Types of Metallic Fibres and Their Production

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 3000 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.