Protective textiles are a part of technical textiles that are defined as
comprising all those textile-based products that are used principally for
their performance or functional characteristics rather than their aesthetic
or decorative characteristics. Textile materials in the form of woven,
knitted, nonwoven and braided structures or a combination of these
structures are being used for protective textiles (Figure 1). Most fabrics
are two-dimensional but an increasing number of three-dimensional protective
textile structures are being developed and produced. The properties of
fabrics depend on the characteristics of the constituent yarns or fibres and
on the geometry of the formed structure.
Woven fabrics are the most common type of textile structures used for
protective applications. Depending on the degree of interlacement, basic
weave structures may be classified as plain, matt, twill and satin/sateen
with thousands of derived structures. Woven fabrics consist of two sets of
yarns mutually interlaced into a textile fabric structure. The threads that
run along the length of the fabric are called warp or ends, while the
threads that run along the width of the fabric from selvedge to selvedge are
referred as weft or picks. Warp and weft yarns are mutually positioned under
the angle of 90°.
The number of warp and weft yarns per unit length is called warp and weft
density. The warp and weft yarns in a woven fabric could be interlaced in
various ways that is called a weave structure. A crimp is the ratio of the
yarn actual length to the length of the fabric it traverses. The crimp
influences the fibre volume fraction; fabric thickness and fabric mechanical
properties. A cover factor is the fraction of the total fabric area that is
covered by the component yarn. Fabric area density and cover factor
influence strength, thickness, stiffness, stability, porosity, filtering
quality and abrasion resistance of fabrics.
It is the simplest weave; it has the minimum repeat size of 2. The type
of fibre in the yarn used for making fabric will influence the fabric’s
characteristics. The yarn used for might be flat, monofilament, twisted or
textured multifilament or it has been spun from natural or synthetic staple
fibres. The stiffness of the raw material used for producing the yarn and
the twist factor of the yarn affect the weavability and stiffness of the
fabric. Very highly twisted yarns are used in cases that require certain
special characteristics in plain weave yarns. Fabrics produced from such
yarns will have a good amount of extensibility or will be semi opaque.
Plain fabrics can be woven as warp or weft faced fabrics. The warp faced
plain fabrics have much higher warp cover factor than weft cover factor.
Also the warp thread density is twice the weft thread density for same
linear densities of warp and weft yarns. There will be a great difference in
the crimp values of warp and weft (warp has much higher crimp). Thus by
choosing suitable cover factors and yarns, most of the abrasion on the
fabric will be taken by the warp yarn, thereby protecting the weft yarns.
The weft faced plain fabrics have much higher weft cover factor than the
warp cover factor. The weft crimp far exceeds the warp crimp. Weft faced
plain fabrics have the disadvantage that they are more difficult and
expensive to weave and hence are restricted.
Triaxial woven structure
Rib knit structure
Triaxial braid structure
Figure 1. Examples of woven (top left), knitted (top right), 3D Woven
(bottom left) and braided (bottom left) structures used for protective
These are derivatives of plain weaves. They may warp, weft or matt ribs
according to the dominance of the float of threads in warp or weft or both.
These weaves have lesser number of interlacements. Therefore, more number of
threads can be inserted in a given space to obtain a higher cover without
jamming the threads.
In warp rib fabrics the warp ends/cm exceed those of the weft yarns. And
thus have a high warp crimp and low weft crimp. The situation reverses in
weft ribs. Rib weaves with long floats face the problem of overlapping
adjoining yarns. Weft ribs are uneconomical to weave because of higher weft
thread density per unit length. The possibilities are better with two picks
inserted at the same time.
Simple matt weaves tent to imitate plain weaves due to equal dominance of
warp and weft floats.
The warp and weft threads in matt weaves can be floated unevenly to
obtain special technical effects. Large repeats of matt weaves are avoided,
as the structure tends to become unstable. If they are to be used, some kind
of fancy weave or binding is required. Matt weaves can have higher cover
factors due to lesser binding points. When constructed closely they can have
better abrasion and filtration properties and greater resistance to water
penetration. When constructed more openly matt weaves have a greater tear
resistance and bursting strength. Weaving costs can also be reduced if two
or more picks can be inserted simultaneously.
These weaves give a diagonal line effect in the fabric, which runs from
one selvedge end to the other. The minimum repeats size of the weave is 3.
The direction of the twill line may be ‘Z’ or ‘S’. The twill angle
can be easily varied. Twills have longer floats, fewer intersections and
more open construction than plain weave fabrics with identical construction
details. Weft faced twills cause less strain in weaving as compared with
warp faced twills, since lesser number of warp ends has to be lifted so as
to allow weft picks to pass below them. If the twills are woven upside down,
it becomes difficult to inspect the warp yarns during weaves. More
combination of twills can be had with increase in size of repeat.
Satin sateen weaves
These weaves are produced either warp or weft faced. Unlike simple twills
they do not show continuous diagonal lines in fabric and tend to give smooth
surface due to more floats. The warp thread density/cm is greater than weft
in case of satin. In case of sateen weaves it is vice versa. The weaves are
constructed on a minimum repeat size of 4. Though satins / sateen’s can be
constructed with many repeat sizes, 5 end satins/sateen’s are most common,
as they give moderate cover factors and firm fabrics.
Knitted fabrics are textile structures assembled from basic construction
units called loops. There exist two basic technologies for manufacturing
knitted structures: weft and warp knitted technology.
Weft knitted fabrics
The repeating unit of the knitted fabric is called loop. The feature of
the weft knitted fabric is that the loops of one row of fabric are formed
from the same yarn. A horizontal row of loops in a knitted fabric is called
a course and vertical row of loops is called a wale. The stitch density is
the number of stitches per unit area in the knitted fabric. The stitch
length is the length of a yarn in a knitted loop and is an important factor
that determines the properties of the weft knitted fabric.
The cover factor is a number that indicates the extent to which the area
of a knitted fabric is covered by the yarn. The higher cover factor
indicates a more tight structure and vice-versa. The fabric area density is
a measure of the mass per unit area of the fabric. In weft knitted fabrics
the loops are formed successfully along the fabric width. The yarn is
introduced more or less under the right angle regarding the direction of the
The feature of the weft knitted fabric is that the neighboring loops of
one course are created of the same yarn. The simplest weft knit structure
produced by the needles of one needle bed machine is called plain knit or
jersey knit. The plain knit has different appearance of both sides of the
fabric. A structure produced by the needles of both needle beds is called
rib structure or double jersey having the same appearance on both sides of
Weft knitted fabric can be produced on a number of different types of
knitting machines. Circular or flat bar machines using a latch needle can
produce both fabrics and knitting garments. Straight bar or circular
machines using a bearded needle can produce shaped knitwear. Many machines
can produce a double fabric structure with differing knitted structure on
each fabric face. Spacer yarns can be inserted between the front and back
fabric, thus creating a complex three layer structure. The properties of
each layer are determined by the fibre, yarn properties and structure of
that layer. These structures can be tailored for specific applications and
are useful in the protective textile field.
Warp knitted fabrics
In warp knitted technology every loop in the fabric structure is formed
from a separate yarn called warp mainly introduced in the longitudinal
fabric direction. The most characteristic feature of the warp knitted fabric
is that neighboring loops of one course are not created from the same yarn.
To accomplish the warp knitted structure every needle along the width of the
fabric must receive yarn from the individual guide. The function of the
guide is to lead and wrap the warp yarn around the knitting needle during
the knitting process. The loop structure in the warp knitted and weft
knitted structure is similar in appearance. The warp knitted structure is
very flexible and regarding construction it can be elastic or inelastic. The
mechanical properties are in many cases similar to those of woven
structures. The best description of warp knitted fabrics is that they
combine the technological, production and commercial advantages of woven and
weft knitted fabrics.
Warp knitted fabrics can be produced on a number of different types of
knitting machine. Raschel machines using a latch or compound needle produce
high pile upholstery fabrics, industrial furnishing fabrics and bags for
vegetables. Tricot machines using bearded or compound needle produce lace,
nets, and outerwear fabrics. Weft insertion with, for example, elastic yarns
or fleeces can produce directionally orientated fabrics. Warp knitted
fabrics are commonly used in linings for protective clothing and laminated
with polyurethane foams to provide a strong flexible base for the foam.
Nonwovens are a class of fabric that are produced directly from fibres,
and in some cases directly from polymers, thereby obviating a number of
intermediate processes such as spinning, winding, warping, weaving/knitting.
Hence nonwovens can be produced inexpensively for both single use and
durable applications. Nonwovens are produced in two distinct steps:
1. Web formation: arrangement of fibres into a 2D sheets, and
2. Consolidation: bonding the fibres together to create a nonwoven
Web formation methods
Web formation may be classified into dry laid, spun laid and wet laid
Dry laid process
Dry textile fibres are carded, using a carding machine similar to the
once used in the spinning industry, to arrange the fibres in a 2D sheet with
fibre orientations predominantly in the machine direction. The web is
subsequently folded using a cross – lapping machine to increase the web
thickness and to achieve transverses fibre orientation. In some cases,
conventional carded and cross-lapped webs are combined to produce a web with
bi-directional fibre orientation. Alternatively, an aerodynamic system is
used for creating a web random fibre orientation.
Spun laid process
This is a method of producing fabrics directly from polymer chips, hence
eliminating the entire textile supply chain. Fibres are extruded from a
spinneret similar to conventional melt spinning process. These fibres are
attenuated (stretched) using high-velocity air streams before depositing on
a conveyer in a random manner. The spun laid process is the most commonly
used method for producing both disposable and durable nonwovens for
There are other related systems such as flash spinning, melt blowing and
electro-spinning. Flash spinning involves extrusion of a polymer film
dissolved in a solvent; subsequent evaporation of the solvent and mechanical
stretching of the film results in a network of very fine fibres. These
fibres are subsequently bonded to create a smooth, microporous textile
structure used for protective applications. The melt-blowing process
produces microfibres by attenuating the polymer jet, coming out of the
spinneret, using high-velocity air jet. Since the polymer is stretched in
the molten state, extremely fine fibres can be produced. Because of the lack
of molecular orientation, melt-blown fibres are weak and hence are generally
used in conjunction with other type of non-weaves. For example, a composite
nonwoven consisting of melt-blown layer and a spun-bond layer is becoming
popular for medical protective applications
Wet laid process
Developed from the traditional paper making process, relatively short
textile and wood fibres are dispersed in large quantities of water before
depositing on as inclined wire mesh. These materials find application in
hospital drapes and filters.
Fibrous webs can be consolidated using a number of techniques depending
on the area density and the desired properties. They can be classified into
mechanical, chemical, thermal and stitch bonding processes.
Needle punching and hydro-entanglement are two complementary mechanical
processes. Relatively thick webs (150 to 1000 g/m2) are felted with the aid
of oscillating barbed needles. The hydroentanglement process uses high
velocity water jets to consolidate relatively thin webs (< 140 g/m2). The
resulting spun laced fabrics are highly drapable and hence popular for
medical protective clothing.
Fibres are bonded with a suitable adhesive and subsequently cured under
heat. Saturation bonding is seldom used for protective applications, as this
process results in a relatively stiff non-porous material. Spray and print
bonding instead of saturation bonding improves the flexibility and
Relatively thin webs are passed through a heated calender, resulting in
partial melting and bonding of fibres. Thermal bonding is a high-speed
process and hence commonly used in conjunction with spun laids.
Cross-laid webs are stitched together with a relatively large number of
needles across the width. Alternatively, stitch bonding is also used to bond
a series of non-interlaced thread systems.
3D woven fabrics
Protective textiles, especially produced for ballistic applications,
consist of a number of fabric layers stitched or quilted together. An
alternative and cost effective method would be to weave all the layers
together. Relatively thick fabrics consisting of a number of wrap and weft
layers can be produced on conventional and specialised 3D weaving machines.
The warp and weft yarns are held together with interlacing z-yarns:
orthogonal and angle-interlocked are the two prominent structures used. In
theses structures, most of the yarns remain non-crimped and hence these
structures have high in-plane modulus and high longitudinal wave velocity.
Potentially, 3D weaves have a number of advantages over broad cloth:
● Fabrics can be woven with much higher cover factors since there
are only small percentages of interlacing yarns.
● Warp and weft yarns have very little or no crimp at all in 3D
weaves. Hence, coarser yarns can be used as opposed to fine yarns being used
in 2D fabrics, to minimize the effect of crimp.
● Labour cost can be reduced as a result of using coarser yarns and
eliminating subsequent stitching processes.
Braided textile structures
Braided textile structures are manufactured with mutual interwining of
yarns in a tubular form. There are three typical braid structures: diamond,
regular and hercules. Diamond structure is obtained when the yarns cross
alternatively over and under the yarns of opposite direction. The repeat
notation is 1/1. Regarding this way of notification, the regular braid
structure has notation 2/2 and hercules 3/3.
The braids are mostly produced in a regular structure. Generally braids
are produced in a tubular form of biaxial yarns direction. By insertion of
longitudinally oriented yarns (middle-end-fibre) into the structure the 3
axial braids is obtained. Moreover in the centre of the tubular braid,
additional fibres called axial fibres can be inserted. When the number of
braiding fibre bundles is the same, the tubular braid increases the fibre
volume fraction more than the flat braid.
The main feature of the braid is the angle of interwining that can vary
between 10–80° and depends on: the yarn fineness, the type of the
structure (biaxial or triaxial), cover factor (tightness of the structure)
and the volume ratio of the longitudinal yarns. Since the braids have
tubular form, they are often replaced with the filament winding structures.
In this respect it has been proven that the braids can be competitive
regarding the price. The braid is a flexible product and can be adjusted to
various shapes. With the special device called mandrel the braids can be
shaped into various forms directly on the machine at the manufacturing
In some cases of protective textile application there is a need for
connecting several layers of different textile structures. The reason could
be increasing the thickness of composite perform before impregnation with
resin. Several layers of the fabric are stacked upon each other till desired
thickness is achieved, and then, the fabrics are assembled by sewing,
stitching, needle punching or knitting. Depending on the thread size and
stitching density, the latter can contribute to increasing through thickness
strength, stiffness and delimitation resistance of the composite.
1. N Gokarneshan: Textile Asia, July 2007, 48-50.
2. R A Scott: Textiles for Protection, Woodhead Publishing, Cambridge,
3. G Demboski, and G B Gaceva: Bulletin of the Chemists and Technologists
of Macedonia, 2005, 24, 77-86.
4. A R Horrocks, and S C Anand: Handbook of Technical Textiles, Woodhead
Publishing, Cambridge, 2000.
5. A Ormerod, and W S Sondhelm: Weaving -- Technology and Operations,
Textile Institute, Manchester, 1999.
6. D J Spencer, Knitting Technology, Pergamon Press, Oxford, UK, 1986.
Note: For detailed version of this article please refer the print version
of The Indian Textile Journal May 2008 issue.
Department of Textile Technology,
SSM College of Engineering,
Komarapalayam,Tamil Nadu 638 183.