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Appendix B
Textiles and Garments for
Chemical and Biological Protectioni
Frank K. Ko
INTRODUCTION
Textiles and garments are important components of the soldier sys-
tem. They are the soldier's second skin, the barrier between the soldier
and the surrounding environment. Although the global and national
political climate has changed, and defense concepts and doctrines along
with them, the basic role of clothing in protecting the soldier has re-
mained the same.
As the battlefield environment becomes increasingly complex, we
need to ask the fundamental question from time to time whether textile
and garment manufacturing technology are keeping pace with current
and projected demands. Do we have the fiber materials to meet specific
needs? Do we have the yarn technology to convert fibers to linear fibrous
assemblies? Do we have the fabric formation technology to convert fibers
and yarns to planar or three dimensional (3D) fibrous assemblies? Do we
have the garment assembly technology to join fabrics together to form
chemical-biological (CB) protective garments? Do we have the finishing
and coating materials and technology for advanced CB protective gar-
ments? Do we have the detection technology to monitor the residual life
of the barrier system?
1The following material was prepared for the use of the principal investigators of this
study. The opinions and conclusions herein are the author's and not necessarily those of the
National Research Council.
182
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APPENDIX B
FIGURE B-1
Army, 1994.
183
Garments
Armor \
Textiles
(fiber, yarn, fabric)
, Shelters
Gloves ' / \ Masks
Boots Parachutes
Textiles for the protection of deployed U.S. forces. Source: U.S.
Textiles are fibrous materials that include natural and synthetic fi-
bers; linear assemblies of these fibers, such as yarn and rope; and two-
dimensional (2D) and 3D assemblies of fibers in various fabric forms.
These fibrous assemblies constitute the structural backbone of a broad
range of military products, including garments, body armor, gloves,
boots, shroud lines, masks, and shelters (see Figure Bug.
Military textiles provide battlefield, environmental, physiological,
and physical protection (Table Bug. These protective functions are often
required simultaneously and must not interfere with each other. For ex-
ample, a barrier to protect against a chemical warfare agent must be
completely impermeable, which interferes with physiological protection
requirements that demand permeability to prevent heat stress.
This discussion is focused on CB protective textiles and garments. A
review of the literature is followed by a description of the evolution of the
requirements for CB textiles and a review of the current CB textile sys-
tems. Next, material technology (the current state of fiber, yarn, fabric,
and garment technology) is assessed in terms of the nation's readiness.
The performance of textile structures relevant to CB protection is
expressed in terms of performance maps. On the basis of the require-
ments and the performance maps, development trends in CB protection
are then presented. Finally, the outstanding technical issues are described.
REVIEW OF THE LITERATURE
The published literature in the public domain is limited. Information
is scattered in a few chapters, monographs, and mostly in proceedings of
workshops and conferences. Morris (1977), for example, summarized the
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STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
TABLE B-1 General Requirements for Protective
Textiles
Battlefield Protection
Chemical agent barrier
Flame-resistance
Thermal-radiation protection
Ballistic protection
Camouflage
Low noise generation
Environmental Protection
Insect proof
Windproof
Air-permeability insulation
Waterproof
Snow-shedding
Physiological Protection
Minimum heat stress
Windproof
Air-permeability insulation
Moisture-vapor permeability
Self-sterilizing
Physical Protection
Durability
Low weight and bulk
Resistance to soiling
Self-sterilizing
Source: Morns, 1997.
requirements and classifications of protective clothing for defense pur-
poses but only briefly discussed CB textiles.
The most relevant summary of the state of CB protective textiles was
presented at an Industrial Fabric Association international conference in
1982 at which the threats of chemical warfare were described by Colonel
Hidalgo of the U.S. Army Chemical School. He explained how the doc-
trine that led to the establishment of CB protective concepts (or funda-
mental principles) was formulated. The fundamental principles are:
(1) contamination avoidance; (2) protection (individual and collective);
and (3) decontamination (Hidalgo, 1982~. These same concepts largely
define the U.S. CB protection philosophy today.
Dr. Roy Roth, while working at the U.S. Army Natick Research, De-
velopment and Engineering Center (NRDEC) (now called the Soldier and
Chemical Biological Command's [SBCCOM] Soldier Systems Center at
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APPENDIX B
185
Natick) outlined the development of requirements and provided solu-
tions and directions. Much of his discussion is still applicable today, and
some concepts are just beginning to be implemented. Based on his inter-
pretation of the Army Training and Doctrine Command's battlefield sce-
nario, AirLand Battle 2000, Roth believed that a battlefield CB protective
uniform would replace the overgarment concept of the 1970s and 1980s.
He then pointed out the shortcomings of activated carbon-based protec-
tive garments (e.g., limited field life, as the activated carbon absorbs per-
spiration, thus depleting chemical agent sorption capabilities). Besides
protection by carbon sorption, Roth introduced new concepts, such as
chemical decomposition of agents and semipermeable barriers that com-
bine sorption and decomposition.
Roth also discussed the technologies for implementing these concepts
through textile materials. He focused especially on the development of
multifunctional fibers, yarns, and fabrics engineering, which has led to
new engineering technologies, especially melt-blown nonwoven fabrics.
He also introduced the notion of a generic type of uniform for the joint
service of the Army, Navy, and Air Force, which led 15 years later to the
current joint service lightweight integrated suit technology (ISLIST) uni-
form (Roth,1982~.
At the same conference, Mr. Vachon of ILC raised the issue of avail-
ability and cost of fibrous material from the contractor's point of view. He
pointed out that heat stress was a problem with the microporous Teflon
film, as well as the long cycle time for testing and product qualification.
To remedy the lack of research in CB protective textiles during the
1970s, several research programs were initiated by NRDEC in the 1980s.
For example, to evaluate the effect of fiber architecture on the transport
properties of garments, a three-year study was contracted to the Textile
Research Institute, under the direction of Dr. Bernie Miller. This program
resulted in a new experimental technique based on the finding that the
liquid breakthrough resistance in fabric structures could be optimized by
symmetric design of the fabric surface (Miller, 1986~.
Considering the importance of fabric structures in CB protection,
NRDEC also contracted with Drexel University, under the Textile Center
of Excellence Program, to carry out a study on the feasibility of improving
the performance of CB protective textiles by fabric engineering. The Drexel
study revealed that the transport properties of a fabric could be engi-
neered by modifying fabric construction, yarn materials, and yarn geom-
etry and that a lighter and more air-permeable fabric could be designed
and fabricated than the current 50/50 nylon/cotton shell fabric without
sacrificing mechanical properties. Because of the lack of a quick and accu-
rate testing method for liquid/vapor penetration, the effectiveness of the
experimental fabrics for CB protection could not be tested (Ko and
Geshury, 1997~.
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STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
As part of the NRDEC/Drexel Textile Center of Excellence Program,
an update of current CB protective concepts was presented in the 1996
Workshop on Chemical Protective Textiles jointly organized by NRDEC
and Drexel University (Ko and Song, 1996~. The topics covered in this
workshop included barrier mechanisms for liquid and vapor agents; the
characterization of barrier effectiveness based on liquid transport proper-
ties; modeling the interaction of fabric structure and physiological re-
sponses; a review of textile materials and structures for chemical protec-
tion; water and oil repellents; design of chemical protective textiles; design
of chemical protective clothing; human factors in protective clothing de-
sign; and reactive systems for protection and decontamination. The work-
shop concluded with a projection of future protective systems and the
announcement by Dr. Donald Rivin of NRDEC of the LIST preplanned
product improvement (P3I) program.
Other sources of information on CB protective textiles are the pro-
ceedings of a series of workshops sponsored by the American Society for
Testing Materials (ASTM) (McBriarty and Henry, 1992) and the ASTM
special technical conference series. The ASTM articles tend to focus on
test methodologies and are concerned primarily with protection in indus-
trial environments. The Scandinavian Symposium on Protective Cloth-
ing, held every other year, covers a broad range of topics related to CB
protective textiles. The role of nanotechnology in soldier protection was
discussed in a recent Army workshop in Boston (Gibson and Reneker,
1998~. Nanofiber structures and various reactive polymers can now be
tailored for specific forms and functions.
The Army Research Office, along with other Army laboratories, has
started a multidisciplinary university research initiative (MURI) involv-
ing researchers from North Carolina State University, the University of
Akron, and Drexel University. Although the topics are basic in nature, the
emphasis is on CB and ballistic protection.
In summary, research in CB protection textile technology was quite
limited until the early 1980s when the threat of CB warfare from the
Soviet bloc spurred research and development (R&D) in CB textiles and
led to the development of the LIST garment. Considerable R&D (mostly
developmental) is being conducted in the private sector, mainly on the
agents and environments in industrial environments, which differ mark-
edly from those encountered by ground soldiers. The most closely related
industrial research is on protection from agricultural pesticides, which
are somewhat similar to nerve agents. No significant breakthroughs in CB
protective textiles are expected until new multifunctional fiber materials
in a broader range of dimensional scales and structural geometries are
available in an integrated design for manufacturing environments.
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APPENDIX B
HISTORICAL DEVELOPMENT AND REQUIREMENTS FOR
CB PROTECTIVE TEXTILES
187
The requirements for CB protective barriers have evolved through
the years. This evolution was described in a lecture by Dr. Roy Roth
(1982), which includes excellent background on the development of CB
protective textiles. The following excerpt is taken from Dr. Roth's lecture:
In the late 1960's the Army research effort had led to the develop-
ment of a new biological protective clothing system. At the same time,
under the Nixon administration, the government's policy to abstain from
use of chemical warfare agents led to significant action. First, although
the chemical biological protective clothing developed at the time was
adopted by the Army in 1970, no production of the system was autho-
rized. Such research funds as were available were committed to other
higher priority projects, with virtually no funds being committed to fur-
ther research in chemical protective clothing in the years thereafter.
The clothing system adopted at that time was intended for ground
soldiers, and more importantly it was intended to be used essentially in
a defensive mode. It was a system that a soldier would use if attacked
and which would permit him to move to a safe area. It was specifically
not envisioned for use by ground or air combat vehicle crewmen. For
most of such applications, the excessive bulk and heat stress provided
by the uniform would limit the crewmen's activities.
In the following seven years from 1970 to 1977, not only was rela-
tively little research conducted in this area, but equally importantly, the
battlefield scenario changed significantly. The development of a highly
mechanized army employing large numbers of ground vehicles and he-
licopters de-emphasized the concept of the individual combat soldier
covering large amounts of terrain on his own.
Another change that occurred in this period was the aggressive de-
velopment of chemical warfare tactics by the Soviet government. In the
late 1970s it was apparent that the Soviet bloc nations were mentally,
physically and emotionally equipped to use chemical biological agents
in offensive modes. There was ample evidence emerging that the Soviets
were organically and logistically equipped for this purpose. Down to
the unit level, the Soviet army trained with and dispersed its agents,
such as to make it obvious that the Soviet forces would be ready, will-
ing, and able to use such chemical biological agents on the battlefield as
if they were conventional weapons.
It was equally clear that in 1977 the US was unprepared for such a
situation. It is hard to imagine the nature of the obstacle confronting us
in order to turn this situation around, starting with what we had. First
there was a realization that chemical biological protective clothing was
at best a product with substantial limitations. As noted earlier, it was
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STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
designed for defensive operations, and because of its bulk and warmth
it was unsuitable for conducting extensive offensive operations, particu-
larly in a warm environment.
We had, as noted, conducted no significant research in this area
during the period 1970 to 1977. We had certainly not kept up with the
times in terms of extracting what little we could from research and de-
velopment in the civilian sector. On the other hand, it is an area in which
little industrial research is conducted. Perhaps the nearest area of relat-
ed industry activity is in the agricultural pesticides, many of which are
first cousins to the nerve agents in today's military arsenal. However,
little effort has been devoted to protecting against such agents in the
context of an aggressive ground soldier.
To better appreciate the nature of the technical problems confront-
ing us, we can stand back and attempt to analyze the problem in simple
objective terms. Our concern is the human body, which suddenly finds
itself in an alien environment comprised of an array of unwanted chem-
icals which are present in gaseous form, aerosol dispersed clouds, or in
liquid and possibly solid form.
The eyes and the oral nasal cavities are readily accessible routes for
such materials to enter the body. Some agents may be percutaneous and
enter the body at any time they can reach exposed skin. The affects on
the body will vary from skin inflammation to attacks on the nervous
system. The end effects, depending on the agent, will run the gamut
from incapacity to death. The time required to render the soldier ineffec-
tive is extremely short.
Between the soldier and a hostile environment we need a barrier, or
at least a filter, that will screen out the unwanted agents. A wide variety
of materials exist that provide this. However, almost all of them have
one or more glaring deficiencies, which rule out their use as clothing
items.
In the protective clothing area, the problem is far more complex
than the typical materials research problems, which can find their solu-
tions in sciences such as physics, chemistry, metallurgy, and so forth.
When we get to clothing systems, the typical materials engineer finds
himself confronted with some severe additional constraints. The materi-
als we want must, at the very least, be able to bend and breathe in order
to permit movement and avoid heat stress. Moreover, the material must
be capable of being mass-produced at a reasonably low unit cost and
ideally must be capable of being maintained for extended use in the
field.
Among other features, it should include the ability to be camou-
flage printed, as well as to be laundered and decontaminated ... The
material should present the strength, durability and abrasion resistance
that we need for clothing in a rugged environment. Since they will be
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APPENDIX B
worn in contact with the skin, there are requirements for tactile comfort
and the absence of dermatological affects. Finally, the end items must be
capable of withstanding extended storage under a range of tempera-
tures and humidity without degradation.
For the ground soldier the foregoing fills many of the requirements,
but for the man in combat vehicles on the ground or in the air, where a
flame hazard exists, we must add the additional requirement of non-
flammability.
We want to provide a barrier between the man and the environ-
ment without simultaneously creating heat stress. This would appear to
present a contradiction. We want a material that is on the one hand
permeable to air and body moisture vapor, and at the same time we
want it to present a protective barrier to unwanted chemicals in any
form.
A selective barrier is desirable, and the basic protective overgarment
system we adopted in 1970 achieves this by using activated carbon in
sorptive matrix to filter out the agents. The carbon is contained in a
polyurethane foam matrix, which, unfortunately, carries a number of
penalties, not the least of which is the heat stress it produces.
Beginning in 1978 the Natick Laboratories began rebuilding the
technical base in this area, while at the same time the Defense Depart-
ment began production of the CP [chemical protective] overgarments.
The development of this production market stimulated interest in the
research area as well. A few firms that understood the shortcomings of
the current product began to turn their efforts to the problem of produc-
ing an improved overgarment material. Because of the nature of the
problem and the long period of dormancy of research, we also recog-
nized a need to have industry more completely understand both the
perspective and potential that we foresaw, in hopes of stimulating still
further research activities.
Within the Department of Defense, it was also recognized that the
government would have to support such research, and, by 1979, sever-
al complimentary actions had been undertaken.First, Natick Laborato-
ries and the Army Research Office conducted a seminar for industry
and academic institutions to describe the problem and the potential
needs. Secondly, a combined Defense Department loins Services Tech-
nical Plan was put together with short range, intermediate, and long
range objectives. In addition, a formal announcement was published in
the Commerce Business Daily indicating the Army's initiation of a multi-
million-dollar research effort, and approximately twenty-four firms in-
dicated interest in participating in this program. Some are here repre-
sented today.
Subsequently in late 1979, eight firms responded with proposals,
and research and development contracts were awarded to four major
189
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STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
organizations. In addition, unsolicited proposals resulted in several oth-
er contracts being awarded, and the net result was a multimillion-dollar
commitment to development of improved chemical protective material.
The response by industry has been heartening, and results to date
are very encouraging. While many of the materials that have been pro-
duced are still being subjected to live agent testing, there is evidence
that a new generation of overgarment materials may be within sight. We
expect to extract from the technological base one or more materials to go
into field tests in the year ahead.
The Army's Training and Doctrine Command has recently devel-
oped the scenario entitled AirLand Battle 2000. This is an attempt to
look at the future in terms of the way the Army would operate in the
battlefield in the year 2000 while at the same time stimulating the devel-
opment of new ideas to serve the battle scene. One message that be-
comes clear is that we will in the future depart from today's concept of
an overgarment and will be requiring a battlefield uniform that inher-
ently possesses chemical protection. That places an unusual demand on
the garment in terms of extended life in the battlefield and its ability to
be maintained by conventional laundering procedures.
Today's CP [chemical protective] materials have a limited field life
because a soldier's perspiration will be absorbed by the activated car-
bon. The greater the number of sorptive sites that are occupied by chem-
icals in the perspiration, the less the material will be able to absorb un-
wanted agents.
For this reason, the garment of the future will either have to avoid
the use of activated carbon or incorporate means by which the sweat
poison mechanism may be defeated or minimized. We believe it is pos-
sible to achieve the latter. There are also some signs that future genera-
tions of garments may not have to depend on activated carbon.
The overgarment existing today has this configuration: The outer
shell consists of the 5-ounce nylon/cotton blended twill, the inner com-
ponent, the so-called active part which contains the activated carbon
impregnated into approximately a 90-mil polyurethane foam, has a liner,
two-ounce nylon tricot. The bottom two layers are laminated together,
and the top layer essentially floats and is put on as the garment is
manufactured.
To do this, you reduce the weight in bulk, stressing again, putting
this into a combat uniform configuration as opposed to a defensive
mode, increase shelf life, adding fire retardancy as best we can, particu-
larly for tank and air crewmen, and making it launderable. It should be
launderable not only in combination with being decontaminated, should
there be a threat, but since it hopefully will be the combat uniform it
should be launderable during the time that it is being worn when there
is no threat . . .
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APPENDIX B
Durability, camouflage, you tend to look at this whole thing, re-
member Alec Guinness and the man in the white suit. Well, we can't
even do that, we have to have camouflaging to go along with it. Water
repellency, as I mentioned, perspiration resistance and petroleum prod-
ucts, nontoxic as far as materials go and compatibility with other items,
. . . whether they be a backpack or a detection kit and so forth. It must all
be compatible with those systems, too.
There are many different material systems being investigated to at-
tempt to achieve these objectives. ... Some of them are based on active
carbon power, some of them are based on active fiber yarn, some of
them are based on what I call barrier film.
Perhaps a simpler way of demonstrating the scope of the program
is to sort out the various efforts in terms of mechanisms or approaches
involved. These are the three broad categories, which comprise the tech-
nical approaches that exist right now. Approach one is based on sorptiv-
ity, using activated carbon in various forms. Approach two is based on
trying to develop and put into a uniform some way of actually destroy-
ing the chemical threat by decomposition. Number three, is based on
either a combination of the above or individually a barrier of some sort
. . . in the first category, based on carbon powder. Instead of the polyure-
thane foams other possible foams might have advantages, being more
permeable, being substantive to the carbon, etc., so that the activity of
the carbon may remain higher.
Technology allows us to make hollow fibers into which we could
put activated carbon powder. Technology permits us to make fibers in
situ along with carbon powder. Essentially you would be laying down a
web of material. Technology permits putting in carbon powder along
with melt-blown materials such as polypropylene. I draw particular at-
tention to . . . what I call the nonwoven area, which I think would have
some very interesting possibilities.
From the carbon fiber standpoint, this is also being pursued. In gen-
eral it is noted or to emphasize the expense increases as we go from
powder to fiber and within fiber from staple down to fabric. iThere] are
different forms of carbon fiber, using staple. It can be done by conven-
tional techniques, putting down either wet laid or dry laid nonwovens.
We can flock carbon fiber onto various substrates. We can make engi-
neered fabrics out of carbon yarn either with other materials to strength-
en it or in other configurations. We can start with fabrics, which are one
hundred percent activated carbon and use it somehow. It is fairly weak
and brittle to begin with, so it would have to be protected.
Presently carbon fiber is not available in any reasonable quantity
domestically. It is only available overseas Japan or England), and that is
a deficiency. If this approach is successful, we would have to have a
domestic source.
191
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STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
The second broad category, protection by chemical decomposition,
is not new in concept but is new in terms of materials and technology
we are applying to the problem. These approaches may hold an answer
to some of the longer range needs. It has been known in the literature
that there are materials that can hydrolyze the threats. It has been shown
that certain ion-exchange resins will do this. It is a question of how we
incorporate them into a fabric, and are they active enough to really de-
compose the threat during a dynamic situation.
There has been recent publicity about some enzymes that have been
isolated primarily from squid, which are known to hydrolyze certain
live agents. We have the same question. Is it possible to immobilize
these somehow and attach them to fabrics, and if so, will it have all of
the other properties that are needed, that were listed earlier?
You begin to think, well, are these possible to launder, to decontam-
inate, etc. Finally, there are efforts directed to the third approach. It
reflects an attempt to combine some of the foregoing approaches by
developing an engineered material system. Given the present and ex-
pected future threat, representing an array of different agents, such a
system would have growth potential, which is necessary given the rap-
idly changing technological world in which we live.
Ideally, of course, it would be nice to have a semipermeable barrier
that will keep out the agents and will breathe, will allow moisture vapor
to go through and from a waterproofing standpoint will keep out liquid
water. Ideally, as I say, it would be better to have that without the need
for an absorptive material.
I think most of the approaches and techniques, which I talked about,
can tend to identify here. It is best to go around them again to repeat
them, starting with carbon, putting carbon powder again into a textile
material, whether it be embedded in the fiber or in a hollow fiber, trying
to use carbon fibers in one form or another. Your approach of using
reactive materials, whether they be, for example, ion-exchange resins, is
more of the idealized situation that I just mentioned as a possibility.
On the next one, the barrier film actually exists right now. That's
the composition of the butyl rubber overboot and is the system, which
the Soviets have gone toward. Unfortunately, it maximizes heat stress
and is completely impermeable, which is not a desirable situation for a
combat uniform.
Another possibility is using activated fibers again, laminated struc-
tures and the possibility of using nonwovens in one form or another.
The impetus given to this program and the results to date will lead
to continued funding of research and development efforts in chemical
protection material. From a production standpoint, there is no question
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STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
Fabric Performance Characteristics
Fabric performance characteristics are based on the interaction be-
tween fiber (material properties), yarn, fabric geometry, and finishing
treatment. Obvious characteristics of fabrics for textile applications are:
(1) comfort; (2) aesthetic value; (3) functionality and durability; and
(4) ease of care.
Garments
The garments and protective textile structures for the soldier are pro-
duced by direct fiber-to-fabric or yarn-to-fiber processes. Yarn-to-fabric
structures include woven and knitted fabrics. Fiber-to-fabric structures
are known as nonwoven structures. A wide variety of fiber architectures
can be generated from the three basic fabric processes (weaving, knitting,
and bonding), resulting in a wide range of interlacing (bonding) density,
fiber orientation/distribution, and formability/conformability. For ex-
ample, woven fabrics include biaxial, biaxial, and multiaxial interlacing
of yarns; and interlacing density varies from high density in the plain
weave construction to low density in the satin weave construction. Knit-
ted structures (interlooped structures) are characterized by high porosity
and conformability. Knits are classified into warp knits (yarns are intro-
duced across the machine) and weft knits (yarns are introduced along the
machine). The openness of knitted structures can be reduced and the
stability of the structure enhanced by the insertion of directional yarn.
Inserted yarns can be organized from unidirectional, orthogonal, and bi-
directional to multidirectional.
Nonwoven structures are primarily formed by direct conversion of
fiber-to-fabric by mechanical or chemical bonding. These fiber-based
structures are characterized by high areal coverage to areal density ratio.
Nonwoven fabrics are extremely versatile because they can combine fiber-
based and yarn-based structures. Mechanically bonded nonwoven fabrics
can be produced by needling or fluidjet entanglement. These structures
tend to be bulky but quite conformable. Chemically bonded nonwoven
fabrics are less bulky but tend to be paper-like and nonconformable. Be-
cause of the simplicity of processing and high productivity of nonwoven
fabrics, industry has a strong incentive to use nonwoven structures for
primary garment fabrics. However, their paper-like consistency has been
a major obstacle to the popular acceptance of nonwoven structures.
The current JSLIST garment is a combination of all three textile struc-
tures. Woven structures are used in the shell; the liner is warp knitted;
and the structure that carries the activated carbon absorbents is a non-
woven fabric (or foam).
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APPENDIX B
Automated Garment Manufacturing
207
The automation of garment manufacturing in the United States is
well behind that of Japan. Complete automation of the tailored apparel
manufacturing system was developed in Japan under a nine year Minis-
try of International Trade and Industry funded contract begun in 1982.
According to Berkowitch (1996~:
A consortium of 28 enterprises from all segments of the industry
cooperated in the project. The seed for the initiative lay in the uncertain
future faced by a labor-intensive, low-tech industry in a high-wage econ-
omy and in the potential for a domestic production capability that had
low labor requirements and was flexible, just in time, and quality orient-
ed. The undertaking was ambitious it called for having a bolt of cloth
at one end and tailored garments ready for shipment at the other, with-
out the intervention of human hands in between. It anticipated that man-
ufacturing time would be cut in half. Technically, the challenge was to
apply robotics to the manufacture of sophisticated sewn articles using
diverse flexible materials. By the time the project concluded in 1990,
essentially all process elements had been demonstrated in the produc-
tion of tailored women's jackets of woven and knit cloths, patterned and
dyed in solid colors.
In the future, individual modules of the production line optimized for
making specific garments or garment parts are likely to find their way
into the domestic industry in Japan.
Fabric Performance Maps
The properties of textile structures can be characterized in terms of
geometric and performance properties critical to CB protection. The per-
formance maps outline the region of performance of various fabrics. To
facilitate comparisons on the same basis, the fabric performance maps for
yarn-to-fabric and fiber-to-fabric structures are discussed separately.
Because of the broad range of possibilities, the performance maps are
qualitative, rather than quantitative.
Critical Properties
The properties included in the performance maps reflect the basic
requirements of CB protective textiles: (1) reduction in weight; (2) reduc-
tion in bulk; (3) reduction of heat stress (increased comfort); and (4) in-
creased durability. These requirements can be translated into four geo-
metric parameters and four performance parameters. The geometric
parameters include:
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STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
· Porosity (the amount of open space in a unit volume of fabric). As
fiber diameter and yarn diameter increase, the structure tends to
become more porous. The porosity of a fabric is inversely propor-
tional to the areal coverage or cover factor of a fabric. A porous
fabric tends to be lighter and more permeable than a nonporous
fabric.
· Surface Texture. The surface geometry of a fabric is characterized by
the smoothness of the surface, which in turn is governed by fiber
and yarn diameter.
Voluminosity (a reflection of the bulkiness of a fabric for a given
areal density [mass per unit areas. A fabric tends to be more volu
.
~ ~ ,
minous if the fiber/yarn diameter is larger and the freedom of fiber
mobility in the geometric repeating unit is high. Voluminosity is
directly related to fiber thickness.
Thickness of the fabric. Like voluminosity, thickness is related to
fiber and yarn diameter. The larger the fiber and yarn diameter,
the thicker and bulkier the fabric.
The performance parameters include:
· Permeability (the ease of air or liquid flow through a fabric). The
permeability of a fabric increases when the porosity increases.
· Compressibility (the ability of a fabric to resist transverse [through
the thickness] compression). A voluminous fabric tends to be more
compressible than a nonvoluminous fabric. Compressibility de-
creases with the stiffness of the fiber and yarn, which is signifi-
cantly influenced by fiber diameter. As fiber diameter increases,
the bending stiffness and longitudinal compressive stiffness of the
fiber increases geometrically.
· Extensibility (the ability of a fabric to stretch and conform). Fabric
extensibility is affected by fabric geometry and inherent fiber bend-
ing elongation.
· Toughness (the durability of the fabric). A high-strength fabric with
high elongation at break usually has high toughness.
Yarn-to-Fabric Structures
Interlooped structures, such as weft knits, tend to be more porous,
more voluminous, and bulkier and thicker than other yarn-to-fabric struc-
tures. Interlaced structures, such as woven fabrics, tend to be less porous,
less bulky, and thinner. The performance of all yarn-to-fabric structures is
largely determined by the linearity and interlacing density of the yarns.
For example, weft knits have high extensibility, are extremely comfort
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APPENDIX B
209
able, and are very compressible. Because of the openness of the loop
geometry, weft knits are highly permeable. Because of the high linearity
of the multiaxial (noncrimped) warp knit structure, these fabrics have
limited extensibility and low toughness. The permeabilities of woven and
multiaxial warp knit fabrics are lower than those of weft knit fabrics.
Figures B-5 and B-6 show the qualitative performance maps for the geo-
metric and performance properties of the yarn and fabric.
Fiber-to-Fabric Structures
Fiber-to-fabric structures are generally known as nonwoven fabrics.
The simplicity of the manufacturing processes by which fibers are con-
verted directly to fabrics (thus bypassing the yarn-formation stage) has
great appeal to the industry (especially the apparel industry) because of
high productivity and cost savings. But nonwoven fabrics do not have
good drapability/conformability characteristics. Of the two major classes
of nonwoven fabrics (chemically bonded and mechanically bonded), me-
chanically bonded systems (e.g., needle felts and spunlaced systems) tend
to be more voluminous, bulkier, thicker, and more porous. Chemically
bonded nonwoven fabrics tend to be more paper-like, thin, nonbulky,
and less porous. As a result, mechanically bonded nonwoven fabrics are
more permeable, more extensible, and more compressible.
The performance map shows only a partial view of the toughness of
nonwoven fabrics. A spun-bonded system, because of the high strength
of the continuous filaments and the strength of the bonds, has a high level
of shear resistance, tear resistance, and toughness. The needle felt fiber
(e.g., Kevlar), can also be quite tough, even capable of arresting fragments
from a ballistic projectile.
A summary of the performance map of fiber-to-fabric structures is
shown in Figures B-7 and B-8. The effect of fiber orientation (fiber archi-
tecture) on permeability is illustrated in Figure B-9. Nonwoven fabric,
because of its torturous fiber architecture, is significantly less permeable
than woven fabric under the same fiber volume fraction. In nonwoven
fabrics, fiber dimension engineering can further modify coverage or porosity.
Finer fibers provide significantly higher fabric coverage (Ko and Pastore,
1985~. Based on the general performance map, experimental evidence,
and simulated results, we can conclude that fiber architecture and fiber
diameter are very important in controlling the geometric and performance
characteristics important for CB protective textiles.
FUTURE DIRECTIONS
The requirements for the next generation of CB protective garments
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210
.~
to
to
o
to
STRATEGES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
Smooth
Surface texture
Rough
Rib knit
Purl knit
Jersey
Raschol
WiWK
so
Wovens
Braids
Thin
Thickness
Thick
tQ
To
Fiber (yarn) diameter
Porosity a:
Cover factor
Fiber diameter
~Surface texture cc
A. Modular length
o
lo.
Fiber mobility
Volumininosty a:
Fiber diameter
Thickness ~ Fiber(yarn)diameter
FIGURE B-5 Geometric properties of knit and woven fibers. Source: Ko and
Song, 1996.
I
(a
(a
s
Low
Compressibility
High
Rib knit
Purl knit
Jersey
Raschol
Braids
Wovens
tQ
WiWK
~r
lo MWK so
Low Extensibility High
Fiber diameter
Permeability ~
Fiber volume fraction
Compressability ac
Fiber stiffness
P)
fir
_.
Voluminosity
Fiber elongation
Extensibility ~
Yarn linearity
Strength x elongation
Toughness ec Stiffness
FIGURE B-6 Performance properties of knit and woven fibers. Source: Ko and
Song, 1996.
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APPENDIX B
I
Smooth
Surface texture
Rough
Needle felt
Spunlaced
Spunbonded
Resin bonded
Film/membrane
Thin
211
Thickness
Thick
Fiber (yarn) diameter
Porosity ~
Cover factor
Fiber diameter
Surface texture oc
Modular length
Fiber mobility
Volumlnoslty ~
Flber diameter
Thickness cc Fiber(yarn) diameter
FIGURE B-7 Geometric properties of nonwoven fibers. Source: Ko and Song,
1996.
Low
Compressibility
High
Needle felt
Spunlaced
C,3
C,3
I
Spunbonded
Resin bonded
| Film I
Low
Extensibility
High
Fiber diameter
Permeability <=
Fiber volume fraction
con
Cal
P)
Is
~-
Voluminosity
Compressablllty cc
Fiber stiffness
Extensibility cc
Fiber elongation
Yarn linearity
Thickness cc Strength x elongation
Stiffness
FIGURE B-8 Performance properties of nonwoven fibers. Source: Ko and Song,
1996.
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212
STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
For yarn in general, low permeability to
air, vapor and light dictate; 600
1 ) High circularity coefficient for the
component fibers;
2) Surface smoothness for the component 500
fibers;
3) Low state of aggregation (packing factor) ~
achieved, forexample, by utilizing ~400
multiplanner crimp fibers and low twist. co
For fabric in general, maximum
translation of yarn properties for low
permeability requires:
1 ) Low number of yarns per unit length and
width of fabric;
2) Low cover factor factor-warp and filling;
3) High crimp level-warp and filling;
4) Maintenance of yarn circularity
5) Weave types containing the minimum
number of continuous intersections.
High permeability requires essentially the
converse of these characteristics.
300
200
200
4 layers
· 0/90 cloth
\ --- - -- Random mat
a, \Woven
_ " \
"` ~
Nonwoven '. ~.
_ be".
100 1 1 1 1 1 1
0.2
0.3 0.4 0.5 0.6
Fiber volume fraction
FIGURE B-9 Effects of fiber orientation on permeability. Source: Ko and Song,
1996.
have not been quantified or defined. New analytical methods will have to
be developed for the new classes of fibrous materials and structures.
Multifunctional materials will require special function polymeric fibers
and hybrid yarns consisting of two or more polymers and their ultrafine
filament derivatives. Yarns and fabrics consisting of the ultrafine fibers
will require sophisticated processing and finishing techniques. The unique
surface texture and multifunctional nature of these new textiles will re-
quire computer-aided design and manufacturing for reproducibility and
flexible manufacturing for meeting mission-specific demands. The pro-
duction economics will require high-speed, automated processes, includ-
ing fiber spinning, fabric formation, printing (camouflage), and garment
manufacturing. The capability of the U.S. defense industry to develop
and field advanced CB protective textiles and garments will require the
cooperative participation of research institutions as well as the fiber-
textile-garment industry.
CONCLUSIONS
It is generally accepted that the impermeable system provides the
most complete protection against CB agents, whereas the permeable sys-
tem, which breathes and allows moisture vapor to escape, cannot protect
against aerosol and liquid agents (Wilusz, 1998~. Impermeable barriers,
however, cause serious heat stress by trapping bodily moisture vapor
inside the system. An incremental improvement can be achieved using a
semipermeable barrier backed with a sorptive layer. This system allows
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Representative terms from entire chapter:
protective textiles
APPENDIX B
TABLE B-6 Trends In Chemical/Biological Protective Textiles
213
Current
Future
Fiber material Monofunctional Multifunctional
Fiber geometry (diameter) Micro >lOpm Nano
214
STRATEGIES TO PROTECT THE HEALTH OF DEPLOYED U.S. FORCES
process development drastically reduced. Having gradually lost its
equipment manufacturing segment, it relies on developments from for-
eign manufacturers for process modernization. The attention given to
quality bears primarily on uniformity and processibility. Introduction of
product variants is kept to a minimum and frequently prompted by
pressure from imports in the lower half of the market. The mills have
not been challenged by the specialty products covered in this report.
These products are practically unavailable here because the currency
exchange rate makes them exorbitantly expensive. The situation would
likely change, though, were their prices to drop as a result of offshore
manufacturing. Development of specialty products based on novel con-
cepts has also been curtailed on the assumption that the U.S. consumer
would not support the premium. The industry clearly continues to aim
at a volume business and shows reluctance to diversify. Further evi-
dence of this reluctance is found in the industry's phaseout of mid- and
long-range research and in the focus of its limited technical resources on
existing businesses. Both steps emphasize the overriding importance of
short-term payoff.
Japanese and American strategies thus differ, and the contrast has
grown over the years. Indeed, several developments presented in this
report originated in the United States. But, as time went on, the industry
here turned its attention elsewhere, while the Japanese latched onto the
trends and improved on them. Time will tell which of the two will pre-
vail in the barrier-free, fiercely cost- and quality-competitive world. . .
As these trends continue, the U.S. textile and garment industry will
be dependent on foreign textile materials and machinery technology. If
we wish to assess the readiness of the U.S. textile-garment industry to
meet the CB protective textile and garment requirements, we must ask
several questions. Do we have the necessary multifunctional fiber materi-
als? Do we have the necessary specialty, ultrafine fiber, yarn, and fabric
processing technologies? Do we have quick-response garment manufac-
turing technologies that can meet changing needs? Unfortunately, the
answer to all of these questions is no.
Recognizing that U.S. industry is not prepared at the material or tech-
nological level to respond to the need for a selectively permeable uniform
for the soldiers, the Department of Defense has taken the initiative by
supporting R&D at universities and industry. Rapid advances in
nanotechnology and biotechnology should stimulate the development of
new material and processing concepts. New engineering design tools and
manufacturing technologies will be necessary, however, for these innova-
tive concepts to be translated into product realities.
APPENDIX B
215
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