44 eBook PSP | Yarn Technology (Filament Yarn)
Figure 3.2 Principle of twist texturing
Consider extreme cases. The adjacent helical coils in Figure 3.1(a) take up a great deal of
space and we have a so-called ‘bulky’ yarn. The other model, Figure 3.1(b), consumes
relatively little space and we have a low bulk, high stretch yarn. As the yarn is extended,
the intermittently snarled filaments are progressively converted to straight parallel
filaments. There is a great deal of yarn stored in the snarls, and, consequently, there is a
surprisingly large extension of the yarn before the snarls are fully converted to straight
parallel filaments. Furthermore, the tension needed to pull out the snarls is relatively low,
and thus the yarn behaves as a low-modulus material (until all the snarls are removed).
Of course, as the filaments change from the snarled to the straight condition, they are
subjected to torsional and bending stresses, and energy is stored in the extended yarn.
Once the tension is removed, the yarn attempts to return to a minimum energy state and
contracts. Thus, the stretch yarn behaves rather like a rubber band and its principal
characteristic is the enormous and almost elastic extension that becomes possible. A
practical yarn is an intermediate between the extremes. There are varying proportions of
each kind of minimum energy shape according to the method and conditions of texturing.
Also, there are modifying factors. Helical portions tend to intermesh, parallel portions tend
to migrate (and become non-parallel), many filaments fail to reach their minimum energy
state, and many filaments interfere with one another.
eBook PSP | Yarn Technology (Filament Yarn) 45
Consequently, there is a wide range of combinations of bulk and stretch that can be
achieved, but generally the higher the stretch capability, the lower the bulk. Of course,
even the adjacent coil model provides a yarn with a moderate degree of a stretch because
the helices act as coil springs. In practice, the breaking elongation might vary from 10%
for a bulked yarn to 500% for a stretch yarn.
3.4 False twist texturing
General comment
One of the most important types of yarn modification is false twist texturing. As mentioned
in the last chapter, a running yarn twisted as shown in Figure 3.3 causes a false twist to
be trapped between the feed system and the twister. The feed yarn has little or no twist,
the yarn between A and B has a false twist, and the yarn leaving B has the same twist as
the input. If heat is applied in zone AX and the yarn is cooled in zone XB, then the yarn
approaching B will be heat set in the twisted condition. Overfeeding (not shown) and
untwisting slackened filaments at B facilitates the necessary fiber rearrangement and
separation. (An overfeed is where the input speed is slightly more than the output speed.)
When the filaments relax, the uneven contraction of the filaments causes them to
rearrange themselves laterally. If heat is applied in zone CD, the latent crimp can be
developed to produce a bulked, set yarn in one continuous process.
In the particular case shown, a godet is used to grip and feed the input yarn; however, no
twister is shown for reasons of clarity. All the phases mentioned in the previous section
are embodied in this continuous process. The integration reduces the costs of machinery
and material transportation. The savings have been so large that false twist texturing has
become a major system for yarn production. The means of twisting have changed and the
systems will now be reviewed in a more or less historical sequence.
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Figure 3.4 False twist texturing
Pin twister type of false twist texturing machines
To heat set the twisted filaments and relax them afterward to produce bulk, it is necessary
to heat the running filaments at two places and so we have two-heater machines to
produce the developed yarns. To produce yarns in which the filaments have not been
relaxed only one heater is required. Examples of a two-heater machine are shown on a
small scale in Figure 3.4. It is necessary to use high twist levels to produce adequately
textured yarns; for example, with a 70 denier yarn, one might well use some 80 TPI. (This
would give a TM of about 10 on the cotton system.)
eBook PSP | Yarn Technology (Filament Yarn) 47
Figure 3.4 Manufacture of False twist yarns
To get high production, it is necessary to use very high twisting speeds, of around 500 000
r/min. This calls for special designs of twisting units in which the mass and size of the
rotating element are as small as practical (or the element is eliminated). It also calls for
special bearings or suspension systems. In the pin twister shown in Figure 3.4, the spindle
is frequently less than 00.25-inch diameter × 1.5 inches long (approximately 6.4 mm
diameter × 38 mm) and it is held against drive rollers by a magnetic field; this obviates the
need for a direct bearing. The bearings of the drive rollers have to rotate at only a fraction
of the speed of the spindle (typically 12–15%). It should be noted, however, that the
spindle gets very hot because of air drag and magnetically induced eddy currents within
the metal. Also, the false twist pin (shown inset) is usually made of ceramic or sapphire to
withstand the abrasion caused by the yarn passing over it.
48 eBook PSP | Yarn Technology (Filament Yarn)
A given element of the polymer must reside in the hot environment for a sufficient period
to reach Tg because it takes time to soften the polymer. If, for example, the time is 0.5
seconds, the spindle speed is 500 000 r/min and the twist is 80 TPI, the heater length
has to be at least 52 inches. Thus it can be seen that the heaters must be long.
It also takes a significant time for the yarn to cool sufficiently to freeze it into the twisted
configuration. Thus, a certain distance is needed between the heater and the false twist
pin. The needed heating and cooling lengths increase with spindle speed and this leads to
increases in the threading length. Not only do high-production machines become very tall,
but there is also increasing difficulty in handling the long, heated filaments. The frictional
drag of the yarn over the heater plate is a significant factor. The frictional coefficient is
modified by the fact that the yarn rotates at high speed about its axis as it passes over the
heater plate. At very high speeds, the design of the heater becomes extremely important
and it sometimes becomes necessary to use forced cooling of the yarn leaving the heater.
Where two heaters are used (to produce a set yarn), the threading length is almost
doubled, If the threading is vertical and the two heaters are immediately above one
another, a two-story building becomes necessary for high-speed machines. Alternatively,
more complex threading may be used; for example, the heaters might be inclined vertically.
In all cases, modern machines need a great deal of headroom. Threading up (or ‘stringing
up’) needs skill because of difficulties in handling the hot, high-speed yarns. It might be
added that the use of air to piece and thread godets, and other high-speed elements, is
very common in the filament industry.
To restate, the polymer's temperature must be adjusted to a level between Tg and Tm. The
higher the temperature within these limitations, the better the set, but as the temperature
approaches Tm, the yarn strength deteriorates and significant variances in dye affinity are
likely to be formed. Moisture impacts the setting process and can lead to polymer
breakdown, therefore atmospheric conditions should be regulated. In general, an ambient
temperature of 75 5°F (24 3°C) and relative humidity of 65 2% are employed, however,
the conditions may vary depending on the yarn being textured. Excessive humidity causes
the yarn to drag across contact surfaces, resulting in unpredictable tensions. Which, in
turn, causes variances in the developed bulk. Inadequate humidity results in the
generation of static electricity, therefore regulation is critical on all counts.
eBook PSP | Yarn Technology (Filament Yarn) 49
The feed uptake rates govern the tension of the yarn within the heater. To accommodate
for twist contraction and shrinkage, the feed wheels must be changed to provide an
overfeed of 2 or 3%. Inadequate overfeeding creates excessive tension, which results in
unacceptably high end-breakage levels and poor bulk. Overfeeding causes low tension,
which leads to the creation of tight areas (often referred to as "voids"), poor set, and, once
again, degradation in end-breakage or filamentation rates. Tight areas are seen as
apparently untextured (or weakly textured) yarn segments that appear as fabric flaws.
These tight places are created by the twist sliding irregularly over the false twist pin.
Yarn segments leave the twist pin with the true twist; a twisted segment of yarn cannot
fully acquire bulk. Over-twisting the yarn can have a similar effect. The twist degree
influences the feel and appearance of the fabric; a high twist produces a smooth, fine
texture, whereas a low twist produces a harsh, pebbly appearance. A high twist results in
a comparatively high crimp contraction and hence increased stretch potential. It also
generates more tight places in the yarn and weakens it (up to 20-30% strength loss for
nylon, but very little for polyester or acetate).
To aid drawing and following processes, fiber makers add a finish to the surface of the
filaments soon after extrusion. The finish is designed to prevent static electricity and
friction, however, when heated during the texturing process, any volatile fractions of the
finish are pushed out, resulting in unpleasant odours. Heavier fractions can oxidize or
otherwise degrade, causing difficulties with solids deposit in heater zones. This is
especially true if high heater temperatures are utilized (for example, 400°F, or 200°C).
The loss of the fiber finish can also be an issue, and it is generally preferable to use a
lubricant after texturing. These 'coning oils' replenish the losses and make winding and
fabric production easier.
Any such oil, however, should be stable and capable of being scrubbed away without
affecting the colour or performance of the yarn. A sufficient amount of fiber finish or
additive is required, but excessive quantities should be avoided. Variations in final add-on
levels should also be kept to a minimum. The use of titanium dioxide (TiO2) dulls certain
fibers, affecting the wear rate of guides and pins. Such wear can harm both the quality of
the yarn produced and the efficiency of the operation.
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Soft-winding the yarn packages are required with a single-heater system to allow for
satisfactory later autoclaving to generate set yarns. To allow the crimp to form on two-
heater machines, the yarn must be overfed into the second heater. This degree of
overfeeding is often between 4 and 5%. When used in combination with an autoclave, a
single-heater machine is less efficient than a two-heater machine. Variations between
batches are more likely with the batch process of the autoclave setting, and hence there
is an increased danger of generating barré in the textiles. This is due to variations in bulk
and dye affinity caused by non-constant heat treatment conditions.
Whatever method is utilized, considerable care must be taken to keep all temperatures,
tensions, and twist levels consistent from spindle to spindle, from time to time, and from
batch to batch. The result of a failure to regulate in all of these areas is that streaks and
barré will appear in the coloured cloth. Modern machines are outfitted with control
systems, and tight quality control is implemented through thorough sampling and testing.
However, possible faults in the yarn produced by the machines are rarely noticeable. As a
result, testing on coloured yarn must be conducted at an early stage, before huge
stockpiles amass.
3.5 Textured Yarn Process Techniques and Product Developments
After stretching, all synthetic fibers have a smooth glass-like cylindrical surface, a high
gloss, and a low hygroscopicity. This makes it difficult for fibers to be used in applications
that need greater sanitary and aesthetic features.
As a result, the fibers or filaments are further treated, which is known as 'texturization' or
simply *texturing'. Texturization is defined as the process of combining sumptuous bulk,
increased absorbency, and better hand with a tough performance by permanently
introducing crimps, loops, coils, or crinkles into otherwise continuous threads.
Texturing imparts smooth filament yarn with the aesthetic properties of spun yarns while
also making it non-slippery. Various methods are used to form these straight yarns.
Texturing filament yarns involves a variety of techniques, both physical and thermal. During
the procedure, distortions like crimps, loops, and knots will be added. Because synthetic
fibers are also thermoplastic, the extra feature added to smooth yarns is afterward heat
eBook PSP | Yarn Technology (Filament Yarn) 51
set to keep the character for a longer period. Texturing yarns alters their surface properties,
increasing their bulk, stretch, and cotton-like feel in textiles. A yarn drawn from nylon
stockings is a good example of textured yarn since it has bulky numerous threads with a
very wavy structure. Texturization improves thermal insulation, comfort, and moisture
absorption in materials.
Yarns after texturization differ from the initial yams by high bulkiness, crispiness, porosity,
softness, and maybe high elastic extensibility. As a result, the fabrics made from these
textured yarns exhibit the following advantageous properties:
1. higher bulk
2. greater water sorption
3. increased warmth
4. higher covering power
5. better air permeability
6. better dimensional stability
7. good draping capacity
8. higher hygienic characteristics
9. Pleasing hand and appearance
Texturization is also known as disorientation because it distorts flat continuous filaments
into loops, crimps, coils, or curls over their whole length to increase the bulkiness, porosity,
softness, and elasticity of the material. The textured yarn manipulation method modifies
and changes the molecular arrangement of the filaments. It causes a permanent alteration
in the physical structure of the yarn, resulting in textured filaments that are no longer
parallel to one another. In general, there are three steps.
The first step is to bend the filaments in the yarn, which breaks the inter-fiber connections.
The material is then heated to their respective melting points, which breaks the bonds
between the polymers, allowing the filaments to remain crimped, looped, or in any other
disordered form, and the heated material is immediately cooled to allow new bond
formation between the polymers in the yarn stage itself, making the distorted state
permanent on their structure. When the yarn is untwisted or otherwise freed from its
warped state, the filaments remain coiled or crimped; this sort of yarn may be roughly
categorized into three key groups, such as,
52 eBook PSP | Yarn Technology (Filament Yarn)
Stretch yarns: These yarns have a high stretch and a moderate bulk per unit weight. It
has more than 300% elasticity. These yarns are typically used for stretch-to-fit textiles,
sportswear, and so on.
Modified stretch yarns: These textured yarns have moderate stretch, a high bulk per
unit weight, and helical or planner crampiness. This type of yarn is utilized in shirtings,
suits, and other garments.
Bulky yarn: Bulky textured yarns have a higher bulk with little or no stretch, a loopy
structure, and common extensibility. These yarns are specifically utilized in carpets and
automotive interiors, among other things.
Even though textured yarns are produced using a variety of techniques, all types of
textured yarns share certain characteristics due to the rearrangement of molecular chains
in the structure, such as good air permeability, high bulkiness, and so on, which results in
increased warmth, greater water absorption characteristics, and good dimensional
stability of the product. Because of their bulky nature and lower packing density of
molecular structure, these factors have a stronger effect on the outcomes of fabric
handling values.
3.6 Methods of Texturization
Textured yarns are continuous filaments that have been modified by physical, chemical, or
thermal changes in the structures so that they are no longer straight or homogeneous. All
man-made and natural fibers can be treated to produce yarns with some degree of stretch
and recovery, but the machine selection should be based on the end-use requirements
and product specifications. For example, heat setting in a twisted condition of filament will
cause the texture effect in thermoplastic materials, whereas texturization is only possible
in non-thermoplastic materials using the Air jet texturing (AJT) process. As a result, proper
machine and process conditions are necessary. A textured yarn, a continuous filament
yarn that has been treated, introduces crimps, coils, loops, or other fine distortions along
the lengths of the filaments. These effects may be created in the filament using a variety
of techniques such as False Twist Texturing, Air Jet Texturing, the BCF process, Edge
crimping, Stuffer box crimping, and so on.
eBook PSP | Yarn Technology (Filament Yarn) 53
Figure 3.5 Flat and textured yarn
Twisted filament yarns
It is unnecessary to twist continuous filament yarns to impart strength; nevertheless, some
small amount of twist is inserted merely to control the fibers. An untwisted bundle of
filaments is difficult to handle because odd filaments and loops project from the surface
of the bundle. These tend to catch up in guides, tangle with adjacent yarns, or otherwise
cause difficulty. Some man-made fibers tend to balloon out quite severely because they
accumulate electrical charge. Filaments or loops protruding from the yarn are often called
wild filaments. Even a low level of twist in the yarns helps to reduce the number of these
wild filaments; a twist inserted for this purpose is called a producer twist.
Filament yarns are sometimes twisted to a fairly high level to break up the luster of the
yarn or to impart some other attribute to the yarn for effect purposes. However, high twist
levels reduce the tenacity of the yarn and make the yarn leaner (i.e. have a smaller
diameter).
Another use of twist in filament yarns is to create texture. A false twisted yarn will coil or
snarl if it is subject to the correct sequence of twist, set, and untwist. If properly relaxed,
these textured yarns become bulky and have many desirable features. A major advance
was made when it was realized that the process of false twisting provided the opportunity
to carry out such a sequence in a continuous manner. To understand how that works, it is
necessary to be knowledgeable about false twists.
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3.7 False twist
The flat geometry and smooth surface of man-made fibers are one of their key drawbacks.
The waviness or crimp of the fiber enhances volume, resilience, moisture absorption, and
so forth. Texturing techniques have been developed to address this issue. The most
frequent texturing approach is false twist texturing.
The false-twist texturing process may be examined using three key factors known as 3T:
tension, twist, and temperature. These settings can be changed to change the qualities of
the textured yarn. The major process factors to adjust 3T are the draw ratio, D/Y ratio, and
heater temperatures.
The D/Y ratio refers to the ratio of the disc surface speed to the yarn speed. The D/Y ratio
is computed as follows:
D/Y = min) min) (m/yarn of speed
-------------------------------------------------------------------
throughput circumference (m/speed discs ntial (1)
When the D/Y ratio is low, the yarn tension before the twisting unit is low, while the
tension after the twisting unit is high [3-5]. This condition may result in yarn damage.
The draw ratio, as depicted in Figure 1, is the ratio of center shaft speed to input shaft
speed and is computed as follows:
draw ratio = center shaft speed (m/min)
----------------------------------------
input shaft speed (m/min)
The draw ratio has an impact on the finished yarn's linear density, toughness, molecular
orientation, dye absorption and dyeing uniformity, residual shrinkage, fiber breakages, and
so on.
eBook PSP | Yarn Technology (Filament Yarn) 55
3.8 Stuffer box
Through the yam guide and tension roller, the yarn is transported from the supply package
to the hot stuffer box. The filament is compressed by the pressure roller. The yarn is pulled
from the stuffer box and gathered on the take-up bobbin after passing through the yarn
guide and traversal guide. The procedure entails compressing the filaments into a limited
region within a heated chamber.
Figure 3.6: Stuffer box texturing
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3.9 Air Jet process
Figure 3.7 Air Jet Texturing
The Air Jet Texturing process is the only process for non-thermoplastic polymers, cellulosic
or non-organic filaments texturization. In this process, filaments are fed over a tiny blast of
air that forces the filaments into the loops. One or more end of filament yarns is overfed at
a constant rate inside the air jet, which blows quickly depending on the amount of
overfeeding, it varies from 15% to 150% between the inlet and outlet feeds respectively,
the material process flow in the air jet Texturing machine is shown in Figure 3.7. The speed
of the air Texturing machine is about 400m/min to 500m/min, this made gainful air
Texturing of finer yarn counts of up to 100dtex with a continuous string of smaller and
larger loops. The individual filaments are compacted by the air stream, which stabilizes the
loops. An advance in air-texturing over the years has relied only on the growth of air-jet
nozzle modification since it’s contributing the major portion of the Air jet material output.
Newer nozzles have led to the processing of a wide range of yarns at greater processing
speeds, lower energy consumption, and lower noise levels.
Several filaments of different deniers and various material types can be mixed to construct
the ideal Air Jet Textured Yarn (ATY) for specific end-use applications. ATY is generally made
from partially oriented yarn (POY), ATY is a yarn with millions of small loops, which give it a
distinct feeling and look at the output. Whereas, Drawn textured yarns (DTY) generally
produce a crimped yarn structure without a loop. The loops in ATY contribute to the bulk
eBook PSP | Yarn Technology (Filament Yarn) 57
and loft of a fabric, whereas DTY produces crimp in every filament creating the bulk and
volume of a fabric. ATY can offer an entirely different aesthetic look and hand value
compared to other fabrics. The manufactured yarns are used for sewing thread
applications, apparel fabrics, fancy yarn articles, automotive interior fittings, home
furnishing fabrics, carpets, fire blankets, etc.
3.10 BCF Process
High bulk yarns are created and processed by nonlinearity in individual filaments in a
Bulked continuous filament (BCF) process. The materials handled in this texturization
process are comparable to those used in man-made filament manufacture; the only
difference is in the material gathering area. Bulky yarns can be shrunk and stretched to
introduce shrink differentials in their structure, resulting in bulked, fluffed, and twisted
yarns. Because of the highly bulky structure, this is also known as carpet yarn. The
structural difference between spun yarn and bulked continuous filament yarns is
represented in Figure 3.7 below.
Figure 3.8 Spun yarn and BCF yarn Structural arrangements
Polymer granules are extracted using spinneret, which is identical to the filament
production process; after quenching and drawing, the material stretch value is 1-4%, which
decreases the denier of the carpet yarn. Plug formation occurs during the material
processing through the Jet nozzles. Plug formations are determined by the position of the
holes and the number of holes in the jet configuration. The perforated cooling drum at the
output region will revolve and collect the material, changing the nature of the substance
into a textured form. Finally, the heat-set fiber is sewn or tufted into the primary carpet
backing, with the number of yarns used and the proximity of the tufts to one another
determining the carpet's density. In the kitchen or bathroom floor textured carpet, which
will avoid slippery nature and also it will enhance the aesthetic look of the room.
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3.11 Knit-de-Knit
The fundamental idea of knit-de-knit texturing is simple. If a fabric is knitted, heated, and
cooled and the thermoplastic yarn is unraveled from the fabric structure, then the yarn is
found to have a texture set into it. The newly unraveled yarn has repeating deformations,
but these can be manipulated to redistribute the zigs and zags of individual filaments and
create a textured yarn. It is used for certain specialty yarns. For example, where low-bulk,
lustrous fabrics are required using a fiber such as Quiana® (a high-cost nylon used as a
high-fashion silk substitute), then the knit-de-knit process might be appropriate. In such
specialty markets, it is aesthetic results that are more important than high productivity and
low price.
Knit-de-knit texturing may be used on drawn fiber to produce a crimp of a knitted-loop
shape. In this process, yarn is knitted into a tubular fabric, set in place using heat, and
then unraveled to produce textured yarn. Knit de knit is a special technique for creating
textured yarn. Whereas special machines are used with other texturing techniques, Knit-
de-knit relies on ring knitting and heat setting.
Firstly, the yarn is knitted into a tube on a knitting machine. Once the fabric is finished, it
gets steam treated (or dyed, depending on the exact method), which fixates the
crimps/loops. Afterward, the fabric gets unknitted, creating a yarn with the typical loops as
can be seen in the picture on the left (desktop version) / above (mobile version).
Materials for Knit de Knit
Not every yarn is suitable for Knit de knit. Natural yarns for example cannot be heat set
(thus not keeping the crimp form after the steaming process) whereas some synthetic
polymers would melt during heat setting.
Edge Crimped Method
The yarn is taken from the supply package to the edge-crimping unit through the guide
rollers. The crimping unit consists of the input rollers and output rollers. separated by a
heater and knife for crimping. After the crimping, the yarn is collected at the bobbin using
the traversing guide. The yarn, drawn over the edge of a knife or steel plate is strained by
different types of bending strains. The yarn side contacting the knife is compressed while
the opposite side is stretched.
eBook PSP | Yarn Technology (Filament Yarn) 59
During the movement of the yarn, the point of bending is constantly changing its position,
both in the parallel and radial direction of the yarn. As a result, the yarn after cooling
acquires a coiled spring configuration. In addition to crispiness, due to bending, the yams
are also given crimp due to the change in orientation of the molecules, induced during
bending.
Conclusion
Technology is the real partner of innovation in the industry today. In the field of the
texturization process, air interlacing jets with better presentation can be anticipated. They
will fulfill the needs of accelerating process speeds, and on the other hand, they will take
care of escalating process permanence. The outcome will be a yarn with greater bulk,
higher stretch, and more beautiful properties as per requirements. High flexibility of the air
Texturing process with an application range from approx. 22dtex to 18,000dtex, makes all
kinds of yarn possibilities, with a great number of yarn combinations. Predominant
applications of these yarns are in the areas of hosiery, ladies’ wear, sports and leisure
wear, and also in textile automotive linings. The level of the market increase in air-textured
yarns will depend on the future Research and development activities of various end-use
applications
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04
TECHNICAL FILAMENT YARN
This topic covers technical filament yarn. It covers aramid fiber,glass, carbon, and HDPE filament
yarn.
eBook PSP | Yarn Technology (Filament Yarn) 61
4.1 Introduction
Filament yarn is another form of textiles fiber besides staple fiber yarn. Technical textile is
developed by technical fiber as well as technical yarn. Various type of technical yarns is
developed by manufacturers. There have been many types of filament yarns that are
developed for technical applications.
Technical yarns are produced for the manufacture of technical textiles. As the range of
technical textiles is rapidly increasing, an understanding of the range of yarns available
and their properties is important, to be able to meet the requirements of the intended end-
use.
Filament yarns have gained many functional properties such as UV resistance, flame
retardant (FR), anti-bacterial properties, etc. One of the most preferred methods for
producing these types of products is adding micro and nanoscale additives to polymer raw
material in the chip form during the filament yarn production in industry and especially,
the melt spinning method is preferred for these types of studies. As a result, end products
with unique properties are produced by using this method for different areas of use.
4.2 Aramid Fiber
Aramid fiber was the first organic fiber used as reinforcement in advanced composites with
a high enough tensile modulus and strength. They have much better mechanical properties
than steel and glass fibers on an equal-weight basis. Aramid fibers are inherently heat- and
flame-resistant, which maintain these properties at high temperatures. The chemical
structure of the chain molecules is such that the bonds are aligned along the fiber axis,
giving them outstanding strength, flexibility, and abrasion tolerance. The aramid fiber
derives its strength from strong bonding between relatively short molecules.
The first fiber of this class to be developed was Nomex from DuPont which appeared in the
1960s. Aramid fiber was commercialized in the 1960s and is widely used in ballistic
protection. The fibers offer a set of properties that make them particularly useful in armor,
clothing, and a wide range of applications. Aramid fibers were first used in vehicle armor
in the 1970s. This yarn is of only medium tenacity but is nonflammable and widely used
62 eBook PSP | Yarn Technology (Filament Yarn)
for the production of fireproof clothing, electric insulation, etc. However, only a few years
later, aramid fibers (Kevlar by DuPont also) with chains containing p-disubstituted benzene
rings appeared. In addition to good thermal stability, these fibers also possess outstanding
mechanical properties.
Aramid fibers have superior resistance to heat, low flammability, and high resistance
to organic solvents. Aramid fibers start to degrade at about 500°C. The “inert” aspects of
aramid fiber offer excellent versatility for a wide range of applications. However, aramid
fibers are sensitive to ultraviolet (UV) light, acids, and certain salts. Aramid fibers have
been used extensively in body armor, vehicle armor, military helmets, protective gloves,
and fireproof suits for firefighters.
Aramid fiber is a chemical fiber in which the fiber-forming substance is a long-chain
synthetic polyamide where at least 85% of the amide linkages are attached directly to two
aromatic rings. Nomex and Kevlar are two well-known trade names for aramid fiber, owned
by Du Pont. Aramid fibers have high tenacity and high resistance to stretch, to most
chemicals, and high temperatures. The Kevlar aramid is well known for its relatively
lightweight and for its fatigue and damage resistance. Because of these properties, Kevlar
29 is widely used and accepted for making body armor. Kevlar 49, on the other hand, has
high tenacity and is used as reinforcing material for many composite uses, including
materials for making boat and aircraft parts. The Nomex aramid, on the other hand, is heat
resistant and is used in making firefighters’ apparel and similar applications.
Aramid yarns are more flexible than their other high-performance counterparts such as
glass and Kevlar, and thus are easier to use in subsequent fabric-making processes, be it
weaving, knitting, or braiding. Care should be taken, though, as aramid yarns are much
stronger and much more extensible than conventional textile yarns, which could make the
fabric formation process more difficult.
eBook PSP | Yarn Technology (Filament Yarn) 63
4.3 Glass Filament Yarn
Glass is an incombustible textile fiber presenting high tenacity. It has been used for fire-
retardant applications and is also commonly used in the insulation of buildings. Because
of its properties and low cost, glass fiber is widely used in the manufacture of
reinforcement for composites. There are different types of glass fibers, such as E-glass, C-
glass, and S-glass. E-glass has a very high resistance to attack by moisture and has high
electrical and heat resistance. It is commonly used in glass-reinforced plastics in the form
of woven fabrics. C-glass is known for its chemical resistance to both acids and alkalis and
is widely used for applications where this type of resistance is required, such as in chemical
filtration. The S-glass is a high-strength glass fiber and is used in composite manufacturing.
Glass filament yarns are brittle compared to conventional textile yarns.
4.4 Carbon Filament Yarn
Carbon fiber filaments are composite materials formed by infusing fragments of carbon
fiber in a polymer base, similar to metal-infused filaments but with tiny fibers instead.
Carbon fiber is a remarkably strong material and makes the filament much firmer and
more rigid. Making the filament harder reduces the risk of scratches or other damage when
a 3D-printed model comes into contact with another object. However, it is more likely to
break when dropped compared to regular PET-G filament.
4.5 HDPE Filament Yarn
HDPE refers to high-density polyethylene. Although the basic theory for making super-
strong polyethylene fibers was available in the 1930s, commercial high-performance
polyethylene fiber was not manufactured until recently. Spectra, Dyneema, and Tekmilon
are among the most well-known HDPE fibers. The gel spinning process is used to produce
the HDPE fiber. Polyethylene with an extra high molecular weight is used as the starting
material. In the gel spinning process, the molecules are dissolved in a solvent and spun
through a spinneret. In solution, the molecules which form clusters in the solid state
become disentangled and remain in this state after the solution is cooled to give filaments.
The drawing process after spinning results in a very high level of macromolecular
orientation in the filaments, leading to a fiber with very high tenacity and modulus.
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Dyneema, for example, is characterized by a parallel orientation of greater than 95% and
a high level of crystallinity of up to 85%. This gives unique properties to the HDPE fibers.
The most attractive properties of this type of fiber are: (1) very high tenacity, (2) very high
specific modulus, (3) low elongation, and (4) low fiber density, which is lighter than water.
HDPE fibers are made into different grades for different applications. Dyneema, for
example, is made into SK60, SK65, and SK66. Dyneema SK60 is the multipurpose grade.
It is used, for example, for ropes and cordage, protective clothing, and reinforcement of
impact-resistant composites. Dyneema SK65 has a higher tenacity and modulus than
SK60. This fiber is used where high performance is needed and maximum weight savings
are to be attained. Dyneema SK66 is specially designed for ballistic protection. This fiber
provides the highest energy absorption at ultrasonic speeds.
PTFE (polytetrafluoroethylene)
PTFE (polytetrafluoroethylene) fibers offer a unique blend of chemical and temperature
resistance, coupled with a low fraction coefficient. Since PTFE is virtually chemically inert,
it can withstand exposure to extremely harsh temperatures and chemical environments.
The friction coefficient, claimed to be the lowest of all fibers, makes it suitable for
applications such as heavy-duty bearings where low relative speeds are involved.
PBI (polybenzimidazole)
PBI (polybenzimidazole) is a manufactured fiber in which the fiber-forming substance is a
long-chain aromatic polymer. It has an excellent thermal resistance and a good hand,
coupled with very high moisture regain. Because of these, the PBI fiber is ideal for use in
heat-resistant apparel for firefighters, fuel handlers, welders, astronauts, and racing car
drivers.
PBO (polyphenylenebenzobisoxazole)
PBO (polyphenylenebenzobisoxazole) is another new entrant in the high-performance
organic fibers market. Zylon, made by Toyobo, is the only PBO fiber in production. PBO fiber
has outstanding thermal properties and almost twice the strength of conventional para-
aramid fibers. Its high modulus makes it an excellent material for composite
reinforcement. Its low LOI gives PBO more than twice the flame-retardant properties of
meta-aramid fibers. It can also be used for ballistic vests and helmets.
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Types of Technical Filament Yarns
The followings are the most used technical filament. They are:
1. Aramid Filament Yarn: Nomex and Klever by Dupont
2. Glass Filament Yarn: E-glass, C-glass, S-glass.
3. Carbon Filament Yarn
4. HDPE Filament Yarn: Spectra, Dyneema, Tekmilon.
5. PTFE (Polytetrafluoroethylene)
6. PBI (Polybenzimidazole)
7. PBO (Polyphenylene benzobis oxazole)
Properties of Technical Filament Yarn:
The entire filament has not same characteristics. It is required to know the specifics of
the filament yarn. The following are the properties of filament yarn.
Aramid Filament Yarn: Nomex and Aramid Filament Yarn
Klever by Dupont High tenacity properties
It has high resistance to stretch, chemicals, and
Glass Filament Yarn: E-glass, C- temperature.
glass, S-glass.
Carbon Filament Yarn Klever Yarn
HDPE Filament Yarn: Spectra, Light in weight
Dyneema, Tekmilon. Its fatigue is less
PTFE (Polytetrafluoroethylene) It has damage-resistance properties
PBI (Polybenzimidazole)
Nomex
it has high-resistance properties
High tenacity properties.
it is difficult to dye glass fiber
it is brittle in nature
It causes irritation
It has a high tensile modulus
It is brittle in nature
It has a very high specific modulus
It is very high in tenacity
It has low elongation properties
It has a low fiber density
Its chemical and thermal resistance is good
Low friction coefficient resistance is another
characteristic of PTFE
Excellent thermal resistance and a good hand
It is used for the clothing of firefighters, fuel
handlers, welders, and racing car drivers.
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References
Cook, J. G. (2004). Handbook of Textile Fibers. Woodhead Publishing.
Horrocks, A. R., & Anand, S. (2016). Handbook of Technical Textiles. Woodhead Publishing.
Lawrence, C. A. Fundamentals of spun yarn technology / Carl A. Lawrence. p. cm. Includes
bibliographical references and index. ISBN 1-56676-821-7 (alk. paper) 1. Spun yarns.
2. Spun yarn industry. 3. Textile machinery. I. Title. TSI480.L39 2002 677′.02862—
dc21 2002034898 CI
Lord, P. R. (2003). Handbook of Yarn Production: Technology, science and economics.
Woodhead Pub.
Wray, G R. (1969) New Trends in Yarn Production, Modern Yarn Production. Columbine
Press.
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