Technical textiles are textile material and products manufactured primarily for their performance and functional properties rather then aesthetic or decorative purpose. Aesthetic properties are not much important for the Technical Textiles. The performance and functional properties are in sense with the agri to aerospace application. Based on the end uses, fibre selection to the method of processing are the keys to new product development in the textile arena. Over all growth rates of Technical Textiles in the world are about 4.0%per annum but the apparel and home textiles are at the rate of 1.0%.
2.0 Classification of technical textiles
Technical textiles application cycle is shown in the figure 1,it gives a vivid picture on the divisions of the technical textiles, which is a self-explanatory. Some of the major divisions are discussed below.
2.1 Agro Textiles:
Textiles used in Agriculture is termed as agro textiles. The essential properties required are Strength, elongation, stiffness, porosity, bio-degradation, resistance to sunlight and resistance to toxic environment. The applications includes all activities concerned with the growth and harvesting of live products and foodstuffs, such as gardening and land scaping, agriculture, forestry, animal husbandry and in fences.
2.2 Conveyer belts:
For Industrial applications and in power transmission technical textiles are used in Conveyer belts. Carcass is a fabric inside the conveyor belt, which is responsible for the strength and stretch properties of the belt. This carcass is made with layers of woven fabrics bonded together. Skim an adhesive layer used between the plies and carcass to enhance the bonding, which is made up of open weave fabric. High strength, shape retention, abrasion resistance and good UV resistance are required properties for carcass and skim.
2.3 Geo textiles:
Woven and Nonwoen textile materials used by the civil engineering industry to provide support, stability, separation and drainage at or below ground level. The application areas include civil engineering, earth and road construction, dam engineering, dump construction, soil sealing and in drainage systems. Strength, extension, durability, low moisture absorption, puncture resistance, thickness, good hydraulic properties and transmission properties, biological heat and chemical resistance are the essential properties for the Geo textiles.
2.4 Protective clothing:
Protection against heat, flame, water, and hazardous environment are obtained by suitable usage of the technical textiles with high performance fibres. Based in usage Chemical resistance, heat resistance, durability, moisture absorption, comfort, cut resistance and impact resistance properties are required.
The scopes of Mobiltech are plenty. Application areas include construction of automobiles, shipbuilding, aerospace, rail vehicles, motorcycles bikes, airbags, tyres. Each Car has to utilize at least 17 kgs of textile materials. Essential properties are good sound absorbency, UV resistance, strength retention, durability, formability, filtration efficiency, and abrasion resistance, bursting resistance and degradation resistance.
2.6 Buildtech:
Textile and composite materials used in the construction of buildings, dams, bridges, tunnels and roads. The applications are in form of membranes, lightweight solid constructions (awnings and canopies), civil and industrial engineering, temporary construction, interior construction, in and on earth, in water and traffic route construction. Glass, polypropylene and acrylic fibres are used to prevent cracking of the concrete, plastic and other building materials. Adhesive like epoxy resins also used in the textile reinforcement. An awning is an architectural projection that provides weather protection, is an identity or decorative and wholly supported by the building to which is attached. Canopy is also an architectural projection comprises of a rigid structure over which a covering is attached. Fabrics used for roofing needs some special quality like whether resistance, UV resistance .A range of Coated fabrics are used for roofing purpose. In Seol, Koria, Gieger engineers Inc. has engineered Teflon coated roof over a play ground with a capacity of 64000 seats stadium is one of the example for new technocrats vision.
2.7 Hometech:
Textile and composites used in the furniture, upholstery and interior furnishing, carpets, floor coverings. Depends on the environment and place, the selection of the fibre and fabric has to be made.
2.8 Medical textiles:
The applications are in health, hygiene and rescue services. It is commonly used as Sutures and bandages. The properties required are bio-degradability, fungal and microbial resistance and suitability to human body. Bio textiles is a term used in the medical textile applications, these are textile elements used in specific biological environments. This performance depends on the interaction with the cells and biological fluids in terms of bio-stability and biocompatibility. These bio textiles classified in to following main classes.
1.Grafts, 2.Implants, 3.Prostheses, 4.Sutures& wound dressings and 5.Slow release drug delivery systems.
Grafts are the structure placed inside the body to correct the damages or malformations. Grafts are made from variety of materials ranging from silk protein to modern synthetic polymers. Examples of grafts are vascular grafts and stent grafts. Implants are the textile structures used for tissue reconstructions and growth. It is used in hernia repair and pelvic injury repair this are made from woven, knitted and braided structures. Prostheses used to replace damaged body parts such as teeth, limbs or eyes. Sutures and wound dressing used for a very long times .it passed through wide revolutionary stage from silk to synthetic fibres. Slow drug delivery systems are gradually gaining importance over the conventional dosing systems. Hollow fibres with nano particle based system used for the delivery of drug to a specific part of a body to prevent over dosage.
3.0 Progress of Technical textiles in Global Market
Present market opportunities and in free quota regime, the prospects for the technical textiles increasing to cater the needs of the requirements. Table 1 shows %age of technical textile materials in the world during 2005. Out of which Filter clothing, furniture, hygiene medicals, building & construction materials growth rates are very significant.
With keep in mind the over all growth rate of technical textiles (4.0%).There are plenty of opportunity for new entrepreneurs to step in to this market to gain their share.
With keep in mind the over all growth rate of technical textiles (4.0%).There are plenty of opportunity for new entrepreneurs to step in to this market to gain their share.
3.1 Growth of textile material
In general the technical textiles are made in to fabric form from conventional weaving to composite layers. It is interesting to note down that the Nonwoen and composite production methods has considerable market share, which is shown in the Table 2. This is due to relative high production rates and suitability to the end uses.
4.0 Fibres for Technical Textiles
The usages of fibres in the technical textile area are not only the high functional fibres alone, but also the natural (due to bio-degradability and compatibility) and common man-made fibres occupied considerable share, which is shown in table 3.
4.1 Domestic fibres:
Cotton, silk polyester, polyamide are used in medical applications. PP and Polyester are used in geo textiles and dry/liquid filtration due to its compatibility. Jute and coir (Ligno-Cellulosic) used in biodegradable products and in packaging industry. Nylon is been used in the anti- ballistic, Cord, protection and filtration applications.
4.2 High functional fibres:
High functional fibres are having high technical properties based on the end uses. The properties are high tensile strength, high modulus, good chemical resistance, high dimensional stability, cut resistance and low thermal shrinkage.
4.2.1 Kevlar:
It is Para-Aramide fibre based on terephthalic acid and p-phynelene diamine. It is highly oriented and high crystalline (90%) fibre. It is having good fibre tenacity (about 25gfpd),and high thermal resistance and low thermal shrinkage. This fibre is used for anti ballistic apparel, helmet, industrial protective clothing, gloves, in hot gas filtration, structural composite for air crafts, optical fibre cable sheath, high pressure and automatic hoses, sail cloths and as special tyres cords.
4.2.2 Carbon:
It is produced by extruding precursor of acrylics, pitch or specially purified viscose rayon in to filaments, then carbonized to get carbon. After carbonization the fibre processing is a difficult one, hence the precursor fibre may be converted in to fabric, there after it is carbonized to get the required product. Final carbon content could be around 92% by weight. High stiffness to weight ratio (for aero space structure applications), softness, high thermal resistance are the special properties of the carbon fibres.
4.2.3 P-phenylene-2.6-benzobisoxazole (PBO):
It is having very high strength (42gfpd) and tensile modulus of 1300-2000gfpd, which is greater then the any known fibre. Good flame resistance and heat resistance (68%-LOI) and high decomposition temperature (600a C). It is used in the anti ballistic vests, protective apparel for fire fighters, lightweight armor for vehicle and for personal.
4.2.4 Ultra high molecular weight poly-ethylene (UHMWPE):
It is having high molecular weight (10 6), produced by Gel spinning technique. It is having Low (0.97) specific gravity, high Chemical & abrasion resistances and high strength comparable to Kevlar. It is used in anti ballistic protection, floatable ropes, and nets.
4.2.5 Glass:
t is an inorganic and isotropic fibre. High strength, chemical resistance, electrical, resilience, flame resistances and low elongation at break are the salient features of glass. It has a high specific gravity (2.5-2.7), it is used in industrial applications including fire proof, filtration, insulation and in reinforcement.
4.2.6 Alumina silica:
Ceramic fibres reported with a very high temperature resistance, used for furnace insulation and hot air filtration.
4.2.7 Melamine:
These fibres having 50% by weight of melamine cross-linked polymer (specific gravity about 1.44).It is having outstanding heat blocking properties with low thermal conductivity and good elongation at break (about 18%).
4.2.8 Basalt:
It is produced from the basaltoid rocks. Basalt derived from minerals of Plagiocene and pyroxene. This is used for the production of high temperature resistance and chemical resistance products.
4.2.9 Noviloid:
This fibre produced with 65% of cross linked novolac, it posses excellent flame retardant properties and recommended to use up to 150aC in the presence of air and in absence of air it can be used up to 250aC . This can with stand up to 1000aC in short period exposure to flame.
4.2.10 Fiber composites for chemical protection:
Acetate, PET, PVC and ploy carbonate sheets used to get clear vision in face shield and goggles. Rubber, PVA, Teflon composite materials used in gloves as a protection layers. TYVAK (spun bonded Ploy ethylene) used in coats and jackets as barrier to chemicals.
5.0 Technical yarns:
Technical yarns are replacing the traditional usage of textiles in critical applications. The manufacturing of sewing threads, interlinings, and wadding and insulation materials with high functional fibres plays a critical role in medical and industrial application.
6.0 Electronics in Textiles:
The electronics may soon be integrated in to the textiles in all areas. These Interactive electronic textiles (IET) may find useful in many traditional, fashion and industrial textile applications in form of communication, entertainment, health and safety. A wearable computing is a new form of human computer interaction. This wearable computer is just more then a wristwatch or regular eye glasses. Prerequisites of wearable computers are constancy, augmentation and mediation. New developments of wearable computers are made with merging IC s seamlessly in fabric to develop fabric keyboards. Interactive touch voice and body heat activation are being developed. To develop more appealing wearable electronics, conductive materials are being used to transform traditional textiles and apparel products into light weight wireless wearable computing devices. Materials such as metallic, optical fibres, conductive threads, fabric coatings, and inks are being used to supply conductivity and create wire less textile circuitry. Additional components including input and out put devices, sensors and power supply are necessary to create IET. DETECT (registered trade mark), USA, has been developing single and multiple layer sensory fabrics. Piezoelectric materials, MEMS (Micro electro mechanical systems) used in sensors for receive and respond to stimuli enabling the electronic functions related to the user. The development of the market for electronics in textiles cannot be accurately mapped out. Of course, smart cloths are likely to reach the shops in and around two to three years. The price of the electronics as a whole should not exceed 10 to 20 percent of the total costs of the cloths for capturing good market. Research to support IET development is being conducted in many universities. Growing consumer interest in mobile, electronic devises will initiate the demand for IET products.
7.0 Intelligent Textiles
Textile products, which are, respond to the external stimuli for specific purpose are called Intelligent Textiles. These are classified as
7.1Textiles incorporating Phase change materials (PCM)
These are materials used in clothing as encapsulated form to change from its phase from solid to liquid and vice versa to maintain a comfortable body temperature in severe conditions. The energy stored or released by the phase change materials (eg. paraffin) depending on the activity of the wearer. This may be used in the car seat covers, gloves boots and hats. It is used to prevent the body from over heating or over cooling.
7.2 Textiles incorporating Shape memory polymers (SMP)
Shape memory materials are those, which can revert from the current shape to a previously held shape, usually due to the heat. These shape memory polymers poses different properties below and above its standard temperature. These materials are used in medical applications, for maintenance of body temperature.
7.3 Textiles incorporating chromic materials
Materials, which are changing color reversibly according to the external environment conditions. These are photo chromic and thermo chromic materials. Photo chromicsm is a chemical process in which a compound under goes a reversible changes between two states having separate absorption spectra. Thermo chromic system heat changes the color of chromophore. On removal of heat source the color reverses to its thermally more stable state. Photo chromic and thermo chromic materials are used for fashion and military clothing.
7.4 Textiles incorporating conductive materials.
The conductive fibres are of two types .
1. Electrical conductive fibres.
2. Optical conductive fibres.
The electrical conductive fibres integrate the latest wicking finishes with high metallic content in textiles that still retain the comfort required for clothing. With addition of nickel, metallic coatings of varying thickness, these fibres provide a versatile combination of physical and electrical properties for a verity of demanding applications, such as thousand-fold increase in thermal conductivity.
The optical conductive fibres use per floro polymers, which are most transparent in the near infrared region. Conductive fibres used for the development of military clothing, motion capturing and in tracking of objects. These fibres can be woven in to fabrics to form radiation shields, optical filters and bar codes.
8.0 Summary
The Technical Textiles development in the present period is seems to be aggressive and real benefits will be realized soon. The integration of the application of the textiles in and with other fields like chemical, electronics, medical and environment shows the path for progress.
9.0 References:
Hand book of Technical textiles, edited by A.R.Hrrocks and S.C.Annand, Textile Institute Publications-2000 edition.
Industrial Textiles, by Sabit Adanur, Wellington seris-1995 edition.
Textile terms and Definition, textiles institute publications 1994 edition.
Manufactured Fibre Technology, V.B.Guptha and V.K.Kothari, Chapman hall, London-1997edition.
www. technicaltextiles.com
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