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Ultrasound Energy:

Ultrasound energy is sound waves with frequencies above 20,000 oscillations per second, which is above the upper limit of human hearing.

Ultrasound energy generation

The ultrasonic waves can be generated by variety of ways. Mostly it is produced by piezo-electric and magnatostrictive transducers.

Mechanisms of Ultrasound Energy:

1. Increasing swelling of fiber in water.
2. Reducing glass transition (Tg) temperature of the fiber.
3. Reduce the size of the dye particles. It helps to enhance the transport of the dye to the fiber.

Applications of Ultrasound Energy:

1. It degraded starch followed by ultrasonic desizing could lead to considerably energy saving as compared to conventional starch sizing and desizing.
2. The scouring of wool in neutral and very light alkaline bath reduces the fiber damage and enhance rate of processing.
3. It is more beneficial to the application of water insoluble dyes to the hydrophobic fibers.
4. Among the textile fibers, polyester is structurally compact fiber with a high level of crystallinity and without recognized dye sites.
5. Ultrasonic waves accelerate the rate of diffusion of the disperse dye inside the polyester fiber.

Benefits of Ultrasound Energy:

1. Energy savings by dyeing at lower temperatures and reduced processing times.
2. Environmental improvements by reduced consumption of auxiliary chemicals.
3. Increased color yields. 
4. Enzymatic treatments supplemented with ultrasonic energy resulted in shorter processing times, less consumption of expensive enzymes, less fiber damage, and better uniformity treatment to the fabric.

Abstract

Lyocell is a new generic name given to a cellulosic fiber which is produced under an environmentally friendly process by dissolving cellulose in the tertiary amine oxide N-methylmorpholine-N-oxide (NMMO). Lyocell fiber shows some key advantageous characteristics over other cellulosic fibers; for instance, a high dry and wet tenacity and high wet modulus. For the majority of the last century, commercial routes to regenerated cellulose fibers have scoped with the difficulties of making a good cellulose solution by using an easy to dissolve derivative (e.g. xanthane in the case of viscose rayon) or complex (e.g. cuprammonium rayon). For the purpose advanced cellulosic fibers are defined as those made from a process involving direct dissolution of cellulose. The first examples of such fibers have now been generically designed as lyocell fibers to distinguish them from rayon’s, and the first commercial lyocell fiber is Courtaulds’ Tencel.

This paper will consider all developments of fiber from manufacturing to chemical processing; also consider the key applications of the lyocell fiber, concentrating on its application in textile, apparel and nonwoven fabrics.

Introduction
Lyocell is the first in a new generation of cellulosic fibers made by a solvent spinning process. A major driving force to its development was the demand for a process that was environmentally responsible and utilized renewable resources as their raw materials. The first samples were produced in 1984and commercial production started in 1988. A wide range of attractive textile fabrics can be made from lyocell that are comfortable to wear and have good physical performance. This physical performance combined with its absorbency also makes lyocell ideal for nonwoven fabrics and papers. The cellulose fibers produced by direct dissolution have the generic name of Lyocell. Cellulose is one of the most abundant natural resources on earth, and there has been extensive research on the films, plastics, and fibers from this material. The history of cellulose fibers dates back to the 1860s, when the first rayon fibers were commercialized by Courtaulds. But the so-called rayon process includes toxic chemical treatments to block hydroxyl groups of cellulose to prepare a spinnable solution, mostly it causing an ecological problem. Many attempts have been made to invent new solvents to directly dissolve cellulose, and some successful results have been reported. Among these, N-methylmorpholine- N-oxide (NMMO) hydrate turned out to be the best solvent, leading to the commercial success of cellulose fibers under the trade name of Tencel by Courtaulds in 1994.

Figure: 1, Raw Materials for lyocell Fiber (Oak logs)

Other lyocell process includes Lenzing Lyocell. These processes are advantageous because they are environmentally benign, using nontoxic NMMO hydrates instead of toxic carbon disulfide, which can be almost totally recycled. The lyocell fiber has a highly crystalline structure in which crystalline domains are continuously dispersed along the fiber axis. This offers good wet strength as well as excellent dry strength, which makes lyocell water-washable. Further, it shrinks less when wetted by water and dried than other cellulose fibers such as cotton and viscose rayon. Recently, a new lyocell process, which has some characteristic, features similar to the Tencel process. The new process dissolves finely powdered cellulose in molten NMMO hydrate within 5 minutes by means of a pasting stage, which causes much less decomposition of cellulose. Further, this process can use NMMO hydrates with a hydration number (n) greater than 1 because it adopts a plasticating extruder. The value of n plays a significant role in the phase behavior of cellulose solutions. It also affects the physical properties of the fibers spun from the solution; Fig.2. show the Lyocell processes consume lower amounts of water, but a similar magnitude of energy.

Figure: 2 Ternary diagram showing the effect of temperature on the dissolution Cellulose in NMMO

The Properties of Lyocell
Comparisons of lyocell with viscose and other cellulosic in both laboratory and test markets proved that the fibers were sufficiently different to deserve separate marketing strategies. Table.1. shows various physical properties of lyocell with other fibers

Lyocell is:

• Stronger than any other cellulosic fibers, especially when wet
• Easy to process into yarns and fabrics alone or in blends
• Easy to blend (unique fiber presentation)
• Easy to spin to fine count yarns
• Very stable in washing and drying
• Thermally stable
• Easy to dye to deep vibrant colors
• Capable of taking the latest finishing techniques to give unique drape
• Comfortable to wear

Table 1: The comparison properties of lyocell with different cellulosic fibers

Property	Lyocell	Viscose	Cotton	Polyester (PET)
Dry Tenacity (cN/Tex)	38-42	22-26	20-24	55-60
Wet Tenacity (cN/Tex)	34-38	10-15	26-30	54-58
Dry Elongation (%)	14-16	20-25	7-9	25-30
Wet Elongation (%)	16-18	25-30	12-14	25-30

The Courtaulds’ Lyocell Process
The Courtaulds’ semi-commercial production system is illustrated in Fig.3. Dissolving grade wood pulp is mixed into a paste with NMMO and passes through a high-temperature dissolving unit to yield a clear viscous solution. This is filtered and spun into dilute NMMO, whereupon the cellulose fibers precipitate. These are washed and dried, and finally baled as staple or tow products as required by the market. The spin-bath and wash liquors are passed to solvent recovery systems which concentrate the NMMO to the level required for re-use in dissolution.

Figure: 3 Courtaulds’ Lyocell Process

Lyocell Conversion
Lyocell is similar in strength to polyester and stronger than cotton and all other man-made staple fiber cellulosic’s. It also has very high dry and wet modulus for cellulosic fiber in both the dry and wet states, the properties of lyocell fiber is shown in bellow the table. These properties allow customers great scope for making strong yarns in blend with virtually all the other commercially available staple fibers. They also lead to excellent efficiencies in converting these yarns to woven add knitted fabrics. All man-made cellulosic’s lost strength and modulus when wetted, but lyocell reduces by much less than others. This is important in determining how properties of the fabric are developed during dyeing and finishing.

Yarn Manufacturing
Once lyocell fiber has been produced, either as cut staple fiber or continuous tow, it will be converted to yarns and fabrics by a range of conventional textile processes. The most common way of using lyocell fiber is as cut staple, with 1.4 and 1.7 dtex fibers cut to 38 mm and converted into a spun yarn using machinery developed over many years for handling cotton fibers that are similar in dtex and length to lyocell. Lenzing lyocell is made by a wet-cut route and has different processing characteristics. The fiber can be processed on conventional machinery, usually requiring a few setting changes in order to optimize processing performance.

Thus lyocell will open very easily with little nep formation. In sliver and roving, the fibers pack together, giving high cohesion and therefore requiring high drafting forces. Lyocell yields very regular yarns with high tensile strength and few imperfections. Lyocell blends well with other fibers, including cotton, viscose, linen, wool, silk, nylon and polyester. Lyocell adds strength to the yarn as well as enhancing the performance and aesthetic properties of the final fabrics. Minimal carding power is required, as the fiber is very open. In drawing, sliver detectors may need to be re-set to adjust for the low bulk of the lyocell. In roving, the twist should be low to avoid too high a cohesion. Optimization is very important at this stage of the process.

Yarn steaming should be avoided wherever possible. Steaming cellulosic fibers, amongst other things affects fiber dye affinity, twist liveliness and splice strength. The dye affinity for cellulosic fibers reduces with increasing steam temperature and the influence on lyocell fiber is greater than for other cellulosic, such as cotton and viscose. Therefore steaming should be avoided unless this can be extremely well controlled. Twist liveliness can be reduced in other ways, such as by storing yarn on ring tube for 16–24 hours in a high humidity environment prior to winding.

Fabric manufacture
Weaving of lyocell fabrics can be successfully carried out on most conventional looms and in a wide range of constructions. The construction needs to be carefully engineered with the dyeing/finishing route to develop the best performance and aesthetics. Very tight constructions can give problems in dyeing and tend to give fabrics with poorer easy-care performance.

Dyeing and finishing of lyocell
The dyeing and finishing of lyocell fabrics is the key to their success. There are three characteristics of the fibers that can be manipulated to give fabrics with attractive and differentiated aesthetics- the ease of fibrillation, the high nodules and the wet swelling characteristics. Fibrillation can yield the characteristic ‘peach skin’ effect surface touch of fabrics made from this fiber, but un wanted and uncontrolled fibrillation can also impair the fabric quality, much of the dyeing and finishing development has been focus on this aspect.

A lyocell is a cellulosic fiber; it can be dyed with colors normally used on cotton. Compared with unmercerized cotton, lyocell, except with a few reactive and vat and a number of direct dyes (pale shades), dyes to a heavier depth by exhaust techniques and therefore many shades can be attained at lower cost, particularly with reactive dyes. The dyeing mechanism for most classes of reactive dyes is similar. First the reactive dye is exhausted on to the cellulose fiber using salt. In the second stage of dyeing, alkali is added to fix the dye; dyeing behavior of lyocell is shown in bar chart 1 

Many of modern reactive dyestuffs contain two or three reactive groups. A key discovery, made early in the development of lyocell, was that these multifunctional dyestuffs can crosslink the fiber and there by prevent or inhibit the fibrillation of the fiber. Since manipulation of this fibrillation is critical for the development of the fabric aesthetics.

Bar chart: 1 Dyeing Behavior of Lyocell with Other Cellulosic Fibers

Easy-care lyocell
As with any fabric, chemical finishing is an important aspect of the process and this is especially true when considering the finishing of open-width processed lyocell fabrics. In such processing, resin treating is the method of controlling fibrillation. If too little resin is fixed then fabrics will fibrillate on subsequent washing, too much and physical performance deteriorates. It is also important to include appropriate softeners and auxiliary products into the chemical finish so that performance and handle are appropriate to the customer’s requirements. The application of ~2–3% omf (on mass of fiber) fixed resin appears to be optimal for easy-care properties, dependant on the fabric construction and weight. Application levels of 2% omf are needed to stop fibrillation on domestic washing. In addition to the resin, the choice of softener can have a large effect on the easy-care performance of fabrics, and it is important to consider the whole formulation and build it up to give the required performance. Silicone micro-emulsions penetrate yarns more than the macro-emulsions. Polyethylene dispersions aid sewing and build the handle of the fabric, whilst some soft acrylic-based chemicals can increase the abrasion resistance. It is also worth remembering that caustic soda or liquid ammonia treatment in preparation will help to increase the easy-care rating of lyocell fabrics.

Fibrillation:
This can be defined as the longitudinal splitting of a single fiber filament into micro fibers. The splitting occurs as a result of wet abrasion, particularly against metal. The fibrils formed can be so fine that they become virtually transparent and give a frosty appearance to the finished fabric. The samples fig 4 shows an example of a non-fibrillated (a) and a fibrillated (b) lyocell fabric. The fibrillated fabric gives frosty appearances. In case of extreme fibrillation, the loose fibers on the surface of the fabric fibrillate and then tangle together to form very light colored pills. The appearance of the fabric becomes totally unacceptable.

(a)                                                            (b) Fig 4 shows an example of a non-fibrillated (a) and a fibrillated (b) lyocell fabric.

Applications
Lyocell feels like silk, and drapes luxuriously. Compared to cotton, Lyocell wrinkles less, is softer, more absorbent, and much more resistant to ripping. In material physical properties, Lyocell is more like cotton than rayon. Like other cellulosic fibers, it is breathable, absorbent, and very comfortable to wear. In fact, Lyocell is more absorbent than cotton or silk, but slightly less absorbent than wool, linen, or rayon.

Lyocell has good resiliency: it does not wrinkle as badly as rayon, cotton, or linen, and some wrinkles will fall out if the garment is hung in a warm moist area, such as a bathroom after a hot shower. A light pressing will renew the appearance, if needed. Also, slight shrinkage is typical in Lyocell garments. Lyocell is a stable a fiber better than cotton or linen. Lyocell is more expensive to produce than cotton or rayon, but is included in many everyday items. Staple fiber is used in apparel items such as denim, chino, underwear, other casual wear clothing & towels. Filament fibers are used in items that have a silkier appearance such as women’s clothing and men’s dress shirts. Lyocell can be blended with a variety of other fibers such as silk, cotton, rayon, polyester, linen, nylon, and wool.

Lyocell – a versatile, high performance fiber for nonwovens
The early stages of the commercialization of lyocell were focused towards the fashion textile apparel sector. However, this has changed during the first years of the twenty-first century so that lyocell is now targeted equally into the industrial sector, with particular emphasis on the key nonwovens markets of wipes, filters and feminine hygiene products. The key difference between traditional textile production and nonwovens production is the omission of the yarn stage from the production process. In nonwovens manufacture, the fibers are formed into a web and a fiber bonding or entangling process is used to impart integrity and control the function, hand and appearance of the resulting nonwovens’ substrate. Staple fiber grades are produced to suit carded dry laid, air laid and wet laid processes.

Lyocell is also used in

• Conveyer Belt
• Specialty Paper
• Medical Dressing
• Surgical swabs, drapes, gowns
• Floppy disc liners, filtration cloth
• Lining materials

Conclusion
Cellulose is one of the most abundant natural resources on earth, and there has been extensive research on the films, plastics, and fibers from this material. This century modified cellulose were investigated with eco friendly route, lyocell is one among these. Lyocell is not only environmental friendly fiber; it offers more desirable properties like highly crystalline structure in which crystalline domains are continuously dispersed along the fiber axis, good wet strength as well as excellent dry strength, which makes lyocell water-washable. Further, it dye uptake more, shrinks less when wetted by water and dried than other cellulose fibers such as cotton and viscose rayon.

References:

1. Bates I, Mauchru E, Phillips DAS, Renfrew AHM, Su Y, Xu J (2004) Cross-linking agents for the protection of lyocell against fibrillation: synthesis, application and technical assessment of 2,4-diacrylamidobenzenesulphonic acid. Color Technology 120:293–300. doi:10.1111/j.1478-4408.2004.tb00233.x
2. Chae DW, Chae HG, Kim BC, Oh YS, Jo SM, Lee WS (2002) Physical properties of lyocell fibers spun from isotropic cellulose dope in NMMO monohydrate. Text Res J 72:335–340. doi:10.1177/004051750207200410 
3. Chavan RB, Patra AK (2004) Development and processing of lyocell. Indian J Fiber Text Res 29:483–492 
4. Colom X, Carrillo F (2002) Crystallinity changes in lyocell and viscose-type fibers by caustic treatment. Europe Polymer Journal 38:2225–2230. doi:10.1016/S0014-3057(02)00132-5 
5. Goswami P, Blackburn RS, Taylor J, Westland S, White P (2007) Dyeing behavior of lyocell fabric effect fibrillation. Color Technology 123:387–393 
6. Goswami P, Blackburn RS, El-Dessouky HM, Taylor J, White P (2009) Effects of sodium hydroxide pre-treatment on the optical and structural properties of lyocell. Europe Polymère Journal 45:455–465. doi:10.1016/j.eurpolymj.2008.10.030 
7. Jakob B. and E. Agster, “Pretreatment and Finishing of Lyocell Woven Fabrics”, International Textile Bulletin, No. 3, page 18-26 (1998).
8. J. M. Taylor, M. J. Bradbury and S. Moorhouse, “Dyeing Tencel and Tencel A100 with Poly-Functional Reactive Dyes”, AATCC Review, No. 10 page 21-24 (2001).
9. J. M. Taylor and A. L. Harnden, “An Introduction to Tencel Processing”, International Dyer, August 1997, page 14.
10. K. Gandhi et. al., “A Novel Route for Obtaining ‘Peach Skin Effect’ on Lyocell and its Blends”, AATCC Review, No. 4 page 48-52 (2002)
11. http://www.tencel.com
12. http://www.lenzing.com
13. http://www.everything2.com
14. http://www.madehow.com
15. http://en.wikipedia.org/wiki/Lyocell accessed on 14-06-10 
16. http://www.fibersource.com 

Introduction:

A bulletproof jacket, bulletproof vest, ballistic vest or bullet-resistant vest is an item of personal armor that helps absorb the impact from firearm-fired projectiles and shrapnel from explosions, and is worn on the torso. Soft vests are made from many layers of woven or laminated fibers and can be capable of protecting the wearer from small-caliber handgun and shotgun projectiles, and small fragments from explosives such as hand grenades. This textiles are commonly worn by police forces, private citizens who are at risk of being shot (e.g., national leaders), security guards, and bodyguards, whereas hard-plate reinforced vests are mainly worn by combat soldiers, police tactical units, and hostage rescue teams.It is also called safety textile.

Fig: Bulletproof jacket.

History of Bulletproof Jacket:

Fig: A test in 1901.

Humans throughout recorded history have used various types of materials as body armor to protect themselves from injury in combat and other dangerous situations. The first protective clothing and shields were made from animal skins. As civilization became more advanced, wooden shields and then metal shields came into use. Eventually, metal was also used as body armor, what we now refer to as the suit of armor associated with the knights of the Middle Ages. However, with the invention of firearms around 1500, metal body armor became ineffective. Then only real protection available against firearms was stone walls or natural barriers such as rocks, trees, and ditches. It was not until the late 19th century that the first use of soft body armor in the United States was recorded. At that time, the military explored the possibility of using soft body armor manufactured from silk. The project even attracted congressional attention after the assassination of President William McKinley in 1901. While the garments were shown to be effective against low-velocity bullets, those traveling at 400 feet per second or less, they did not offer protection against the new generation of handgun ammunition being introduced at that time. Ammunition that traveled at velocities of more than 600 feet per second. This, along with the prohibitive cost of silk made the concept unacceptable. The U.S. Patent and Trademark Office lists records dating back to 1919 for various designs of bullet proof vests and body armor type garments. One of the first documented instances where such a garment was demonstrated for use by law enforcement officers was detailed in the April 2, 1931 edition of the Washington, D.C., Evening Star, where a bullet proof vest was demonstrated to members of the Metropolitan Police Department. It was not until the late 1960s that new fibers were discovered that made today’s modern generation of cancelable body armor possible. The National Institute of Justice or NIJ initiated a research program to investigate development of a lightweight body armor that on-duty policemen could wear full time. The investigation readily identified new materials that could be woven into a lightweight fabric with excellent ballistic resistant properties. Performance standards were set that defined ballistic resistant requirements for police body armor.

How does it work?
When a handgun bullet strikes body armor, it is caught in a “web” of very strong fibers. These fibers absorb and disperse the impact energy that is transmitted to the bullet proof vest from the bullet, causing the bullet to deform or “mushroom.” Additional energy is absorbed by each successive layer of material in bullet proof vests, until such time as the bullet has been stopped.

Fig: Additional energy is absorbed by each successive layer of material in the ballistic panel.

Because the fibers work together both in the individual layer and with other layers of material in the vest, a large area of the bullet proof vest becomes involved in preventing the bullet from penetrating. This also helps in dissipating the forces which can cause non penetrating injuries to internal organs. Unfortunately, at this time no material exists that would allow body armor to be constructed from a single ply of material.

Raw Materials:
A bulletproof vest consists of a panel, a vest-shaped sheet of advanced plastics polymers that are composed of many layers of either Kevlar, Spectra Shield, or, in other countries, Twaron (similar to Kevlar) or Bynema (similar to Spectra). The layers of woven Kevlar are sewn together using Kevlar thread, while the nonwoven Spectra Shield is coated and bonded with resins such as Kraton and then sealed between two sheets of polyethylene film. The panel provides protection but not much comfort. It is placed inside of a fabric shell that is usually made from a polyester/cotton blend or nylon. The side of the shell facing the body is usually made more comfortable by sewing a sheet of some absorbent material such as Kumax onto it. A bulletproof vest may also have nylon padding for extra protection. For bulletproof vests intended to be worn in especially dangerous situations, built-in pouches are provided to hold plates made from either metal or ceramic bonded to fiberglass. Such vests can also provide protection in car accidents or from stabbing. Various devices are used to strap the vests on. Sometimes the sides are connected with elastic webbing. Usually, though, they are secured with straps of either cloth or elastic, with metallic buckles or Velcro closures.

The Manufacturing Process:

Manufacturing process of Bulletproof Jacket

Some bulletproof vests are custom-made to meet the customer’s protection needs or size. Most, however, meet standard protection regulations, have standard clothing industry sizes and are sold in quantity.

Making the panel cloth
To make Kevlar, the polymer poly-para-phenylene terephthalamide must first be produced in the laboratory. This is done through a process known as polymerization, which involves combining molecules into long chains. The resultant crystalline liquid with polymers in the shape of rods is then extruded through a spinneret (a small metal plate full of tiny holes that looks like a shower head) to form Kevlar yarn. The Kevlar fiber then passes through a cooling bath to help it harden. After being sprayed with water, the synthetic fiber is wound onto rolls. The Kevlar manufacturer then typically sends the fiber to throwsters, who twist the yarn to make it suitable for weaving. To make Kevlar cloth, the yarns are woven in the simplest pattern, plain or tabby weave, which is merely the over and under pattern of threads that interlace alternatively.

Unlike Kevlar, the Spectra used in bulletproof vests are usually not woven. Instead, the strong polyethylene polymer filaments are spun into fibers that are then laid parallel to each other. Resin is used to coat the fibers, sealing them together to form a sheet of Spectra cloth. Two sheets of this cloth are then placed at right angles to one another and again bonded, forming a nonwoven fabric that is next sandwiched between two sheets of polyethylene film. The vest shape can then be cut from the material.

Cutting the panels:

Fig: Cutting the panels.

Kevlar cloth is sent in large rolls to the bulletproof vest manufacturer. The fabric is first unrolled onto a cutting table that must be long enough to allow several panels to be cut out at a time; sometimes it can be as Kevlar has long been the most widely used material in bulletproof vests. To make Kevlar, the polymer solution is first produced. The resulting liquid is then extruded from a spinneret, cooled with water, stretched on rollers, and wound into cloth. A recent competitor to Kevlar is Spectra Shield. Unlike Kevlar, Spectra Shield is not woven but rather spun into fibers that are then laid parallel to each other. The fibers are coated with resin and layered to form the cloth long as 32.79 yards (30 meters). As many layers of the material as needed (as few as eight layers, or as many as 25, depending on the level of protection desired) are laid out on the cutting table. A cut sheet, similar to pattern pieces used for home sewing, is then placed on the layers of cloth. For maximum use of the material, some manufacturers use computer graphics systems to determine the optimal placement of the cut sheets. Using a hand-held machine that performs like a jigsaw except that instead of a cutting wire it has a 5.91-inch (15-centimeter) cutting wheel similar to that on the end of a pizza cutter, a worker cuts around the cut sheets to form panels, which are then placed in precise stacks.

Sewing the panels:
While Spectra Shield generally does not require sewing, as its panels are usually just cut and stacked in layers that go into tight fitting pouches in the vest, a bulletproof vest made from Kevlar can be either quilt-stitched or box-stitched. Quilt-stitching forms small diamond of cloth separated by stitching, whereas box stitching forms a large single box in the middle of the vest. Quilt-stitching is more labor intensive and difficult, and it provides a stiff panel that is hard to shift away from vulnerable areas. Box-stitching, on the other hand, is fast and easy and allows the free movement of the vest. To sew the layers together, workers place a stencil on top of the layers and rub chalk on the exposed areas of the panel, after the cloth is made, it must be cut into the proper pattern pieces. These pieces are then sewn together with accessories to form the finished vest making a dotted line on the cloth. A sewer then stitches the layers together, following the pattern made by the chalk. Next, a size label is sewn onto the panel.

Finishing the Vest
The shells for the panels are sewn together in the same factory using standard industrial sewing machines and standard sewing practices. The panels are then slipped inside the shells, and the accessories—such as the straps—are sewn on. The finished bulletproof vest is boxed and shipped to the customer.

Quality Control:

Fig: It is checked for defects by National Institute for Justice (N.I.J.)

Bulletproof vests undergo many of the same tests a regular piece of clothing does. The fiber manufacturer tests the fiber and yarn tensile strength, and the fabric weavers test the tensile strength of the resultant cloth. Nonwoven Spectra is also tested for tensile strength by the manufacturer. Vest manufacturers test the panel material for strength, and production quality control requires that trained observers inspect the vests after the panels are sewn and the vests completed. Bulletproof vests, unlike regular clothing, must undergo stringent protection testing as required by the National Institute of Justice (NIJ). Not all bulletproof vests are alike. Some protect against lead bullets at low velocity, and some protect against full metal jacketed bullets at high velocity. Vests are classified numerically from lowest to highest protection: I, II-A, II, and III-A, III, IV, and special case (those for which the customer specifies the protection needed). Each classification specifies which type of bullet at what velocity will not penetrate the vest. While it seems logical to choose the highest-rated vests (such as III or IV), such vests are heavy, and the needs of a person wearing one might deem a lighter vest more appropriate. For police use, a general rule suggested by experts is to purchase a vest that protects against the type of firearm the officer normally carries. The size label on a vest is very important. Not only does it include size, model, style, manufacturer’s logo, and care instructions as regular clothing does, it must also include the protection rating, lot number, date of issue, an indication of which side should face out, a serial number, a note indicating it meets NIJ approval standards, and—for type I through type III-A vests—a large warning that the vest will not protect the wearer from sharp instruments or rifle fire. Bulletproof vests are tested both wet and dry. This is done because the fibers used to make a vest perform differently when wet. Testing (wet or dry) a vest entails wrapping it around a modeling clay dummy. A firearm of the correct type with a bullet of the correct type is then shot at a velocity suitable for the classification of the vest. Each shot should be three inches (7.6 centimeters) away from the edge of the vest and almost two inches from (five centimeters) away from previous shots. Six shots are fired, two at a 30-degree angle of incidence, and four at a 0-degree angle of incidence. One shot should fall on a seam. This method of shooting forms a wide triangle of bullet holes. The vest is then turned upside down and shot the same way, this time making a narrow triangle of bullet holes. To pass the test, the vest should show no sign of penetration. That is, the clay dummy should have no holes or pieces of vest or bullet in it. Though the bullet will leave a dent, it should be no deeper than 1.7 inches (4.4 centimeters). When a vest passes inspections, the model number is certified and the manufacturer can then make exact duplicates of the vest. After the vest has been tested, it is placed in an archive so that in the future vests with the same model number can be easily checked against the prototype. Rigged field testing is not feasible for bullet-proof vests, but in a sense, wearers (such as police officers) test them every day. Studies of wounded police officers have shown that bulletproof vests save hundreds of lives each year.

Future Developments:

Fig: Future development (High comfort, protection and low garment weight).

• The Defence Department of Canada posted a contract tender Monday asking companies for proposals for high- tech body suits that could help Canadian soldiers carry bigger loads into battle. 

• The Pentagon agency eventually awarded a contract to Sarcos, a Salt Lake City, Utah, and company now owned by Raytheon that produced a test version this year. Known as the XOS Exoskeleton, it uses a single engine and hydraulics to assist movement. Included in the Pentagon’s Future Warrior Concept are a powerful exoskeleton, a self-camouflaging outer layer that adapts to changing environments and a helmet which translates a soldier’s voice into any foreign language. The future soldier will also benefit from ‘intelligent’ armour, which remains light and flexible until it senses an approaching bullet, then tenses to become bullet proof. 

• Bullet-proof brassieres designed to be comfortable and injury-proof have been issued to 3,000 policewomen in Germany for their protection. The brassieres are made of cotton or polyester and are padded. Unlike bullet-proof vests, they have no metal or plastic under-wire or fasteners that can pierce skin and injure the wearer when a bullet hit the body armor.

Bullet-proof brassiere

• Super carbon nanotube vest which bounces back the incoming projectiles have been developed in the University of Sydney.

Fig: Carbon nanotube

• Dragon Skin is a type of ballistic vest made by Pinnacle Armor. It is currently produced in Fresno, California. It’s characteristic two-inch-wide circular discs overlap like scale armor, creating a flexible vest that allows a good range of motion and can allegedly absorb a high number of hits compared with other military body armor. The discs are composed of silicon carbide ceramic matrices and laminates, much like the larger ceramic plates in other types of bullet resistant vests.

Fig: Dragon skin

• The armor is available in three basic protection levels: SOV-2000, which has previously had certification to Level III protection; SOV-3000, which is rated as Level IV by the manufacturer, but has not officially certified as such; and a rating-unspecified “Level V” variant not available to the general public. 

• SOV-2000 armor is made of an imbricated overlapping configuration of high tensile steel discs encased in an aramid textile cover. Different layout configurations with variations in coverage are available. 

ABSTRACT

Over the last 5 years the global fibre market has moved further into a global commodity market. This change is redefining and accelerating global trade patterns at all levels of the high value chain. The development of special fibers is the consequence of merging fundamentals scientific and technical knowledge, as there is a quest for high performance fibres. Thus, constant and continued endeavors of fibre scientists jointly ventured with material technologies had made dreams into reality. These special fibres totally provide the potential for providing new technology. Over all world textiles, challenging a continued growth of hi-tech fibres in various fields. These fibres have high tenacity, high strength to weight ratio which are the prerequisites characteristics of industrial textiles.

These find applications in every walk of life including Space, Ocean, composites, aircrafts, defense automobile and many more. Our present paper deals with these special fibres and explores the wealth of their properties and application.

INTRODUCTION: -
Up to this time, two types of fibers have been available to human society, natural fibers that have existed for 4000 years and synthetic fibers. Artificial silk invented was a human dream. Then nylon introduced was finer than spider’s thread, stronger than steel and more elegant than silk.

Today synthetic fibers are not a mere alternative to natural fibers but are new materials of high functionality and high performance, which play a key role in the field of high technology. These new materials can be designed and produced according to nature of their utilization. Synthetic fibers are made to replace natural fibers and to some extent it is succeeded. High performance fibers are developed now a days fibers of high modulus and high strength can now be produced from synthetic polymers of light wt and are widely employed in space. Due to limitations of natural fibers, synthetic fibers are developed and now-a-days developments are done in the fibers to achieve desired properties.

The need for ultra light fibers of high strength is increasing as high technology responds to changes in the social environment so, developments are going on in the synthetic fibers. In future decades, metals are expected to be replaced by newly developed synthetic fibers, which can be superior to metal with respect to their strength and modulus. In all the fields, there is wide application of fibers.

Kevlar	Application cables, rope making, fiber reinforcement, Industrial paper, friction products, thermo chromic fiber changes color as per environmental conditions.
Solar – X	Stores solar energy
BEMBERG Micro-porous membrane (BMM)	Diagnosis and treatment of AIDS

HIGH PERFORMANCE FIBRES:-
High performance fibres refer to high strength, high modulus, and wear resistant deformation resistant and high temperature resistant fibres. The high performance fibre industry is targeting those areas which are the domain of glass, polyester and nylon fibre reinforcements. Major applications for the high performance fibres are transportation, aerospace, protective clothing, marine ( ropes and sails), hostile thermal and chemical environments ( replacement for asbestos ) and leisure activities industries ( golf clubs and tennis rackets ). Some of the successful high performance fibres are mentioned below.

It is having high molecular weight (106), 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.

ALUMINA SILICA:-
Ceramic fibres reported with a very high temperature resistance, used for furnace insulation and hot air filtration.

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%).

DOMESTIC FIBRES:-
Cotton, silk polyester, polyamide are used in medical applications. PP and Polyester is 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.

ARMID FIBRES (PPTA) :-
Kevlar was the first Armid fibre produced by Du. Pont. Poly (p-phenylene Terephthalamide ) PPTA is the polymer from which Kevlar Armid fibres are produced. The term Armid was adoped to distinguish the group from the aliphatic polymide. Prior to 1985 Du Pont was the company producing commercial quantities of PPTA, HM – 50. PPTA is generally synthesized via an acid chloride condensation of terephthaloy1 chloride (TPC ), with p- Phenylene diamine (PDA)

PPTA fibres have been designed for high strength applications. On an equal weight basis, these Armid fibers are up to 10 times stronger than steel fibres of the same diameter. Along with exceptional strength, Armids are also exceptionally stable in many corrosive environments.

Acrylic fibers: -
Acrylic fiber's remarkable performance creates the year-around comfort consumers demand while producing a range of fabric advantages apparel manufacturers can utilize regardless of the season.

Moisture Transport Is The Key To Comfort.
Acrylic fiber, with its inherent polarity (the ability to attract and convey moisture), is the leading synthetic fiber for natural moisture transport (wicking), and is superior to fibers with topical finishes, which wash away. Acrylic fiber provides lifetime wicking capability to fabrics made from it. With acrylic garments in warm or cold climates, whether in active wear or spectator wear, you feel more comfortable because moisture management controls comfort.

Increased Comfort In The “Dermisphere”: -
The dermisphere is the air space between your skin and your clothing (as shown in fig). The type of fibers and construction of the fabric directly affect the climate in your dermisphere, and determine how comfortable, or uncomfortable, you are regardless of the air temperature or activity in which you are engaged.
A “dermisphere” covered by MICROSUPREME acrylic micro fiber. The skin is dry and comfortable because moisture is picked up by the fibers and transported to the garment’ souter surface where it evaporates. The uncomfortable alternative is a damp (either hot or cold) dermisphere caused by fibers, which are not effective at insulating or transporting moisture

Moisture dissipation: -
In the moisture dissipation test, fabrics are “spun dry” to evaluate drying time. All fabrics are started with their own percentage of moisture based on the fiber’s moisture regain. Cotton, retaining the greatest amount of moisture and having the highest dry time, is used as a comparison. Data are expressed in percentages as compared to cotton, i.e. MICROSUPREME acrylic micro fiber dries 75% faster than cotton.

Fabric %	drying time faster than cotton
MICROSUPREME Coolmax Aquatec® Nylon Tactel®	75% 70% 70% 60% 35%

MICROSUPREME Acrylic Microfiber Takes Acrylic Into A New Dimension of Performance.
Garments made from fabrics of MICROSUPREME acrylic fiber take performance to a new dimension of creativity. Because of acrylic’s ability to transport moisture and increase the “comfort-ability” of a garment, fabric designers can create constructions for all four seasons, enabling both the spectator and active participant to benefit. You not only get performance, but also luxurious touch and drape previously thought impossible. Due to its lower specific gravity, acrylic fiber also produces fabrics having more bulk without extra weight. Independent tests show that MICROSUPREME acrylic micro fiber is superior in comfort performance compared to other leading fibers.

MICROSUPREME Acrylic Micro fiber - The Right Choice For All Reasons And Seasons.
Acrylic, especially micro denier, not only creates greater comfort for the wearer, it also brings significant fabric advantages to all kinds of apparel.

• Comfortable.
• Soft, lasting hand
• Fabulous drapes.
• Easy washing, wrinkle resistance.
• Beautiful, full-color dyeing.
• Brightly colorfast.
• Odor and mildew resistance.

For cold weather apparel acrylic provides outstanding insulation and warmth without extra weight.

Uses: -

• Outerwear-Pile Fabrics
• Thermal Underwear
• Socks/Tights
• Sweaters
• Sleepwear

Microfiber acrylic: -
The new fiber is developing to be like cotton. There are `crevasses` in the fiber that diffuses light. This results in a more natural looking fiber, while regular acrylic is smooth and refracts light, giving the fiber an overall shine.

Low pill acrylic: -
Now a day’s low pill acrylic fiber also manufactured. That is especially good for school, career and military uniforms and a high performing fiber for socks. Along with all this `antimicrobial acrylic`, `acrylic blends`, and `acrylic-acetate blends also manufactured.

Magic fiber for AIDS diagnosis and treatment: -
Ashai Chemical Industry Co. have developed a porous hollow fiber membrane BEMBERG MICROPOROUS MEMBRANE [BMM] to filter out and isolate AIDS virus [acquired immune deficiency syndrome virus] and hepatitis type B in blood. BMM is made from cellulose fiber [BEMBERG] regenerated from cuprammonium solutions of cotton linters.

Synthetic polymers are known to cause blood clotting as a result of protein adsorption. However, regenerated cellulose is free from this problem, and for this reason, is used for the artificial kidney in the form of hollow fiber. In order to allow proteins to permeate, but isolate viruses using the same membrane, it is necessary to have homogeneous pores in the membrane, which are larger than proteins but smaller than viruses. To produce such cellulose membranes having homogeneously distributed pores of predetermined diameter. Spherical B-type hepatitis virus and AIDS virus have a diameter of 42 nm and 90-100 nm. Respectively. Thus the membrane needs to have pores of 30-40 nm or 40-75 in diameter, respectively, to isolate these viruses. A single layer of membrane is not sufficient to isolate such viruses completely. Consequently BMM has a multi-layer structure of 100-150 layers. This manufacturing multi layer hollow fiber membrane is produced by wet spinning from cuprammonium solution of cotton linter mixed with an organic solvent. The solution undergoes phase separation and is composed of two phases made up of concentrated and a dilute organic solvent. The concentrated phase forms a continuous organic solvent layer, and the dilute phase make up small organic solvent holes of a uniform size in the cotton linter solution. When spun, the resulting hollow fiber is made of 100-150 layers of cellulose membrane, with pores of a predetermined diameter [see Photo6.2] The pore size and the degree of crystallinity of BMM depends on many external factors such as temperature, solvent composition, component purity and time. Usually BMM is 300 to 400 um in outer diameter, 250 to 350 um in inner diameter, and is composed 40 um in thickness. The actual module is made of 300 BMM hollow fibers which together are 3 cm in diameter and 15 cm in length. Each layer of BMM has over a billion pores, which enables complete filtration and isolation of the viruses.

Uses: -
It is capable of removing virus from plasma and so suppresses its multiplication. AIDS virus immersed into lymphocytes, grows there, and then overflows into plasma. If the isolation rate of virus from plasma is fast, the clinical progress of AIDS can be suppressed. This suppression of the AIDS virus can allow the reactivation of the metabolic functions of the human body, so that treatment efficiency will improve when combined with other medical treatments.

Other applications of BMM are found, for example, in the complete isolation of virus during plasma medicines manufacture, the administration of fractionated plasma-producing medicines for hemophiliacs, and the prevention of virus infection during ordinal plasma transfusion.

BMM is also useful for the isolation of hepatitis non-A non-B virus and in the study of unknown viruses or other physiologically active substances

Super absorbent fiber: -
In last few years, super absorbents in fiber from have become a commercial reality. The recent commercial availability of super absorbent fibres has spurred an enormous amount of development activity in many market applications including telecommunications, packaging, horticulture, electronics and disposable hygiene products. Most recently the potential to benefit from their outstanding properties in a wide range of medical products have been recognized. The product is marketed as ‘OASIS’. The product is based upon similar polymer chemistry to that for powders that is a cross-linked copolymer of acrylic acid. The advantages that fiber offers compared to fibers is due to their physical form, or dimensions, rather than their chemical nature. Whilst they do absorb fluids to a similar level as powders, they do, however, do it faster. This is due to the small diameter of the fibers, which is about 30 microns, which gives a very high surface area for contact with the liquid. Also the fiber surface is not smooth .It has a crenulated structure with longitudinal grooves. These are believed to be beneficial in transporting moisture along the surface. The lubricant has also been selected to enhance this wetting effect and results in a very high rate of moisture absorption. Typically the fiber will absorb 95% of its ultimate capacity in 15sec.

PROPERTIES

Property	saline	water
Free swell absorbency. Retention (0.5psi) Absorbency under load(0.25g/g)	40g/g   30 g/g   23 g/g	80 g/g   60 g/g   45  g/g

 

When the fibers absorb fluid it does not its fibrous structure. The resulting hydrogel is an entangled mass of swollen fibers. The gel has coherence and strength. A feature of the process is that the gel characteristics can be altered according to the end use requirements.

When the fibers are allowed to dry out they return to their original form and are still absorbent. When the super absorbents absorb heterogeneous fluid such as blood, milk, or lattices the total absorbency is reduced due to deposition on the surface which access of water. In the case of blood proteins are absorbed on the surface attached by the carboxylic acid groups in the polymer. With milk, the removal of the water causes the emulsion to break depositing faton the surface in addition to protein absorption. The magnitude of this effect is naturally affected by the surface to volume ratio of the super absorbent. The ratio about 8 times higher for oasis super absorbent fiber compared to typical super absorbent powder.

The following features that may be required for use in medical product can be build up into nonwoven containing super absorbent fibers: -

• High absorbency, even under pressure
• Softness and flexibility
• Low migration of the super absorbent when dry and wet
• High rate of liquid up-take.
• Fabric dispersion when wet

Super absorbent fabrics can contribute to the design of highly absorbent products because they can be incorporated at high levels in the non-woven fabrics. This leads to fabrics of low weight with high absorbency

This feature of fibers not to migrate is a very important advantage. It allows the Super absorbent to be blended at high levels into an open structure without it falling out or its distribution in the fabric changing during storage, transport and use. This natural advantage gives more flexibility as to where the absorbent can be located.

The rate at which a non-woven fabric will absorb a liquid is a very important feature, which will particularly influence the likelihood of leakage in a hygiene product. It is a particular feature of super absorbent fibers that they absorb aqueous fluids very rapidly. Their free swell absorbency after only 15 seconds is equal to, or greater than, their retention capacity. This compares to less than half this absorbency for super absorbent powder containing fabrics. For all aqueous fluids a very rapid rate of absorption is always observed compared to powders.

A unique advantage of a super absorbent in fiber form is that staple yarns can be spun in blends with other fibers. Yarns can be produced on warp woollen, DREF and semi worsted spinning systems but warp spinning is the preferred route as the lack of twist provides a yarn free to swell easily. It is possible to blend Oasis in these yarns with both natural and synthetics fibers.

Applications in medical products: -
Non-woven fabrics and yarns containing OASIS fiber superabsorbent can be used for numerous applications where the properties of absorbency and/or swelling can be of use.

Disposable Incontinence Products:
High levels of super absorbent fiber can be incorporated into absorbent cores allowing the constructing of thin products with high absorbency.

Wipes and absorbed pads: Addition of oasis to pads and wipes to improve their ability to rapidly immobilize large amounts of blood and other aqueous spillages in operating theatre, Analytical laboratory or general hospital use.

Disposal containers:
Superabsorbent non-woven fabrics can be used as a lining for containers designed for the disposal of items contaminated with hazardous fluids to prevent leakage.

Drapes:
In surgical gowns, oasis can be incorporated around the arm and neck cuffs to prevent blood ingress.

Wound care:
Oasis can be included within secondary wound care products to provide additional capacity to absorbs wound exudates. This helps to decreases the frequency of dressing changes.

Ostomy bags:
Oasis can be incorporated into ostomy and colostomy products and waste management devices to quickly solidify body fluids to improve ease of disposal.

Miscellaneous products:
A number of other applications in the medical field are currently being evaluated including:

• Headbands for sweat control by surgeons,
• Diagnostic testing,
• Hand sticks,
• Dental pads.

The above figure shows use of multimode fibers in medical. So we can say that fiber plays an important role in our life.

Bard backs smart fibres for surgery :-
Shape-memory polymers have the potential to completely revolutionise medical surgery, as well as having a broad range of other applications, and the first product developed by mnemo Science was smart suture that ties itself into the perfect knot. This means that potentially, surgeons will be able to seal hard-to-reach wounds with the aid of a shape-shifiting thread that knows how to tie itself and never needs to be removed. The new ‘smart’ biodegradable plastic fibre can knot itself when heated to a few degrees above body temperature. Researchers belive the same material could be made to last much longer and one day be used for self repairing medical devices and also to shrink otherwise bulky implants such as screws that hold bones together.

Spider silk: -
What is spider silk made of? It is a fibrous protein secreted as a fluid, which hardens as it oozes out of the spinnerets, which are mobile finger-like projections. As the fluid oozes out, the protein molecules are aligned in such a way that they form a solid; the process is not yet well understood. The spider hauls out the silk with its legs, stretching, fluffing it up or changing it in other ways to suit the purpose at hand.

Spider silk

Weight for weight, spider silk is up to 5 times stronger than steel of the same diameter. It is believed that the harder the spider pulls on the silk as it is produced, the stronger the silk gets. Spider silk is so elastic that it doesn’t break even if stretched 2-4 times its length. Spider silk is also waterproof, and doesn’t break at temperatures as low as -40C.

There are 7 types of silk glands and “nozzles” but no spider has all 7 types

Fig. Two types of silk releasing tubes.

The material is elastic and only breaks at between 2 - 4 times its length. In the pictures a strand of a social spider, stegodyphus sarasinorum, is shown as normal size, stretched 5 times and 20 times its original length. Spider’s silk is made up of chains of amino acids. In other words, it is simply a protein .The two primary amino acids are glycine and alanine. Spider silk is extremely strong — it is about five times stronger than steel and twice as strong as Kevlar of the same weight. Spider silk also has the ability to stretch about 30- percent longer than its original length without breaking, which makes it very resilient

Aramids: -
High tenacity aramide fiber: -
Organic fibers. Closely related to the nylons, aramids are polyamides derived from aromatic acids and amines. Because of the stability of the aromatic rings and the added strength of the amide linkages, due to conjugation with the aromatic structures, aramids exhibit higher tensile strength and thermal resistance than the aliphatic polyamides (nylons). The para- aramids, based on terephthalic acid and p-phenylene diamine, or paminobenzoic acid, exhibit higher strength and thermal resistance than those with the linkages in meta positions on the benzene rings. The greater degree of conjugation and more linear geometry of the para linkages, combined with the greater chain orientation derived from this linearity, are primarily responsible for the increased strength. The high impact resistance of the para-aramids makes them popular for “bullet-proof” body armor. For many less demanding applications, aramids may be blended with other fibers.

High resistance aramide fibers: -
Teiji conex is a meta linked aromatic polyamide fiber known for its heat resistance .it is a synthetic organic fiber comprised of polymetaphenylene iosthalic amide, which is formed by reaction from meta-phenylenediamine and isophthaloyl chloride. It decomposes at 4000C and having LOI 30. It is a white, highly functional fiber, which can be used for clothing to industrial material.

Continuous meta-type amide bonds to benzene rings render the following properties: -

1. High melting point and decomposition point.
2. High glass transition point.
3. Low oxidation decomposition rate.

General properties: -

• High modulus.
• High tenacity with low weight.
• Low electrical conductivity.
• High cut resistance.
• High chemical and temperature resistance.
• Low thermal shrinkage.
• Excellent dimensional stability.
• Do not corrode.

Cut resistance aramide fiber: -
HDPE (high-density polyethylene): -
It can be extruded using special technology to produce very high molecular orientation. The resulting fiber combines high strength; chemical resistance and good wear properties with lightweight, making it highly desirable for applications ranging from cut-proof protective gear to marine ropes.
Since it is lighter than water, ropes made of HDPE float. Its primary drawback is its low softening and melting temperature.

Spectra fiber 1000: -
High-strength, lightweight polyethylene fiber: -
Spectra® fiber 1000, the second in a series of Spectra® fibers, was developed to meet customers’ needs for increased performance. It is available in a multitude of deniers for use in a wide range of applications. This extended chain polyethylene fiber has one of the highest strength to weight ratios of any manmade fiber. Spectra® fiber 1000 has a tenacity 15 – 20 percent higher than that of Spectra® fiber 900. Spectra® fiber is, pound-for-pound, 10 times stronger than steel, more durable than polyester and has a specific strength that is 40 percent greater than aramid fiber. Specific performance is dependent upon denier and filament count.

Characteristics:

• Light enough to float (.097 Specific Gravity)
• High resistance to chemicals, water, and UV light
• Excellent vibration damping
• Highly resistant to flex fatigue
• Low coefficient of friction
• Good resistance to abrasion
• Low dielectric constant makes it virtually transparent to radar

Uses: -

• Police and military ballistic vests and helmets
• Composite armor for vehicles and aircraft
• Marine lines and commercial fishing nets
• Industrial cordage and slings

Melamine : -
Definition for Melamine Fiber:
A manufactured fiber in which the fiber-forming substance is a synthetic polymer composed of at least 50% by weight of a cross-linked melamine polymer.

Fiber is primarily known for its inherent thermal resistance and outstanding heat blocking capability in direct flame applications. This high stability is due to the cross linked nature of the polymer and the low thermal conductivity of melamine resin. In comparison to other melamine fiber offers an excellent value for products designed for direct flame contact and elevated temperature exposures.

Moreover, the dielectric properties and cross section shape and distribution make it ideal for high temperature filtration applications. It is sometimes blended with aramid or other performance fibers to increase final fabric strength.

Production: -
The production process is proprietary. It is based on a unique melamine chemistry that results in a cross-linked, non-thermoplastic polymer of melamine units joined by methylene and dimethylene ether linkages.In the polymerization reaction, methylol derivatives of melamine react with each other to form a three-dimensional structure. This structure is the basis for the fiber’s heat stability, solvent resistance, and flame resistance.
Characteristic: -

• White and Dyeable .
• Flame resistance and low thermal conductivity
• High heat dimensional stability.
• Processable on standard textile equipment

Uses: -

• Fire Blocking Fabrics: Aircraft seating, fire blockers for upholstered furniture in high-risk occupancies.
• Protective Clothing: Firefighters ‘turnout gear, insulating thermal liners, knit hoods, molten metal splash apparel, heat resistant gloves.
• Filter Media: High capacity, high efficiency, high temperature bag house air filters.

Piezoelectric ceramic fiber: -
Lead Zirconate Titanate (PZT) active fibers, from 80 to 250 micrometers in diameter, are produced for the AFOSR / DARPA funded Active Fiber Composites

Consortium** (AFCC) Program and commercial customers. Cera Nova has developed a proprietary ceramics-based technology to produce PZT mono-filaments of the required purity, composition, straightness, and piezoelectric properties for use in active fiber composite structures. CeraNova’s process begins with the extrusion of continuous lengths of mono-filament precursor fiber from a plasticized mix of PZT-5A powder. The care that must be taken to avoid mix contamination is described using illustrations from problems experienced with extruder wear and metallic contamination.

Manufacturing:
CeraNova has developed a proprietary extrusion and firing method to ake round, straight and contamination free PZT fibers having composition and piezoelectric performance suitable for AFC use.

Raw materials and mixing:
PZT-5A powder is mixed under high-shear conditions with a proprietary binder formulation until a homogeneous blend is achieved.

The PZT particle size is submicron. Binders are added sequentially during the mixing process. As only 100 kilograms of mix are required to produce sufficient fiber for 20,000 AFC packs per year, mixing capacity will not constrain future AFCC production requirements.

Batch blending and remixing improves mix consistency and extrusion performance. Great care is taken to avoid contamination as this can result in extruder die blockage or unacceptable defects in fired fibers.

Figure: Cross section (a) and top view (b) of Continuum Control’s Active Fiber Composite using an experimental electrode system. Note conformability of electrode around fiber. Fiber diameter is 130 micrometers; electrode spacing is 1 mm with a width of 0.5 mm.

Fig. shows the some of the single PZT fibers.

Properties: -

• Diameters from 5 microns to 250 microns.
• Flexible and lightweight.
• Converts waste mechanical energy into electrical energy (vibration, motion)
• When the fibers are exposed to an electric field, they mechanically deform.

Uses: -

• Used in sonar, ultrasound, acoustic reproduction, energy harvesting, smart materials, smart sporting goods, and medical applications.
• Can be used to power independent Electronic Systems

Bicomponent fiber: -
Recently designed a bicomponent spin pack that resulted in spinning a very unusual fiber (see below). This fiber is a type of island-in-the-sea bicomponent where a dissolvable polymer (blue) is used to surround islands of a standard polymer such as polypropylene, nylon or polyester. In this case the fiber was spun with a 50/50 ratio of polyethylene and polypropylene. It is not know at this time if this same cross-section can be obtained with other polymer combinations.
After dissolving away the blue polymer, the resulting fiber consists of a single high denier snowflake center surrounded by multiple round and oval shaped microfilaments. The large core should provide good fiber and fabric strength and large surface area for absorption, and the microfilaments will provide softness as well as absorption. This type of fiber should be ideal for filtration applications both in woven and nonwoven construction. The dual shape microfilaments will enhance the loft of the fabric while the grooves in the core filaments may enhance particle trapping and absorption.

Power fibers that store solar energy: -
Heat regenerating fibers are produced from ceramic composites by applying heat insulation processing technology, which utilizes the far infrared radiation effect of ceramic. When heated ceramics radiate far infra –red radiation, which penetrates into the material and heats it homogeneously by activating molecular motion. Zirconium, magnesium oxide or iron oxide can be blended into synthetic fibers, because these materials radiate Ca.60 mW far infrared of wavelengths 8-14 um at a body temperature of 36 0C. These heat reradiating fibers are used for sports wear, bead-sheets, bed-cover materials ,etc.

A futuristic fiber material solar-α has been developed, which absorbs and preserves the optical energy of the sun. solar-α has been employed for a downhill skiing suit. In addition to its smooth surface and aerodynamic form, this downhill suit aimed to increase the insulating efficiency by solar-α in order to warm the muscle and bring out its best power.

Oxygen consumption must be reduced t o minimum to bring out power efficiently from muscle in severe climatic conditions. Zirconium carbide compounds are used is used for their excellent characteristics in absorbing and storing heat in a new type of solar system, including domestic water heaters and large-scale generators turbine. Zirconium carbide traps heat energy. It absorbs visible

rays and reflects the light of long wavelength, which makes up 95% of sunlight, and converts it into stored heat energy. Descente researchers applied these characteristics of Zirconium carbide on polyamide or polyester fibers. They developed the technology to enclose Zirconium carbide powder within the core of synthetic fibers (as shown in fig.)
The cloths made of these fibers solar-α absorbs solar visible radiation efficiently and converted it into heat in the form of infra-red radiation which released in the clothing.
Body-responsive hollow fiber :-
Hollow fiber has been scientifically proven to significantly increase oxygenated blood flow, which cans increase circulation and build strength. For diabetics, this improvement in skin oxygenation can accelerate wound healing and help eliminate pain due to decreased 90 blood flow. For people not affected by diabetes, this skin oxygenation helps speed recovery after exercise, boost energy levels and improve overall circulation.

Diabetics face two major issues neuropathy, or the loss of sensation, and atherosclerosis, or hardening of the arteries, which reduces the circulation of blood in the body. Atherosclerosis can lead to a number of conditions, including aching feet, leg pain and problems with wound healing. Symptoms include cold feet, pain in the legs when walking and pain in the feet when reclining. When worn on or near the skin, Hollow fiber responds to available light and the energy produced naturally by the body, converting light and they body’s own energy in to the necessary wavelengths that make this usually unavailable energy accessible to the body-improving the body’s circulation and oxygen levels.

In addition to helping diabetics, this breakthrough textile has been shown to improve physical performance and recovery time among those without circulation problems. Holofiber is already being lauded by some of the world’s top athletes, including top ranked female triathlete and Olympic silver medalists Michellie jones, who has been testing Holofiber for nearly two years. “As a professional athlete, you want everything you can possibly find to help get the best performance possible, “she said. “That’s one of the things I like about Holofiber – the fact that it helps with recovery and circulation. What better way-there’s no extra effort, and it really helps and benefits you.” World’s leading experts in diabetic foot complications, proved the effectiveness of Holofiber products in increasing oxygen levels in diabetic subject. There was a”… statistically significant change in transcutaneous oxygen – or the oxygen delivery to the skin – in hands and feet, on subjects wearing Holofiber gloves and socks compared to those wearing comparable non-Holofiber gloves and socks.”

Among the manufacturers already offering Holofiber products or planning to introduce them are wickers in its t-shirts, shorts, sock and glove liners, Super feet in custom insoles, Achieve 02 in diabetic and medical socks and Callaway Golf in shoes. Holofiber is a proprietary product with a patent pending. It is a responsive material for textiles and other uses, and is not an additive or coating applied by spraying or dipping. Its properties do not wash or leach out of the fabric. All of the Holofiber material are incorporated into the fibre and are non-toxic and biologically benign

POLYESTER : -
FORMALDEHYDE FUMES ABSORB POLYESTER: -
A polyester fiber can be spun and woven into fabrics for upholstery, which will adsorb the fumes released by the formaldehyde adhesives used to make furniture. The fibers, and so the fabrics made from them, contain a nitrogen compound that is firmly bonded to the surface. It is this that absorbs the gas.

The tests are conducted in environments in which the level formaldehyde was as high as 14 parts per million [ppm]. The fabrics reduced this level to just 0.06 ppm in 24 hours, the upper safety limit is considered to be 0.08 ppm. This fiber so much useful in the industry, for worker apparel and other purposes also.

Lightweight and air-insulating polyester fiber:
Sinkong Synthetic Fibers Corp. has adopted a new spinning technology to create Thermo Tech, a lightweight and air-insulating polyester fiber with a hollow cross-sectional area. The functional fiber is suitable for sportswear, thermal underwear, socks and bed sheets
The hollowness of the fiber can be up to 30 percent, yielding a lower fiber density and enabling air to be trapped within the fiber to preserve body heat. The firm, resilient fiber lends a cotton like hand, rich feel, wrinkle-free and easy-to-clean properties to fabrics.

Thermo Tech is available in SDY and FOY versions in 60d/50f, 75d/50f, 75d/30f and 75d/36f specifications.

Cross sections of some of the new developed fibers: -

Cross sections of some of the new developed fibers

Kevlar: -
Five times stronger than steel, Kevlar is a synthetic fiber of the DuPont corporation that was first created in 1965 by scientists Stephanie Kwolek and Herbert Blades. Since that time, Kevlar has been utilized in a wide variety of applications and has helped save thousands of lives through its use in bulletproof vests. Sometimes referred to as a Space Age material, it is the chemical structure and processing of Kevlar that makes it so strong. More specifically, Kevlar contains both aromatic and amide molecular groups. When molten Kevlar is spun into fibers at the processing plant, the polymers produced exhibit a crystalline arrangement, with the polymer chains oriented parallel to the fiber’s axis. The amide groups are able to form hydrogen bonds between the polymer chains, holding the separate chains together like glue. Also, the aromatic components of Kevlar have a radial orientation, which provides an even higher degree of symmetry and strength to the internal structure of the fibers.
Strength is not, however, the only advantageous feature of Kevlar fiber. Kevlar is also lightweight, flexible, and resistant to chemicals and flames. Together these characteristics make Kevlar extremely useful to humans. Some of the common items that contain Kevlar include sports equipment, such as skis and tennis rackets, highly protective gloves, parachutes, and tires. Kevlar is also frequently used to construct lightweight ropes, which have been used for such crucial applications as mooring the large vessels of the United States Navy and securing the airbags in the landing apparatus of the Mars Pathfinder

Fiber optics
Optical fibers are thin strands of super-clean glass (fused silica), about the size of a human hair. Almost all fibers used today are single strands. Fiber bundles find use primarily in coherent and image transmitting optical systems. There are also plastic fibers for inexpensive, short distance transmission. The basic design of an optical fiber consists of two components - the core and the cladding. They build an optical waveguide, which conducts optical power (photons) in the form of light rays. Core and cladding differ primarily in the refractive index of the glass. The core’s refractive index is slightly higher than the cladding’s, thereby creating a boundary for a circular wave-guide. Fiber optic signaling in data transmission is increasingly being used in high-density applications. In the military, the Standard Electronic Modules (SEM) of the Standard Hardware Acquisition and Reliability Program (SHARP) are widely used for high density electrical interconnects in card-edge-to-backplane interfacing.

The advantages of fiber optics can be summarized as:

• Insensitive to EMI, RFI and EMP
• Does not radiate energy
• Low transmission losses
• Wide transmission bandwidth
• Unaffected by Lightning
• Lightweight & non-corrosive.
• Absolutely safe in explosive environments

CONCLUSION: -
Natural fibers have good properties but have some limitations; to overcome those synthetic fibers are produced. Still they have some drawbacks, to remove them developments are going on. Now days, almost in all the fields’ fibers are used. Fibres can replace even metals, so enormous developments are done in fiber field. Now the aspect of eco-friendly, environment friendly (fiber) have came in future. Now in that respect development, research is going on.

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