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Nonwovens / Technical Textiles

Specialty Fabrics Find A Home

The growing protective fabric and body armor markets present opportunities for specialty fabric and fiber manufacturers.

Richard G. Mansfield, Technical Editor

S ome of the first documented references to the use of body armor in warfare were made in ancient Egypt (circa 3000 B.C.). They describe a wraparound garment that extended from armpits to knees reinforced with quilting and supported by shoulder straps. During this period, the Sumerians used helmets that were tight-fitting caps of beaten copper. In Syria (circa 1400 B.C.), the national costume - a sleeved shirt - was reinforced with bronze scales and used as armor for charioteers.

More Recent History Of Body Armor

After the assassination of President William McKinley in 1901, Congress showed interest in the development of body armor. Garments were developed that were effective against low-velocity bullets traveling at 400 feet per second or less, but these proved ineffective against the new generation of bullets that traveled at speeds of up to 600 feet per second. The manufacturing cost at the time - $80 per unit - also was prohibitive. Archduke Franz Ferdinand of Austria was said to be wearing body armor of this type when he was assassinated in 1914. He had the bad luck to be shot in the head.

A new generation of ballistic vests was introduced during World War II. The flak jacket, used mainly by the military, was made of ballistic nylon and provided protection from munitions fragments. It was very cumbersome and was ineffective against most rifle and pistol bullets.

The United States witnessed a dramatic increase in law officer fatalities from 1966 to 1971, when the number of law officers killed in the line of duty more than doubled. The majority of the fatalities occurred from handgun fire. To address this problem, the National Institute of Law Enforcement and Criminal Justice - predecessor of the Washington-based National Institute of Justice (NIJ) - initiated a research program to investigate the development of a lightweight body armor that on-duty police could wear full-time.

The investigation identified new materials that could be woven into a lightweight fabric with excellent ballistic-resistant properties. The National Bureau of Standards - now known as the National Institute of Standards and Technology (NIST), headquartered in Gaithersburg, Md., and Boulder, Colo. - mounted a parallel effort. Of all the developments by NIJ in the 1970s, the most significant was the use of Wilmington, Del.-based DuPont's Kevlar® aramid fiber. NIJ Technology Assessment Program Manager Lester Shubin and Army Land Warfare Technology Specialist Nicholas Montanarelli tested fabric made with Kevlar at a gun range and found that bullets did not go through it.

From 1971 to 1976, more than $3 million of NIJ funds were used for the development of body armor. The research and development program was a team effort involving private companies and government agencies. Private contractors included El Segundo, Calif.-based Aerospace Corp. and Mitre Corp., located in Bedford, Mass., and McLean, Va. Government agencies involved in the program included Edgewood Arsenal, Aberdeen Proving Grounds, the US Army Soldier Systems Center,  NIST, the Lawrence Livermore Laboratory, the Federal Bureau of Investigation and the Secret Service.

The development of body armor by NIJ took place over several years and was a four-phase effort. In 1975, an extensive test of the new Kevlar body armor was conducted using 15 urban police forces in cities having populations of more than 250,000. The tests involved 5,000 garments, including 800 purchased from commercial sources. The tests showed the body armor could be worn without restricting the police officers' ability to do their jobs, and, more importantly, that the vests worked.

The demonstration body armor issued by NIJ was designed to ensure the wearer a 95-percent probability of survival after being hit with a .38 caliber bullet at a velocity of 800 feet per second. Furthermore, the probability of requiring surgery if hit by a projectile was to be 10 percent or less.

A final report released in 1976 concluded that the new ballistic material was effective in providing a lightweight and wearable bullet-resistant garment for full-time use. Private industry recognized the market potential for the new body armor, which soon became commercially available.

Police officers' most common threat is from a gun, while correctional officers' major threat is from stab wounds. In response to the needs of the correctional community, NIJ developed a performance standard for stab- and puncture-resistant body armor in cooperation with other organizations in the United States and the United Kingdom.

Military Protection

Though it protects well, armor is one of the heaviest items worn or carried by troops. Engineers on the Ballistics Technology Team at the US Army Soldier Systems Center, Natick, Mass., are working to develop better and lighter ballistic protection systems for our troops. "The Army is putting the best available armor materials into soldiers' armor," said Philip Cunniff, a research mechanical engineer at the center. "Part of our work in the Ballistics Technology Team is to develop new materials and techniques to lighten the load of those armor systems."

In the 1990s, an improved version of Kevlar helped lighten vests by 25 percent and increased ballistic protection. The team's objective is to reduce the weight of armor by another 25 to 30 percent without losing performance. As part of this project, they are working with a range of high-performance fibers.

Fibers For Ballistic Fabrics

Kevlar, patented in 1966, was based on the work of Stephanie L. Kwolek and Herbert Blades of DuPont. The first DuPont plant for the fiber was built in Richmond, Va., in 1971, and commercial production  began in 1972.

Kevlar is an exceptionally strong material: Currently, it is produced in three grades, and even the weakest is much stronger than steel and only half as dense. It is used for many applications such as bulletproof vests, where strength and low weight are top priorities. Over the years, DuPont has continued to improve the fiber properties to boost its performance in ballistic applications.

DuPont's development and marketing efforts for ballistic fabrics have included programs such as the International Association of Chiefs of Police (IACP)/DuPont Kevlar Survivors Club and the Partners Program™ to aid in protecting the lives of law enforcement and correctional officers.

Teijin's Twaron™ Para-Aramid Fiber

The Netherlands-based Akzo Nobel's fibers business unit developed Twaron®, a super-strong para-aramid fiber, in the early 1970s. In 1976, the first pilot plant for Twaron was built, and by 1985 five plants were operational on two sites. At the end of 2000, Twaron activities were taken over by Teijin Ltd., Japan, and a major capacity increase was completed in 2003. Teijin projects an 8- to 10-percent increase in the worldwide aramid fibers market in future years, and is adding another 5- to 10-percent increase in capacity. To support Twaron use in ballistic applications, Teijin maintains a shooting range in Germany and conducts ballistic fabric production at the Textile Technical Institute in Germany.

Twaron CT microfilament is used in ballistic products such as helmets and in vehicle laminates that can be incorporated during production or as an aftermarket addition. The Twaron laminate is used in cars, security vans, combat vehicles, trucks for United Nations missions and aircraft.

After a ceramic plate breaks up a bullet, the Honeywell Spectra® Shield backing absorbs the remaining energy. Photo courtesy of Honeywell Specialty Materials/Honeywell Spectra, and Design Manifesto

Honeywell's Spectra® Fiber

In the mid-1970s, A.J. Pennings, Ph.D., and his associates developed a method for gel spinning high molecular weight, high-density polyethylene to produce ultra-high-strength polyethylene fibers. Some of these patents were assigned to Stamicarbon, The Netherlands. Development was pursued by The Netherlands-based DSM Dyneema BV, and some of this technology was licensed to AlliedSignal Inc. - now the Colonial Heights, Va.-based Advanced Fibers & Composites business unit of Honeywell International Inc., Morris Township, N.J. In the United States, AlliedSignal commercialized the high-strength fibers as Spectra 900™. This ultra-high-molecular weight polyethylene (UHMWPE) fiber has strength in the 32 to 35 grams-per-denier range. AlliedSignal pursued ballistic fabric uses for Spectra including protective clothing and hard composite armor systems under the trade name Spectra Shield®. After acquiring AlliedSignal in 1999, Honeywell has continued to develop Spectra and products made from the fiber.

Pound for pound, Honeywell Spectra fiber is 10 times stronger than steel and 40 percent tougher than aramid fiber. The company has been making Spectra Shield ballistic armor for more than 15 years. The shield technology lays parallel strands of man-made fiber side-by-side and binds them in place with a resin. The layers of tape are then cross-plied at right angles and fused under heat and pressure into a composite structure. The nonwoven structure causes the energy of the projectile to dissipate rapidly.

Honeywell has developed a family of products for ballistic uses around its Spectra fiber. Spectra Shield Plus LCR is a soft armor product that is 25-percent lighter than the original product. Spectra Shield PCR is used for hard armor applications such as rigid armor plates, breast plates, vehicle armor, blast containment and riot shields. The latest version of this product is 30-percent lighter than the original version. SpectraFlex® is used in soft body armor. Spectra Shield Plus Flex combines Spectra fiber and Shield technology and is 25-percent lighter than the original version. Gold Flex® combines Shield technology with aramid fibers and provides body armor manufacturers with additional design flexibility.

Spectra Shield composite material forms a basis for small arms protective insert plates used in the Interceptor vest used by US troops in Iraq and Afghanistan.

In June 2004, Honeywell announced a $20 million investment to boost Spectra fiber production at its facilities in Chesterfield County, Va., to meet customer demand. The expansion will be completed in the second quarter of 2005.

DSM Dyneema’s UHMWPE Dyneema™ fiber is used in ballistic products such as protective vests.

DSM's Dyneema™ Fiber

DSM Dyneema BV's Dyneema™ UHMWPE fiber is produced in The Netherlands at DSM's facility, and in Japan through an agreement with Japan-based Toyobo Co. Ltd. In the United States, it is produced not only under license to Honeywell as Spectra, but also by DSM at its new fiber production plant in Greenville, N.C. The plant produces 1.2 million pounds per year of the high-strength fiber, much of which will be used in ballistic products.

DSM was selected by C&D Aerospace, Huntington Beach, Calif. - a builder of aircraft interiors - to collaborate on the design of secure aircraft cockpit doors. Dyneema fiber is being used in this application because of its ballistic properties and low weight. The first aircraft door panels were used in Boeing 737 and 757 planes, and in planes made by Bombardier, Quebec, and Empresa Brasileira de Aeronáutica S.A., Brazil.

Toyobo's Zylon™ PBO Fiber

Zylon™ - a polyphenylene benzobisoxazole (PBO) fiber manufactured by Toyobo - has excellent thermal properties and almost twice the tensile strength of conventional para-aramid fibers. It is available in a variety of forms including filament, chopped fiber, staple fiber and spun yarn. Fiber properties include high tensile strength, high modulus, thermal stability and flame resistance.

Body armor made from Zylon provides excellent protection at a light weight, according to the company, and has been responsible for saving a number of lives since its introduction into protective apparel.

Magellan's M5® Fiber

Magellan's M5® fiber is a promising product for use in ballistic fabrics. M5, the brainchild of Doetze Sikkema, Ph.D., was conceived as part of his advanced polymer research with Akzo Nobel. Eugene H. "Gene" Vetter, CEO, Magellan Systems International LLC, Richmond, Va., acquired the Akzo technology and hired Sikkoma as chief scientist. Magellan is scaling up the production of the fiber and building a production plant, and is working with DuPont on this development. In addition to very high tensile strength and excellent high-temperature properties, M5 shows plastic behavior in compression.

Ballistic Products Will Grow

There is a potentially large market for ballistic fabrics in commercial and military aircraft. The threat of commercial aircraft terrorism using missiles and other explosive devices could well require ballistic fabric protection for vital parts of aircraft.US military activities in the Middle East and other parts of the world  require better ballistic fabrics and composites, not only for the individual soldier, but for all types of military vehicles as well. In the last five years, government and industrial research and manufacturing organizations have teamed up to improve ballistic fabrics and applications.

October 2004