in its general sense, means simply a fibre that is made from metal. The generic term “metallic” was adopted by the U.S. Federal Trade Commission and is defined as: A manufactured fibre composed of metal, plastic-coated metal, metal-coated plastic, or a core completely covered by metal. Thus, metallic fibres are: fibres produced from metals, which may be alone or in conjunction with other substances.
These metal filaments were made by beating soft metals and alloys, such as gold, silver, copper and bronze, into thin sheets, and then cutting the sheets into narrow ribbon-like filaments. The filaments were used entirely for decorative purposes, providing a glitter and sparkle that could not be achieved by other means.
As textile fibres, these metal filaments had inherent short comings which restricted their use. They were expensive to produce; they tended to be inflexible and stiff, and the ribbon-like cross-section provided cutting edges that made for a harsh, rough handle; they were troublesome to knit or weave, and they had only a limited resistance to abrasion. Apart from gold, the metals would tend to tarnish, the sparkle being dimmed with the passage of time.
Despite these shortcomings, the metallic ribbon-filament has remained in use for decorative purposes right up to the present day. The development of modern techniques of surface-protection has brought cheaper metals into use; aluminium foil, for example, may be anodized and dyed before being slit into filaments which are colourful and corrosion-resistant.
Ribbon-filaments are now manufactured in considerable quantity, e.g. as tinsel, but they remain an essentially decorative material. The filaments are weak and inextensible, and are easily broken during wear; they lack the flexibility that is essential in a genuine textile fibre.
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.
Metallic fibres of this type are now widely used in the textile industry, and are produced in a range of colours and forms by many manufacturers. They remain, however, essentially decorative materials and their applications are restricted to this type of use.
Metal-foil and metal-coated yarns are characterised by a flat ribbon-shape with knife-slit edges. Metallic fibres of this type are now widely used in the textile industry and are popularly known as “Lurex” yarn (Trade name).
The main constructions of metallic yarns in order of commercial importance are as follows:
i) Mono ply yarns made from polyester film of 12 or 24 um thickness, metallised and coated both sides either with dear or coloured lacquer (Lurex C 50 and C 100) or with heat and chemical resistant resin-lacquer (Lurex-TE and TE 100). Lurex TE 50 and TE 100 are non-tarnishing and have greatly enhanced resistance to scouring and dyeing treatments of suppleness, brilliance, and yield.
ii) Laminated yarns based on one layer of aluminium foil sandwiched between two layers of 12 um thick polyester film using clear or coloured adhesives (Lurex MF 150). This yarn has higher strength and abrasion resistance.
iii) Mono ply yarns made from 12 um polyester film (transparent - Lurex N 50) or treated with a surface dispersion to give a rainbow effect (Lurex N 50 Irise).
iv) Lurex yarn types C 50, N 50 (Transparent and Irise), and TE 50 can also be obtained supported with two ends of either 17 dtex or 33 dtex monofil nylon. Metallic yarns are usually described in terms of the nominal thickness of the composite film(s) and not the overall thickness of the yarns; the thickness of the resin-lacquer coating or adhesive layer is ignored.
Chemical nature:
The modern and cheap metallic yarn consist of filaments of aluminium covered with plastics: two kinds of plastics are mainly used for the covering. The first and most common is cellulose acetate-butyrate and the second and better is Mylar, DuPont’s polyester film which is chemically similar to Dacron and Terylene. The mixed ester of cellulose with acetic and butyric acids is used more popularly than cellulose acetate, mainly because it has a lower melting point and is more easily worked.
Lurex MM
Lurex MM is different from other varieties of Lurex which consist of a sandwich of aluminium between two films of cellulose acetate-butyrate or Mylar. Lurex MM has a basis of metallised Mylar produced by the vacuum deposition of aluminium on Mylar film. A layer of metallised Mylar is either, (a) bonded to one layer of clear Mylar or (b) sandwiched and bonded to two layers of clear Mylar.
Colour is introduced with the adhesive. The important difference is that the metallic layer in Lurex MM consists of discrete particles and not a continuous ribbon. This construction gives Lurex MM particular softness and thinness, and it affects some other properties, too.
Width and yield:
The ribbon-like shape of metallic yarns makes width an important factor and all Lurex designations bear a width reference. The amount of yarn cover and metallic lustre of a fabric depends upon the width. Lurex is slit to seven standard widths: 1/128, 1/100, 1/80, 1/64, 1/50, 1/32 and 1/16 inch. The 1/64 inch width is established as standard for weaving and knitting yarn. The various types and widths of metallic yarns are not designated by any standard textile yarn numbering system. Yields are in yards per pound.
Gauge:
Metallic yarns are described by width and by gauge. The gauge is the thickness in one hundred thousandths of an inch of the two layers that form the Lurex sandwich. The gauge figure does not indicate total yarn thickness because it does not take into account the adhesive, pigment or the aluminium layer. For e.g., 260 Butyrate Lurex consists of two layers of 0. inch cellulose acetate-butyrate with a inch aluminium foil and adhesives between its total thickness is 0.003 2 inch, indicating that the two layers of adhesives must each be about 0. inch. A 260 gauge 1/64 inch yarn yields about 10,500 yards per lb. corresponding roughly to about 430 denier, 1 gauge = 0. inch.
Supported Lurex:
When additional strength and/or special effects are desired, Lurex is available in combined form. Most combining yarns are continuous filament yarns: silk, nylon, fortisan, cotton and rayon are commonly used. Combining is usually done on a hollow spindle twister and is carried out in such a way that the metallic yarn remains flat and the supporting yarn wraps around it. The number of turns per inch in the support yarn can vary but usually number 6.
a) All properties are based on 1/64 inch width yarn gold and silver only.
b) Reflectance results are reported from photo volt reflectometer with green filter against an ASTM standard measuring 89.9%.
c) Some ‘whitening’ can occur on Lurex at boil. This is due to a mechanical pick up of water by the bonding adhesive or protective film and may be cleared by drying.
d) Flammability is evaluated on fabrics. Figures reported are typical for Lurex provided that the accompanying fibres and/or finishes do not influence the behavior of Lurex
New developments:
a) Multi-Functional Textiles
b) Sensing yarn, woven/knitted into garments.
c) Intelligent textile applications.
d) Heatable textiles as the heating element.
e) Conductive seam ribbons for Clean room garments.
f) Stimulation electrodes knitted into garments.
g) Weavable /knittable lead wires.
h) Heatable textiles.
i) EMI Shielding wall-coverings and other textile structures.
METAL FIBRE PROPERTIES
Metal Fiber Fineness
Due to its history as a wire drawn product and its abnormally high specific gravity, metal fiber sizes are typically described in terms of their actual diameter in microns as opposed to their linear weight in denier. As an illustration, a single human hair is 70 micron in diameter, and the current working range of bundle drawn stainless steel fibers is from 1- micron diameter to 100-micron diameter. Most textile applications utilize fibers in the range of 8 to 14 microns. As a way of comparison with polyester, a 12-micron metal fiber has the same diameter as a 1.4 denier polyester fibre.
(a) Electrical Conductivity / Electro-Magnetic Shielding
Certainly, the most distinguishing property of metal fibers is its electrical conductivity. When compared on a sq.cm basis, metal fibers can be classified as true conductors. Carbon fibers and anti-static finishes, on the other hand, are electrically classified as Semi-conductors. These differences can be significant in anti-static applications where atmospheric humidity is low and washing durability is an issue. Tests have been run on fabrics with a grid of stainless steel spun yarns where the same anti-static behavior is maintained after more than 200 wash cycles. In Europe it is reported that stainless steel is the only fiber type to consistently exceed EN after washings.
This high electrical conductivity also leads to good EMI shielding characteristics. Stainless steel fibers have long been utilized as an additive to plastic casings as a way to shield internal components from electromagnetic radiation. As concerns around EMI shielding grow, these conductive plastic applications have expanded a variety of textile applications for metal fibers. Garments, seals, gaskets and wall-coverings are all commercial application areas for shielding fabrics. There is even ongoing research into the possible therapeutic value of such fabrics for various medical treatments.
(B) Heat Resistance and Strength:
Since the early ’s a growing market segment for solid metal fibers has developed in the area of industrial, heat-resistant textiles. There exist many industrial environments that operate above the long-term working temperature of fiber glass and aramid fibers. This is especially true in glass forming processes where temperatures can range from 450 to C. In this particular application, there are other fibers that can withstand these temperatures from decomposition or melting standpoint, but they experience such a significant loss in strength or flexibility, that their resistance to mechanical load dramatically affects the fabric life.
Yet another important attribute to metal fibers is the ability of certain metals to behave in a chemically inert way, regardless of the environment that they are exposed to.
MANUFACTURING BRAND
Metallic yarn of the type discussed here is manufactured by American and French firms under different trade names. Some of these are:-
Properties:
i) Chemical resistance:
Metallic yarns, although protected at the top and bottom of their flat sides, are vulnerable at their cut sides. However, as the area exposed is small, tarnishing due to atmospheric exposure is negligible. Chemical attack is serious only if the chemical is one that dissolves aluminium. Any of the Lurex yarns, if immersed in caustic soda, loses metal due to the aluminium dissolving in caustic soda through the cut side of the yarn. Lurex MM is unaffected by 2% hydrochloric acid at 99°C for 2 hours whereas Lurex MF loses metal.
ii) Strength:
Strength of the acetate - butyrate Lurex yarn is not very high, but is sufficient to enable it to be used as warp or weft unsupported. The Mylar coated yams are much stronger because of the strength of the polyester film. They can be used for weaving and knitting.
iii) Heat:
The acetate-butyrate-coated metallic yarns can be washed at temperatures as high as 70°C, otherwise delamination occurs at higher temperatures. Mylar coated yarns can be washed at boil and are safe upto 145°C.
Identification:
The following procedure will identify the three standard types of Lurex yarn:
1. Burn yarn sample - butyrate Lurex yarn has a rancid odour.
2. Immerse in isopropyl alcohol - butyrate Lurex (film portion) will dissolve, Lurex MM and Lurex MF are insoluble.
3. Stretch yarn sample - Lurex MM and Lurex MF exhibit a stretch of 120-150%, butyrate Lurex will stretch about 20-30%. The aluminium in Lurex MF fractures (separates) on stretching, the aluminium in Lurex MM does not fracture on stretching.
SUMMARY:
Constantly being designed with new and multiple functionality, it is an exciting time to be a part of the metal fibre industry. Metal fibres can most assuredly help to take textiles into areas they have never been before.
About the Author:
Anita Desai is working as a Senior Lecturer at the Sarvajanik College of Engineering & Technology since June . She is a B.Tech and an M.Tech from the Government S.K.S.J.T. Institute, Bangalore. She is currently pursuing her Ph.D. from the Central Silk Technological Research Institute, Central Silk Board, Ministry of Textiles, Government of India, Bangalore.
She has to her credit over 30 research and review publications and presentations at both, the national and international level. Her biographical profile has been included in the premier edition of Marquis Who’s Who in Asia – . She can be contacted on:
REFERENCE:
1. Handbook of Textile Fibres - Man-made Fibres, J.Gordon Cook, Merrow Pub.Co., .
2. Identification of Textile Materials, Seventh Edition, The Textile ln Manchester, .
3. Man-Made Fibres, R.W.Moncrief, Newnes Butterworths, London, .
4. Encyclopaedia of Textiles, Prentice-Hall Inc.,USA, .
5. Man-Made Textile Encyclopedia, Interscience Publishers Inc., New York, .
6. Knitting International, June , P. 108-113.
7. Coated textiles principles and application , A.K.Sen, P. 192-201.
8. MANTRA Bulletin, October , P. 1-6.
9. MANTRA Bulletin, November , P. 8-11.
10.Chemical fiber International,Volume 40,November , P. 59-61.
11.Sabit Adanur, Wellington Sears, Handbook of Industrial textile,. P 462-463.
12. www.lurex.com
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Modern metallic fibres of the multi-component type are based largely on aluminium, which provides sparkle, and glitter at fraction of the cost of the early types of decorative fibre based for example, on gold.
The aluminium in these fibres is in the form of a narrow ribbon-filament of either (a) metal foil, or (b) a plastic film which has been vacuum-plated with vaporized aluminium. This is coated with a layer or layers of plastic film. distort
In these composite structures, the metal is protected from corrosive influences of its environment, and from mechanical damage. Multicomponent metallic fibres have achieved great popularity as decorative fibres and are an in facet of the modern textile industry.
TYPES OF METALLIC (M.C.) FIBRE
Metallic (m.c.) fibres may be made in almost infinite variety by using different metals and plastics in their manufacture. Aluminium is, however, the metal most commonly selected, and it is sandwiched between cellulose acetate butyrate, cellophane (cellulose) or polyester films.
The following are the types of yarn commonly produced:
(1)Acetate Butyrate, Aluminium Foil: A continuous flat monofilament composed of aluminium foil laminated on both reflective surfaces with cellulose acetate butyrate film.
(2) Cellophane Aluminium Foil: A continuous flat monofilament composed of aluminium foil laminated on both reflective surfaces with Cellophane film.
(3)Polyester, Aluminium Foil: A continuous flat monofilament composed of Aluminium foil laminated on both reflective surfaces with polyester film.
(4) Polyester, Aluminum Metallized Polyester: A continuous flat monofilament composed of aluminium metallized polyester laminated on its metallized surface or surfaces with polyester film.
(5) Polyester, Aluminium Metallized, Non-Laminated: A continuous, flat monofilament composed of a single layer of aluminium metallized polyester protected on its metallized surface.
The acetate butyrate types of metallic fibre are best used for applications which are not subjected to wet processing of other than very mild forms. Polyester types will withstand wet treatments or dry-heat operations as commonly used with most man made fibres, but reference should be made to manufacturer’s recommendations regarding time, pH and temperature conditions.
NOMENCLATURE AND TERMINOLOGY
In the U.S., the former Metallic Yarns Institute established minimum quality standards for metallic (m.c.) yarns for textile purposes, and prescribed a standard system of designation and terms of reference for these yarns.
The following definition of a metallic yarn was established by the Institute, and in general it is still in common use:
Metallic Yarn: A continuous flat monofilament produced by a combination of plastic film and metallic component so that the metallic component is protected.
Terminology
Metallic yarns are designated by a group of three symbols, each separated by a hyphen, setting forth the two dimensions of width, and gauge or thickness, and generic type.
1. Width. The width of the yarn is expressed as the fraction of an inch to which the yarn has been cut, viz., 1/32, 1/64, etc.
2. Gauge (or Thickness). The thickness or gauge of the yarn is expressed as the sum of the thickness of the plastic film and metallic component in hundred-thousand of an inch, as a whole number, viz., 35, 50, 150, 200, etc.
3. Generic Type. The type of the yarn is expressed on the basis of two components of the laminate - the generic name of the plastic film and the metal.
The components are separated by a comma, viz., Polyester, Foil.
Example: A Polyester/Aluminium Foil Yarn, 1/64 inch wide and 150/100,000 inch thick, is expressed in the industry as:
A manufacturer’s trade name or mark may accompany, but where utilized, either alone or in combination, the above must be separately stated or referred to.
STRUCTURE AND PROPERTIES
The properties of a metallic (m.c.) fibre depend upon the nature of the plastic film used in its production, and of the metal used as the centre of the sandwich.
In general, the fibres behave in a manner similar to man-made fibres spun from polymer on which the plastic film is based. Acetate butyrate metallic filaments, for example, have a resemblance to acetate fibres; polyester type metallic filaments are similar to polyester fibres in their general characteristics.
The nature of the aluminium layer inside the sandwich affects the properties of the metallic filament to a significant extent. In Types 1, 2 and 3, the aluminium is a continuous layer of foil; in Types 4 and 5, on the other hand, it is in the form of discrete particles which have been deposited on a layer of plastic film. The discontinuous layer of the latter type results in a finer, softer and more pliable filament which differ in many respects from those of the foil-type metallic fibres as indicated below. The figures quoted refer to specific metallic fibres of the various basic types, but there is considerable variation in properties between fibres of the same type.
Fine Structure and Appearance:
Metallic (m.c.) 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:
Acetate Butyrate, foil: 2.6 cN/tex (0.3 g/den).
Polyester, foil: 6.2 cN/tex (0.79 g/den).
Polyester, metallized: 11.0 cN/tex (1.25 g/den).
Elongation:
Acetate Butyrate, foil: 30 percent.
Polyester, foil: 140 percent.
Polyester, metallized: 140 percent.
Elastic Recovery:
Acetate Butyrate, foil: 75 percent at 5 percent elongation.
Polyester, foil: 50 percent at 5 percent elongation.
Polyester, metallized: 100 percent at 5 percent elongation.
Flex Resistance:
Relative flex resistances of the main types are in the following ratios:
Acetate Butyrate, foil: 1
Polyester, foil: 18
Polyester, metallized: 70
Abrasion Resistance:
Acetate Butyrate, foil: fair.
Polyester, foil: good.
Polyester, metallized: excellent.
Effect of Moisture Regain:
Acetate Butyrate, foil: 0.1 per cent. Polyester, foil: 0.5 per cent.
Polyester, metallized: 0.25 per cent.
Thermal Properties:
Softening point: Acetate Butyrate, foil: 205°C.
Polyester: 232°C.
Effect of Age:
Nil.
Effect of Sunlight:
Some loss of strength on prolonged exposure.
Chemical Properties:
Acids
Generally good resistance.
Alkalis
Acetate Butyrate: good resistance to weak alkalis; degraded by strong alkalis.
Polyester: these also show similar characteristics. Metal foil types are more resistant.
General
Acetate Butyrate: Similar to acetate yarn. Not affected by sea water, chlorinated water, or perspiration. Generally resistant to bleaches, but sensitive to caustic soda used in peroxide bleaching. Also sensitive to copper sulphate and sodium carbonate at high temperatures.
Polyester: Generally good resistance.
Effect of Organic Solvents
Acetate Butyrate: Attacked by acetone, ether, chloroform, methyl alcohol, tetrachloroethane. Not attacked by benzene, carbon tetrachloride, ethyl alcohol, perchloroethylene, trichloro ethylene.
Polyester: Attacked by acetone, benzene, chloroform, tetra chloroethane, trichioroethylene. Not attacked by carbon tetra chloro ethyl alcohol, methyl alcohol, perchloroethylene, white spirit.
Insects
Not attacked.
Micro-organisms
Not attacked.
Electrical Properties
Metallic (m.c.) fibres conduct electricity - the metallized types having a lower conductivity than the foil types.
METALLIZED (M.C.) FIBRES IN USE
General Characteristics
Appearance:
Metallic (m c) yarns are used in the industry almost entirely as decorative materials. They provide a metallic, g1itter and sparkle that cannot be obtained in other ways. The aluminium foil that provides the glitter in a modern metallic yarn is protected from corrosive materials of its environment by the plastic film in which it is enclosed. It remains untarnished through long periods of wear, and polyester types will withstand repeated launderings without losing their sparkle. Metallic yarns are not affected by sea water or by the chlorinated water of swimming pools and are widely used in modern swimwear.
The dyestuffs used in colouring metallic fibres are usually fast to light and the colour remains bright to match the sparkle from the aluminium foil.
Mechanical Properties:
As metallic (m.c.) yarns are used primarily for decorative purposes, they do not as a rule contribute significantly to the strength of fabrics or garments. Nevertheless they may be used as weft or warp yarns, and are strong enough to withstand the weaving, and knitting operations. If necessary the metallic yarns are combined with support yarns, such as nylon. The plastic film of the metallic yarn is flexible, and the yarns are extensible to a degree that depends upon the type.
Chemical Properties:
Aluminium will corrode and tarnish in air, and in contact with seawater, but in metallic fibres it is protected so effectively that it retains its glitter for long periods. The chemical resistance of a metallic filament is, in general, the chemical resistance of the plastic film. In the case of polyester films, this is outstanding.
If metallic fibres are held in contact with strong alkaline solutions for prolonged periods, the aluminium may be attacked at the unprotected edges of the ribbon. Metallic fibres should not, therefore, be subjected to alkaline reagents of significant strength.
Organic solvents, too, may attack the laminate adhesive or lacquer coating; great care should be taken in dry cleaning to ensure that an appropriate type of solvent is used.
Thermal Properties:
The plastic films in metallic fibres are thermoplastic, and will soften at elevated temperatures. Delamination may occur if the fibres are heated, and acetate types in particular should be processed only at low temperatures.
The plastic film may be permanently embossed by heat and pressure, and special effects may be introduced into the fibres in this way.
Washing:
Acetate butyrate types may be hand washed in lukewarm water with a mild soap. If processed as silks or woollens, they may be safely washed in home or commercial laundry equipment.
Polyester types may be washed at temperatures up to 70°C. Dimensional stability is good and crease resistance is fair.
Most coated polyester yarns will not withstand treatments other than those used for silks or woollens.
Drying:
Acetate butyrate types must be dried at as low a temperature as possible. Polyester types may be dried at higher temperatures as used for polyester fibres, with the exception of most coated types.
Ironing:
Acetate types should be ironed at temperatures no higher than 105°C. Polyester types may be ironed at temperatures up to 130°C. Rayon setting is preferable for both types.
Dry Cleaning:
Metallic fibres may be dry cleaned without difficulty, provided care is taken in the selection of solvent to suit the type of fibre.
End uses: Metallic (m.c.) yarns are used for decorative purposes in almost every field of textile application. Important end-uses include women’s dress goods, upholstery, curtains, table linens, swimwear, packaging, footwear, car upholstery, suits and hats.
MANUFACTURING PROCESS OF METALLIC YARN
Extrusion And Metal Coating
The incorporation of metal into textiles dates back to the Roman era, when they were mainly used for decorative purposes. The tinsel yarns used to add glitter to fabrics were made by flattening thin wire or sheets of noble metals like gold or silver. By the s, aluminium foil strips coated on both sides by cellulose acetate-butyrate, to prevent them from tarnishing, were used. The yarn could be colored by anodizing. All of these yarns had poor compatibility with the more flexible and extensible textile yarns. After the development of vapor-deposited aluminized polyester in the s, 1 mm wide strips of these films were used as yarns, with much improved flexibility.
The American made yarns can best be described as a ham sandwich. The metal foil, metallised pigment and colouring matter might be considered the meat. The meat is placed between two layers of transparent plastic film. The adhesive used between layers to bind all the layers together into one film might be compared to the butter that holds the bread and meat together.
The raw material is a roll of aluminium foil of 0. 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 90-95°C, and a sheet of cellulose acetate-butyrate transparent film is laminated to each side of the foil by passing through squeeze rollers at a pressure of lb/in (Fig. I). The laminated material is then slit into filaments of the required width, the most popular width being 1/64 inch although other sizes from 118 inch to 1/120 inch are also made.
The nature of the adhesive that is used is important and not usually disclosed. Gold is the most important colour which is produced by the addition of an orange-yellow dyestuff to the adhesive. Silver is simply the colour of the aluminium itself. Other colours such as bronze, peacock blue and red are obtained by using the suitable pigment. Multi-coloured efects, e.g. red and green alternating irregularly along the length of the yarn, are obtained by pre-printing the plastic film and laminating in the usual way.
METHODS OF METAL COATING
A. Metal coating with a binder:
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. The coating method may be conventional knife or roller coating. The adhesion, flex, and chemical resistance of the coated fabric depend on the type of polymer used, but they are not highly reflective.
B. Vacuum 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 ºC. 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. Continuous metal film coatings can be formed on just about any surface, film, fiber or fabric with thickness ranging from micron to millimeter. Several metals can be vacuum evaporated, most common being aluminium, copper, silver, and gold. Difficulty arises in the case of metals, which sublime rather than melt and boil.
C. 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 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. The bombardment of the energetic ion on the target results in a transfer of momentum. If the kinetic energy of the striking ion is higher than the binding energy of the surface atoms of the material of the target, atoms are dislodged or sputtered from its surface by a cascade of collisions. Typically, the threshold kinetic energy of the ions should be between 10-30 EV for sputtering from the surface. Some of the ions striking the target surface generate secondary electrons. These secondary electrons produce additional ions, and the discharge is sustained. Considerable heat is generated during 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. The relative rates of deposition depend on sputter yield, which is the number of atoms ejected per incident ion. The sputtering yield varies with the target material and increases with the energy of the incident ion. The method is applicable to a wide range of materials and gives more uniform coating with better adhesion than simple vapour deposition. The process is however, more expensive, and the rate of deposition is lower (30 m/min)
D. Electroless plating:
It is a process to deposit metal film on a surface, without the use of electrical energy. Unlike electroplating where externally supplied electrons act as reducing agent, in electrodes plating, metallic coatings are formed as a result of chemical reaction between a reducing agent and metal ions present in solution. In order to localize the metal deposition on a particular surface, rather than in the bulk of the solution, it is necessary that the surface should act as a catalyst. The activation energy of the catalytic route is lower than the homogeneous reaction 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. Compared to electroplating, electroless coating has the following advantages:
(l) Nonconducting materials can be metallized
(2) The coating is uniform.
(3) The process is simple and does not require electrical energy
Electroless coating is, however, more expensive.
For successful deposition of coatings, only autocatalytic reduction reactions can be used. As such, the numbers of metals that can be coated are not many. Some of the common reducing agents are sodium hypophosphite, formaldehyde, hydrazine, and organo boron compounds. Each combination of metal and reducing agent requires a specific pH range and bath formulation. The coating thickness varies between 0.01 um to 1 mm.
A typical plating solution consists of
a. Metal salt
b. Reducing agent
c. Complexing agents, required in alkaline pH and also to enhance the autocatalytic process
d. Buffers
e. Stabilizers, which retard the reaction in the bulk and promote autocatalytic process.
Some important metal coatings are discussed below:
a. Copper:
The most suitable reducing agent is formaldehyde. The autocatalytic reaction proceeds in alkaline pH (11-14). The commonly used complexing agents are EDTA, tartarate, etc.
b. Nickel:
Sodium hypophosphite is the most popular reducing agent for nickel. The autocatalytic reaction occurs in both acidic and alkaline pH. Sodium citrate is used as buffer and complexing agent. The coating obtained by sodium phosphite also contains phosphorus (2-15%).
c. Silver:
The plating solution consists of ammoniacal silver nitrate with formaldehyde, hydrazine, and glucose as reducing agents. Because the autocatalytic activity of silver is low, thick deposits cannot be obtained. Electroless plating of textiles is being adapted for different functional applications.
SLITTING OPERATION
The slitting operation involves the two main types of cutting by which a metallised polyester film is converted into the tape filaments:
(a) Rough Slitter
(b) Micro Slitter
The metallized polyester film supplied to the slitting operation has the following parameters:
(1) Thickness: Normally ranges between 12 to 25 Microns.
(2) Length: Sheet in the form of roll having the length from to 10,000 meters.
(3) Width: The width of the sheet ranges between 510mm to mm.
ROUGH SLITTER
his slitter cuts the large polyester sheet into Pancakes. The width of the each Pancake is 54mm. In addition side strips of 2mm are kept extra on each side. Thus the resultant width of the pancake is 58mm.
Cutters of different size are used for this operation, for example 0.2mm, 0.23mm, 0.25mm, 0.30mm, 0.376mm, etc. Pancakes are also in the form of rolls supplied to the Micro Slitter.
MICRO SLITTER
The Micro Slitter is a general name given to both slitter and winder for producing the yarn 0.15mm -1 mm wide.
In this operation Pancakes are converted into numbers of tape filaments. It has two main parts,
(a)Cutting Mechanism
(b) Winding Mechanism
Cutting of Pancakes and Winding of tape filaments are carried out simultaneously.
The cutting mechanism consists of two parallel shafts. On each shaft blades are mounted side by side such that the edge of one blade on one shaft slightly touches the edge of the blade mounted on the other shaft. The cutter is mounted on to the shaft with the help of Separator and Support Ring. The width of the tape filament decides the width of the cutter.
The winding mechanism consists of number of winding positions. The winder is driven by a separate motor. The traverse mechanism is also provided for obtaining the parallel wound package. The speed of the winder is 2.5% to 5% higher than that of the cutter.
COVERING MACHINE
Nowadays machines can produce a high quality of covering yarns for even 200, 300, denier of polyester yarn, cotton and even silk, which is applied to stocking, socks and particularly woven elastic fabrics.
The important characters of the machine are the balance and the alignment of spindles and guide rollers. It is well designed for flexibility and anti-wearing by using good quality of materials to each part of character. The specification of machine can be changed according to a pitch and number of spindles.
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