Integrated term project

Bullet proof fabric & vest

Submitted by:Rohan Roy (MUM13AP05)Saima Jafari (MUM13AP13)Programme:F.P.Tech (Sem-2)Batch:2013-17Mentored by:Ms. Aboli Ashok NaikAssistant ProfessorNIFT Mumbai

CERTIFICATE

This is to certify that this Integrated Term Project entitled Bullet-proof fabric and vest submitted to NIFT Mumbai, is a bonafide record of work done by Rohan Roy and Saima Jafari under my supervision from 06/01/2014 to 14/05/2014.

Ms. Aboli Ashok NaikAssistant Professor,NIFT Mumbai

ACKNOWLEDGEMENT

We would like to thank our mentor of this project, Miss A. A. Naik for the valuable guidance, advice, useful comments, remarks and engagement throughout the learning process of this project. She inspired us greatly to work in this project. Her willingness to motivate us contributed tremendously towards our project.We express our deepest gratitude to Mrs. Tapas Nandi for arranging for us the contact of the industry which we have visited frequently during our project. The project would not have been possible without this industrial study.We would also like to acknowledge with much appreciation, the crucial role of Mr. Siddharth Kusumgar who gave the permission to visit his industry and observe all required equipments, processes and the necessary materials to complete the task.Furthermore, we would like to thank Mr. Prasad Kasar and Mr. Pawan who have introduced us to the manufacturing process and willingly shared their precious time with us during our industry visits.

ROHAN ROYSAIMA JAFARIF.P.Tech Sem-2NIFT Mumbai

LIST OF CONTENTSChapter No.TopicPage No.

1IntroductionIntroductionObjective of the studySignificance of the studyLimitations of the study55556

2Review:How do bullet proof vests work?Basic principleHistoryHigh tech ballistic fibresKevlarTwaronSpectraZylonM577711181833404452

3MethodologyWeavingMechanical testsResults and discussionsConclusions5656585963

4FindingsApplicationsTypesGarment constructionDesign and ergonomicsMarket studyGrowth projectionsGovernment initiativesDiscussions on visits to Kusumgar corporatesVisit to manufacturing unit in UmargaonFinishingPrototype636364677171757882848889

5ConclusionConclusion8989

Appendix 1References95

Chapter 1- IntroductionBulletproofing is the process of making something capable of stopping a bullet or similar high velocity projectiles e.g. shrapnel. A 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.Objective of the study To develop an understanding of the basic concept of bulletproofing To critically assess the environmental issues like waste operations by authorities, including volumes/types of materials arising and current disposal/recovery routes To classify and compare the different types of ballistic fibres and their properties To make recommendations to improve the functional effectiveness alongwith cost reduction To make recommendations regarding the use of alternative fibres and mechanisms in bulletproofing To examine the opportunities available for growth of ballistic industries in india to analyse the current position of india in the world market of ballistic in terms of demand and supply and employment To identify barriers and concerns related to ballistic industry in india To assess awareness and perception regarding comprehensive care and necessity of cheap yet effective vests for ordinary soldiers. To assess the knowledge, attitude and practice of the government towards the safety of the soldiers.

Significance of the study The study will help to develop a better understanding of the basic concept of bulletproofing and its necessity in present scenario. The study will be helpful in understanding the position of india in the world market and critically analysing government plans. Various barriers for the indian ballistic industry are explored. Factors determining the cost of a bullet proof vest are studied and hence steps that could be taken to cut down the cost can be suggested.Limitations of the study The study is done on a very small scale. Unavailability of some desirable information in both primary and secondary data. Absence of brand comparison Little is known about the environmental issues related to the topic. No survey is done. Photographs of the manufacturing process are missing because of the sensitivity of the information.

Chapter 2- ReviewHow do Bullet proof vests work? R1Humans have been wearing armor for thousands of years. Ancient tribes fastened animal hide and plant material around their bodies when they went out on the hunt, and the warriors of ancient Rome and medieval Europe covered their torsos in metal plates before going into battle. By the 1400s, armor in the Western world had become highly sophisticated. With the right armor, a person was nearly invincible.All that changed with the development of cannons and guns in the 1500s. These weapons hurl projectiles at a high rate of speed, giving them enough energy to penetrate thin layers of metal. The thickness of traditional armor materials can be increased, but they soon become too cumbersome and heavy for a person to wear. It wasn't until the 1960s that engineers developed a reliable bullet-resistant armor that a person could wear comfortably. Unlike traditional armor, this soft body armor is not made out of pieces of metal; it is formed from advanced woven fibers that can be sewn into vests and other soft clothing.Hard body armor, made out of thick ceramic or metal plates, functions basically the same way as the iron suits worn by medieval knights: It is hard enough that a bullet or other weapon is deflected. That is, the armor material pushes out on the bullet with the same force (or nearly the same force) with which the bullet pushes in, so the armor is not penetrated.Typically, hard body armor offers more protection than soft body armor, but it is much more cumbersome. Police officers and military personnel may wear this sort of protection when there is high risk of attack, but for everyday use they generally wear soft body armor, flexible protection that can be worn like an ordinary shirt or jacket.Basic Principle of Bullets Proof Vest R2The basic principle of bullets proof vest is reduce as much as possible of kinetic energy of the bullet, by using layers of kevlar, it can absorb energy, so that energy is not enough anymore to make a bullet break through the vest. In absorbing the kinetic energy of bullet, Kevlar will deformed inwards and it will be transferred into the pressure to the user's body. The maximum limit pressure should not be more than 4.4 cm (44 mm). If that limit is exceeded, the user will have internal organs injury, which is very dangerous.

To see how this works, think of a soccer goal. The back of the goal consists of a net formed by many long lengths of tether, interlaced with each other and fastened to the goal frame. When you kick the soccer ball into the goal, the ball has a certain amount of energy, in the form of forward inertia. When the ball hits the net, it pushes back on the tether lines at that particular point. Each tether extends from one side of the frame to the other, dispersing the energy from the point of impact over a wide area.

In a bulletproof vest, several layers of bullet-resistant webbing (such as KEVLAR) are sandwiched between layers of plastic film. These layers are then woven to the carrier, an outer layer of traditional clothing material

The energy is further dispersed because the tethers are interlaced. When the ball pushes on a horizontal length of tether, that tether pulls on every interlaced vertical tether. These tethers in turn pull on all the connected horizontal tethers. In this way, the whole net works to absorb the ball's inertial energy, no matter where the ball hits.If you were to put a piece of bulletproof material under a powerful microscope, you would see a similar structure. Long strands of fiber are interlaced to form a dense net. A bullet is traveling much faster than a soccer ball, of course, so the net needs to be made from stronger material. The most famous material used in body armor is DuPont's KEVLAR fiber. KEVLAR is lightweight, like a traditional clothing fiber, but it is five times stronger than a piece of steel of the same weight. When interwoven into a dense net, this material can absorb a great amount of energy.In addition to stopping the bullet from reaching your body, a piece of body armor also has to protect against blunt trauma caused by the force of the bullet.Blunt Trauma R3Blunt trauma, blunt injury, non-penetrating trauma or blunt force trauma refers to physical trauma caused to a body part, either by impact, injury or physical attack; the latter usually being referred to as blunt force trauma.A piece of soft bulletproof material works in the same basic way as the net in a soccer goal. Like a soccer goal, it has to "give" a certain amount to absorb the energy of a projectile.When a ball is kicked into a soccer goal, the net is pushed back pretty far, slowing the ball down gradually. This is a very efficient design for a goal because it keeps the ball from bouncing out into the field. But bulletproof material can't give this much because the vest would push too far into the wearer's body at the point of impact. Focusing the blunt trauma of the impact in a small area can cause severe internal injuries.

The front (left) and back (right) of a hard-armor steel plate. The plate has been shot with several different rifle rounds, all of which were deflected. The highest caliber round created a slight dent in the back of the plate, but none of the shots would have caused significant blunt trauma

Bulletproof vests have to spread the blunt trauma out over the whole vest so that the force isn't felt too intensely in any one spot. To do this, the bulletproof material must have a very tight weave. Typically, the individual fibers are twisted, increasing their density and their thickness at each point. To make it even more rigid, the material is coated with a resin substance and sandwiched between two layers of plastic film.A person wearing body armor will still feel the energy of a bullet's impact, of course, but over the whole torso rather than in a specific area. If everything works correctly, the victim won't be seriously hurt.Since no one layer can move a good distance, the vest has to slow the bullet down using many different layers. Each "net" slows the bullet a little bit more, until the bullet finally stops. The material also causes the bullet to deform at the point of the impact. Essentially, the bullet spreads out at the tip, in the same way a piece of clay spreads out if you throw it against a wall. This process, which further reduces the energy of the bullet, is called "mushrooming."

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.

No bulletproof vest is completely impenetrable, and there is no piece of body armor that will make you invulnerable to attack. There's actually a wide range of body armor available today, and the types vary considerably in effectiveness.Modern soft body armor consists of several layers of super-strong webbing. This material disperses the energy of a bullet over a wide area, preventing penetration and dissipating blunt trauma. This sort of armor, as well as hard armor, ranges considerably in effectiveness, depending on the materials used as well as the armor design.Armor with more layers of bulletproof material offers greater protection. With some bulletproof vests, you can add layers. One common design is to fashion pockets on the inside or outside of the vest. When you need extra protection, you insert metal or ceramic plates into the pockets. When you don't need as much protection, you can wear the vest as ordinary soft armor.To determine how effective a particular armor design is, researchers shoot it with all sorts of bullets, at all sorts of angles and distances. For a piece of armor to be considered effective against a particular weapon at a particular range, it has to stop the bullet without causing dangerous blunt trauma. The researchers determine blunt trauma by moulding a layer of clay onto the inside of the armor. If the clay is deformed more than a certain amount at the point of impact, the armor is considered ineffective against that weaponry.History R4Early Modern eraIn 1538, Francesco Maria della Rovere commissioned Filippo Negroli to create a bulletproof vest. In 1561, Maximilian II, Holy Roman Emperor is recorded as testing his armor against gun-fire. Similarly, in 1590 Sir Henry Lee expected his Greenwich armor to be "pistol proof". Its actual effectiveness was controversial at the time. The etymology of "bullet" and the adjective form of "proof" in the late 16th century would suggest that the term "bulletproof" originated shortly thereafter.During the English Civil War Oliver Cromwell's Ironside cavalry were equipped with Capeline helmets and musket-proof cuirasses which consisted of two layers of armor plate (in later studies involving X-ray a third layer was discovered which was placed in between the outer and inner layer). The outer layer was designed to absorb the bullet's energy and the thicker inner layer stopped further penetration. The armor would be left badly dented but still serviceable.[3] One of the first recorded descriptions of soft armor use was found in medieval Japan, with the armor having been manufactured from silk.Industrial eraOne of the first commercially sold bulletproof armour was produced by a tailor in Dublin, Ireland in the 1840s. Another soft ballistic vest, Myeonje baegab, was invented in Joseon, Korea in the 1860s shortly after the French campaign against Korea. Heungseon Daewongun ordered development of bullet-proof armor because of increasing threats from Western armies. Kim Gi-Doo and Gang Yoon found that cotton could protect against bullets if 10 layers of cotton fabric were used. The vests were used in battle during the United States expedition to Korea, when the US Navy attacked Ganghwa Island in 1871. The US Navy captured one of the vests and took it to the US, where it was stored at the Smithsonian Museum until 2007. The vest has since been sent back to Korea and is currently on display to the public.Simple ballistic armor was sometimes constructed by criminals. During the 1880s, a gang of Australian bushrangers led by Ned Kelly made basic armour from plough blades. By this time the Victorian Government had a reward for the capture of a member of the Kelly Gang at 8,000 (equivalent to $2 million Australian dollars in 2005). One of the stated aims of Kelly was the establishment of a Republic in North East Victoria. Each of the four Kelly gang members had fought a siege at a hotel clad in suits of armour made from the mouldboards of ploughs. The maker's stamp (Lennon Number 2 Type) was found inside several of the plates. The men used the armour to cover their torsos, upper arms, and upper legs, and was worn with a helmet.

The suits were roughly made on a creek bed using a makeshift forge and a stringy-bark log as a muffled anvil. They had a mass of around 44 kg (96 lb), making the wearer a spectacular sight yet proved too unwieldy during a police raid at Glenrowan. Their armour deflected many hits with none penetrating, but eventually was of no use as the suits lacked protection for the legs and hands.

In 1881, Tombstone physician George E. Goodfellow noticed that a Faro dealer Luke Short who was shot was saved by his silk handkerchief in his breast pocket that prevented the bullet from penetrating.[6][7] In 1887, he wrote an article titled Impenetrability of Silk to Bullets[8] for the Southern California Practitioner documenting the first known instance of bulletproof fabric. He experimented with[9] silk vests resembling medieval gambesons, which used 18 to 30 layers of silk fabric to protect the wearers from penetration.Fr. Kazimierz egle used Goodfellow's findings to develop a bulletproof vest made of silk fabric at the end of the 19th century, which could stop the relatively slow rounds from black powder handguns. The vests cost $800 USD each in 1914, a small fortune at the time the modern day equivalent of $18,710 USD. On 28 June 1914, Archduke Franz Ferdinand of Austria, heir to the throne of Austria-Hungary, was wearing a silk bulletproof vest when he was attacked by a gun-wielding assassin. He was shot in the neck and the vest did not protect him.A similar vest, made by Polish inventor Jan Szczepanik in 1901, saved the life of Alfonso XIII of Spain when he was shot by an attacker. By 1900, gangsters were wearing $800 silk vests to protect themselves.First World WarThe combatants of World War I started the war without any attempt at providing the soldiers with body armor. Various private companies advertised body protection suits such as the Birmingham Chemico Body Shield, although these products were generally far too expensive for the average soldier.The first official attempts at commissioning body armor were made in 1915 by the British Army Design Committee, in particular a 'Bomber's Shield' for the use of bomber pilots who were notoriously under-protected in the air from anti-aircraft bullets and shrapnel. The Experimental Ordnance Board also reviewed potential materials for bullet and fragment proof armor, such as steel plate. A 'necklet' was successfully issued on a small scale (due to cost considerations), which protected the neck and shoulders from bullets traveling at 600 feet per second with interwoven layers of silk and cotton stiffened with resin. The Dayfield body shield entered service in 1916 and a hardened breastplate was introduced the following year.The British army medical services calculated towards the end of the War, that three quarters of all battle injuries could have been prevented if an effective armor had been issued.The French also experimented with steel visors attached to the Adrian helmet and 'abdominal armor' designed by General Adrian. These failed to be practical, because they severely impeded the soldier's mobility. The Germans officially issued body armor in the shape of nickel and silicon armor plates that was called 'Lobster armor' from late 1916. These were similarly too heavy to be practical for the rank-and-file, but were used by static units, such as sentries and occasionally the machine-gunners. An improved version, the Infantrie-Panzer, was introduced in 1918, with hooks for equipment.

The United States developed several types of body armor, including the chrome nickel steel Brewster Body Shield, which consisted of a breastplate and a headpiece and could withstand Lewis Gun bullets at 2,700 ft/s (820 m/s), but was clumsy and heavy at 40 lb (18 kg). A scaled waistcoat of overlapping steel scales fixed to a leather lining was also designed; this armor weighed 11 lb (5.0 kg), fit close to the body, and was considered more comfortable.During the late 1920s through the early 1930s, gunmen from criminal gangs in the United States began wearing less-expensive vests made from thick layers of cotton padding and cloth. These early vests could absorb the impact of handgun rounds such as .22 Long Rifle, .25 ACP, .32 S&W Long, .32 S&W, .380 ACP, .38 Special and .45 ACP traveling at speeds of up to 300 m/s (980 ft/s). To overcome these vests, law enforcement agents such as the FBI began using the newer and more powerful .38 Super, and later the .357 Magnum cartridge.Second World WarIn 1940, the Medical Research Council in Britain proposed the use of a lightweight suit of armor for general use by infantry, and a heavier suit for troops in more dangerous positions, such as anti-aircraft and naval gun crews. By February 1941, trials had begun on body armor made of manganese steel plates. Two plates covered the front area and one plate on the lower back protected the kidneys and other vital organs. Five thousand sets were made and evaluated to almost unanimous approval - as well as providing adequate protection, the armor didn't severely impede the mobility of the soldier and were reasonably comfortable to wear. The armor was introduced in 1942 although the demand for it was later scaled down. The Canadian Army in northwestern Europe also adopted this armor for the medical personnel of the 2nd Canadian Infantry Division.The British company Wilkinson Sword began to produce flak jackets for bomber crew in 1943 under contract with the Royal Air Force. It was realised that the majority of pilot deaths in the air was due to low velocity fragments rather than bullets. Surgeon of the United States Army Air Forces, Colonel M. C. Grow, stationed in Britain, thought that many wounds he was treating could have been prevented by some kind of light armor. Two types of armor were issued for different specifications. These jackets were made of nylon fabric and capable of stopping flak and shrapnel, but were not designed to stop bullets. Although they were considered too bulky for pilots using the Avro Lancaster bombers, they were adopted by United States Army Air Forces.In the early stages of World War II, the United States also designed body armor for infantrymen, but most models were too heavy and mobility-restricting to be useful in the field and incompatible with existing required equipment. Near the middle of 1944, development of infantry body armor in the United States restarted. Several vests were produced for the US military, including but not limited to the T34, the T39, the T62E1, and the M12. The United States developed a vest using Doron Plate, a fiberglass-based laminate. These vests were first used in the Battle of Okinawa in 1945.

The Soviet Armed Forces used several types of body armor, including the SN-42 ("Stalnoi Nagrudnik" is Russian for "steel breastplate", and the number denotes the design year). All were tested, but only the SN-42 was put in production. It consisted of two pressed steel plates that protected the front torso and groin. The plates were 2 mm thick and weighed 3.5 kg (7.7 lb). This armor was supplied to SHISBr (assault engineers) and to Tankodesantniki (infantry that rode on tanks) of some tank brigades. The SN armor protected wearers from 9 mm bullets fired by an MP 40 at around 100 meters, which made it useful in urban battles such as the Battle of Stalingrad. However, the SN's weight made it impractical for infantry in the open.PostwarDuring the Korean War several new vests were produced for the United States military, including the M-1951, which made use of fibre-reinforced plastic or aluminium segments woven into a nylon vest. These vests represented "a vast improvement on weight, but the armor failed to stop bullets and fragments very successfully," although officially they were claimed to be able to stop 7.6225mm Tokarev pistol rounds at the muzzle. Developed by Natick Laboratories and introduced in 1967, T65-2 plate carriers were the first vests designed to hold hard ceramic plates, making them capable of stopping 7 mm rifle rounds.In 1969, American Body Armor was founded and began to produce a patented combination of quilted nylon faced with multiple steel plates. This armor configuration was marketed to American law enforcement agencies by Smith & Wesson under the trade name "Barrier Vest." The Barrier Vest was the first police vest to gain wide use during high threat police operations.

In 1971, research chemist Stephanie Kwolek discovered a liquid crystalline polymer solution. Its exceptional strength and stiffness led to the invention of Kevlar, a synthetic fibre, woven into a fabric and layered, that is five times as strong as steel. In the mid-1970s, DuPont the company which employed Kwolek introduced Kevlar. Immediately Kevlar was incorporated into a National Institute of Justice (NIJ) evaluation program to provide lightweight, able body armor to a test pool of American law enforcement officers to ascertain if everyday able wearing was possible. Lester Shubin, a program manager at the NIJ, managed this law enforcement feasibility study within a few selected large police agencies, and quickly determined that Kevlar body armor could be comfortably worn by police daily, and would save lives.

In 1975 Richard A. Armellino, the founder of American Body Armor, marketed an all Kevlar vest called the K-15, consisting of 15 layers of Kevlar that also included a 5" 8" ballistic steel "Shok Plate" positioned vertically over the heart and was issued US Patent #3,971,072 for this innovation. Similarly sized and positioned "trauma plates" are still used today on the front ballistic panels of most able vests, reducing blunt trauma and increasing ballistic protection in the center-mass heart/sternum area.

In 1976, Richard Davis, founder of Second Chance Body Armor, designed the company's first all-Kevlar vest, the Model Y. The lightweight, able vest industry was launched and a new form of daily protection for the modern police officer was quickly adapted. By the mid-to-late 1980s, an estimated 1/3 to 1/2 of police patrol officers[where?] wore able vests daily. By 2006, more than 2,000 documented police vest "saves" were recorded, validating the success and efficiency of lightweight able body armor as a standard piece of everyday police equipment.Recent yearsDuring the 1980s, the US military issued the PASGT kevlar vest, rated at NIJ level II,[citation needed]being able to stop pistol rounds (including 9 mm FMJ) and fragmentation. West Germany issued a similar rated vest called the Splitterschutzweste.Kevlar soft armor had its shortcomings because if "large fragments or high velocity bullets hit the vest, the energy could cause life-threatening, blunt trauma injuries"[citation needed] in selected, vital areas. Ranger Body Armor was developed for the American military in 1991. Although it was the second modern US body armor that was able to stop rifle caliber rounds and still be light enough to be worn by infantry soldiers in the field, it still had its flaws: "it was still heavier than the concurrently issued PASGT (Personal Armor System for Ground Troops) anti-fragmentation armor worn by regular infantry and ... did not have the same degree of ballistic protection around the neck and shoulders."[citation needed] The format of Ranger Body Armor (and more recent body armor issued to US special operations units) highlights the trade-offs between force protection and mobility that modern body armor forces organizations to address.Newer armor issued by the United States armed forces to large numbers of troops includes the United States Army's Improved Outer Tactical Vest and the United States Marine Corps Modular Tactical Vest. All of these systems are designed with the vest intended to provide protection from fragments and pistol rounds. Hard ceramic plates such as the Small Arms Protective Insert as used with Interceptor Body Armor, are worn to protect the vital organs from higher level threats. These threats mostly take the form of high velocity and armor-piercing rifle rounds. Similar types of protective equipment have been adopted by modern armed forces over the world.

Since the 1970s, several new fibers and construction methods for bulletproof fabric have been developed besides woven Kevlar, such as DSM's Dyneema, Honeywell's Gold Flex and Spectra, Teijin Twaron's Twaron, Pinnacle Armor's Dragon Skin, and Toyobo's Zylon. These newer materials are advertised as being lighter, thinner and more resistant than Kevlar, although they are much more expensive. The US military has developed body armor for the working dogs who aid GIs in battle.Since 2004, U.S. Special Operations Command has been at work on a new full-body armor that will rely on rheology, or the technology behind the elasticity of liquids in skin care and automotive products. Named TALOS, this new technology may be used in the future.High Tech Ballistic fibres

High tech ballistic fibres are basically specialized fibres whose usage is not more than 5 percent of the Indian Technical textiles industry. These high performance fibres are used more in developed nations and are wholly imported in India. These are more efficient in the field of bulletproofing than specially finished natural fibres like cotton.There are broadly four classes of high tech ballistic fibres- Poly amide ( PA)- Trade names are Kevlar, Twaron , Artec Ultra High Molecular Weight Polyethylene (PE)- Trade names are Dyneema, spectra. ( Poly[p-phenylene besobisoxazole]) ( PBO)- Trade name is Zylon. (Poly[2,6-dimidazo[4,5-b:4,5-e]-pyridinlene- 1,4(2,5-dihydroxy)phenylene]) (PIPD)- Trade name M5.

Polyamide- Polyamindes are organic molecules which have been produced through polymerisation, in which the monomers are attached by amide bonds (-CO-NH). The poly amide is also known as aramid. Its IUPAC name is Poly paraphenylene terephthalamide. The para word means that the amide group is connected on the 4th carbon of the benzene ring , i.e. the amide groups are attached on opposite sides of the benzene ring. The structure formula is C14H10N2O2.(BSST MATERIAL SCIENCE BALLISTIC FIBRES)Works CitedBSST MATERIAL SCIENCE BALLISTIC FIBRES.

General properties of aramid fibres.R1What is it that Imparts the strength to para Aramid structures-1. The para position is important in providing strength to the structure. The para structure results in lesser steric hindrance in the molecule, and thus increases the strength of the molecule.2. Aromatic rings instead aliphatic chains. We know that aromatic rings are stabilized by resonance, whereas aliphatic chains are not. This is what provides extra strength to the chain.3. Strong intermolecular attractive force due to hydrogen bonding. 4. High degree of Symmetry and regularity in the internal structure.5. High Crystallinity.

R1 Kevlar: R2Kevlar is the registered tradename for a para-aramid synthetic fiber, owned by Du pont incorporated. It is related to other aramids such as Nomex and Technora. World capacity of kevlar production is estimated at about 41,000 tonnes/year in 2002 and increases each year by 510%.Why Kevlar? In the 1960s nylon and polyester represented the state of art in man made fibres. However to acieve maximum tenacity ( break strength) and initial modulus, the polymer needed to be in extended configuration and almost perfect crystalline packing. With flexible chain polymers, such as nylon or polyester, this could be accomplished only by mechanically drawing the fiber after melt spinning. This required chain disentanglement and orientalization in the solid phase, so tenacity and modulus levels were far from the theoretically possible values.In 1965, scientists at du Point discovered a new method of producing an almost perfect polymer chain extension. The polymer poly-p-benzamide was found to form liquid crystalline solutions due to the simple repetitiveness of its molecular backbone. The key structural requirement for the backbone is the para orientation on the benzene ring, which allows the formation of rod like molecular structures. These developments led us to the current formulation of KEVLAR.To illustrate the difference between liquid crystalline polymers and flexible, melt polymers, consider what happens when rod like polymer molecules are dissolved, as opposed to molecules with flexible chains. With flexible chain polymers, random coil configuration is obtained in solution, and even increasing the polymer concentration cannot degree of order. In contrast , with rigid polymers, as the concentration increases, the rods begin to associate in parallel alignment. Randomly oriented domains of internally high oriented polymer chains then develop.Liquid crystalline polymer solutions display a unique behaviour under shear. This unique aspect opened up new dimensions in fiber manufacturing and processing. Under shear forces, as the solution pass through a spinneret ( orifice), the randomly oriented domains become fully oriented in the direction of the shear and emerge with near perfect molecular orientation.The supramolecular structure is almost entirely preserved in the as spun filament structure due to very slow relaxation of the shear-induced orientation. This process is a novel, low energy way to highly orient polymer molecules and to achieve very strong fibers.This is what imparts strength to KEVLAR fibers.This concept is explained below, Step 1: In this, first a sheet is formed by para aramid chains. Multiple number of these sheets are now arranged in a radial stacking to make a rod like rigid structure.

Step 2: These rod like structures are now oriented perfectly in the direction of shear, as shear force is applied. Unlike nylon the fibres become perfectly stretched.

Properties of Kevlar :Physical propertiesThe table below lists the typical physical properties of Kevlar 29 & Kevlar 49.

The second table below compares the properties of Kevlar with other yarns.

Chemical properties:Kevlar is resistant to most of the chemicals but certain strong aqueous acids, bases and sodium hypoclorite can degrade Kevlar particularly over high temperatures and long exposure. The following table shows the effect on the breaking strength of Kevlar due to chemicals.

Effect of Water and PH on Kevlar.

Degradation can occur when KEVLAR is exposed to strong acids and bases. At neutral pH (pH 7), the filament tenacity remains virtually unchanged after exposure at 149 degrees farenheight ( 65 degrees celcius) for more than 200 days. The further the pH deviates from pH 7, the greater the loss in tenacity. Acidic conditions cause more severe degradation than than basic conditions at pH levels equidistant from neutral.Similar behaviour is seen in saturated steam generated from water at various pH levels. The results of the 16 hours exposure at 309 degrees Farenheight ( 154 degrees centrigrade) show maximum strength retention in pH6 to pH 7, with a sharper drop-off on the acdic side . ( figure 2.1).The resistance of KEVLAR to hydrolysis in saturated steam is measured in a sealed tube ( bomb) test. KEVLAR yarn ( 1,500 denier) in a skein form is held at 280 degrees Farenheight for various lengths of time in the presence of sufficient water ( pH 7) to form saturated steam. The strength loss results are determined by comparing strength data measured at room temperature for control and exposed yarns. ( figure 2.2)

Moisture Regain: Moisture regain is the tendency of most fibres to pick up or give off ambient atmospheric moisture until they reach an equilibrium moisture content at a given temperature and humidity level. Relative humidity ( RH) has a significant effect on the rate of moisture absorption by KEVLAR and the equilibrium level reached. The higher the RH, the faster KEVLAR absorbs moisture during the initial phase of moisture gain, and the higher the final equilibrium level.Bone dried KEVLAR will reach a slightly lower equilibrium moisture level than fiber that has never been bone dried. Figure 2.3 illustrates the effect of RH on the equilibrium moisture content obtained from a bone dry yarn of KEVLAR 49. This relationship is linear throughout the entire RH range.The tensile properties of KEVLAR are virtually unaffected by moisture content.

Thermal Properties of KEVLAR:KEVLAR does not melt; it decomposes at relatively high temperatures (800 degrees farenheit to 900 degrees farenheight [427 degree centrigrade to 482 degree centrigrade]) in air and approximately 1000 degrees farenheight in nitrogen, when tested with a temperature rise of 10 degree centrigrade per minute. Decomposition temperatures vary with the rate of temperature rise and the length of exposure.Figure 2.5 and 2.6 show typical thermo- gravimetric analyses ( TGAs) of KEVLAR 49 in air and nitrogen, respectively. TGAs are generated by an instrument that measures weight loss as a function of temperature rise over time. The analyses can be performed in air or in a variety of other atmospheres.For KEVLAR, as temperature increases, there is an immediate weight reduction, corresponding to water loss. The curve then remains flat until decomposition, where significant weght loss is observed.

Effect of Elevated temperature on Tensile Properties

Increasing temperatures reduce the modulus, tensile strength and break elongation of KEVLAR yarns and other organic fibres. This should be taken into consideration when using KEVLAR at or above 300degrees Fahrenheit to 350 degrees Fahrenheit for extended periods of time.Figures 2.7 and 2.8 below compares the effects of exposure to elevated temperatures on the tensile strength and modulus, respectively, of KEVLAR and other yarns.

Effect of Elevated temperatures on dimensional stabilityKEVLAR doesnt shrink like other organic fibres when exposed to hot air or hot water. Most other fibres suffer significant, irreversible shrinkage. KEVLAR has a very small, negative coefficient of thermal expansion ( CTE) in the longitudinal direction. The value of the CTE of KEVLAR is dependent on measuring technique, sample preparation and test method. ( Table II-4)Heat of combustionThe heat of combustion of KEVLAR is measured by an Emerson oxygen bomb calorimeter. Table II-5 compares the heat of combustion of KEVLAR to that of other polyamides and to an epoxy used in making rigid composites.

Specific HeatThe specific heat of KEVLAR is markedly influenced by temperature. It is more than doubles when the temperature is raised from 32 degrees farenheight to 392 degrees farenheight as seen in figure 2.9. further increases are more gradual.

Effect OF Arctic Conditions

Exposure to arctic conditions (-50 degrees Farenheight ) does not adversely influence the tensile properties of KEVLAR ( table II-6). The increase in modulus and the small decrease in break elongation at this low temperature can be attributed to a slight increase in molecular rigidity.

Effect of Cryogenic conditionsKEVLAR shows essentially no embrittlement or degradation at temperatures as low as -320 degrees Farenheight (-196 degrees centrigrade). Flammability, smoke and off- gas generation properties of KEVLAR.

KEVLAR is inherently flame resistant, but can be ignited (limited oxygen index of 29). Burning usually stops when the ignition source is removed; however, pulp or dust, once ignited, may continue to smoulder. In laboratory testing ( table II-7), fabrics of KEVLAR do not continue to burn when the source of ignition is removed after 12 seconds of contact. While the glow time increases with the thickness of the fabric, the burn length does not. No drips are experienced, which can cause flame propagation, a common problem with other organic fibres.KEVLAR is not intended to be used as fuel, nor should it be deliberately burned under any circumstances. The laboratory data shown in table II-8 were generated to provide important information in case KEVLAR is accidently burned.Burning KEVLAR produces combustion gases similar to those of wool- mostly carbon dioxide, water and oxides of nitrogen. However, carbon monoxide, small amounts of hydrogen cyanide and other toxic gases may also be produced, depending on burning conditions. The composition of off-gases from KEVLAR and other fibres under poor burning conditions is shown in table II-8.

Effect of electron radiation on KEVLAR

Electron radiation is not harmful to KEVLAR. In fact, filaments of KEVLAR 49 exposed to 200 megarads show a very slight increase in tenacity and modulus as shown in figure 2.10.

Effect of UV light on KEVLAR

Like other polymeric materials, KEVLAR is sensitive to UV light. Unprotected yarn tends to discolour from yellow to brown after prolonged exposure. Extended exposure to UV can also cause loss of mechanical properties, depending on wave-length, exposure time, radiation intensity and product geometry. Discolouration of fresh yarn after exposure to ordinary room light is normal and is not indicative of degradation.Degradation occurs only in the presence of oxygen, and not enhanced by moisture or by atmospheric contaminants, such as sulphur dioxide. Two conditions must be fulfilled before light of a particular wavelength can cause fiber degradation:i. Absorption by the polymer andii. Sufficient energy to break the chemical bonds.Figure 2.11 shows the absorption spectrum of KEVLAR, along with that of sunlight. The overlap region of these two curves- especially between 300 nm to 450nm- should be considered when specifying outdoor use of unprotected KEVLAR. This range includes the so-called near UV anart of the visible region; for effective protection of KEVLAR from UV degradation, this kind of light must be excluded.Only small amounts of this light occur in artificial light sources, such as ordinary incandescent and fluorescent bulbs, or in sunlight filtered by window glass. however, to avoid possible damage, yarn should not be stored within one foot of fluorescent lamps or near windows.KEVLAR in intrinsically self- screening. External fibres form a protective barrier, which shields interior fibres in a filament bundle or fibric. UV stability increases with size- the denier of a rope.Extra UV protection can be provided by encapsulation:1. By overbraiding with other fibres or2. By applying an extruded jacket over ropes and cables.Whenever a coating, extrudate or film is used, it shoukd not be UV- transparent. Rather, it should have the proper pigmentation to absorb in the 300 nm to 450 nm range.Figure 2.12 shows the UV stability of KEVLAR obtained with a :Fade-Ometer equipped with a xenon arc.

Short Fibres of KEVLARKEVLAR is available in several short forms, including staple and floc ( precision cut) and pulp ( fibrillated).

Kevlar Pulp Kevlar pulp id a highly fibrillated form of the fiber which can be dispersed into many different matrix systems. The fibrillation ( figure 3.2) results in a high surface area of 7m^2/g to 10 m^2/g.Kevlar pulp is non-brittle, so standard mixing and dispersion equipment will not affect the fiber size. KEVLAR pulp is available in wet form ( approximately 50%) for dilute, aqueous dispersions and dry mixes. Various fiber lengths are available to meet your engineering design needs.KEVLAR pulp enhances the performance of elastomers, thermoplastics and thermoset resins, especially where high- temperature performance is required.KEVLAR ULTRATHIX is available for use as a thixotrope in adhesives, sealants and coatings ( figure 3.3). KEVLAR ULTRATHIX disperses easily, and provides both viscosity control and reinforcement in most resin systems.

Precision cut, Short fibres

KEVLAR staple:KEVLAR staple ( figure 3.4 ) consists of precision-cut, short fibers, inch or longer. It is used to manufacture spun yarns, which provide enhanced wear resistance and comfort vs. Filament yarns. Since spun yarns are discontinuous fibers, their applications generally take advantage of barrier properties of KEVLAR, rather than the tensile and modulus properties.KEVLAR staple is also used in felts and non wovens to increase thermal insulation and vibration dampening properties. Other applications include thermoset and thermoplastic resin systems, where KEVLAR increases strength and wear resistance over a wide range of temperatures.

KEVLAR floc: KEVLAR floc ( figure 3.5) refers to precision-cut short fibers, shorter than staple, down to 1mm in length. It can be used as a reinforcement in a wide variety of resin systems. In thermoplastics, it provides increased wear resistance with minimal abrasion on opposing surfaces. In thermoset resins, it provides increased strength, without significantly affecting the viscosity of the system.

KEVLAR M/B Masterbatch

Short KEVLAR pulp is available in a masterbatch form for easy, uniform dispersion in viscous elastomers. When KEVLAR pulp is blended with Various elastomers, it gives enhanced tensile strength ( Table III-1) at elevated temperatures. It also increases the modulus ( figure 3.6), tear resistance, wear resistance and puncture resistance of the resulting compounds. To make it easier to incorporate pulp into elastomers, DU pont offers KEVLAR M/B, a masterbatch concentrate. KEVLAR M/B can also be blended with other elastomers to give desired end- use properties.

R3 Twaron Product Name: Twaron para-Aramid Yarn Chemical Name: Poly-paraphenyleneterephthalamide Synonym: p-Aramid C.A.S. Registry No.: 26125-61-1 Chemical Formula: Polymer (C8H4Cl2O2.C6H8N2)XProduct Use: Strength member in cables Ballistic protection material Elastomer reinforcement Composites, protective apparel

Hazards identification

EMERGENCY OVERVIEW No health risks have so far become available when this fiber product has been handled/processed properly and used for its intended application. Wear appropriate personal protective equipment as needed (see section 8 for additional information).

Appearance and odor: odorless yellow filament yarn, spinning fiber, staple fiber, cut fiber Other information - Fiber finish. The fiber product itself is not toxic. It may, however, contain up to 1.2% of a fiber finish. If the product is intended for special applications, e.g. in the food industry, please consult the manufacturer prior to application. So far no impairment of health has become known in cases where the product has been used for its intended application. The applied fiber finish may evaporate or decompose in cases where the product is heat-treated at temperatures of 266-374F (130-190C). If water is used for further treatment, the waste water generated by the process must be treated in a water purification plant in compliance with local regulations. Residual solvents: none. Fibers and yarns are generally provided with finishes to facilitate processing. If necessary, these finishes, and also coning oils or sizing agents, can generally be removed in an aqueous medium.

POTENTIAL HEALTH EFFECTS Primary Route(s) of Exposure: Eye contact, skin contact and inhalation. Acute Exposure: The fiber product (polymer) is non-toxic. Dust may be irritating to the respiratory tract and cause symptoms of bronchitis. This product has a low order of acute toxicity and ingestion is not expected to cause any harm. Carcinogenicity: IARC, NTP, ACGIH or OSHA does not classify this material as a carcinogen or suspect carcinogen. IARC rated p-Aramid fibrils as non-classifiable as to its carcinogenicity for animals or humans (Class III). Medical conditions aggravated: Inhalation of dust could aggravate existing respiratory condition.

Ingredients of the fibre : INGREDIENTS (w/w) CAS Number Poly-(para-phenylene terephthalamide) 100.0 26125-61-1 Additives: 1. all Twaron p-Aramid Yarn products may contain: Fiber finish (< 1.2%), sodium sulfate (< 3%), absorbed water (< 8%)

2. Specific types of Twaron products may contain: Water-blocking agents < 5% only Twaron type(s) 1052, 1002 PTFE < 40% only Twaron type(s) 1030, 1031 Silicone oil < 22% only Twaron type(s) 1030 Medical white oil < 10% only Twaron type(s) 1031 Modified polyester resin < 7% only Twaron type(s) 1484, 1486 & 1488 Epoxy composition < 0.4% only Twaron type(s) 1014, 1015 & 1016 Polyether-polyurethane < 7% only Twaron type(s) 1684, 1686 & 1688) Aliphatic polyester urethane < 6% only Twaron type(s) 2800 Fiber finish of sodium < 7% only Twaron type(s) 2255 and potassium salts of carboxylic acid

FIRST AID MEASURES

Inhalation: Remove victim to fresh air if person has been exposed to excessive quantities of fiber dust or fly. If breathing becomes difficult, oxygen may be given, preferably under physicians advice. Get medical attention if coughing or other symptoms develop.

Eye Contact: Flush eyes with large quantities of running water for a minimum of 15 minutes. If easy to do, remove contact lenses, if worn. Hold the eyelids apart during the flushing to ensure rinsing of the entire surface of the eye and lids with water. Get medical attention if eye irritation occurs.

Skin Contact: Remove contaminated clothing, shoes and equipment. Flush skin with plenty of water for at least 15 minutes. Wash contaminated clothing and shoes before reuse. Get medical attention if irritation occurs.

Ingestion: Do not induce vomiting, unless instructed by a physician. If victim is conscious, rinse mouth and give water to drink. If vomiting occurs, keep head below the hips to reduce risk of aspiration. Give fluids again. Never give anything by mouth to an unconscious person. Get medical attention as warranted.

Note to Physician: Attending physician should treat exposed patients symptomatically.

Fire Fighting measures

Conditions of Flammability: not flammable or combustible

Flash Point (Method): not determined

Upper Flammable Limit (% by volume): not determined

Lower Flammable Limit (% by volume): not determined

Auto-Ignition Temperature: not determinedExtinguishing Media: This product is not flammable or combustible. If involved in a fire, use extinguishing agents suitable for surrounding materials, such as water fog or spray, dry chemical, foam, carbon dioxide or other Class B agents. Avoid solid water stream. Do not use water if fire was caused by an electrical short circuit.

Fire Fighting Procedures: As in any fire, prevent human exposure to fire, smoke, fumes or products of combustion. Evacuate all non-essential personnel from the fire area. Fire fighters should wear full-face, self-contained breathing apparatus approved by MSHA/NIOSH and impervious protective clothing.

Fire & Explosion Hazards: This product is not defined as flammable or combustible and should not be a fire hazard under normal use conditions. Organic dust can be explosive when ideal conditions of concentration, humidity, temperature and source are met.

Hazardous Combustion Products: Do not inhale explosion or combustion vapors. Thermal decomposition may release toxic and/or hazardous products such as carbon oxides, organic compounds of low molecular weight and hydrogen cyanide in low concentration. Decomposition products are roughly comparable to those of wool.

Physical and Chemical PropertiesPhysical State / Appearance / Odor: odorless yellow filament yarn, spinning fiber, staple fiber, cut fiber Boiling Point: not applicable Bulk Density: not applicable Cloud Point: not determined Evaporation Rate (Butyl Acetate=1): not applicable Melting Point: does not melt Odor Threshold: not determined pH: not determined Partition Coefficient (n-octanol/water): not determined Pour Point: not determined Solubility in water: negligible Solubility in other solvents: not determined Specific Gravity / Density: 1440 kg/m3Vapor Density (Air = 1): not applicableVapor Pressure: not applicable Viscosity: not applicable Conditions of Flammability: not flammable or combustible Flash Point (Method): not applicable Upper Flammable Limit (% by volume): not applicable Lower Flammable Limit (% by volume): not applicable Auto-Ignition Temperature: not applicable

Stability And ReactivityStability: This product is stable at ambient temperatures and atmospheric pressures under recommended storage and handling conditions (see section 7). It is not self-reactive and is not sensitive to physical impact.

Conditions to avoid: Temperatures over 932F (500C) will cause decomposition of the products and molecular disintegration. Strong bases and acids will cause chemical decomposition (hydrolysis) of the molecules if allowed to react for a relatively long duration.

Incompatibilities: Aromatic polyamides react with strong oxidizing agents. If allowed to act on the fibers for a relatively long time, UV light will cause a darkening of their inherent yellow color and will also adversely affect their strength. Polymerization: Hazardous polymerization is not expected to occur under normal temperatures and pressures. Hazardous Decomposition Products: Thermal decomposition may release toxic and/or hazardous products such as carbon oxides, organic compounds of low molecular weight and hydrogen cyanide in low concentration.Toxicological information:INHALATION Acute exposure: The acute LC50 for this product is not available. Repeated dose exposure: The following information does not relate to the intact fibers but only to respirable, fiber-shaped particulates (RFP), which may be found in small numbers in the workplace atmosphere due to abrasive processing. RFP are fragments with diameters of less than 3 m, lengths up to 100 m and a length/diameter ratio of at least 3:1. - Subacute and subchronic exposure: Short term and subchronic (3 months) inhalation studies in rats and hamsters with an extended follow-up of up to nine months have demonstrated that p-Aramid RFP are not biopersistent. Long p-Aramid RFP are quickly transversely broken into smaller fragments and then removed from the lung. However, extremely high amounts of inhaled p-Aramid RFP may inhibit the clearance mechanism. 25 RFP/ml of air has been established as the "no observed adverse effect level" in subchronic study. Inhalation of high concentrations of RFP causes pulmonary inflammation in rats and hamsters and overload phenomena in rats. - Chronic exposure: Lifelong exposure to concentrations of 100 and 400 RFP/ml caused pulmonary fibrosis in rats. The fibrosis was largely reversible after cessation of exposure. No malignant tumors resulted from the lifelong inhalation tests in rats. Instead, proliferative cystic tissue changes were observed in rats after exposure to particulates. They occur mainly in (female) rats and have never been observed in human beings. These cysts were subject of scientific debate for an extended period of time, but current consensus holds that they are not malignant and that their occurrence in animals has no relevance to humans.

Other routes of exposure: Intraperitoneal injections of excessive amounts of p-Aramid RFP caused only a non significant increase in the observed number of mesotheliomas. The validity of the intraperitoneal test for the prediction of carcinogenicity is questionable. SKIN Acute contact: Dermal toxicity for this product is not available. Slight skin irritation has been observed in isolated cases. Chronic contact: No known effects for this product. EYES: While this product has not been tested, it is expected that it would be minimally irritating to the eyes based on tests with similar products. INGESTION Acute exposure: The oral LD50 is not available for this product.. Chronic exposure: No known effects. Sensitization: Not data available for this product. Carcinogenicity: IARC, NTP, ACGIH or OSHA does not classify this material as a carcinogen or suspect carcinogen. IARC rated p-Aramid fibrils as non-classifiable as to its carcinogenicity for animals or humans (Class III). Mutagenicity / Teratogenicity / Embryotoxicity: No data available. Target Organs: Skin, eyes and respiratory tract. Other Toxicological Effects: In the event that the product is to be used in special areas of application, e.g. food industry or the medical/surgical sector, please consult manufacturer beforehand.

Disposal considerations

Waste Disposal: In its unused condition, this product is not considered to be a RCRA-defined hazardous waste by characteristics or listings. It is the responsibility of the waste generator to evaluate whether his wastes are hazardous by characteristic or listing. Dispose in accordance with all local, state and federal regulations. NOTE State and local regulations may be more stringent than federal regulations. Container Disposal: Containers should be cleaned of residual product before disposal or return. Since emptied containers retain product residue, follow label warnings even after container is emptied. Empty containers should be disposed of or shipped in accordance with all applicable laws and regulations.

Ultra High Weight molecular Polyethylene

Ultra-high-molecular-weight polyethylene (UHMWPE, UHMW) is a subset of the thermoplastic polyethylene. Also known as high-modulus polyethylene, (HMPE), or high-performance polyethylene (HPPE), it has extremely long chains, with a molecular mass usually between 2 and 6 million u. The longer chain serves to transfer load more effectively to the polymer backbone by strengthening intermolecular interactions. This results in a very tough material, with the highest impact strength of any thermoplastic presently made.[1]UHMWPE is odorless, tasteless, and nontoxic. It is highly resistant to corrosive chemicals except oxidizing acids; has extremely low moisture absorption and a very low coefficient of friction; is self-lubricating; and is highly resistant to abrasion, in some forms being 15 times more resistant to abrasion than carbon steel. Its coefficient of friction is significantly lower than that of nylon and acetal, and is comparable to that of polytetrafluoroethylene (PTFE, Teflon), but UHMWPE has better abrasion resistance than PTFE. As the name suggests the monomer of this polymer is ethylene shown below.

UHMWPE is a type of polyolefin. It is made up of extremely long chains of polyethylene, which all align in the same direction. It derives its strength largely from the length of each individual molecule (chain). Van der Waals bonds between the molecules are relatively weak for each atom of overlap between the molecules, but because the molecules are very long, large overlaps can exist, adding up to the ability to carry larger shear forces from molecule to molecule. Each chain is bonded to the others with so many Van der Waals bonds that the whole of the inter-molecule strength is high. In this way, large tensile loads are not limited as much by the comparative weakness of each Van der Waals bond.When formed to fibers, the polymer chains can attain a parallel orientation greater than 95% and a level of crystallinity from 39% to 75%. In contrast, Kevlar derives its strength from strong bonding between relatively short molecules.The weak bonding between olefin molecules allows local thermal excitations to disrupt the crystalline order of a given chain piece-by-piece, giving it much poorer heat resistance than other high-strength fibers. Its melting point is around 130 to 136C (266 to 277F),[6] and, according to DSM, it is not advisable to use UHMWPE fibers at temperatures exceeding 80 to 100C (176 to 212F) for long periods of time. It becomes brittle at temperatures below 150C (240F).[citation needed]The simple structure of the molecule also gives rise to surface and chemical properties that are rare in high-performance polymers. For example, the polar groups in most polymers easily bond to water. Because olefins have no such groups, UHMWPE does not absorb water readily, nor wet easily, which makes bonding it to other polymers difficult. For the same reasons, skin does not interact with it strongly, making the UHMWPE fiber surface feel slippery. In a similar manner, aromatic polymers are often susceptible to aromatic solvents due to aromatic stacking interactions, an effect aliphatic polymers like UHMWPE are immune to. Since UHMWPE does not contain chemical groups (such as esters, amides or hydroxylic groups) that are susceptible to attack from aggressive agents, it is very resistant to water, moisture, most chemicals, UV radiation, and micro-organisms.Under tensile load, UHMWPE will deform continually as long as the stress is presentan effect called creep.

Spectra Fibres: Spectra fibre is a high performance technical fibre developed by Alliedsignal. This company has also developed & patented The Shield Technology Revolution Shield Technology - as an entirely new way of making non-woven fabrics and reinforcing composites. AlliedSignal Performance Fibers also converts Spectra fiber into Spectra Shield and SpectraFlex, specialty composites for armor.i. Structure : The spectra fibre is a trade name for a polyethylene polymer fibre developed by the engineers of Alliedshied. The idea of the strength of this fibre comes from the fact that very compact carbon carbon bonds in diamond makes diamond the hardest naturally occurring substance in the world. It is made by the gel spinning process that creates an outstanding molecular orientation within the filament. This is what gives the fiber it's incredible strength near zero stretch and unparalleled strengh. Spectra Shield composite is the high performance armor material used in dozens of applications from soft concelable body armor to hard armored limousine doors and panels. Spectra Shield composite's consists of two unidirectional layers of Spectra fiber arranged to cross each other at 0 to 90 degree angles and held in place by a flexible resin. Both the fiber and the resin layers are sealed between two thin sheets of polyethylene film similar to Saran Wrap. The result is an incredible strong, thin and lightweight non-woven ballistic material that is unbeatable in the test lab and the field.ii. Propetries:1. Physical Properties:

Product FamilySpectra fiberWeight/ Unit Length(denier) / (decitex)Ultimate Tensile Strength(g/den) / (Gpa)Modulus(g/den) / (Gpa)Elongation(%)BreakingStrength (lbs)Density(g/cc) / (lbs/in3)FilamentTowFilament(dpf)

S-900650-926650 / 72230.5 / 2.61920 / 793.6440.97 / 0.0356010.8

12001200 / 133330 / 2.57850 / 733.9790.97 / 0.03512010.0

24002400 / 266729.5 / 2.53915 / 783.9157.70.97 / 0.03524010.0

48004800 / 533326.5 / 2.27885 / 763.62810.97 / 0.03548010.0

56005600 / 622225.5 / 2.18775 / 663.53150.97 / 0.03548011.7

S-10007575 / 8343 / 3.681550 / 1332.970.97 / 0.035401.9

100100 / 11140.5 / 3.471580 / 1352.990.97 / 0.035402.5

130130 / 14438 / 3.251390 / 1133.211.10.97 / 0.035403.3

180180 / 20038 / 3.251310 / 1123.315.10.97 / 0.035603.0

215215 / 23938 / 3.251320 / 1132.9180.97 / 0.035603.6

275275 / 30636 / 3.081320 / 1133.1220.97 / 0.035604.6

375-133375 / 41735 / 3.001200 / 1033.1290.97 / 0.035606.3

375-189375 / 41735 / 3.001200 / 1033.1290.97 / 0.035606.3

435-145435 / 48337.5 / 3.211260 / 1083.3360.97 / 0.0351203.6

435-195435 / 48337.5 / 3.211260 / 1083.3360.97 / 0.0351203.6

650-115650 / 72236 / 3.081175 / 1013.3520.97 / 0.0351205.4

1300-1431300 / 144437.5 / 3.211345 / 1153.3107.50.97 / 0.0352405.4

1300-1591300 / 144435.5 / 3.041300 / 1113.3101.70.97 / 0.0352405.4

1600-1601600 / 177835.5 / 3.041170 / 1003.5123.40.97 / 0.0352406.7

1600-1801600 / 177938 / 3.251380 / 1183.31350.97 / 0.0353604.4

26002600 / 288934 / 2.911135 / 973.51950.97 / 0.0354805.4

Spectra is so light that it floats on water. Spectras high tenacity makes it 8 to 10 times stronger than steel, 40 percent stronger than aramids and stronger and lighter than virtually every other commercial highmodulus fiber. With outstanding toughness and extraordinary viscoelastic properties, Spectra fiber can withstand highload strain-rate velocities. It has excellent vibration damping, flex fatigue and internal fiber-friction characteristics, and its low dielectric constant makes Spectra fiber virtually transparent to radar. High resistance to abrasion Resists corrosion

2. Chemical properties:

It exhibits superior resistance to chemicals, water, and ultraviolet light.iii. Uses: Spectra fibers are used in: Police and military ballistic vests. helmets and hard armor for vehicles and aircraft. Marine lines and commercial fishing nets. Industrial cordage and slings. Cut-resistant gloves and slash-resistant protective gear.

PBO Poly (p-phenylene-2,6-benzobisoxazole) (PBO) is a rigid-rod isotropic crystal polymer. PBO fibre is a high performance fibre developed by TOYOBO (Japan) and has superior tensile strength and modulus to Aramid fibres, such as Kevlar, Technora and Twaron. It also has outstanding high flame resistance and thermal stability among organic fibres. PBO fibre shows excellent performance, in such properties as creep, chemical resistance, cut/abrasion resistance, and high temperature abrasion resistance - far exceeding other Aramid fibres.PBO fibre's moisture regain is low (0.6%) and it is dimensionally stable against humidity. PBO fibre is quite flexible and has very soft hand, in spite of its extremely high mechanical properties.Over the past ten years Future Fibres has pioneered the use of PBO for yacht rigging and has proven it to provide remarkable performance and longevity. PBO's properties deliver the lightest, smallest cables available on the market today.The monomer

ZylonFiber R5Zylon (PBO fiber) is a super fiber with strength and modulus that almost doubles p-Aramid fiber. Zylon has superior creep resistant to p-Aramid fibers and is very heat resistant, with a decomposition Temperature of 650C (1202F) and has extremely high flame resistance. Zylon is not light resistant and shows a decrease in strength with exposure to sunlight. Zylon products for outdoor use have to be protected by convering materials.ZylonFiber Properties: Highest tensile strength and tensile modulus among high-performance fibers Creep resistant Extremely heat and flame resistant Decomposition temperature of 1202F Low shrinkage in hot air Strength decreases in conditions of high humidity Strength decrease with exposure to ultraviolet light and visible light Stable with most organic mediums (methanol, gasoline, brake fluid, etc.) Strength decreases in exposure to strong acids

In the 1970s, DuPont reported that extended chain, all para-aromatic polyamides (aramids) gave high strength, high modulus bres when processed from liquid crystalline solutions. The ability greatly to increase the order in the liquid crystalline state, compared to conventional polymer solutions, offered an excellent opportunity to design and process new Para-ordered polymer systems for bre-reinforced composites. Aheterocyclic compoundis acyclic compoundthat has atoms of at least two differentelementsas members of its ring(s). One class of heterocyclic polymer system that could meet all the harsh requirements for advanced aircraft and aerospace applications and could be obtained in the form of bres was the benzobisazole materials, which have ve-membered rings on either side of benzene rings. Poly(p-phenylene benzobisoxazole) (PBO) and poly(p-phenylene benzobisthiazole) (PBT) have received the most attention,Manufacture of PBO bres

Stoichiometric amounts of amine and TA are heated in 77% PPA at 6080 C for the dehydrochlorination of the amine monomer. The temperature is lowered to 50 C and P2O5 is added to obtain the high degree of polymerization (between 8284%). Rigid rod polymers decompose at high temperatures without melting and can be dissolved in very few solvent systems owing to their aromatic structure and to their rigid molecular backbone. Conventional melt-spinning and solution-spinning technologies cannot therefore be used. These bres, however, can be spun from solutions in PPA via the dry-jet wet-spinning technique.Mechanical properties of Zylon ZYLON (PBO fiber) is the next generation super fiber with strength and modulus almost doubles that of p-Aramid fiber.

ZYLON shows 100C higher decomposition temperature than p-Aramid fiber. The limiting oxygen index is 68, which is the highest among organic super fibers.Light resistance Thermal properties

A significant difference of weight loss behavior is observed at 500C between ZYLON and Aramid fibers.

The strength of ZYLON gradually decreases even at the temperature of less than 100C in high humidity condition. ZYLON fiber should be stored free from high humidity at normal room temperatures.

Abrasion resistance

Chemical resistance Exposure to strong acids causes strength losses. However, ZYLON is more stable than p-Aramid.

ZYLON is stable to alkaline at room temperature. NaClO (bleach) does not cause strength loss for ZYLON at room temperature.

M5 fiber R5

The ballistic impact potential of M5 fiber-based armor systems is estimated using an armor materials by design model for personnel armor; the model is based on a dimensional analysis of the mechanical properties of the fibers used to construct the armor system. The model indicates that M5 fiber-based armor has the potential to substantially decrease the weight of body armor while enhancing or maintaining impact performance. Composite fragmentation armor systems were developed using less than optimal quality M5 fiber and tested under ballistic impact; the performance of these armor systems was exceptional.IntroductionM5 fiber is a high performance fiber originally developed by Akzo Nobel (Brew et al, 1999; van der Jagt and Beukers, 1999; Sikkema, 1999; Lammers et al, 1998; Klop and Lammers, 1998; and Hageman et al, 1999) and currently produced by Magellan Systems International (Magellan). This work describes the potential of M5 as an armor material and illustrates that potential by examining the ballistic impact response of composite materials which contain less than optimal M5 fiber from the early stages of the fibers development.

M5 fiber is based on the rigid-rod polymer poly{diimidazo pyridinylene (dihydroxy) phenylene}; the polymer repeat unit is illustrated in Figure 1. The crystal structure of M5 is different from all other high strength fibers; the fiber features typical covalent bonding in the main chain direction, but it also features a hydrogen bonded network in the lateral dimensions [Klop and Lammers, 1998]. M5 fibers currently have an average modulus of 310 GPa, (i.e. substantially higher than 95% of the carbon fibers sold), and average tenacities currently higher than aramids (such as Kevlar or Twaron) and on a par with PBO fibers (such as Zylon), at up to 5.8 GPa. The first composite test bars that were tested for axial compressive strength confirmed the high compressive properties of the fiber in composite form, with onset of plastic deformation being found at stress levels up to 1.7 GPa in 3- and 4-point bending.An ideal fiber for ballistic protective equipment would be affordable and possess properties that make it an attractive fiber for multiple applications. That is, since the demand for ballistic protective materials is relatively small compared to the demand for affordable high performance structural composite materials, the economies of scale resulting from serving multiple markets should make the fiber more viable.With respect to mechanical properties, such a fiber should possess a high tensile and compressive modulus, high tensile and compressive strength, high damage tolerance, low specific weight, good adhesion to matrix materials (for structural composites) and a good temperature resistance. Up until the discovery of M5, no single fiber has existed with all of these advanced properties in one molecular structure.Problems associated with the inability to effectively de-gas the polymer dope prior to spinning created a situation where air bubbles had formed upstream of the spinneret. Figure 2 is a photograph of an air bubble which had formed over one of the spinneret holes.The fibers produced for this work were washed on bobbins with no tension and heat treatment was performed with low tension. These problems lead to fibers with less than optimal crystal orientation, and hence less than optimal ultimate mechanical properties (e.g. average fiber strength was 4 GPa). Recently completed modifications to the bench-scale spin line to rectify these problems have already resulted in substantially increased fiber mechanical properties (e.g. single fiber strength of 7.2 GPa has already been observed), These are expected to correspondingly increase ballistic impact performance.

Fig. 2. Air bubble formed at spinneret

Despite the fact that the ultimate mechanical properties of the available M5 fibers were lower than we would have estimated to be required in order for the fiber to be a viable high performance ballistic protective material, it was decided to conduct ballistic impact tests to determine whether M5 had intrinsic limitations that might make the fiber unsuitable as a ballistic protective material.PreparationM5 fiber is prepared by a condensation polymerization between tetraaminopyridine and dihydroxyterephthalic acid using diphosphorus pentoxide as a dehydrating agent. The polymer mixture is then heated and extruded to form brightly blue polymer fibers. The fibers are then washed extensively with water and base in order to remove the phosphoric acid generated by the hydration of diphosphorus pentoxide from the polymer.

In order to remove the water from the fiber structure and enable the intermolecular hydrogen bonds to be created and thus greatly increase the strength of the polymer, the fiber is heated and exposed to controlled stress. This aligns the atomic structure of the fiber in a better configuration for tensile and compressive strength.

M5 MECHANICAL PROPERTIESAverage mechanical properties of single fibers which were tested at a gage length of 10 cm are listed in Table 1..

The strength of the fibers tested as part of this work is low compared to the goal mechanical properties for M5. The strength was low even when compared to the best available fibers currently in production; fiber properties are continually increasing with advances in processing of the fiber. Recently, M5 fibers with tensile strength of up to 7.2 GPa and tensile modulus of 344 GPa have been observed. The current best available strength is nearly twice the strength and 25% more stiff than the fiber used as part of this work, despite the fact that these improved fibers were obtained using fiber produced from the same bench-scale batch-process that was used to produce the earlier fiber. M5 fibers investigated as part of this work were observed to be stable after exposure to visible and ultraviolet light. After exposure to Zenon lamp for up to 100 hours, the M5 fibers retained essentialy all of the virgin fiber strength; by comparison, Zylon fibers lost over 35% of the virgin fiber strength at this exposure time.The M5 yarns were similarly stable after exposure to elevated temperature and humidity, as illustrated in Figure 3. After exposure to 180 F and 85% relative humidity (RH) for up to 11 weeks, the M5 yarns retained essentially all of the virgin fiber strength; Zylon yarns lost over 20% of the virgin strength at this exposure time. The scatter in the data for M5 strength loss of Figure 3 is attributed to the (large) defect frequency in the fiber due to previously mentioned processing conditions; scatter in the data for fibers exposed to light was even larger than for the yarns illustrated in Figure 3. Elemental analysis of the M5 fibers indicated that the fibers contained 0.11% phosphorus by weight; Zylon fibers, spun from the same solvent (polyphosphoric acid), were found to contain 0.34% phosphorus. The connection between reduced acid content and poor hot/wet performance is not clear.Fibers fractured under quasi-static tensile stress showed a highly fibrillated fracture morphology, as illustrated in Figure 4. The extensive axial splitting of the fibers is typical of the fibers observed in this work. Recent fiber physics theory, as proposed by Northolt and Baltussen, 2001, has also been used to project the target mechanical properties for M5. This theory allows for the prediction of target mechanical properties for any high strength fiber, and is based on both empirical data and observation of a large number of high strength fibers, including aramids, PBO, and others.

Chapter 3- Methodology ( Weaving) Kevlar fibre is one of the most widely-used impact-proof materials in many industries, finding different applications, particularly in the production of bulletproof and armour materials, wear resistant brakes, and aeronautical materials. Kevlar fibres have also found application in the production of high-performance materials due to their obvious very high strength, distinguishing them from ordinary industrial fibres.To develop bulletproof materials, it is important to understand how they work and interact with a high-speed projectile. When a projectile impacts a fabric, the fibre of the yarn that mainly receives the impact force absorbs a great deal of energy and, thus, produces a counterforce projectile. The impact energy is absorbed in the process of the complicated geometric strength and tensile deformation of Kevlar fibre. The theory predicts that any weaving point brings about a concentration of energy, thus weakening the material, which is the basis a very important rule: the longer the fibre, the better the ballistic resistance. Hence the best conditions for impact energy dissipation are found in fibrous materials without weaving points. To solve this problem, a material of Uni-Direction construction (e.g. Honeywell Co. product) was developed and has been available on the market since 1990. These fabrics have been widely used over the past decades to improve the hardness, stiffness and weight of bulletproof material . However, improving the ballistic resistance of materials still remains an important task for researchers. Fabric construction diagram; a) Plain weave is the commonest weaving method of producing tough fabrics with the shortest inter-weave fibre length and easy-creasing characteristics; b) Twill woven fabric has fewer warp-weft interweaves than plain weave for the same unit area. The fibre is long enough to allow the design of different float yarns; c) Satin woven fabric has the fewest warp-weft interweaves with the longest inter-weave fibre length and high softness in every single unit area; d) Basket weave is a variation of plain weave, in which a few warps cross alternately side-by-side with a few weft yarns. Basket weave fabrics are more pliable and stronger but less stable than 1/1 Plain weave. Basket weave is typically used in the composite industry.The ballistic resistance performance of fabrics does not exclusively depend on the features of the materials impacted but also on many projectile characteristics. Generally, the bullet protection might be affected by the following main factors: As concerns projectiles: (1) the mass and pattern, (2) the velocity, (3) the material it is made of, (4) the shape and size, and (5) the impact surface. As concerns fabrics: (6) the weave construction, (7) the weave density, (8) the strength, (9) the ultimate elongation, (10) the surface stiffness, and (11) the squeezing-through protection.This research was devoted to the testing of para-aramid fabrics of equal specifications in terms of the raw material used and density. However, different woven constructions were tested to study their influence on the impact-proof behaviour of fabrics subjected to impact by projectiles of various types.ExperimentalMaterials A SUZUKI loom was used to weave Kevlar 29 1000d/666f, making fabrics with the same density but of different fabric construction. The density of the fabric construction was 28 roots/per inch. Four popular weave constructions were investigated in this study: Methods

Mechanical test A tensile test was performed using the material strength tester MTS Test Star IIs (Taiwan Textile Research Institute) to investigate the strain-stress behaviour of the materials developed. With the MTS Test Star IIs, (515) cm2 samples of each material were tested dynamically for their tensile-strength behaviour based on Standard ASTM D 638 .Estimation of bulletproof properties Ballistic Impact Test. Ballistic impact tests were performed with various Kevlar woven fabrics in order to determine the limit velocity (V50), which is one of the important bulletproof characteristics of this type of material. To project the projectile at a low speed (below 250 m/s), a firearm with a shortened barrel or reduced explosive charge was used in this study. The low-speed projectiles produced were impacted against Kevlar fabrics of various constructions, and the test results were analysed based on the Ballistic limit Criteria V50 mode (BLC).Ballistic Resistance Energy Methods. Two Energy Methods were used in this research to estimate the bulletproof properties of the materials, namely the constant speed and MIL-STD-662F methods. In both of these the fibre woven fabrics tested are impacted at a constant speed and in a controlled manner. A thick block of Roma Plastilina clay was placed behind the fabric. When the projectile impacted the target, its impact force was transmitted to the plastilina clay through the dispersion of the stress from the fabric, making an indentation on the surface of the plastilina clay (Figure 2). The shape and depth of each indentation can serve for estimation of the bulletproof quality of the product.Constant speed method. The fabric tested was impacted at a constant projectile velocity of 100 m/s, and the indentation was measured after the impact. Then the capability of the fabric construction to resist the projectile was analysed based on this indentation. The constant speed test method used in this study is demonstrated in Figure 3 a. 10 cm diameter width. The test sample was impacted by one bullet, and a clamp was used to prevent the movement of the sample (Figure 3 b). An indentation was clearly observed on the surface of plastilina clay of 4.5 cm diameter width (Figure 3 c) after the test, which was then measured as shown in figure 3d.

MIL-STD-662F is another energy method commonly used to test bulletproof materials. The fabric to be tested is impacted at different speeds due to different powder dosages, and the speed at which the impact brings about a 44 mm indentation on the surface of the plasticine clay behind the fabric assessed is accepted for the limit velocity of a V50 projectile. The bullets used in this study were MIL-P-46593 7.62 mm 44 grain (2.8 g) Fragment Simulating Projectiles (FSP) as specified in MIL-STD-662F, and Roma Plastilina No. 1 clay was applied as witness clay. The speed was adjusted during the test to produce a 44 mm indentation on the surface of the plasticine clay behind the fabric assessed. This controlled speed is accepted as the limit velocity of the fabric. Results and discussion Fabric tensile test The strength and elongation of the fibre woven fabrics tested are summarised in Table 1. These data evidence both the strength and rigidity or pliability of the fabrics with different weave constructions. Among the fabrics tested, 33 basket, 1/1 plain, and 1/3 twill weaves provide the highest strength values ; at the same time these materials demonstrate quite good pliability with tensile elongation 10%. The weakest material is 8H satin.

Comparing 1/3 and 2/2 twill weave materials, one can see that despite the low difference in their strength, they differ appreciably in their rigidity. Moreover, 1/3 Twill is rather pliable, whereas 2/2 Twill is rather rigid. A similar situation was observed for 22 and 33 Basket weave materials: the latter is much more pliable than the former.

Ballistic Impact Test Table 2 shows the limit velocity determined in a low-speed impact test of various constructions of 1000D Kevlar fabric. After conducting a normalisation analysis, it was found that the Plain weave construction has the best ballistic resistance performance. It is worth noting that samples 5 (22) and 6 (33), both of Basket weave construction, differ from each other significantly. The fabric damage model might be the reason for this difference. When a projectile impacts a fabric, its fibres are damaged in various ways: drawn out, broken (torn), or a combination of both. Additionally the piercing of the projectile might be the cause of fibres being pushed from the projectile path, especially in the case of pointed bullets, as is seen in Figs. 5 a and b. Among the fibre woven fabrics tested, Plane weave obviously provides the most stable fabric construction, which must inhibit the projectile from pushing fibres and squeezing through the fabric. In our opinion this is the main reason why Plane weave shows the best bulletproof properties in these tests (Table 2) compared with other weave constructions.Ballistic Resistance Test When different single-layer fabric constructions are subjected to a high-speed FSP impact at fixed energy, a clear bullet mark is left on the surface of the fabric impacted, and an indentation is clearly seen on the surface of the plastilina clay behind the fabric (Figure 3 a and b). The results of the single-layer test for both the indentation and limit velocity are given in Table 3. The cross-section of the FSP is U-shaped, hence it is not easy for it to damage the fabric, indicating a smaller indentation on the surface of the plastilina clay and the better ballistic resistance performance of fabrics against FSP compared with both AP steel-cored or AK-47 Metal bullets. As a result, single-layer indentations brought about by an FSP impact at afixed energy bring about rather few changes in different fabrics varying in the range from 5 to 7 mm (Table 3), making it difficult to establish the ballistic resistance performance of fabrics precisely . However, comparing the dissipated energy normalised (Table 3), it can be concluded that the best results are demonstrated by 1/1 Plain weave (1st line) and 1/3 Twill weave (3rd line). To overcome the problems in the more precise estimation of FSP bullet proof properties, the impact must be carried out at high speed with increased energy, and the difference shall be indicated using the limit velocity. Table 4 shows the FSP limit velocity of a 44mm indentation acquired by impacting 7-layer fabrics of different construction in accordance with the MIL-STD-662F test. Basket 22 and 33 materials differ from each other significantly with respect to the FSP limit velocity (lines 5 and 6 in Table 4), despite both being of a Basket weave construction. When laminated fabric samples were tested, however, 22 had the highest limit velocity against the FSP because it contains a larger quantity of fibres in a unit area, hence the bullet is completely blocked in the material by its fibres under their tensile strength, similar to the situation shown in Figure 5 a.

For other fabric constructions, Figure 6 a shows that the bullet perforates fabrics of Satin weave construction under their squeezing force, results in a decreased ballistic resistance performance. However, the advantage of the longer the fibre, the better the ballistic resistance performance might manifest under conditions of few weaving points with long fibres if the number of fibres were large enough to block the bullet. In fact, the Satin weave construction has long fibres of inadequate density, hence the fibres are drawnout by the bullet, as shown in Figure 6 a, losing their ballistic resistance capability. On the other hand, Plain and Twill weave constructions have a higher density of warp-weft interweaves, thus they can effectively resist the impact of the projectile (Figure 6 b) and bring the ballistic resistance capability of the fibres into full play. The lamination effect of the fabric also contributes to the ballistic resistance performance by improving the stability of the fabric construction. ConclusionsAnalysing the experimental data obtained, it follows that diverse woven constructions behave in various ways under different conditions. However, comparing these data, the following main conclusions can be drawn: Among the samples of Kevlar woven fabrics tested, the 1/1 Plain weave construction demonstrates the best proofing properties against armour-piercing and rifle bullets, particularly at low speeds (low energy). In the high-speed FSP bullet test of multilayer constructions, the 22 Basket fabric had a higher ballistic resistance performance, followed by the 1/1 Plain weave construction; the ballistic qualities of both these weave constructions appreciably exceed those of other fibre woven fabrics. The Satin woven fabric exhibited the weakest bulletproof properties in all the tests, apparently because of the weak stability of its construction. In our opinion, to withstand a projectile impact, fibre woven fabrics should have as strong a stability of their construction as possible. Whereas previous studies showed that 1/1 plain fabrics present the highest V50, our research reveals that basket 22 fabrics have the highest energy absorbing capacity under low speed impact.In all probability, to obtain bulletproof materials that work well enough under different conditions, one should design a multilayer system with several weave constructions of various types, e.g. via a co