3803037 textile m tech theis

8/18/2019 3803037 Textile M Tech Theis

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2." $or%ing Principle:

Frictions spinning technologies works on the principle of open-end or wrap

/Fasciated5Acore spinning. The general principle of working of friction spinning in its

simplest form can be described as below.

Fig. 2.1 The principle of friction spinning

$s in the diagram /Fig.(.15 separating them from slivers generates a stream of fibres

which is transported through a duct. The fibres are then directed towards the nip of two

rotating drums called friction drums .The fibres are collected close to the nip of these

drums. The friction drums have perforations on it and suction from inside holds the fibres

on the surface. There is a long slot inside the friction drums located close to the nip point

along the length of friction drums and the rest of the area inside the perforated drum has a

shield. So the yarn at the nip of the friction drum is sub"ected to a radial force generated

as a result of airflow over yarn.

Fig.2.2 Forces acting on the yarn tail and the vector diagram.

This is shown in figure (.( This radial force serves as a normal load and frictional force

is generated between the yarn and the surface of friction drum. )t can be observed from

the same figure that at the closest pro2imity of the friction drums they rotate in opposite

direction and the frictional force thus developed produces a torBue on the yarn tail.

>ontinuous rotation of the drum produces twist in the yarn leading to gradual integration


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of fibres in the yarn tail. The yarn is withdrawn in the direction of the a2is of the friction

drums and is wound on a bobbin.

." Different types of friction &pinning 'achines:

The principle of various types of commercially available friction spinning machines is

described below.

.1 Dref2 &ystem:

Fig..1 &chematic diagram of Dref2 system

$ schematic diagram of ,ref-( system is shown in figure .1. There is a drafting

system through which one or more slivers are directed to an opening roller clothed with

saw teeth. The opening roller individuali4es the fibres in the strand and they are stripped

from the roller surface by an air -current from blower. The stream or cloud of fibres thus

generated is guided through a duct and finally gets collected at the nip of two perforated

friction drums. There is a suction from inside the two perforated drums that causes the

fibres to be adhered "ust above the nip point. The fibres are thus gradually added to the

open Cend and get twisted thereafter because of the rotation of the drums. The yarn thus

formed is wound on a bobbin. ,ref-( is mainly useful for course counts and reBuires

medium to long staple fibres as input materials.

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.2 'asterspinner (P&) &ystem:

Fig..2 'asterspinner (P&) &ystem:

$s figure .( shows the machine also works on the principle of open-end

spinning like ,ref-( machine but there is a difference particularly with respect to fibre

feed and flow direction and construction of friction drums $ single draw frame sliver is

fed to opening roller which opens the fibre in the same way as it does in rotor spinning.

The stream of fibres is guided through the suction duct making an acute angle to the yarn

withdrawal direction. )t is claimed that feeding the fibre in this particular style improves

the fibre e2tent and orientation of the fibres in the final yarn. Similarly the fibres are

collected on friction drums. 3ence one friction drum is perforated and it acts as suction

drum and the other one is blind solid drum with a special surface to ensure effective

friction transfer.

The yarn is twisted by the drums and then packaged in a bobbin. This machine is

able to produce yarns in the range of 10s-0s using cotton and synthetic fibres up to #0mm

length and their blends

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.Dref system:

Fig.. Dref system:

This is an e2tension of ,ref-( spinning system that adds a drafting system at one

side of the friction drums to attenuate the sliver that finally forms the core of the yarn. )t

is not an open Cend spinning method like ,ref-( or 6S aster spinner. )t works on

friction fibre wrapping i.e. the parallelly delivered fibres or filaments are false twisted

and simultaneously wrapped with sheath fibres in the spinning 4one. $s a result it

produces a core sheath structure of yarn.

The ,ref- spinning system is shown in figure .. This machine runs at a

ma2imum speed of 00 mAmin and the finest count that can be spun is around (0s.?ach

spinning head in this system is composed of following five sections

15 ,rafting unit 1

The drafting unit 1 is meant for supplying the staple fibre core component. There

are two models of this unit. One is suited for short staple fibres up to #0 mm and

processing cotton with filament core.

(5 ,rafting Dnit (

This unit consists of a 1-over C1 and a 1-over C( roller combinations as guide

rollers for slivers two oppositely rotating opening rollers and a transport duct for feeding

the fibres onto a pair of perforated friction drums .The shape of transport duct is such that

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it is conducive for acceleration of the air-current passing through it and thus intended

orientation of fibres in air stream is maintained.

5 Spinning 4one

)t consists of a pair of perforated drums known as friction drums .The

friction drums have air suction from inside. The stream of fibres after being transported

through the duct are collected above the nip point of drums .The surface of the friction

drums have a special coating to attain a better twisting effect.

#5 @inding C up mechanism

$fter passing through the spinning 4one the yarn is drawn off via three outlet

rollers and finally delivered to the winding device. 8etween the outlet rollers and the

winding device there are two deflection rollers that evens out yarn tension and actuates

stop motion.

*." +perations involved in friction spinning:

The basic operation involved in friction spinning process are as follows

15 Opening of slivers

(5 Transporting the stream of slivers through a duct to the yarn formation 4one

5 >ollecting and reassembling the fibres

#5 >onsolidation and twisting of fibres into a yarn

&5 @ithdrawal of the resulted yarn for package formation

*.1 +pening of fi,res:

$ high degree of opening of the slivers almost to the e2tent of individual fobres is

reBuired and this is performed with the help of opening rollers. 3igh drafting of slivers is

also an essential operation where staple fibres are used .The degree of longitudinal

orientation and the straightness of the fibres e2tent a considerable influence on yarn

properties.

*.2 Fi,re transportation through duct:

The fibres from the opening rollers are directed through the transport duct into the

nip of the friction drums .The fibres are in free flight under the influence of air Ccurrent

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through the duct. ,uring this free flight the fibres lose most of its orientation that not

only affects the yarn characteristics but also the spinning limit.

6ord et al./6ord..!. :.Te2t .)nst 1*7+ 5 have reported that there is a

practical problem of assembling fibres in the yarn with good degree of fibre orientation

because of varying amount of turbulence in the fibre transport duct .The fibres in the duct

move at a very high speed but on arrival at the rotating mass of fibres close to the nip of

friction drum they suffer a huge deceleration . This not only disrupts the fibre orientation

but also the mass density of the fibre stream. $s a result fibres are buckled hooked and

looped. $s for e2ample it is shown in /6ord..! . :.Te2t .)nst 1*7+ 5 that the fibre in the

air -stream are carried at a speed of 1000 mA min. Thus the fibres are decelerated from

1000 mA min to only (00 mAmin over a distance of ( mm or so. Though it is intended by

the machine designer to collect the fibres in straight condition in practice it does not

happen. oreover the buckled fibres land from different conditions on the collecting

surface. The design of the duct can e2ercise a great influence on this phenomenon

*. Fi,re collections or -ccumulation:

Fig. *.1 Fi,re collection systems a) on the ingoing perforated friction drum ,)on the

rotating mass of fi,res

The fibers from the transportation duct are deposited on the surface of ingoing

perforated drum and subseBuently carried to the nip or directly on the rotating mass at the

nip. 3ere the fibres encounter a surface that moves at a much slower speed at which they

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were moving through the duct. $s a result fibre buckling is inevitable and fibres in the

yarn body are looped.

Fig. *.2 ffect of counter air flo! and surface velocity on the lying of fi,res on

the perforated friction drum

There are basically two types fibre collection systems presently available in friction

spinning machine /6ord..!. and !ust .:.. :.Te2t.)nst. 1**15.

1. Fibres are made to land on the surface of the ingoing perforated friction drum and

subseBuently transported to the nip of the friction drums.

(. Fibres are collected directly on the rotating mass The two methods have been shown

in figure / #.1 5

)n the first case where the fibres are deposited on the ingoing drum suction is

used to hold them on the surface and finally carried to the rotating mass of fibre. )t has

been stated that the fibres will land end first onto the drum surface and this end of fibre

being firmly held the remainder of the fibre sweeps past because of the effect of inertia

and drag from counter flow of air. This is shown in fig /#.( 5 Others have the opinion

that E Fibres may be trapped at any point along its length because it has a three

dimensional shape as it travels through the feed duct and only portions of it are

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straightened . )t is not certain that the leading end will land first on the perforated

surface this tends to produce hooks E

*.* T!isting of fi,res:

The torBue generated by the friction drum imparts twist in the yarn tail. The twist

integrates the loose fibres at the tail of yarn. The amount of torBue generated is

dependent on fibre to meal friction and the radial reaction pressure at the contact point

of the yarn tail and friction drums. 8oth of these Buantities appear to be uncontrolled in

nature leading to variable slippage of yarn tail. $s a result there is an irregularity in

twist in friction yarns.

Figure. *. Forces acting on the yarn tail and the vector diagram

)n figure / #. 5 it has been shown that ! 1 and ! ( are the normal radial reaction forces

acting on the growing yarn . The corresponding tangential frictional forces are ! 1 and! ( trying to rotate the yarn in opposite direction and thereby producing a torBue.

TorBue G /! 1 H ! (5 /dA(5

@here d G diameter of the yarn

*./ 0arn !ithdra!al:

The yarn delivery speed in friction spinning can be as high as 00mA min .The

spinning tension is very low in this process and hence the end breakage rate is also less.

Therefore tension has practically no influence on the spinning limit .The yarn is wound

on a big package directly and so rewinding is eliminated

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*. T!ist insertion in openend friction spinning:

Figure /#.#5 represents a fibre being applied to the open- end of a yarn in the

friction spinning process. Fibres such as those shown by positions a b c d and e rotate

about the conical end of the yarn 2 y 4. The fibre may be anchored at d while position b

rotates relative to the cone 2y .The resultant structure will consist of fibre abcde may or

may not end up as a perfect spiral. $lso the geometry of the cone 2y may changes as a

function of time and spinning conditions

Fig. *.* Fi,re rotation a,out the conical yarn tail

The fibres arriving in the spinning 4one are carried in to the mesh with the yarn tail byone of the spinning drums. These envelopes of fibres at the open end rotate and twist the

arriving fibres. The fibres near the tip are loosely wrapped around the yarn tail where as

those away from the tip are progressively more tightly wrapped.

6ord et al /6ord..!. :oo.>.@. and $shi4aki.T. :.Te2t .)nst 1*7+5 e2plained how the

swirling mass of fibres tightened up on to the tapered non Crotating and departing yarn

/Fig #.&5 .There was a sort of balloon with a continuous surface shaped like an artist%s

paintbrush. Simulation studies have shown that the envelop of this brush was indented

where it came in into contact with the friction drums. $s fibres tighten on to the tapered

yarn tail their rotational speed is diminished. @hen they are completely tightened on the

structure there us little or no further rotation with respect to the yarn a2is unless there us

considerable instability in the system.

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Fig.*./ T!isting of fi,res as they assem,le on the yarn

The yarn does not emerge in conical form but it is surrounded by rotating sleeve

of fibres of appro2imately cylindrical form .The rotating sleeve is formed by the fibres

arriving from the feed unit. The fibre sleeve rotates on the perforated drum surface particularly slippage free without any movement in the direction of sleeve a2is and the

actual yarn tail is formed within this sleeve during this period of tail formation the fibre

sleeve does not rotate. SubseBuently the fibres are transferred from the rotating sleeve on

to the non-rotating core which is a2ially withdrawn. The twist is imparted to the yarn by

the rotation of the fibre sleeve while fibres are being peeled from it. The fibres from

within the sleeve are peeled off through the rotation of the fibre sleeve and wound up in

the I direction of the yarn tail. The fibre sleeve and the mode of yarn formation are

shown in Fig /#.'5

Fig. *. Fi,re sleeve and mode of yarn formation

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/." Formation of friction spun yarn:

a)

,)

Fig./.1 Dref2 yarn formation structure

$s the figure /&.15 depicts the friction drums are longer than the width of the fibre

feed .The yarn formation therefore occurs along two parts of the friction drums first in

4one1 the fibre supply 4one and second in 4one ( where the forming yarn receives no

more fibres .6awrence et al /6awrence.>.$ Fundamentals of Spun !> ress (00( 5 has observed that the fibres landing on to the friction drums in 4one 1

form a conical yarn end or tail between the drums.

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a)

,)

Fig. /.2 Transportation3 deposition and t!isting of fi,re in Dref2 spinning

Figure / &.( a 5 shows that the fibres traveling from the opening roller to the

friction drums and figure / &.( b5 shows the fibres landing and being twisted to form the

yarn. The fibres are individually twisted onto the conical yarn tail during their deposition.

The formation of ,ref-( yarn structure is therefore a buildup of fibre layers from the

sliver feed.

$s the forming yarn length moves in the direction of take-up the separated fibres from

each consecutive sliver are deposited onto the previous layer. Thereby the fibres present

in particular sliver become integrated into the corresponding concentric layer of the yarnJ

the fibres from the first sliver farthest from the delivery rollers forming the center of the

yarn. )t is therefore possible to produce the yarns with each concentric layer being

composed of different fibre type. )t is evident that any migration between layers is very

small and that the yarn is much more compact in the region of the core. Since spinning

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The fibres are individually twisted on to the sleeve during their deposition. The

fibers may be deposited preferably at the interface of the sleeve and drum surface

/fig.&. b.5 or directly on to the fibre sleeve /fig.&. c5.

,) 4)

5

d)

Fig ./.) 0arn formation in finecount friction spinning

The hypothesis is that the leading end of a fibre makes first contact with the

friction drum surface and the momentum of the trailing end causes the fibre length to

fillip over its leading end as the fibre is being twisted into the rotating sleeve. This fillip-

over action tends to give some degree of fiber straitening and results in the sleeve fibers

having an S Ctwist heli2. The preferred state of fibre deposition at the sleeve drum

interface is obtained by employing only one perforated drum with applied suction the

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other drum /friction drum5 being a solid surface and by poisoning the e2it of fibre of the

fibre transport channel close to the interface /fig.&.#5.

Fig. /.* Fi,re deposition at the sleevefriction drum interface

Fibre ends pro"ecting from the rotating sleeve provides the means of capturing the

leading ends of the depositing fibres for the later to be twisted on to the sleeve. Fibres

may also be captured as illustrated in fig./&.&5

. Fig././ Fi,re capture ,y rotating sleeve

$t /a5 the fibre approaches and is pulled into the interface of the sleeve and the first

drum surface. The sleeve rotates at the surface velocity K< L K!1. )t is however lightly

that the torsions resistance of the sleeve is sufficiently small that slippage between itself

and drum is negligible in comparison with the ,ref-( system. $t /b5 the fibre contacts

the second drum surface or is entangled in the sleeve and moves towards the second

interface. )n positions /c5 and /d5 the fibre becomes twisted on to the sleeve.

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Fig./&.'5 depicts how fibres forming the sleeve are subseBuently twisted on to the conical

tail of the yarn. The leading ends of the fibres in the rotating sleeve become attached to

the yarn tail /figure a5 and as the yarn length is pulled away by the delivery rollers the

attached fibres are I-twisted on to the tail /fig b5. The fig. Shows a fibre with S-heli2

angle M being twisted with I-heli2 angle N on to the yarn tail at a point where locally the

diameter is indicated as Ed /fig.c 5 from the geometrical parameters given in the

diagram /fig c and d5the fallowing eBuation can be derived for the yarn twist

/Stalder.3.and Soliman.3. elliand Te2tilber 1*7*5

Fig./. T!isting of fi,res onto yarn tail

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Yarn (

1 / A 5cos /sin A 5

P1 /( A 5 Q

R AV

G AV

D T Y Twist Y

d T

π γ γ

π

−= = +

+

@here D R G Fiber Sleeve ,iameter

T AV G $verage yarn twist

Y G!atio of ,rum Surface Speed to


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prepared few sketches from the original photograph of the yarn tail and those sketches

have been depicted for better understanding in fig /&.+5. )t can be observed that the fibres

away from the yarn tip are more tightly wrapped.

8ut according to Stalder and Soliman /Stalder.3.and Soliman.3. elliand

Te2tilber 1*7* 5 the separated fibres after landing on friction drums surface proceeds

towards the nip where it e2periences a torBue generated by the friction drums. This

causes the fibres to form a rotating sleeve continuously pass onto the non- rotating yarn

end that rests co-a2ially within the sleeve. a seed yarn has to be fed initially around the

stationery yarn end once one of its end gets entangled by the yarn. The yarn is

withdrawn and the process continuous.

/.2 Formation of sleeves:

Fig. /.6 Fig. /.7

/Formation of cylindrical sleeve of fi,res (Fi,res transfer from feed channel to

yarn) tail via fi,rous sleeve)

Stalder and Soliman /Stalder.3.and Soliman.3. elliand Te2tilber1*7*5 have

established with ultra high speed photography that there is a stationery conical yarn tail

and it is surrounded by a more or less cylindrical sleeve of fibres as shown in /fig &.7

and &.*5 . )t us reported that fibre sleeve rotates on the perforated drum particularly

slippage free without any movement in the direction of the a2is. The actual yarn tail is

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formed within this sleeve. )t is difficult to perceive the idea that the sleeve which is not

positively gripped between the drums can rotate in slippage free state. 6ord and !ust

/6ord..! and !ust. :.. :.Te2t.)nst 1**05 has suggested the e2istence of torpedo

shaped fibre sleeve that contains the tapered yarn tail.

." Fi,re consolidation and t!isting:

Fig.." Theoretical tor8ue distri,ution along rthe length of fi,re assem,ly

The two friction drums rotate in the same direction but at the close vicinity they

move in opposite directions. The vector diagram of forces has been shown in fig /'.05

.The amount of torBue can be calculated as under

1 (/ A (5 R R

Torque y F F F

µ = + ÷

@here , y G local yarn diameter and other notations are as stated earlier and

F G the force produced due to air flow over the yarn

The geometry of the system has a great influence in deciding the ratios R1 /F and R2 /F

and so the separation between the torBue rollers /g5 and the local yarn diameter / y5.

)n open Cend friction spinning the yarn tail is tapered and fibres are added continuously

to it. Thus yarn formation takes place. There is a mass eBuilibrium between the arriving

fibres and the outgoing yarn but the linear density of the forming yarn is not constant.

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,epending upon the local force gradient the yarn dimension changes along the length of

the formation 4one .The theoretical torBue distribution is shown in figure /'.05. 8ut in

practice the effective yarn diameter in the formation 4one the coefficient of friction and

the reaction forces along the length of the friction drums are not constant and sometimes

unpredictable. This causes a deviation in the torBue distribution from the ideal theoretical

one. >onseBuently the twist distribution along the length of yarn varies .The twist

distribution also gets affected by the changing stiffness of the fibrous material and

various annular layers of fibres in the yarn are likely to have different twist level. The

behavior of the tip of the tail was interesting. TorBue built in the tip of the tail but was

released by intermittent slippage which caused the tip to rotate relative to the rest of the

tail for short period of time. There was a sort of slipAstick phenomenon and when the slip

part was operative the tail was Buite unstable E )t has been reported by 6ord ; !ust

/6ord..!.and !ust .:.. :.Te2t.)nst. 1**05.

.1 Fi,re integration at yarn tail:

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Fig. .1 Fi,re transfer process from rotating sheath to nonrotating core

)t is important to know how the fibres from sleeve get transferred to the yarn tail

continuously. @rapping of fibres around the open end of the yarn would need a relative

speed to be generated between the sleeve and the yarn tail and establishment of a

connection between them by fibre to be wrapped. There could be three options=

15 $ rotating sleeve holding stationery tapered tail within it.

(5 $ non-rotating sleeve holding a rotating tapered tail.

5 $ rotation of both sleeve and tail in the same direction but at different speeds.

Though the possibilities of first two have been stated the third alternative has not been

suggested. 9rause et al./ 9rause 3.@. Soliman 3.$. and Stalder.3. :.Te2t . )nst.

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1**15 suggested that fibres are added to the yarn tail through a transient location in the

form of a rotating fibre sheath or sleeve .)t is termed as epicycle theory and describes

how fibre is withdrawn from a rotating sheath and transferred to a non rotating yarn

end. )t is said that the fibres are transferred from the perforated drum to the rotating

sheath in the same way as ink in a rotary printing machine is passed to the papers. 8ut

how the non-rotating tail catches a fibre has not been suggested.

This process of fibre transfer from rotating sheath to non-rotating yarn core has

been suggested by 6ord and !ust /6ord..!.and !ust .:.. :.Te2t.)nst 1**05 and

showed in fig /'.15 .)t is reported that the rotating sheath has a number of fibres ends

pro"ected from the surface of the sheath .these hair strand out Buite rigidly when the

sheath rotates .$n approaching fibre easily gets trapped as the hair is folded back and

new fibre continues to be trapped until the centrifugal force straightens out the hair

again .Thus fibres are added to the rotating sheath .The fibres are peeled of the inner

surface of the rotating sheath and are laid on the non-rotating core attached to the

outgoing yarn .The centrifugal force forms a barrier to this transfer .Once the fibre is

anchored in the core there is probably no difficulty but when a new fibre attempts to

make the transfer it can do so only if it is entangled with one already in transit .)f the

fibres are randomly placed on the inside surface of the rotating sheath some of the

entanglement is likely to act so as to prevent a clear peeling action .)f there were an

eBual number of fibre connections in both the forward and backward directions .there

would not be any pilling action .There are some disputes as pointed out by 6ord and

rust /6ord..!.and !ust .:.. :.Te2t.)nst. 1**15 .They are confident that there is always

a slippage between the rotating sheath or sleeve and perforated drums the claim of

9rause et al/9rause 3.@. Soliman 3.$. and Stalder.3. The Te2tile )nstitute 1**7

$nnual @orld >onference The Te2tile )nstitute anchester1**7.5 that the sheath

surface speed is particularly same as that of friction drum.

The alternative way /6ord..!.and !adhakrishnianh.. :.Te2t.)nst 1*75 by which

fibres can be captured at the yarn tail does not reBuire other fibres for gripping .This

mechanism reBuires that the suction draws the fibre into the nip between the yarn tail

and ingoing roller .

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Fig. .2 The process of loop formation.

The different stages have been depicted in fig /'.(5. $s the process of self Centrapment progresses the fibre do curl back towards the yarn in the vicinity of nip between the

outgoing drum and yarn tail .)t is possible to spin a loosely constructed yarn with "ust one

roller. 8ut in two-roll case the fibre end may then become entangled with the yarn or it

may pass between the yarn tail and the second roll. $ loop is thus formed below the yarn

tail.

E $ loop may be formed by one of the two mechanisms. First if the yarn tail is assumed

to be cylindrical a loop can be formed when the fibre tip is caused to curl back towards

the tail and comes into contact with it. The magnitude of that loop is then determined by

the local shear. The relative fibre velocities f 1 and f ( /the fibre velocities at the point of

contact with the ingoing and outgoing rollers respectively5 are related to the shear

between the perforated roller and the yarn tail. )f f ( f 1 the loop diminishes if f ( L f 1 the

loop grows and if f ( G f 1 the loop remains constant in si4e. The second mechanism is

related to the first .)n this case we take into account the shape of the tail which is usually

tapered at the tip and again upstream of the fibre accumulation 4one .)f a cone is placed

between two cylinders rotating in the friction spinning process and a fibre is allowed to

wrap around the cone by the action of rotating cylinders a loose wrapping occurs at

positions at which the cone diameter is less than that of the drive 4one. There will be

loops above and below the point of contact of the cone and the cylinders. This occurs

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owing to the reBuired slippage between the cone and cylinder in the regions not in the

drive 4one

.2 &tructure of friction spun yarns:

The structure of friction yarn is different from that of other yarns is characteri4ed

by poor fibre orientation buckled and folded fibre configurations and loose packing of

fibres in yarns. The structure is determined by the way the fibres are assembled into

yarn .The structure has a significant effect on properties .The appearance of O?-friction

spun yarn is closer to ring yarn though there is a varying degree of twist present in

different layers of the yarn. 8ut ,ref- yarns have a distinct core sheath structure where

the core is false twisted /6ord..!. :oo.>.@. and $shi4aki.T. :.Te2t .)nst 1*7+5 and the

sheath has wrapped fibres at various heli2 angles around the core .$lagha et al./ $lagha

.:.O2enhan Te2t. !es. : 1**#5 have reported that percentages of fibres near the yarn

center is greater for yarns produced at higher speeds /i.e. high core packing density5

whereas higher packing density towards the outer sections is observed for the yarns

produced at lower speeds .The packing density at middle layers remains unaffected by

production speeds. They also added that in general the fibre angle increases from center

to surface of yarn. $ccording to them the yarn consists of highly twisted core but core

twist e2hibits a sharp reduction as production speed is increased beyond (00-mA min.

Sett et al /Sett.S.9.ukher"ee.$. and Sur.,. elliand

Te2tilber 1**&5 have reported that ,ref-( yarn consists of entangled fibres with a very

irregular helical structure .The mean fibre heli2 is stated to be more widely distributed

as compared to ring and rotor

The fibre e2tent in friction yarns is found to be of the order of &0

/6awrence.>.$ Foster.@. @ilding..3oward.$ and 9udo.! :.Te2t.)nst 1*77.5

whereas the same for ring and rotor yarns are *0- *& and +0-70 respectively .The

low average fibre e2tent can be ascribed to folded and buckled fibre configuration in the

yarn which also account for its poor strength .

. &tac%ed cone model of + friction yarns:

)t has been described by different researchers /6awrence.>.$ Foster.@.

@ilding..3oward.$ and 9udo.!.'th)nternational )I)! T?UT)6?

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as shown in fig /'.5 . $ fibre follows a helical path originating somewhere at the

surface and gradually moving towards the ape2 of the conical surface as in fig /'.5 .

The same fibre is confined to a particular conical surface only. !ust and 6ord

/!ealff..6. Seo. . 8oyce..>. Schwart4.. and 8acker.S. Te2t .!es.:. V.. 5 have

shown that the amount of position deviations from the conical surface is very small. )n

absence of such positional deviations there will be no interminglingJ crossing or

bonding of fibres to give a well interlocked structure because of the shear strength

between layers the structure will collapse even at lower stresses.

Fig. . - simplified model of friction yarn

.* 'igration in Friction 0arns:

)n ideal migration for conventional ring yarns a fibre would have been a confined

in particular cylindrical layer. )n such a case discrete cylindrical layers of the yarn could

have been easily separated. 8ut orton and


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difference in the twisting process. The tension variation in the fibres results in

migration .)n friction spinning the level of spinning tension is relatively low .So

migration as e2pected in ring yarns can not be achieved in friction yarns. 3ence the

parameters described by 3earle et al /upta.8.S. Te2t 3earle.:[email protected]. and. !es. :. 1**&5

to measure migration in ring yarns are not suitable to estimate migration in friction

yarns.

8ut $lagha et al./ $lagha .:.O2enhan Te2t. !es. : 1**#5 have a different

opinion .They have reported that mean fibre position of friction yarns are Buite similar to

yarns produced on ring and rotor system e2cept when friction yarns are produced at

speeds higher than (00 m A min .3owever amplitude of migration /rms5 was found to

highest for friction yarns .

Stalder and Soliman /Stalder.3.and Soliman.3. elliand Te2tilber 1*7*5 have

established with photography that the sleeve rotates on the perforated friction drum

without any slippage .The twist per meter is higher inside a friction yarn than at its

surface though it is dependent on the spinning system .8ut 6awrence et al./

6awrence.>.$ Foster.@. @ilding..3oward.$ and 9udo.! ' th )nternational )I)!

T?UT)6? S


29/51

(5 rocess parameters and

5 aterial parameters

5." Influence of 'achine parameters:

5.1 Design of +pening 9oller:

The opening roller in friction spinning machine have a strong influence on yarn

properties .The design of opening roller particularly clothing characteristics such as type

of teeth wire point density and surface finish of teeth is of paramount importance.

Simpson and urrey /Simpson.:. and urray..F. Te2t.!es.: 1*+*5 have found that

for rotor spinning a combing roller with forward rake angle 1&W yielded better results in

respect of fibre paralleli4ation and yarn strength .,yson /,yson.?. :.Te2t.)nst 1*+#5

have reported that fibre breakage can be minimi4ed with low wire point density of the

clothing and running the opening roller at low speed .3e pointed out that that optimum

wire design should have a front angle of 7*X.3e also added that pinned type roller has a

gentle effect on fibre which reduces fibre breakage.

There may be one or two opening roller running at different speeds depending on the

type of machine. )n ,ref- friction spinning machine there are two opening rollers

running at a speed of 1(000 rpm /,r. ?rnst Fehrer-$5. Dlku-et-al. /Dlku.S. O4ipek.8.

$car.. Te2t. !es.:. 1**&5has reported that the fibre breakage increases with opening

roller speed on a open-end friction spinning machine of S6 /asterspinner5. They have

found a clear correlation between fibre length characteristics and opening roller speed for

cotton polyester and viscose fibres but for acrylic fibres the degree of association

between these two factors is small. This means that the e2tent of fibre breakage or

damage is dependent on the type of fibrous material. So the selection of opening roller

types and speed significantly influences the yarn properties such as strength and

elongation

!ust and 6ord /!ust .:.. and 6ord ..!. Te2t.!es.: 1**15 have

reported an increase in yarn tenacity when the opening roller assembly in ,ref C

machine is replaced with suction roll and an opening roller from a latt 771 rotor

spinning system. The change in opening roller also led to improvement in fibre

(*


30/51

orientation before being assembled onto the yarn tail and finally increased the fibre e2tent

in the yarn.

5.2 Design of transportation duct=

The design of transport channel and its angle of inclination with respect to the

yarn withdrawal direction also influence the yarn Buality .)n case of rotor spinning

6awrence and >hen /6awrence.>.$ and >hen.9.I. :.Te2t.)nst. 1*775 have shown that a

narrow rectangular cross-section of the transport channel will improve the straightness of

fibres in duct as well as in yarn and thus the yarn strength .This behavior is also e2pected

in case of friction spinning but the e2tent of fibre straightness is far more poor because of

the much less speed of the friction drums .This matter is further complicated because of

the fact that the fibres from the feed duct can land on the ingoing drum or directly on the

rotating mass of fibre called Esleeve .8y feeding fibres directly on sleeve helps to obtain

higher yarn strength .

The strength of the yarn is also affected by the angle of the feed duct to the yarn

withdrawal direction. !ust and 6ord /!ust .:.. and 6ord ..!. Te2t.!es.: 1**15 have

observed that with 0X feed angle the yarn was strongest. @ith #&X '0X and +&X there

were a gradual drop in yarn strength but they were close to each other. 8ut all them have

a significant different in yarn strength compared to that the twisting or wrapping of fibres

are more effective and tight though the fibre e2tent is somewhat less.

5. Design of friction drum:

The twisting mechanisms of friction spinning system are of various types which

e2ercise a strong influence on yarn properties especially on strength. These devices

/6unenschloss.:. and 8rockmanns.9.:. )nt.Te2t.8ul. 1*7*5 can consist of a5 two

perforated suction drums b5 one perforated suction drum and one solid blind drum cc5

one perforated suction drum one perforated but without suction and d5 one perforated

suction drum with a supporting disk etc. The system with one perforated friction drum

and one solid roller e2hibit lowest yarn tension /Stalder.3.and Soliman.3. Te2tile $sia

1*7+5.So the kind of twisting device has a strong influence on yarn tension and

conseBuently on yarn strength.

0


31/51


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S'01**(. 5 have reported that for a constant optimum twist the yarn tenacity for viscose

fibre gradually decreased with higher production ie delivery speed . $lagha et al

/$lagha .:.O2enhan Te2t. !es. : 1**#5 have found reasonable co relation between

change in yarn tenacity with production speed and emigrational characteristics. They

have pointed out that increase in production speed are related to change in yarn structure

and so to strength. Fibre heli2 angle reduces whereas yarn diameter increases as the

production speed is increased. From the same study it has been pointed out that a higher

production speed leads to higher core packing density. $lso at low delivery speed the

packing density at the outer surface is relatively high. The yarn consists of high twisted

core but this abruptly reduces as the production speed is beyond (00 mAmin.

6. Friction drum speed:

The friction drum/s5 are the elements in the machine that imparts twist in the yarn. )t has

been reported by admanabhan and !amakrishna /admanabhan.$.!. and

!amakrishnan.R. )nd.:.F.Te2t.!es. 1**5 that strength of ,ref- yarns increases with

increase in friction drum speed from 000 to &000 rpm. )t is understood that the yarn

twist is directly influenced by the speed of friction drum for a constant delivery speed. $s

drum speed is increased the twist in the yarn becomes more.

Fig. 5." &etting of a) Transportation duct ,) &uction slot

(


33/51

6.* &uction pressure:

9onda et al /9onda.F. Okamura. erati.$.$. Te2t. !es. :. 1**' 5 have reported that

the effect of suction pressure /in the yarn formation 4one 5 on yarn structure and

mechanical properties .$n increase in air pressure leads to a linear rise in yarn tension

and so yarn tenacity. @hen the air suction pressure increases the yarn is held more

firmly against the surface of friction roller and the amount of frictional forces increases

and thus the yarn tension. The mean fibre speed along the feed channel increases as the

suction pressure increases. Thus the fibre orientation inside the feed channel and finally

the fibre length utili4ation in the yarn improves .$s a result increased fibre packing

density and fibre e2tent produce stronger yarn structure. They have also reported the

breakage behaviour of yarn produce at lower suction pressure is dominated by fibre

slippage. @hereas the yarn produced at high suction pressure breaks sharply indicating

dominance of fibre breakage over slippage.

6./ &pinning tension:

Spinning tension is one of the most critical parameters and it is highly variable in

friction spinning. The spinning tension in friction spinning is in the range of &-1& cR

which is considered too low compared to ring and rotor spinning. ,ue to low spinning

tension yarn strength as well as yarn breakage during spinning is less. Stalder and

Soliman /Stalder.3.and Soliman.3. elliand Te2tilber 1*7* 5 have shown

mathematically as well as verified e2perimentally that the spinning tension is influenced

by the factors vi4 air force on the yarn tail co efficient of friction between metal and

fibre and yarn tail diameter . They have also commented that these variables are not easy

to measure and difficult to vary during spinning operation. $s the spinning tension is low

sufficient friction among the fibres is not developed and conseBuently yarn strength is

low. 9onda et al /9onda.F. Okamura. erati.$.$. and


34/51

pressure yarn is held more firmly to rotating friction surface and as a result friction

between yarn surface and the surface of friction roller increases.

6. 0arn diameter:

Spun yarn diameter in general depends on fibre properties method of twisting

amount of twist packing density and processing parameters. )n friction spinning the yarn

tail in the yarn-forming 4one is rotated by friction drum. erati et al / 5 have reported

that as the yarn diameter decreases the length of yarn sub"ected to frictional forces is

reduced which reduces torBue accumulation and yarn tension resulting in loss of spinning

tension. Thus yarn diameter plays important role in yarn tension during friction spinning.

@hen the yarn diameter is less then the gap between friction drums lack of contact

between the yarn and both friction surfaces simultaneously results in lesser magnitude of

frictional force generation. Though the yarn tail is voluminous the tip of yarn in this 4one

is unstable /6ord..!.and !adhakrishnianh.. :.Te2t.)nst 1*7+5 . oreover fiber in this

4one do not have sufficient cohesion and the forces e2perience by the yarn tail is

negligible /erati.$.$. 9onda.F. Okamura.. and aarui.?. Te2t.!es. : 1**+5.

.@. and

$shi4aki.T. :.Te2t .)nst 1*7+5 have also pointed out that / y-g5 is an important factor so

far torBue is concerned where g is separation or gap between friction drums and yG the

local yarn diameter at yarn formation 4one.

7." Influence of 'aterial parameters:

7.1 4oefficient of friction:

)n case of O? Cfriction spinning system consisting of one perforated drum and one blind

drum it has shown that by increasing the coefficient of friction between fibre and

perforated drum on relation to that of fibre and the blind drum /Stalder.3.and

Soliman.3. Te2tile $sia 1*7+5 causes the torBue available for twisting to increase .Thus

spinning tension and finally the yarn strength increases.

#


35/51

7.2 Fi,re fineness:

The study taken by 6awrence et al. /6awrence.>.$ Foster.@. @ilding..3oward.$ and

9udo.!. 'th )nternational )I)! T?UT)6? S


36/51

This chapter deals with material specifications sample preparations and test

methods.

Fi,res:

>otton fibres of fibre length of &mm length /mean length after 1' noil e2traction5

and fineness .*+ micronaire and olyester fibres of ##mm and fineness 1.( denier

were used for making the yarns.

Preparation of yarn sample:

,ref-( friction spun yarns were produced from ,ref- machine on ,ref-( mode. The

cotton and polyester slivers of .79te2 and (.7+9te2 were used for the above

purpose.

Three sets of + yarn samples of *7.# &* and #(.( te2 yarn were produced

keeping drum speed 100rpm and delivery speed of 110 mpm. , ? F . ; 3.

- &tructure ; &tructure 4 &tructure D &tructure

&tructure F &tructure < &tructure = &tructure

'


37/51

Structure $= >omposed of 100 polyester

Structure 8= Three inside layers of polyester and two outside layers with cotton

Structure >= Three outside layers with cotton and two inside layers of polyester

Structure ,= Three outside layers with polyester and two inside layers with cotton

Structure ?= Three inside layers of cotton and two outside layers with polyester

Structure F= Three cotton layers sandwiched between two layers of cotton

Structure = Three polyester layers sandwiched between two layers of polyester

Structure 3= >omposed of 100 cotton

The delivery speed of drafting unit ( was calculated as

AV

V Nm n m

=

× ×

V A G ,elivery speed

N mGetric count to be spun

nGRumber of slivers fed

mGgmAmtr of fed sliver

KG,rafting speed

Sample $rrangement of

sliver in drafting

unit ))

K(

/mAmin5

K( mAmin K( mAmin

$ 0.+(' 0.##( 0.17

8 >> 0.'+* 0.#1 0.(*+

> >>> 0.'&+ 0.# 0.(77

, >> 0.'+* 0.#1 0.(*+

? >>> 0.'&+ 0.# 0.(77

F >>> 0.'&+ 0.# 0.(77 >> 0.'+* 0.#1 0.(*+

0arn Testing

+


38/51

The following tests were carried out to assess the effect of sheath composition on twist

and tensile behaviour of ,ref-( friction spun yarn. $ll the tests were performed on

sample conditioned in a standard atmosphere of '& ± ( !3 and (+ ± (Y >

T!ist

$ mechanical twist tester was used to calculate the twist. The yarn samples 0f 10- inch

length were twisted in the direction of original twist . Twisting was continued till the

break and the number of turns reBuired to break the yarn /R15 was noted . The test was

repeated but this time twisting in a direction opposite to the direction of original twist and

again the number of turns reBuired to break the yarn /R(5 was noted. The test was

repeated #0 times for each sample. The twist was then calculated by using the following

relationship

( 1/ 5

*.+(

N N TPM

−= ×

Tensile properties

Iwick universal tensile tester was used to evaluate the tensile properties . Tenacity and

breaking e2tension of ,ref-( yarns were measured at 1&0 mmAmin cross head speed with

&00 mm gauge length. The average of #0 test results were taken for each sample.

&tructural integrity

The decay /a measure of structural integrity of the fibre assembly in the yarn5 was

evaluated by carrying out the cyclic loading test after (& cycles of loading and unloading

7


39/51

under constant load condition /(0 breaking load of the weakest yarn in the group5 on a

Iwick universal tensile tester . The decay was calculated using the following relation=

(& 1

1

100 A A

Decay A

−= ×

@here A1- $rea of hysteresis curve at first cycle

A2 -$rea of hysteresis curve at twenty fifth cycle

9esults and discussions (F+9 T$I&T)

The value of twist in different structures is given in table1and figure/ 5 is the

graphical representation of the results . From the table it is seen that the

*


40/51

Twist of Yarns

0

50

100

150

200

250

300

A B C D E F G H

structure

T w i s t ( T P

98.4 tex

59 tex

42 tex

Fig >ariation of T!ist for different structures

Ta,le :1

#0


41/51

ZKalues inside the bracket indicate >K

From the table it is seen that the twist in the structures range from 1/.2 tpm to

25.*. )t is clear from the Table 1 and Fig 1 that the twist in structure $ is the highest

/1+#.&5 at all count level. The level of twist reduces as the outer polyester layers are

replaced by cotton as in the case of structures 8 ; >. Similar decreasing trend in twist is

also observed in structures , and ? where the inner polyester layers are replaced by

cotton .@hen the cotton layers are placed in between two innermost and outermost

polyester layers as in the structure F the twist reduces and when the innermost and

outermost polyester layers are replaced by cotton /Structure 5 the twist reduces as

compared to the structure $ though the reduction is not very significant. Similar

observation is valid for other counts as well. The twist is seen to increase from 1+#.& to

('+ for structure $ from 1'0 .( to (&*.( for structure 81&'.* to ('.# for structure >[

+0 .# to (#1.& for structure ,1'(.+ to (#1.& for structure ?1&'.( to (#7.& for structure F

and 1''.7 to (''.+ for structure . $s the count of yarn become finer the amount of

twist friction spun yarn also increases.

&tructure T!ist (TP')

76.* te /7 te *2 te

$ 1+#.&

/&.#5

(1.+

/&.*5

('+.#

/7.*58 1'0.(

/1(.#5

((0.7

/#.*5

(&*.(

/#.#5

> 1&'.*

/+.15

(07.

/&.05

('.#

/7.*5

, 1+0.#

/&.*5

(0*.(

/7.*5

(#1.1

/7.05

? 1'(.+

/&.5

(0#.&

/&.&5

(#1.&

/7.&5

F 1&'.(

/10.*5

(1(.'

/'.#5

(#7.&

/'.&5

1''.7

/&.#5

((*.+

/'.+5

(''.+

/+.'5

#1


42/51


43/51

@hen all other parameters are constant the pressure difference ( ) !∆ would be

proportional to total specific surface area of fibres. The specific surface area in turn is

inversely related to fibre diameter. Finer the fibre the lesser is the diameter and more

would be the specific surface area. )n the present cotton-polyester blended yarn the

polyester is finer than cotton. 3ence more is the proportion of polyester more will be the

specific surface area of fibre agglomerates on the friction drum and hence more would be

the pressure difference

d) The diameter of the rotating sleeve in the nip of the two rotating drums.

)n case of structure $ /100 polyester5 the coefficient of friction /fibre to metal 5

for polyester is more than the coefficient of friction /fibre to metal 5 of cotton the fibre to

fibre friction at the interface of each layer will also be more as the fibres are of same

generic nature so the resistance to untwisting of previously laid layer will be more.

3ence the overall twist in the yarn is more.

)n case of structure 8 the last two layers are of cotton. @hile the last three layers

are of cotton for structure >. 3ere the late deposition of cotton layers causes less twist

generation in them. The frictional coefficient between cotton and polyester is also less

and the fibre to fibre friction and fibre to metal friction for cotton is also less. These

cotton layers will not be able to trap the generated twist in the previously laid polyester

layer and the twist in cotton layer will also be less because the normal force which will be

acting on them is less as compared to that on polyester as they are coarser. The fibre

length of cotton being less may hinder the wrapping of the structure. So the twist in

structure 8 reduces as compared to structure $ and it reduces further with additional

numbers of cotton layers in structure > for similar reasons. )t may also be mentioned

here that last cotton layers generate less twist and there retention is also less the resultant

effect is less reali4ation of twist in the yarn.

)n case of structure , and ? the initial layers are of cotton. $s these cotton layers arrive

the friction drum first the generation of twist on them will be more and their untwisting

#


44/51

will be resisted by the subseBuent polyester layer. So the structure , posseses

comparable twist as in structure $. 3owever in case of structure ? the amount of twist in

last two polyester layer might be less due to there short residence time. 3ence the overall

twist in structure reduces with further increases in cotton component. The twist in

structure F were three cotton layers are sandwiched in between two polyester layer is less

than structure $. Though the initial polyester layer can generate more twist in it but the

last layer of polyester may not be able to generate much twist due to less residence time

which may be insufficient in restricting the untwisting action of the previously laid cotton

layers due to the following reasons=

15 The inner cotton fibre layers will not be able to generate much twist as compared to

polyester layer being placed at that position.

(5 The frictional condition of the fibres at the interface of the last two layers may be

insufficient in restricting their untwisting.

5 The last polyester layer itself will posses less twist.

)n case of structure the twist increases in comparison to structure F. $lthough

the initial and final layers are of cotton but the presence of intermediate three layers of

polyester is probably the reason for the structure showing higher twist as compared to

structure F.

One interesting point to note here that the twist in structure > and F are same

when the count is coarse. The presence of two polyester layers at the 1st and (

nd layers are

likely to receive more twist owing to their feed position while three cotton layers at rd

#th and &

th position in the case of structure > might have caused to yield moderate twist

value. )n case of structure F contribution from the outermost polyester layer in restricting

the untwisting of the inner cotton layers might have contributed in generating moderate

twist as in structure >.

Twist has been found to increase as the yarn becomes finer.

Ta,le 2 Tenacity of 0arns

##


45/51

&tructure Tenacity (g?te)

76.* te /7 te *2.2 te

-

+./1(.(5

10.1/1&5

*.7/1.75

;*.(

/*.&510.(/1(5

*.*/10.'5

4

*.1/7.#5

*.(/*.75

7.*/*.(5

D

7.*

/+.#5

*.#

/10.#5

7.*

/10.&5

*.0

/'.15

*.#

/7.75

*.7

/1'.*5

F

*.'

/+.'5

*.&

/+.15

*.(

/*.75

<

+.'

/11.5

*.1

/10.#5

7.(

/11.(5

=

7.&

/&.75

*.&

/+.+5

*.#

/*5

Tenacity of Yarn

0

2

4

6

8

10

12

A B C D E F G H

Structure

T e n a c i t y ( g / t

98.4 tex

59 tex

42.2 tex

Figure-

#&


46/51

9eferences1. $lagha .:.O2enhan )nfluence of roduction Speed on the Tenacity and

Structure of Friction Spun hattopadhyay !. )nfluence of lying on the Tenacity8reaking ?2tension and

Fle2ural !igidity of $ir- "et Spun


47/51

1(. >oulson.$. F. @. and ,akin. . ,oubled yarns art/15 to /5. :.Te2t.

)nst.#7T(0+-T(*(/1*&+5.

1. ,akin. . ,oubled yarns art/#5 to /&5 :.Te2t. )nst.#7T(*-T( /1*&+5.1#. ,eussen.3 >onventional and Rovel Short Staple Spinning Systems illiand

Te2tilber /?nglish part 5 11A7* ?&(-?&/1*7*5.

1&. ,ref C Spinning System-Operating )nstructions. Te2tilmaschinenfabrik ,r. ?rnstFehrer-$.

1'. ,yson.?. $ Study of Open ?nd Spinning by >ircumferential $ssembly with

?special !eference to the Spinning of odified !ayon art/15=Fibre presentation :.Te2t.)nst '&&77-&*#/1*+#5.

1+. Fehrer.? Friction Spinning= The State of the $rt Te2tile onth Sept 11&-11'

/1*7+517. Fischer.:$utomated rocess for Twisting \uality ly onference The Te2tile)nstitute anchester1**7.

1. 9rause 3.@. Soliman 3.$. and Stalder.3. Fibre Flow in Friction Spinning

:.Te2t . )nst. 7(/15 11-11#/1**15.(. 6au


48/51

. 6awrence.>.$ and >hen.9.I. $ Study of the Fibre Transfer >hannel ,esign in

!otor Spinning art/15 and /(5 :.Te2t.)nst.+*/5'+-#07/1*775.

#. 6awrence.>.$ Foster.@. @ilding..3oward.$ and 9udo.!.$ Study of theStructure and roperties of Friction Spun .$ Fundamentals of Spun !> ress(00( publication

'. 6inda.8.9.and Sawhney.$..S. >omparision of ,ref- >otton .@. and $shi4aki.T. The echanics of Friction Spinning:.Te2t .)nst+7/#5(#-(/1*7+5.

*. 6ord..!.and !adhakrishnianh.. Tenacities of lied Friction Cspun !otor-spun

and !ing-spun omparative Study of the roperties of >otton . Schwart4.. and 8acker.S. echanicalroperties of Fabrics @oven from


49/51

&&. !ust .:.. and 6ord ..!. Kariation in hanges in a Friction Spinning achine Te2t.!es.: '1/115'#&-'&&/1**15.

&'. Salhotra.9.!. >hattopadhyay.!. 9aushik.!.>.,. and ,hami"a .S. TwistStructure of Friction Spun


50/51

+&.


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3803037 textile m tech theis

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