· Indian Journal of Fibre & Textile Research Vol. 29, December 2004, pp. 4 19-428

Process-structure-property relationship of polyester-cotton MVS yarns: Part I -Influence of processing variables on yarn structural parameters

G K Tyagj' & Dhirendra Shannab

The Technological Institute of Textile & Sciences, Bhiwani 1 27 02 1 , India

and

K R Salhotra

Department of Textile Technology, Indian Institute of Technology, New Delhi 1 1 0 0 1 6, India

Received /6 April 2003; revised received and accepted 3/ December 2003

The influence of twisting jet pressure, delivery speed, nozzle distance, yarn linear density and yarn composition on the structural parameters of polyester-cotton yarns spun on Murata Vortex Spinner (MVS 8 10) has been studied. It is observed that the MVS yarns have about 50 - 60% core fibres and remaining as wrapper or wild fibres. The structure of MVS yarn has been classified into four main categories, viz. tight wrappings, long wrappings, irregular wrappings and unwrapped. The tight wrappings are found to increase with the increase in jet pressure but at very high jet pressure, they get converted into irregular wrappings. The long wrappings increase with the nozzle distance while unwrapped structure decreases with both jet pressure and nozzle distance up to a certain level. The finer yarns have low proportion of core fibres. The wrapper and wild fibres increase with the jet pressure but at very high jet pressure of 6.0 kg/cm2, the wild fibres increase significantly. An increase in delivery speed leads to a further increase in wild fibres.

Keywords: Air-jet spinning, Delivery speed, Murata Vortex Spinner, Nozzle distance, Polyester-cotton yarn, Twisting jet pressure

IPC Code: lnt. CI.7 DOl H 4/02, DO I H 7/00, D02G 3/00

1 Introduction In the past few years, the rur-Jet spinning has

received progressively increasing attention and can be used to process all varieties of materials. An extensive study has been carried out by researchers to establish process-structure-property relationship model so as to engineer the yarn of desired characteristics. Grosberg et al. 1 studied the effect of delivery speed, jet pressure and yarn linear density on the four types of structural classes of air-jet spun yarns. Chasmawala et al.2 observed the effect of first nozzle pressure and main draft on the types of fibre in polyester fibre jet-spun yarns. Lawrence and Baque studied the effect of first nozzle pressure and delivery speed on the three types of structural classes of jet-spun yarns. Rajamanickam et al.4 investigated the effect of first and second nozzle pressures, blend ratio and yarn linear density on the structure and properties of polyester/cotton jet­spun yarns. All these studies have been carried out on

"To whom all the correspondence should be addressed. Phone: 242561 ; Fax: +9 1 - 1664-243728; E-mail : drgktyagi@rediffmail.com "Present address : ML V Textile Institute, Bhilwara 3 1 1 00 1 , India

yarns spun on MJS machines. Recently, MIs Murata Machinery introduced Murata Vortex Spinner (MVS 8 1 0), a modified version of the established jet spinning system. Though there are several references over-viewing5-7 the system and the yarn structure, the role of process parameters in influencing the structural changes of MVS yarns has not been reported so far. The present study, therefore, aims at investigating the effect of some processing variables on the structural parameters of polyester-cotton MVS yarns.

1.1 Principle of Yarn Formation

The drafted strand of fibres after coming out of the front rollers approaches the air-jet nozzle and is twisted by the force of air-jet stream. This twist motion tends to flow upwards. The needle protruding from the spiral orifice prevents this · upward propagationS (Fig. I) , Therefore, the upper portions of some fibres are separated from the nip point between the front rollers, but they are kept 'open'. After the fibres have passed through the orifice, the upper portions of the fibres begin to expand due to the whirling force of jet air stream and they twine over

420 INDIAN 1. FIBRE TEXT. RES., DECEMBER 2004

Fig. I-Principle of yarn formation8

the hollow spindle ('A' in Fig. 1 ) . The fibres twined over the spindles are whirled around the fibre core and made into MVS yarn as they are drawn into the hollow spindle.

The distance between the nip of front roller and the tip of spindle, as indicated by L in Fig. 1 , affects the physical characteristics of MVS yarns greatly. The larger the distance, the more are the 'upper portion open' fibres, resulting in a yarn closer to real-twist yarn in characteristics. However, if the distance is too large, the waste fibre rate will also be extremely large. Therefore, in general , the distance is kept slightly shorter than the average length of fibres to be processed.

2 Materials and Methods

2. 1 Sample Preparation

Two sets of yarns of 1 4.7 and 1 9.6 tex were spun from blends of polyester and cotton fibres on the air­jet spinning machine. The specifications of the polyester and cotton fibres used in the study are given in Tablel . A predetermined quantity of combed cotton and polyester fibres was mixed and processed on a Lakshmi Rieter's blowroom line. The conversion to the drawn sliver was carried out by using Lakshmi Rieter's Card C 1 13 and a draw frame DO/6. Three drawing passages were given to the carded slivers to produce finisher sliver of 3.0 ktex. The drawn slivers were spun into yarns on Murata Vortex Spinner (MVS 8 10). Eight baby cones of about 1 00 g each were prepared under each experimental condition. Furthermore, the yarn samples with different parameters were spun on the same position to avoid any drum-to-drum variations.

Table I -Specifications of polyester and cotton fibres

Characteristic

Length, mm Linear density, dtex Tenacity, cNltex Breaking extension, %

"2.5% Span length

Polyester fibre

44 1 .33

52.88 1 8.7

Cotton fibre

36.02" 1 .42 28.6 6.7

Table 2-Experimental plan for the variables used

Combination Level of variable No. Twisting jet Delivery Nozzle

pressure speed distance

(Xl) (X2) (X3) 1 - 1 - I 0 2 1 -1 0 3 - 1 1 0 4 1 I 0 5 - 1 0 - 1 6 0 - 1 7 - 1 0 8 1 0 9 0 - 1 - I 10 0 I - I I I 0 - I I 1 2 0 I 1 1 3 0 0 0 1 4 0 0 0 1 5 0 0 0

Table 3-Actual values corresponding to coded levels

Level Variable Twisting jet Delivery speed Nozzle distance

pressure, kg/cm2

m/min m m

(Xl ) (X2) (X3) - I 4 250 20 0 5 270 2 1

6 290 22

2.2 Experimental Design

The yarn ' samples were spun according to the 3-factor Box-Behnkan9 design as shown in Table 2. The actual values corresponding to coded levels are given in Table 3 . The order of spinning yarn samples was randomized to avoid any systematic error. The following second order polynomial was fitted to ascertain the relationship between the response (yarn structural parameters) and the independent variables (processing variables):

3 3 3 Y = bo + L/j;x; + �>;;x/ + Lbijx;xj

;=1 ;=1 ;=1

where y is the measured response; bo, bi, bii and bij, the coefficients of regression equations; and i & j, the

TYAGI et at.: POLYESTER-COTION MVS YARNS: PART I 421

integers with i < j. The regression coefficients of the response y were found using the experimental results.

2.3 Structural Measurement

2.3.1 Structural Classes

• The yarn structure, observed by using Leica stereo microscope, was classified into four main classes (Fig. 2). Class-I structure has parallel core of fibres uniformly which is tightly wrapped by a ribbon of fibres. The angle of wrap is generally around 45°. Since MVS yarns consist of about 50% core fibres and about 50% wrapper fibres, many sections of this class contained crimped core. In these tight wrappings with crimped core, troughs and crests are formed by the crimped core fibres. Class-II structure is similar to class-I structure but with long regular wrappings. Since there are· about 50% core and 50% wrapper fibres, the structure seems to be just like that of twisted two-ply yarns (Fig. 2b). Here also, some sections contain crimped core but have a lower amplitude in comparison to class-I. The core and

(a)

(b)

wrapper fibres form the troughs and crests alternately. Class-III structures have parallel core of fibres wrapped by fibres at varying angles. At certain sections, the wrappings are in opposite directions. Further, the yarn sections having very low proportion of wrapper fibres or loose wrappings were considered in this class. Class-IV structure has no wrapper fibres. Generally, the core fibres are untwisted but there are sections which have some residual twist. Ten readings, each of one metre yam length, for each sample were taken to assess the structural classes.

2.3.2 Fibres Types

The tracer fibre technique was employed to classify the fibre types. About 1 % of the fibres were dyed and mixed during the blending of polyester/cotton fibres before the lap preparation stage. The polyester tracer fibres were dyed red and cotton tracer fibres were dyed black. Methyl salicylate was used to optically dissolve the undyed fibres so that the path of the coloured fibres could be easily traced. The fibres were

(e)

(d)

Fig. 2-Four types of structural classes of MVS yarns [(a) class-I, (b) class-II, (c) class-III, and (d) class-IV]

422 INDIAN J. FIBRE TEXT. RES., DECEMBER 2004

categorized into three types, viz. core, wrapper and wild, as used by Rajamanikam et a1.4• If a fibre exhibited both wrapper and· core characteristics, the following rule was used: if seven or more coils were exhibited by the wrapper and remaining in the core, it was classified as wrapper fibre, otherwise it was classified as core fibre because a normal wrapper fibre exhibited 1 2- 1 7 coils. Three hundred tracer fibres of each fibre type were observed for each sample.

Tables 4-6. Only significant terms have been included in the final equations by using forward step-wise regression procedure. These final equations were tested for goodness of fit by using Fischer F-test. The negative coefficient of a variable in a response surface equation indicates that a particular property decreases with the increase in that variable, while positive coefficient of the variable indicates that the property increases with the increase in that variable. But the trend is modified with the sign and magnitude of the coefficient of the squared terms and the interaction between the two variables. The relationship between response and variable is shown with the help of 3-D graphs (Figs 3 and 4). Since in most of the cases, the blend ratio does not affect the trend, the effect of only 80/20 blended yams has been shown in these figures.

3 Results and Discussion

3.1 Statistical Analysis

The response surface equations for the . yam structural parameters along with the square of multiple correlation coefficient are shown in

Table 4--Response surface equations for structural classes bf MVS yams

Response Yarn linear Blend ratio Response surface equation density, tex (Polyester/cotton)

Class-I 19.6 80120 27.55-1 .57x,-1 . I br{).93xr4.78x,2 + l .OOX,X2 65/35 23.04-1 .47x,-O.46x2-O.5 b3--'2.95x,2 -O.63x2 2

14.7 . 80120 24.09- 1 .96x,-O.55xrO.54x3+0.96x/ -O.86x3 2+0.60X,X2 65/35 22. 17-1 .96x,-O.42x2-O.56x3-1 .28x,2

Class-II 1 9.6 80/20 55. 14-O.80x,+ 1 .52x3 -3.31x/ 65/35 54.38-1 .00x,-O.63x2+ 1 .08x3 -3.92x32

14.7 80/20 49. 17-0.94x,-O.66x2+0.83x3-0. 75x,2-1 .57x3 2 +0. 75x,X2

65/35 50. 7 1-0.85x,-O.60x2+O.83x3-1 .39x3 2 +0. 70X,X2 Class-III 1 9.6 80/20 13 .55+3.40x,+0.77x2+3.28x,2+2.63x32-O.85x,X2

65/35 1 7.50+4.07x,+ 1 .02x2+3.85x,2+2.70X3 2 14.7 80120 22.20+ 3.53x,+0.88x2+2.02x3 2-1 .42x,x2-0.90x,x3

65/35 23. 1 2+ 3.37x,+0.66x2+ 1 .22x,2-1 .35x,x2 Class-IV 19.6 80/20 3.73-1 .02x,-O.63x3+1 .57x,2+0.64x32

65/35 4.08-1 .60x,-O.90x3+ 1 .47 X2 2 + 1 .32x3 2 14.7 80/20 3.96-O.63x,+O.32x2-O.68x3+O.77x,2+O.47x32+O.45x,X3

65/35 4. 1 8-O.56x,+0.36x2-O.45x3+0.52x,2 +0.55X3 2

Squared multiple regression coefficient (R2)

0.91 0.9 1 0.91 0.87 0.89 0.9 1 0.90 0.8 1 0.95 0.95 0.92 0.89

· 0.89 0.84 0.95 0.8 1

Table 5-Response surface equations for fibre types (polyester tracer fibre) of MVS yams

Response Yam linear Blend ratio Response surface equation Squared multiple density, tex (Polyester/cotton) regression coefficient(R2)

Core fibres 19.6 80/20 56.28-1 .52x,-O.80x3+0.77x,2-O.67x32+O.67x,x2 0.89

65/35 54.2Q-l .46x,-O.70x3+O.75x,2-O.57x32+0.60x,x2 0.89

14.7 80120 52. 1 8- 1.43x,-O.52x3-O.78x32 0.82 65/35 49.88-1 .28x,-O.88x3 0.71

Wrapper fibres 1 9.6 80120 24.7Q-1 .3b,- I . l Ox2-3.7b,2 0.88 65/35 24.65-O.87x,-O.7b2

-3.70x,2 0.88 14.7 80120 26.27-O.98x,-O.77x2-3. 15x,2+O.92x,x2

0.89 65/35 25.41-1 .20x,-O.47x2 -2.33x,2 0.84

Wild fibres 19.6 80/20 1 9.40+2.83x,+ l .OOx2+O.76x3+2.88x,2 0.85 65/35 2 1 .47+2.33x,+O.67x2+2.9 b,2-O.82x,x2

0.89 14.7 80/20 2 1 .90+2.42x,+ 1 .0Ix2+3.27x2 2-1 .37 X,X2

0.92 65/35 24.44+2.48x,+2.82x,2 0.84

TYAGI el al.: POLYESTER-COTTON MVS YARNS: PART I 423

Table 6-Response surface equations for fibre types (cotton tracer fibre) of MVS yarns

Response Yarn l inear Blend ratio Response surface equation Squared multiple density, tex (Polyesler/cotton) regression coefficient (R2)

Core fibres 1 9 .6 80/20 58.23-2. 1 7xl-0.76x3 0.70 65/35 56.68- 1 .50xl-0.7 1x3+0.85x,2_0.52x3 2 +0.55x,x2 0.89

1 4.7 80/20 54.7 1 - 1 .43x,-0.5 1xrO.85x/ +0.50X,X2 0.85 65/35 52.27- 1 .3 1x,-0.88x3 0.73

Wrapper fibres 1 9.6 80/20 22.07-1 .25x,-0.92xr 3.64x,2 0.87 65/35 2 1 .99-0.85xl-0.66xr 3.48x, 2 +0.68X2

2 0.89 14.7 80/20 22.86- 1 .02x,-0.73x 2 -3.33xI 2 -0.66x/+0.77xlX2 0.9 1

65/35 22.52- 1 .28x, -2.46x,2 0.80 Wild fibres 19.6 80/20 1 9.82+3.42x,+ 1 .5 1x2+3.39x,2 0.8 1

65/35 2 1 .22+2.35x,+0.65x2 +0.50X3+2.64xI2_0.72xlX2 0.94 1 4.7 80/20 22.62+2.46x,+0.96x2+ 3.56x,2 +0. 8 I x2

2- 1 .27\x,X2 0.94 65/35 24.98+2.60x,+2.86xI

2 0.85

3.2 Structural Classes

3.2.1 Class-I

The variation in class-I structure with different processing variables has been shown in Table 7 and by response surface equations in Table 4. It can be observed that the proportion of class-I is significantly influenced by all the three variables used in the experiment. It is clearly observed from Fig. 3 (a) and from the response surface equations (Table 4) that for 1 9.6 tex 80/20 PIC yarns, class-I structure in general first increases and then decreases with the increase in jet pressure. Response surface equations (Table 4) show similar trend for 65/35 blend. For 1 4.7 tex yarn, Fig. 3(a) shows a decrease with the increase in jet pressure. The decrease in class-I structure for 1 4.7 tex yarn is from 8. 1 % to 24.5% with the increase in jet pressure from 4 kg/cm2 to 6 kg/cm2. With the increase in twisting jet pressure, the wrapper fibres whirl around the core with a greater force, resulting in an increase in tight wrappings (class-I) while the unwrapped portions decrease. But at very high jet pressure (6.0kg/cm2) in case of 1 9.6 tex yarns, due to the air turbulence, the tight regular wrappings change significantly into irregular ones. In case of 1 4.7 tex yarns, the optimum pressure is achieved just at 4.0 kg/cm2 and hence any further increase in this pressure reduces the class-I structure. The delivery speed has more or less a negative effect on the formation of class-I structure, which decreases from 3 .2% to 1 8 . 1 % as delivery speed increases from 250m/min to 290m/min. It may be accounted to the fact that the open end fibres tend to wrap the main strand of fibres more unevenly at higher delivery speed, resulting in the change of tight regular wrappings into irregular ones. Moreover, some sections of the yarn escape to

be bound by the wrapper fibres at higher delivery speed, causing the increase in unwrapped sections. Further, there is interaction between pressure and delivery speed in case of 80/20 blends of both fine and coarse yarns (Fig. 3 a), in the sense that the decrease in class-I structure with the increase in delivery speed is not so much at higher jet pressure as is there at lower jet pressure. Increasing the nozzle distance from 20mm to 22mm decreases the class-J structure by 2. 1 - 10.5%.

3.2.2 Class-ll

It can be observed from Table 7 and response surface equations in Table 4 that all the three parameters have significant effect on the proportion of class-II structure with the nozzle distance having maximum effect followed by pressure and delivery speed, except for 1 9 .6 tex (80/20 PIC) yarn where the effect of delivery speed is not significant. It is evident from these tables that the proportion of class-II structures increases with the increase in nozzle distance initially followed by a little drop in these long wrappings at maximum nozzle distance. There is an increase of about 1 .5-8.2% in class-II structures with the increase in nozzle distance from 20mm to 22mm. The long wrappings decrease with the increase in jet pressure and delivery speed. With the increase in jet pressure, the wrapper fibres whirl around the core with a greater force, resulting in the formation of tight wrappings and hence the reduction in the proportion of long wrappings.

3.2.3 Class-Ill

It can be observed from Table 7 and response surface equations in Table 4 that the proportion of class-III structure is significantly influenced by the

424

'$. 1!' " ;:; � '" '" .. U .... 0 c "€ 0 Q. 0 ct

= '" '" .. u .... o c .g <; Q. o ct

'" '" .. u .... o c .g <; Q. o ct

INDIAN 1. FIBRE TEXT. RES., DECEMBER 2004

� 1

�g 21

(b)

(c)

(d)

Fig. 3-Variation in proportion of structural classes of 80/20 PIC MVS yarns with twisting jet pressure, deli very speed and nozzle distance [(a) class-I, (b) class-II, (c) class-III, and (d) class-IV]

TYAGI et at.: POLYESTER-COTTON MVS YARNS: PART I

(b)

. (c) Fig. 4-Variation in proportion of polyester fibre i n 80/20 PIC MVS yams with twisting jet pressure, delivery speed and nozzle distance

[(a) core fibre, (b) wrapper fibre, and (c) wild fibre)

425

426 INDIAN J. FIBRE TEXT. RES., DECEMBER 2004

Table 7-Proponion of different structural classes of MVS yarns

Combi- Class-I Class-II Class-III Class-IV nation 1 9.6 tex 1 4.7 tex 1 9.6 tex 1 4 .7 tex 1 9.6 tex 1 4.7 tex 1 9.6 tex 1 4.7 tex

No. SO/20' 65/35' SO/20' 65/35' SO/20' 65/35' SOI20'

1 25.3 2 1 .6 27.3 23.7 56.6 5 5 . S 50.7

2 20. 1 1 7 .3 22.S 1 7.9 55 .3 53.5 46.9

3 23.2 20.9 25.9 22.4 55 .6 54.0 4S. 1

4 22.0 I S.0 23.S I S. 8 53.9 53.2 47.3

5 25.6 22.0 26.0 2 3 . 5 50.9 50.4 47.4

6 22. 1 1 9 . 2 2 1 .2 20. 1 4S.7 47.6 45.3

7 23.3 20.5 24.8 2 1 . 8 5 3 .9 52.5 48. 1

8 20.6 1 8 .7 20.5 1 8.9 52.7 50.4 47.3

9 30. 1 23.7 25.7 23 .2 50.0 50.6 47.4

1 0 26.7 22.2 24. 1 22.0 5 1 .6 4S.9 45.5

1 1 29.2 23.0 24.9 22.7 52.6 52.3 49.0

1 2 23.9 20.8 22.5 20.9 54.2 5 1 .0 47.8

1 3 28.3 24. 1 24.9 22.9 56.0 5 5 . 2 50. 1

1 4 26.9 22.3 23.5 2 1 . 1 53.9 53.0 49.6

15 27.S 22.7 24.3 22.4 54.7 56.0 48.5

, Blend ratio (Polyester/cotlon)

process parameters with jet pressure having maximum effect followed by delivery speed and nozzle distance. Both the jet pressure and delivery speed have positive contribution to the formation of class-III structures. The class-III structures increase by about 2 1 .5-7 1 . 1 % with the increase in jet pressure as more and more proportion of the unwrapped sections gets converted into one of the three types of wrapped structures. But at very high jet pressure (Fig. 3c), there is steep rise in the class -III structure as the air turbulence converts the regular structure into irregular ones. Increased delivery speed also increases the class-Ill structures by about 4.4-20.6% as regular wrappings get converted into irregular ones at higher delivery speed. Further, there is interaction between pressure and delivery speed (Fig. 3c), in the sense that there is increase in class-£II structure with the increase in delivery speed at low jet pressure, but at higher jet pressure there is no change or little reduction as delivery speed increases from 250 m/min to 290 mlmin .

3.2.4 Class-IV

It evident from Tables 4 and 7 that all the three parameters are having �ignificant effect on the proportion of class-IV structure. In general, the proportion of unwrapped sections (Class-IV) first decreases with the increase in jet pressure and nozzle distance but then levels off or increases slightly. However, it increases continuously by 1 .9-35 .2% with the increase in delivery speed.

65/35' SO/20' 65/35'

52.4 1 2. 1 1 5 .5

4S.9 20.7 25.0

50.2 1 4.4 1 7.4

49.5 1 9.6 26. 1

49.4 1 6.0 20.4

47.7 24.0 2S.7

50.5 1 6.5 2 1 .2

49.6 2 1 .9 27.3

49.5 1 4.6 1 7.9

47.4 1 6.5 20.2

50.8 1 5 .0 1 9. 2

49.7 I S . I 22. 1

52.3 1 2.7 1 7. 5

5 1 .5 1 4.7 1 9 . 1

50.2 1 3. S 1 7.3

3.3 Fibre Type

3.3.1 Core Fibres

SO/20'

1 6.S

26.S

20.0

24.3

1 9.7

28.5

22.7

27.9

22.0

25 . 1

22.3

25.6

2 1 .3

23.0

23.2

65/35' SO/20' 65/35" SOI20' 65/35'

1 9 . 1 6.0 7 . 1 5.2 4.8

29.6 3.9 4.2 3.5 3.6

2 1 .7 6.S 7.7 6.0 5.7

26.8 4.5 2.7 4.6 4.9

20.9 7.5 7.2 6.9 6.2

27.4 5.2 4.5 5.0 4.8

22.2 6.3 5.8 4.4 5 . 5

27. 1 4 .8 3 .6 4.3 4.4

22. 1 5 . 3 7 . 8 4.9 5.2

25.0 5 . 2 S.7 5.3 5.6

22.5 3.2 5 . 5 3 . 8 4.0

2 5 . 1 3 . 8 6. 1 4. 1 4.3

2 1 .3 3.0 3 .2 3.7 3 . 5

23.4 4.5 5 .6 3.9 4.0

22 .5 3.7 4.0 4.0 4.9

The effect of various process parameters on the proportion of fibre types is shown in Tables 8 and 9 and by response surface equations in Tables 5 and 6. It is evident that both the polyester and cotton tracer fibres follow more or less the same trend. Hence, in Fig. 4, only the proportion of polyester fibre types has been shown. It can be observed from the tables and Fig . 4(a) that the pressure and nozzle distance have significant effect on the proportion of core fibres while the delivery speed, though does not have direct effect, affects through interaction with jet pressure. With the increase in jet pressure and nozzle distance, more and more wrapper fibres are generated causing the reduction of the order of 3 .5 - 1 2. 1 % and 0 .7-4.6% respectively in the proportion of core fibres. Further, the finer yarns are having less proportion of core fibres than the coarser ones.

3.3.2 Wrapper Fibres

It is evident from Tables 8 and 9 and response surface equations in Tables 5 and 6 that the pressure and delivery speed have significant effect on the proportion of wrapper fibres with pressure having maximum influence. From Fig. 4(b), it is observed that the wrapper fibres increase initially and decrease thereafter with the increase in jet pressure. The increased delivery speed causes one end of the some of the wrapper fibres to escape to be caught inside the main strand, thus reducing the proportion of wrapper

TYAGI et al.: POLYESTER-COTION MVS YARNS: PART I 427

Table 8-Proponion of polyester tracer fibres in MVS yarns

Combination Core fibre No. 19.6tex 1 4.7 tex

2

3

4

5

6

7

8

9

1 0

1 1

1 2

1 3

1 4

1 5

80/20" 65/35a 80/20a 65/35a

59. 1

54.5

58.2

56.3

58.5

55.3

57.2

54.7

56.5

56.9

54.7

54.2

57. 1

55.2

56.7

56.8

52.5

56.0

54. 1

56.3

53.3

55.4

52.9

54.7

54.5

52.6

52.3

55. 1

54.4

53.5

54.4

50.2

52.9

50.5

52.8

50.6

52.5

49.8

5 1 .9

52.4

5 1 .2

50.0

53.0

5 1 .6

52.7

5 1 .9

48.7

50.7

48.5

5 1 .5

48.9

49.7

47.4

49.9

5 1 .7

48.3

49.5

5 1 .5

50.7

49.4 a Blend ratio (Polyester/cotton)

Wrapper fibre 1 9.6 lex 1 4.7 tex

80/20a 65/35a 80/20" 65/35"

23.3

1 9 .2

2 1 .8

1 8 .7

2 1 .7

20.0

22.4

20.8

26.3

24.0

26.8

22.3

24.5

25.4

23.6

23.5

20.4

2 1 .5

1 9 .3

2 1 .2

20.4

2 1 . 1

20.2

25.2

23.7

26. 1

25.0

23.2

25.6

23.8

26.0

2 1 . 1

22.4

2 1 .2

23.9

22.8

24. 1

23.4

26.6

25. 1

27.2

26.0

26.3

27.2

25.5

25.6

2 1 .4

24.2

20.8

23.4

22.3

23.9

23.0

25.5

24.3

26. 1

25.5

25.6

24.9

26.0

Wild fibre 1 9.6 tex 1 4.7 tex

80/20" 65/35" 80/20" 65/35"

1 7 .6

26.3

20.0

25.0

1 9.8

24.7

20.4

24.5

1 7 .2

19 . 1

1 8 .5

23.5

1 8.4

1 9.4

1 9.7

1 9.7

27. 1

22.5

26.6

22.5

26.3

23.5

26.9

20. 1

2 1 .8

2 1 .3

22.7

2 1 .7

20.0

22.7

1 9.6

28.7

24.7

28.3

23.3

26.6

23.4

26.8

2 1 .5

22.5

2 1 .6

24.0

20.7

2 1 .2

2 1 .8

22.5

29.9

25. 1

30.7

25 . 1

28.8

26.4

29.6

24.6

24.0

25.6

25.0

22.9

24.4

24.6

Table 9-Proportion of cotton tracer fibres in MVS yarns

Combination Core fibre Wrapper fibre Wild fibre No. 1 9.6 tex 1 4.7 tex 1 9.6 tex 1 4.7 tex 1 9.6 lex 1 4.7 tex

80/20" 65/35a 80/20' 65/35" SO/20a 65/35" SO/20a 65/35" 80/20a 65/35" S0/20" 65/35"

2

3

4

5

6

7

S

9

1 0

1 1

1 2

1 3

14

15

6 1 .3

57. 1

60.5

53.2

60.8

57.4

59.5

57.0

58.6

59. 1

56.9

56.4

57.3

59.5

5S.9

59.4

55. 1

5S.7

56.6

58.9

56.0

5S. 1

55.4

57.3

57.0

55.2

54.S

57.6

57.0

55.8 "Blend ratio (Polyester/cotton)

57.0

52.7

55.4

53. 1

55.3

53.0

54.9

52.3

54.4

55.0

53.8

52.6

55.7

54.2

55.3

54.3

5 1 .0

53.2

50.9

54.0

5 1 .3

52. 1

49.9

52.3

54. 1

50.7

5 1 .9

53.S

5 1 .6

53.0

20.5

1 6.S

1 9.4

1 6.3

19 . 1

17 .4

19 .7

I S .2

23.0

2 1 .3

23.7

19.6

2 1 . 1

22.3

23.5

fibres by about 1 . 1 -20.3%. Moreover, the yarns with higher proportion of polyester fibres have more wrapper fibres.

3.3.3 Wild Fibres

It is clear from Tables 8 and 9 and response surface equations in Tables 5 and 6 that all the three parameters have positive effect on the proportion of wild fibres, though the nozzle distance is having

2 1 .4

1 8 .3

1 9.5

1 7 . 1

1 9.0

1 8.4

1 8 .9

1 8 .2

23.0

2 1 .6

23.7

22.9

20.S

2 1 .5

23.2

2 1 .8

1 7 .2

1 8.5

17 .0

20. 1

1 8 .7

20.5

1 9.5

22.7

2 1 .5

23.4

22.2

22.5

23.3

2 1 .8

22.4

18 . 1

2 1 .3

1 7 .5

20.6

1 9.3

2 1 . 1

20.2

22.5

2 1 .4

23.0

22.7

22.0

22.8

23.3

1 8 .2

26. 1

20. 1

30.5

20. 1

25.2

20.S

24.S

I S .4

1 9.6

1 9.4

24.0

2 1 .6

I S .2

17 .6

1 9.2

26.6

2 1 .8

26.3

22. 1

25.6

23.0

26.4

1 9.7

2 1 .4

2 1 . 1

22.3

2 1 .6

2 1 .5

2 1 .0

2 1 .2

30. 1

26. 1

29.9

24.6

28.3

24.6

27.9

22.9

23.5

22.8

25.2

2 1 .8

22.5

22.9

23.3

30.9

25.5

3 1 .6

25.4

29.4

26.8

29.9

25.2

24.5

26.3

25.4

24.2

25.6

23.7

significant effect only in the cases of 1 9.6 tex 80120 polyester tracer fibre and 1 9.6 tex 65/35 cotton tracer fibre. The proportion of wild fibres increases by 1 1 .5-5 1 .0% with the increase in jet pressure as more and more fibres are detached from the main strand forming the wrappings; if one end of the some of these fibres fails to be tucked inside the main strand, the wild fibres are formed. But, at very high jet pressure (Fig. 4c), more and more wrapper fibres

428 INDIAN J. FIBRE TEXT. RES., DECEMBER 2004

change into wild fibres, thus increasing their proportion significantly. The increased delivery speed also enhances their proportion by 0.6-24.0% as more and more wrapper fibres get converted into wild fibres at higher delivery speed. Nozzle distance has significant effect on the reduction of core fibres, but its effect is not significant either on wrapper fibres or wild fibres, except in the cases of 1 9 .6 tex 80120 polyester tracer fibre and 1 9.6 tex 65/35 cotton tracer fibre, though the reduced core fibres should be converted into one of these two. This may be due to the fact that the reduced core fibres get partly converted to wrapper fibres and partly to wild fibres. Hence, there is no significant effect of nozzle distance on the proportion of wrapper or wild fibres.

4 Conclusions 4.1 MVS yarns consist of about 50-60% of core

fibres and the rest as wrapper/wild fibres. The proportion of three types of fibres is dependent upon the process parameters. The wrapper and wild fibres increase with the increase in jet pressure but at very high jet pressure (6.0 kg/cm2), the wild fibres increase significantly. The wild fibres further increase at higher delivery speed. The finer MVS yarns have less proportion of core fibres than the coarser ones. The yarns with higher proportion of polyester fibres have more wrapper fibres.

4.2 Tight regular wrappings (class-I) increase initially and decrease thereafter in case of 1 9.6 tex yarns while decrease continuously in case of 1 4.7 tex yarns as the jet pressure increases from 4.0 kg/cm2 to 6.0 kg/cm2. The tight regular wrappings convert into irregular ones significantly at very high jet pressure. Class-I structures further reduce with delivery speed and nozzle distance.

4.3 The long regular wrappings improve with the nozzle distance but drop slightly at very high nozzle distance. These further reduce with increasing jet pressure and delivery speed.

4.4 The unwrapped sections decrease with increasing jet pressure and nozzle distance but increase slightly with the increase in delivery speed.

References 1 Grosberg P, Oxenham W & Mia M, J Text Insl. 78 ( l 987) 1 89.

2 Chasmawala R, Hansen S M & Jayaraman S, Text Res J, 60 ( 1 990) 6 1 .

3 Lawrence C A & Baqui M A, Text Res J, 6 1 ( 199 1 } 1 23.

4 Raj amanickam R, Hansen S M & Jayaraman S , J Text IIlS1, 89 ( l 998) 2 14.

5 Rozelle W N, Text World, 1 49 ( 1 999) 73.

6 Artzt p, Mellialld Text, 8 1 (2000) E 1 16.

7 Stalder H, lilt Text Bull, 49 (2003) 35.

8 Operating Mallllal of M VS No.BIO (Murata Machinery Ltd.), 2000, 0-28.

9 Box G E P & Behnken D W, Technometrics, 2 ( I 960} 455.