Wrapped yarns have been developing since
70s. Due to its special structure, the yarns have many advantages such as
high tenacity and regularity , these kinds of spinning methods cater the
needs of fancy and high performance yarns .
Wrap spinning works on the principle of
wrapping. The feed stock, generally a drawn sliver drafted in a five-roller
drafting system. The drafted strand runs through a hollow spindle without
receiving true twist. Simultaneously, a continuous filament yarn, unwound
from a bobbin on the hollow spindle is wrapped helically over the drafted
strand of fibres forms wrap spun yarn. The wrap spun yarn therefore consists
of a twistless core (parallel fibres) wrapped helically by a continuous
filament as shown in Figure 1. These yarns are also known as cover-spun
yarns and the method of spinning is also known as hollow-spindle spinning.
Hollow-spindle Spinning System
Many manufacturers offered different
process of wrap spinning and popularly known wrap yarns (PL yarns) from
Spindelfabrik Suessen, Germany. It uses four or five roller drafting
arrangements, depending on the raw material to be processed .
The Parafil« hollow spindle rotates up
to 35,000 rpm. The hollow spindle is designed as a false twisting assembly.
The fibre strand does not pass directly after entering the vertical spindle
instead, shortly after entering the spindle; this strand is led out again
and back around the spindle with a wrap of about one-quarter of the spindle
periphery. In this way, as the spindle rotates, the strand is provided with
twist between the drafting arrangement and head of the hollow spindle. These
turns of twist are cancelled out again in the spindle head in accordance
with the false twist principle. This twist prevents the strand from falling
apart in the length prior to filament staple fibres wrapping with filament.
A wrap spun yarn consists of non-twisted
parallel bundle of staple fibres held together by helically wrapped filament
as shown in Figure 2. The proportion of the filament in the yarn is about 2
- 5%. Due to helical wrapping of the filament and by radial pressure,
necessary cohesion between the individual staple fibres is improved. This
imparts desired strength to the yarn. The number of wraps per unit length in
a standard PL yarn is approximately the same as the amount of twist in a
comparable ring spun yarn.
S-Allma« Wrap Spinning
series of hollow-spindle wrap-spinning machines designed to produce count in
the range of 0.6 Nm to 50 Nm. S-Allma« wrap spinning is available in three
levels of traverse length (SM-6, SM-8 and SM-10 with traverse length of 15
cm, 20 cm and 25 cm respectively). It has 48 spindles with speeds up to
30,000 rpm and production rate 200 m/min. The delivery roller and spindle
speeds can be varied infinitely and draft is adjustable according to the
linear density .
The 3 or 4 roller drafting assembly
allows selection of either the clamping point or draft methods with a draft
range of 5 - 59. Fibre length between 50 - 220 mm can be processed
effectively. Electronic monitoring used to identify the faults and improves
yarn quality. Special features of the drafting assembly include
self-alignment of the spinning triangle to the centre of the spindle and
continuous suction at the draft rollers, which eliminates roller lapping and
assist for self cleaning in spinning zone.
Pneumatic threading is an optional
attachment to hollow spindle and speeds up the operating time. A
photoelectric cell monitor equipped to detect end-breaks to stop the spindle
when a break occur .
Gemmill & Dunsmore« Wrap Spinning
Another one wrap spinning apparatus for
the wrap yarn production is Gemmill & Dunsmore« wrap spinning system.
It has five-roller drafting system and provides draft up to 300. Heavy
slivers and ropes are also processed without much difficulty. The inclined
(45░) drafting system is also adjustable according to process parameters.
'X' Direction Filament-Wrapping System
Similar to Hollow-spindle system 'X'
direction filament wrap spinning system is used for fancy and
high performance yarns production. This yarns produced by wrapping around a
twisted or twistless fibrous core by filament or yarn. Twist can be applied
in either the right hand (Z) or left hand (S) direction or both as shown in
Filament-wrapped yarns can be produced
at a much higher production rate than conventional ring spun yarn.
It can eliminate slashing operation. Twistless cover spun
yarns also produced by using wrapper as water soluble adhesive filaments and
core as no twist fibres.
In conjunction with the no-twist yarn
production, X direction filament-wrapped yarns developed as
shown in Figure 1. The theory behind the X-wrapping technique is the
adaptation of the Chinese puzzle principle, in which a braided, finger-size
tube becomes tighter around a finger when a pulling force is being applied
along the longitudinal axis in an attempt to pull the tube off from finger.
A simplified explanation for the
tightness is that a compression force is being generated along the wall when
being pulled. The Chinese puzzle phenomenon is analogous to the X-wrap yarn
when used in dynamic processing. The stress exerted on the X wrap yarn
during weaving/knitting will actually cause the criss-cross filament wraps
to tighten around the fibrous core and thus cause the yarn to become
stronger rather than weaker. This approach is similar in principle to that
of the Machie Spinmach system, which was designed primarily for worsted and
semi worsted yarns 
Investigation shows that X-wrap yarn has
higher yarn strength and elongation than a conventional wrap yarn and it can
be produced as one-step process. X-wrap yarn costs more to produce in terms
of filament, but from preliminary yarn data it may be feasible to make
X-wrap yarns with fewer wraps/metre than Z or S wrap yarns and thus hold
down filament cost.
Comparing 120 wraps per metre (wpm) over
512 wraps per metre, yarns with higher wpm possess higher strength and
elongation than the lower wraps per metre yarns. A comparative study on
twistless cotton fibres and polyester wrapper filaments, the following
results were realised at 99% confidence levels.
Double Z-wrap yarn was about 8% stronger
than single Z-wrap yarn, its elongation was only about 73% that of the
Z-wrap yarn. The double Z-wrap yarn might have been over-wrapped and thus
caused the low elongation. On the other hand, the X-wrap yarn was 54%
stronger than Z-wrap yarn, and its elongation was about 17% higher.
Fancy Yarns Production in Wrap Spinning
Fancy yarns made by the wrap-spinning
process with suitable machine parameters, filaments and yarns.
A particular boucle-derivative yarn
(terry-pile profile) can be produced from wrap spinning.
The designing and development of fabrics
involve skillful use of materials, structures, colours, patterns, finishes,
and textures. This last quality can be in great demand at certain periods in
the fashion cycle and can best be exploited by the application of fancy wrap
Terry-Pile Fancy Wrap Yarns
The terry pile was produced by a
profusion of short fibres in the profile, overfed to give a raised effect in
fabric similar to that of a chenille yarn. Profile evenness was required to
give good structure, colour, and surface effect on the fabric, and the
amount of overfeed imparted to the components would determine the pile
height and thus the aesthetics, both visual and tactile.
Suitable end-uses for the yarn would be
in sportswear/leisurewear, in pile fabrics for appeal such as terry, stretch
terry, and toweling. Also provides raised effects in furnishing and
household fabrics for toweling, bedspreads. Absorbency, easy-care wash and
wear, durability, softness, abrasion resistance, good colour and
wash-fastness, etc, are achieved with terry pile wrap yarns.
To suit these performance requirements,
cotton or blends are often used. Cotton provides soft, absorbent properties,
and, when it is blended with other types of fibre, such as polyester or
nylon cater the needs of durability, abrasion resistance and strength can be
improved and the costs reduced through the use of the cheap synthetic fibres.
It is important to consider basic 'Pile' height and evenness.
The 'Terry-pile' cotton yarn retains
softness and absorbency. It had a simple design appeal through its use of
natural fibres. Differential dyeing process can be used to achieve deep
colouring. The produced yarns used for decorative and functional purpose
with necessary texture and colour. The actual properties and its aesthetic
appeal were determined by the type of blend, the fibre length and fineness,
and the inherent qualities of the fibres.
The design potential realised in using
the 'Terry-pile' profile in fabrics was immense. Very interesting
three-dimensional effects were produced from matt, shiny, and reverse
dyeing. This method of colouring the yarns after spinning allowed for
hank-dyeing of the yarns rather than dyeing on cone, which would give a
softer and bulkier yarn. The piece-dyeing of fabrics would allow for a rapid
response time to meet the demands of fashion markets and enable the spinner
to avoid stocking uneconomic quantities of dyed-fibre stocks. Furthermore,
the 'Terry-pile' yarn are a cheaper type of pile yarn, capable of being
produced at very high speeds on the most up-to-date machinery.
High performance Yarns Production in
Wrap Spinning System
The wrap spinning system also used to
produce high performance wrap yarns by utilising the high performance fibres
in the core or wrap especially in the cut resistance gloves. Some production
methods of high performance yarns are listed here .
Three-ply Wrap Yarn (One core & two
wrap components) Three-ply yarn has a core strand and two covering strands.
A first covering strand may be wire or fibreglass, is wrapped around the
core strand, and second covering strand, which is preferably a yarn or
filament wrap around both the core strand and first covering strand in
opposite directions, relative to each other is shown in Figure 5.
Four-ply Wrap Yarn (Two core & two
Four-ply yarn has two core strands
placed parallel or twisted to each other and wrapped by two covering strands
in opposite direction relative to each other around the core. The first core
is of multifilament and second core is of wire (metallic) component and two
covering strand are of suitable multifilament, which is shown in Figure 6.
Five-ply Wrap Yarn (Two core & three
Core component is formed by two
strands preferably metallic wire and fibreglass. The cover component has
three strands, a first or innermost strand wrapped around the core, a second
strand wrapped around the innermost strand and a third or outermost strand
wrapped around second strand. Strands are wrapped in opposite directions
relative to each other around the core. A typical figure of two core &
three-wrap component is shown in Figure 7.
Five-ply Wrap Yarn (Three core & two
Five-ply wrap yarn consists of three
core strands and two covering strands which is shown in Figure 8. The three
core strands may be twisted or braided together and placed parallel to each
other (metallic wire, fibreglass and high tenacity synthetic filaments). The
covering strands are wrapped in opposite directions relative to each other
about the core strands.
Six-ply Wrap Yarn (Two core & four
Six-ply wrap yarn is shown in Figure 9,
a pair of covering strands form first cover component and two additional
covering strands forming second cover component. Wrapping was performed in
opposite directions relative to each other. The core may
include two strands one of high-density polyethylene and second of metallic
wire, either twisted together or placed parallel to each other.
Elastomeric Core & Staple fibre Wrap
The Figure 10 shown is a schematic
illustration of the elastomeric core & staple fibre wrap yarn. These
yarns are distinguishable from ring core spun yarns. The wrapper fibres are
twisted around the exterior and encase the core in elastomeric core &
staple fibre wrap yarns. Whereas in ring core spun yarns, it do not include
such twisted outer wrapper fibres. Additionally, there is no residual twist
in the present in the wrap yarns as is present in ring core spun yarns.
Differential twist wrapped yarns
Xin Li et al discussed on the
differential twist wrapped yarns production with wrap and plied wrap yarns.
The wrap yarn and differential twist wrapped yarns (wrap yarns are combined
and plied by conventional twister) are shown in Figure 11 a and b. False
twist is inserted by hollow spindle to the core and that is removed when
wrapper yarn is wrapped over it. Three natures of twists influence on the
differential twist wrap yarns. Those are self-twist, wrapping twist and
The self twists of core yarns and wrap
yarns changes the wrap qualities. This difference leads to differential
twist in wrapping strand. Wrapper yarn twist leads to wrapping yarn and core
yarn deformation due to torsion and bending. The curvature of two kinds of
deformations are given by
t = ▀ Sin ▀/R
k = Sin2 ▀/R.
t = torsion
k = bending
R = radius of helical line in the yarn.
▀ = Helical angle when the helical
radius is R.
Torsion deformation results from yarn
relative turning in to its section bringing about the twist. The bending
deformation makes the wrapping yarn wind on to the core yarn. Torsion
deformation is in the twisting course while plying the wrap yarns by
conventional twisting. This provides the core yarn with self-twist while the
wrapping yarn has both torsional and bending deformations. Torsional
deformation of core induces self-twist, while the wrapping yarn has both
torsional and bending deformations. Its torsional deformation provides
self-twist and bending deformation that allows it to wind on core yarns.
The torsion/unit length (t') in radians
along the axis is given by
t'= t = Sin ▀ Cos ▀/R.-----1
If the twist in the twisting course are
t radians and yarn length change (which alter twisting) is not considered
Sin▀ = tR Cos ▀ -----2
from eq 1 and 2
t'= t Cos2 ▀------3
t' = Twist change in twisting course
The helical angle ▀ of the core yarn
when nearing to zero differ from ▀w of the wrap yarn. The twist changes are
different. For the core yarn, its twist changes is given as
t'c = tc ▒ t Cos2▀c
While the wrapping yarn's twist changes
t'w = tw ▒ t Cos2▀w tc = Core yarn twist before twisting course
t'c = Core yarn twists after twisting
tw = Wrapper yarn twist before twisting
t'w = Wrapper yarn twist after twisting
course +ve sign shows the twist in same direction of core and wrapper yarn
former twist. - sign shows the twist in opposite direction of core and
wrapper yarn former twist.
Bend deformation makes the wrap yarn to
wind on core yarns. So wrapping twist after twisting course is (plying of
wrapped yarn by conventional twisting)
Tw'= Tw ▒ t
T = Wrapping twist before plying of
wrapped yarn by conventional twisting.
Tw' = Wrapping twist after plying of
wrap yarn by conventional twist. + ve sign shows the twist in same direction
as wrap former - ve sign shows the twist in opposite direction .
When twist and twist direction of tc',
tw' and Tw' are different than it form differential twist wrapped yarn. Two
single yarns with same structure and twists after twisting course do not
show differential twist.
The wrap spun yarns have four kinds of
1) Same directions of wrapping and
2) Opposite direction of wrapping and
twisting twist (with wrapper twist is greater than twisting twist.).
3) Opposite direction of wrapping and
twisting twists (with wrapper twist is equal to the twisting twist).
4) Opposite direction of wrapping twist
with twisting twist (with wrapping twist is lesser than twisting twist).
The first and second kind of twist
assists for improvement in regularity and tenacity. If the angle of wrap is
lesser than the wrapping yarn makes surplus wrap yarn over the core
component and structure becomes unstable.
Influencing Parameters for Wrap Yarns 
Wrap Density and Core-wrapper ratio
Unevenness, imperfections and mechanical
properties are greatly influenced by both blend compositions (core-wrapper
ratio) and wrap density.
With increase in wrap density the
breaking extension, abrasion resistance and hairiness index are decrease,
whereas initial modulus, toughness and flexural rigidity increase. Initially
tenacity increases and then decreases with increase in wrap density, whereas
percentage of coefficient of variation does not show any trend.
Core-wrapper ratio will be selected
according to the nature of utility. Normally the wrap yarns core% will be in
the range of 80 - 98%. It may be increased depending on the yarn
By using different types of fibres,
yarns and filaments (such as cotton, polyester, nylon, Kevlar, glass, jute,
acrylic, aramid, HDPE etc,) in the core and staple fibres and or filaments
as wrappers, required fancy and high performance yarns can be produced.
Properties of Wrap Spun yarns
The hollow-spindle wrap spinning process
allows for innovative and unique design effects. Its versatility can be seen
when compared and contrasted with other systems and types of yarn available.
Jute/Acrylic Wrap Spun Yarn
Jute/acrylic blended wrap yarn
properties at different blend proportions were studied. Wrap
spinning yarns (140 tex) were made with 100% jute, 100% acrylic and
different proportions of jute/acrylic with polyester multifilament (50
denier/27 filaments). Wrapper yarns were produced in Suessen Parafil 2000
wrap spinning machine and analysed for 280,315 and 350 wraps per metre.
The higher extensibility of acrylic
fibre helps wrapper filament to orient along the yarn axis with increased
radial packing, resulting into greater strength. Apart from this, increase
in tenacity may also be attributed to the increase in number of fibres in
the yarn cross-section because of the use of finer acrylic fibres. Hence, in
this case, decrease in stronger jute component and packing co-efficient with
the increase in acrylic fibres in blend does not have much bearing on the
tenacity of the hollow spindle spun yarns(Parafil yarn).
However, with the increase in wrap
density at a fixed blend ratio in jute/acrylic blended wrap spun yarn, the
tenacity increases up to 315 wraps/metre and then decreases with the further
increase in wrap density.
This result may be viewed under the
effect of two opposing influences.
1) With increase in wraps/metre, the
yarns becomes more compact, ie, the fibres in the yarn pack more closely
resulting in higher inter-fibre friction due to higher radial compressive
force by higher number of wraps/metre, ultimately causing increase in
2) With the very large number of wraps/metre
the contribution in tensile load sharing by the wrapper filaments in the
parallel direction of the yarn axis reduces, which results in decrease in
Extension at Break
With the increase in proportion of
acrylic fibre in jute/acrylic blended wrap yarn, the extension at break
increases continuously showing highest breaking extension for 100% acrylic
wrap yarn. This may be due to the increase in proportion of higher
extensible acrylic fibre in the core material. However this must be
carefully examined that the variation of wrap density for any wrap yarn does
not have much bearing on breaking extension.
With the variation of blend ratio the
initial modulus does not show any definite trend, but 100% jute wrapped yarn
exhibit higher initial modulus than that of 100% acrylic yarn. This
phenomenon may be due to the higher initial modulus of jute fibre as
compared to acrylic fibre. Again, a gradual decrease in initial modulus is
noticed with increase in wrap density for all types of yarn due to load
bearing mechanism of wrap spun yarns.
Toughness and Flexural Rigidity
With the increase in acrylic content in
the yarn with definite wrap density, the toughness increases which is
expected due to the greater extensibility of acrylic fibre. It is also
noticed that with the increase in wraps/metre for a yarn of same blend
ratio, the toughness index increases.
The specific flexural rigidity decreases
with the increase in acrylic component at all levels of wrap density. This
may be due to the less rigidity of acrylic fibre as compared to jute fibre.
Interestingly, with the increase in wraps/metre, the specific flexural
rigidity first increases and then decreases. It is also observed that the
conventional jute yarn shows lower flexural rigidity as compared to wrapped
jute yarn, which may be due to the migratory fibre structure of conventional
The flex abrasion resistance increases
with the increase in acrylic content in the yarn at comparable wrap density.
The above phenomenon may be due to the inherent property of the acrylic
fibre. Again with the increase in wrap density the abrasion resistance shows
decreasing trend for all type of yarn. The above trend may be due to greater
cutting effect because of increased yarn packing.
Jute Viscose Wrap Spun Yarn
Jute viscose yarns of HDPE and PP
wrapper show the same trend in tenacity values ie, with increase in the wrap
density. At very low wrap density the force exerted by the wrapper filament
is not strong enough to pack closely the fibrous core, which results in low
inter-fibre friction between the individual fibres. With increase of wrap
density, the fibrous core becomes more compact and more coherent. This may
due to the action of higher radial compressive forces exerted by continuous
wrapper filament. With increase of wrap density up to 240 wraps/metre in
case of jute yarns, the hairiness index values decreased and their after
with further increase in wrap density up to 240 wraps/metre, the filament to
fibre contact area is increased which in turn might have reduce hairiness
Limitations of Wrap
Yarns Some of the limitations of
filament-wrapped yarn are:
1)Tenacity of yarn depends on filament
2) Filament yarn is expensive, although
the extra cost may partially be offset by the elimination of slashing costs.
3)The wrapped yarn with a twistless core
lacks abrasion resistance and therefore tends to pill or shed during weaving
when used as warp yarns.
4) More specifically, when tension is
applied on the one-directional wrapped yarn (either Z or S), such as in the
weaving operation, stress starts to build up on the filament wrapper and
elongation begins. Consequently, wraps per unit length of the core decrease,
resulting in less control of the core fibres by the wrapping filament.
5) When a heald or reed rubs against the
fibres in the yarn during weaving, the fibres will shed from the yarn and
may form small pills. Fibre shedding and pilling weakens the yarn and causes
end breakage and loom stoppage during weaving. The remedy is to develop a
wrapping technique that will keep the fibres in the twistless core in the
wrapped yarn under control during weaving and knitting .
Advantages of Wrap Yarns
Wrap spinning system is used to fulfill
increasing demands on style changes in knitting and carpet industries.
Strength and elasticity are quite comparable with those of conventional
yarns. These two properties depend on the selection of the correct degree of
filament twist for particular yarn and its end use and the angle of wrap is
also important. The relaxation characteristics of wrap yarns are similar to
those of conventional two-fold yarns. Pliability of the wrapped yarns is
superior to that produced by other systems. With conventional yarns, neps
and slubs tend to come to the surface, but with wrapped yarns they tend to
stay in the centre, because of the absence of twist. There are fewer yarn
breaks, and because of the larger packages from the machine there are fewer
knots or splices compared with conventional systems.
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Staple-fibre Yarns Covered with a Filament, Textile Inst Ind 12, pp 271-272.
2. Plummer H S (1985): Wrap Spinning New
Life, Am Textiles 5, pp 45-49
3. Mahendra Gowda R V (2006): "Wrap
spinning", New Spinning Systems, Second Edition (Published by NCUTE),
4. Machinery Catalogue, Gemmill &
Dunsmore Ltd, Venture Works, Lund Street, Preston PR1 1YH, UK, (October
1983) "G&D's Latest in Wrap Spinning and Fancy Yarn
Production", Textile Horizons, pp 39
5. Machinery Catelog, Saurer-Allma GmbH,
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wrap-spun market", Textile Horizons.
6. Gain L Louis and Harold L Salaun
(March 1986), "X-Direction-Wrapped Yarn", Textile Research
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7. Seidel, Leon E (1979): An Answer to
Spun-Like Yarns, Textile Ind. 143 (3), pp 32- 36.
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M H (1980): Cotton Wrapped Yarns -- A Process to Eliminate Sizing and
Desizing, Textile Research Journal, Vol 50, pp 108-114.
9. Oxenham W (Feb-1984): Showcase for
New Systems of Yarn Making, Textile Month, pp 34-28.
10. Mole K and Knox J S (1989): The
Properties and Uses of Specific Hollow-spindle Yarns, Journal of Textile
Institute, No. 3, pp 44-453.
11. Nathaniel H Kolmes et al: Harold F
Plemmons (June 13, 1995), "Surgical Glove and Yarn", United States
Patent, US005423168A, pp 1-8.
12. John Joseph M Rees, Signal Mountain,
Tenn; Leonard L Hixon Jr, Dalton, Ga.,(Dec-1997): System for Forming
Elastomeric Core/Staple Fibre Wrap Yarn Using a Spinning Machine, United
States Patent Application Publication Rees et al, No: (US005701729A).
13. Xin Li, Jianchun Zhng, Jiexin Li
(Feb 2002): Differential Twist Wrapped Yarns Made on Hollow Spindle Spinning
Machine, Textile Research Journal,Vol 72, pp 181-185.
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N C (June 1997): Some studies on Properties of Wrapped Jute/Acrylic (Parafil)
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Note: For detailed version of this
article please refer the print version of The Indian Textile Journal
December 2008 issue.
Bannari Amman Institute of Technology,
Sathyamangalam, Tamil Nadu.
Bannari Amman Institute of Technology,
Sathyamangalam, Tamil Nadu.
S Praveen Prakash Bannari
Amman Institute of Technology,
Sathyamangalam, Tamil Nadu.
S Josuva K Kumar
Bannari Amman Institute of Technology,
Sathyamangalam, Tamil Nadu.
Dr N Anbumani
PSG College of Technology, Coimbatore