Special Knitted Fabrics and Finishes Part-1
BGMEA University of Fashion Technology
Although ‘Technical textiles’ have attracted considerable attention, the use of fibers, yarns and fabrics or knitted fabrics for applications other than clothing and furnishing is not a new phenomenon. Nor is it exclusively linked to the emergence of modern artificial fibers and textiles. Natural fibers such as cotton, flax, jute and sisal have used for centuries(and still are used) in applications ranging from tents and tarpaulins to ropes, sailcloth, and sacking.
In some of the most developed markets, technical products already account for as much as 50% of all textile manufacturing activity and output. The technical textiles supply chain is a long and complex one, stretching from the manufacturers of polymers for technical fibers, coating and special membranes through to the converters and fabricators who incorporate technical textiles into finished products or use them as an essential part of their industrial operations.
There is continual erosion of the barriers between traditional definition of textiles and other ‘flexible engineering’ materials such as paper and plastics, films and membranes, metals, glass and ceramics. What most participants have in common are many of the basic textile skills of manipulating fibers, fabrics and finishing techniques as well as understanding of how all these interact and perform in different combinations and environments.
The definition of technical textiles adopted by the authoritative Textile Terms and Definitions, published by the Textile Institute, is ‘Textile materials and products manufactured primarily for their technical and performance properties rather than their aesthetic or decorative characteristics.’
Such a brief description clearly leaves considerable scope for interpretation especially when an increasing number of textile products are combining both performance and decorative properties and functions in equal measure. Examples are flame retardant furnishings and breathable leisurewear. Knitted fabrics are the third major class of fabric, after woven and nonwoven fabrics. Knitted fabrics widely used as undergarments specially bra or brassiere, panty, bikini etc.
TECHNICAL OR INDUSTRIAL TEXTILES: WHATS IN A NAME
The leading international trade exhibition for technical textiles , Techtextile (organized biennially since the late 1980 by Messe Frankfurt in Germany and also in Osaka, Japan), defines 12 main application areas-
- Agrotech: agriculture, aquaculture, horticulture and forestry
- Buildtech: building and construction
- Clothtech: technical components of footwear and clothing
- Geotech: geotextiles and civil engineering
- Hometech: technical components of furniture, household textiles and floor coverings
- Indutech: filtration, conveying, cleaning and other industrial uses
- Medtech: hygiene and medical
- Mobiltech: automobiles, shipping, railways and aerospace
- Oekotech: environmental protection
- Packtech: packing
- Protech: personal and property protection
- Sporttech: sport and leisure
SCOPE OF FLEXIBLE ENGINEERING MATERIALS
DEVELOPMENT IN THE FIBER MATERIALS: NATURAL FIBERS
- Until early in the 20th century, the major fibres available for technical and industrial use were cotton and various coarser vegetable fibres such as flax, jute and sisal. They typically used to manufacture heavy canvas-type products, ropes and twines, and were characterized by relatively heavy weight, limited resistance to water and microbial/fungal attack as well as poor flame retardency.
- Jute fabrics were widely used for sacking, furniture and carpet manufacturing, roofing felts, twine and a host of other applications.
- Wool prove far less versatile and economic for most industrial applications although it is still valued for its insulating and flame retardency properties and finds use in several high temperature and protective clothing applications.
- Silk is an even more exotic fibre, rarely used in technical applications other than for highly specialized uses such as surgical thread.
The first commercially available synthetic fibre, viscose rayon, was developed around 1910 and by the 1920 had made its mark as reinforcement material for tyres and subsequently, other mechanical rubber goods such as drive belts, conveyors and hoses.
POLYAMIDE AND POLYESTER
Polyamide (nylon) fiber, first introduced in 1939, provided high strength and abrasion resistance, good elasticity and uniformity as well as resistance to moisture. Its excellent energy absorbing properties proved invaluable in a range of end-uses from climbing ropes to parachute fabrics and spinnaker sails. Polyamide reinforced tyres are still used much more extensively in developing countries.
The contrasts to Western Europe where average road speeds are much greater and the heat-resistant properties of viscose are still valued.
The low cost and easy processability of this fiber, combined with its low density and good abrasion and moisture-resistant properties, have allowed its rapid introduction into a range of application such as sacks, bags and packaging, carpet backings and furniture lining as well as ropes and netting.
Properties of polyolefines such as their poor temperature resistance and complete hydrophobicity have been turned to advantage in nonwovens.
It can also play in hygiene applications such as coverstock for diapers (nappies).
HIGH PERFORMANCE FIBERS
First and foremost these are the aramids, both the highly temperature-resistant meta aramids (widely used in protective clothing and similar applications) and the high strength and modulus para-aramids (used in a host of applications ranging from bulletproof vests to reinforcement of tyres, hoses, friction materials, ropes and advanced composites)
GLASS & CERAMICS
Glass has, for many years, been one of the most underrated technical ﬁbres. Used for many years as a cheap insulating material as well as a reinforcement for relatively low performance plastics (ﬁbre glass) and (especially in the USA) rooﬁng materials, glass is increasingly being recognised as a sophisticated engineering material with excellent ﬁre and heat-resistant properties. It is now widely used in a variety of higher performance composite applications, including sealing materials and rubber reinforcement, as well as ﬁltration, protective clothing and packaging.