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CHAPTER 3

MATERIALS AND METHODS

3.1 INTRODUCTION

This Chapter is concerned with material and methods used in the

study. For assessment of different yarn and fabric characteristics, mostly

standard methods were used.

3.2 MATERIALS

Microfibres of viscose, modal, lyocell, and blends of these fibres

with cotton were used. Details of fibre properties are given in Table 3.1.

Table 3.1 Details of materials used

Type of fiber Fibre fineness (dtex)

Length (mm)

Tenacity (cN/tex) Elongation (%)

Micromodal 1.0 34 33 15 Normal modal 1.3 34 35 13 Microlyocell 0.9 34 35 14 Micro viscose 0.9 38 22 21 Normal viscose 1.3 38 25 20 Micro polyester 0.9 38 54 19 Normal polyester 1.3 38 61 14 Cotton 3.9 29 22 7 Micro polyester filament 83/136 - 40 32 Normal nylon filament 85/68 - 38 40 Lycra filament 83/34 - 10 600

3.3 METHODS

Microfibres were processed in semi-high production and high-

production cards for optimization of process parameters, and yarn samples

were produced in ring, compact and rotor spinning systems to study the

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structural and mechanical properties. Knitted fabric samples were made from

the yarns to evaluate physical, mechanical and comfort properties. The

experiments were designed to study the effect of carding variables on the

sliver quality and yarn characteristics produced from various spinning

technologies.

3.4 EXPERIMENTAL PLAN

Figure 3.1 shows the experimental plan for production of yarns.

Figure 3.1 Experimental plan

# - 20Ne(29.52 tex) micromodal yarn was produced from ring spinning (35TpcmTex0.5/112αm) and rotor spinning (35TpcmTex0.5 /112αm & 39 TpcmTex0.5 /124αm )for studying yarn structure namely fibre migration and mechanical properties. ^ - 50Ne(11.81 tex) micromodal and microlyocell yarn samples from ring and compact spinning were produced at 3 different twist levels (32, 35, 39 TpcmTex0.5 / 100,110,125αm) for studying handle and mechanical properties. A total of 120 cops of yarn samples were produced for ring and compact systems of spinning (10 cops/twist level/fibre/system) for the study. *- Weft knitted single jersey fabrics were produced from 30Ne(19.68 tex) micro modal/PET yarns and 25Ne (23.62 tex) viscose yarn, dyed and tested for fabric properties.

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Figure 3.2 Process flow chart of ring and compact spinning for

microfibre

Tables 3.2 - 3.10 give details of the machines, process parameters

for carding, spinning and knitting used for the study.

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Table 3.2 Details of spinning machines used

Process Machines

Blow room

Mixing bale opener

Scutcher with krischner beater

Carding

Drawframe

Speedframe

Ring frame

Compact spinning

Trumac

Trumac

Trumac

Lakshmi Rieter C-1/3

Rieter-RSB851

Lakshmi LF1440

Lakshmi Rieter G5/1

Suessen EliTe

Table 3.3 Details of Carding process parameters

Parameter SHP HP

Lap hank (Ne) 0.0017 0.0020

Card sliver hank (Ne) 0.155,0.170,0.185 0.18 , 0.20 , 0.22

Licker- in speed (rpm) 550 940

Cylinder speed (rpm) 260 360

Doffer speed (mpm) 12.8,16,19.2 120,140,160

Flat speed (mm/min) 50.8,101.6,152.4 254,304.8,355.6

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Table 3.4 Details of Cardwire details

Cylinder wire ECC* Height- 2.0mm Rib- 0.65 Angle – 63 deg 760 PPSI

Doffer wire ICC* Height- 4.0mm Rib- 0.80 Angle - 55 deg 322 PPSI

Tops ICC Height- 8.0mm Angle - 75 deg 348 PPSI

Licker - in ICC Height- 5.5 mm Angle - 80 deg 5 TPI

* ECC – English Card Clothing, ICC – Indian Card Clothing

Table 3.5 Details of process variable and its code

Run Code

Doffer Speed (m/min)

X1

Delivery hank Ne (ktex)

X2

Flat Speed (mm/min)

X3

SHP HP SHP HP SHP HP

1 19.2 120 0.155(3.8) 0.18(3.28) 152.4 254

0 16 140 0.17(3.47) 0.20(2.95) 101.6 304.8

-1 12.8 160 0.185(3.19) 0.22(2.68) 50.8 355.6

Table 3.6 Details of Spinning process parameter (Micromodal)

Ring spinning Count 20 Ne/29.5 tex

Rotor spinning Count 20Ne/29.5 tex

Machine Make : Trytex

Ring yarn twist factor : 3.7αe /112αm Spindle speed (rpm) : 13,500/16000 Break draft : 1.3 Traveller : 6/0

Machine Make :BD-SD ELITEX

Rotor-ET yarn twist factor :3.7αe /112αm Rotor-HT yarn twist factor : 4.1αe /124αm

Rotor dia.(mm) : 42 Rotor speed (rpm) : 71,580

Opening roller speed (rpm) : 8100

Rotor-ET = Rotor- Equal Twist Rotor-HT = Rotor-High Twist

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Table 3.7 Details of spinning process parameters

Process Particulars

Ring and Compact 50Ne(11.8tex)

Ring and Compact

50Ne (11.8tex) Ring 25Ne (23.6tex)

Ring 25Ne (23.6tex)

Ring 30Ne (19.68 tex)

Type of fibre Micromodal Microlyocell Micro/regular

polyester Micro/regular

viscose Micromodal

Machine make LR G5/1(Ring)

SuessenELiTe(Compact)

LR G5/1(Ring)

SuessenELiTe(Compact

LR G5/1(Ring)

LR G5/1(Ring)

LR G5/1

TpcmTex0.5 / αm

32, 35, 39 / 100,110,125 32, 35, 39 / 100,110,125

30/94 30/94 30/94

Spindle speed 18000 18000 15000 15000 16000

Traveller 6/0 6/0 5/0 5/0 5/0

Table 3.8 Details of knitting machine used

Type of Fabric Single Jersey

Machine Name BMW

Machine Speed 28 rpm Gauge 24 Cylinder Diameter 14 No. of Feeders 18 Total no. of feeders 108 0 Needle type Groz-Beckert

Table 3.9 Socks knitting machine details

Name of Machine Lonati socks knitting machine

(Double Cylinder)

Gauge 14

Number of needles 168

Number of feeders 8

Speed (rpm) 180

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Table 3.10 Details of arrangement of yarns in feeders

Feeders Socks-A Socks-B

F1 Lycra Lycra

F2 E E

F3 E E

F4 Cotton/Nylon MicroModal/MicroPET(F)

F5 E E

F6 Nylon MicroPET(F)

F8 Cotton Micromodal

3.5 TESTING OF FIBRES, YARN AND FABRICS

3.5.1 Testing of Single Fibres

The following properties of fibres were studied:

1. Fibre fineness

2. Fibre strength

3. Fibre elongation

Fiber denier and single fiber tenacity and elongation were evaluated

using an instrument developed by Lenzing based on Bureau International pour

la Standardization Fibres Artificielles, (BISFA) 1998 and ASTM D-3822-01

standards. Sample size was 50 grams and twenty readings were taken.

3.5.2 Testing of Card Sliver

The following properties were evaluated for card sliver.

1. Effective length (Baer sorter)

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2. Mean length(Baer sorter)

3. Short fibre content(Baer sorter)

4. Neps(Manual neps/gram)

5. Strength (Stelometer)

6. Elongation(Stelometer)

7. Evenness (Uster)

8. Cutting/combing ratio

9. Orientation index

10. Sliver cohesion(Instron)

(AFIS used for correlation of values from baer sorter in SHP

cards only).

For evaluating the output sliver quality parameters such as effective

length, mean length, short fibre content both AFIS and bear sorter method

were used for SHP cards.

3.5.3 Manual Testing

For estimation of the mean length and short fibre content, baer

sorter was used. In this method of length measurement, we can evaluate

different length groups of fibres both visually and numerically. The basic

procedure used in comb sorters is implemented to construct the comb sorter

diagrams from which the fibre length parameters are estimated.

Advanced Fibre Information System (AFIS) is based on

aeromechanical fibre processing followed by electro optical sensing and then

by high speed micro processor based computing and data reporting. The fibres

penetrate a collimated beam of light and scatter and block the light in

proportion to their optical diameter and direct relation to their time of flight

through the sampling volume. From the wave forms which are micro seconds

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in deviation, the pertinent data are acquired, analyzed and stored in the host

computer for interpretation.

The AFIS Nep classification module counts and sizes seed coat

neps. The Classification module is able to identify the distinct electrical wave

forms produced by fibres, fibre clumps and seed coat neps etc. It uses digital

signal processor to classify all incoming wave forms and calculate nep size.

Table 3.11 gives details of card sliver tests.

Table 3.11 Details of tests conducted for card sliver

Parameters Measured

Instrument Sample Size No. of test done

Mean length (mm) Short fibre content %, Neps per gram.

Uster AFIS Multidata Module(Only for SHP cards)

0.450 g per Sample

4 readings per sample

Mean length (mm) Short fibre content in %.

Baer sorter 2 samples of 15mg each

Average of values from 2 patterns per sample

Neps per gram. Manual Counting 5 samples of 1 g each

Average of values from 5 counting’s

Strength and elongation

Stelometer 15 5 readings/sample

Evenness Uster tester-4 15 10 readings/sample

Fibre orientation in sliver

Lindsley’s method 2 2 readings/sample

Sliver cohesion Instron ASTM D 2654

15 5 readings/sample

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3.5.4 Fibre Configuration in Card Sliver

The term “fibre arrangement “ is applied to a combination of

factors such as the parallelization of the fibre along the sliver axis, the degree

of fibre straightness and the presence of curved or hooked fibre. In the present

study an apparatus was designed on the principle outlined by Lindsley (1951)

and the method utilized to measure fibre orientation consisted of the

following operations: The sliver specimen was given a marking to indicate the

direction in which it was delivered by the machine since this affects the

results. The sliver was then clamped between the three plates A, B and C

which rests on three blocks. The widths of the plates A, B and C being ½”, 1”

and 1/2” respectively. The sliver was cut at the edge C1 with a sharp blade.

The plate C was removed and the sliver was combed well. The combed

portion of the fibres was weighed. The plate C was then replaced to reclamp

the combed sliver fringe. The fiber portion extending beyond the edge C1 was

cut and weighed. The plate C was removed and the remaining trapped

material was cut at C2 and weighed on an accurate balance. The same

procedure was repeated for the reverse direction also. The subscripts ‘f’ and

‘r’ denote the forward and reverse direction of combing respectively. The

following notations were used for the measurement of orientation in this study:

C = weight of combed out fibres

E = weight of fibre ends projecting over the line of cut after

combing, and

N = Weight of sliver portion clamped under the cutting plate

after combing.

Lindsley (1951) used two coefficients viz. the “combing ratio”

which is equal to C/E+N and the “orientation index” which is equal to

(1-E/N) × 100 for evaluation of the results.

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3.6 TESTING OF YARNS

The following properties of yarn were studied.

1) Yarn tenacity

2) Yarn elongation

3) Imperfections

4) Hairiness

5) Yarn structure (fibre migration)

6) Yarn abrasion

7) Yarn friction

8) Yarn compression

9) Yarn bending

10) Yarn wicking

11) Yarn surface (SEM)

The yarns were tested for tenacity, elongation, evenness,

imperfections and hairiness using Uster Tensorapid and Uster Evenness

Tester (UT-4). Yarn hairiness was measured using Zweigle hairiness tester.

Here the S3 value (index) was used for the analysis. The packing density was

calculated from yarn specific volume using the following formula:

Specific Volume (cm3/g) = 78570 × d2 /Tex (3.1)

where, d is the yarn diameter in cm and Tex is the yarn linear density.

Table 3.12 gives with the various testing methods employed to

study the properties of yarn.

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Table 3.12 Details of yarn characteristic tests

S. No.

Yarn Characteristic test

used Instrument used

Test method/Procedure

Sample size

Numberof test done

1 Yarn evenness, imperfection and hairiness index-H(cm/cm)

Uster UT-4 ASTM-D-1425-96 10cops 10

2 Single thread tenacity and breaking elongation

Uster tensorapid ASTM D 2256 Uster standard method-CRE-5m/min

10 cops 20 test/cop 200 readings

3 Hairiness Frequency and index(Zweigle)

Zweigle G566 ASTM-D-5647-01 10 cops 10

4 Fibre migration study

SUMKA-Microscope with CCD camera

Tracer fibre technique

10 tracer fibres

30-45 readings/tracer fibre

5 Yarn diameter & overall density

Uster-UT4-OM module

Uster standard method

5 cops 1 test/cop

Total 5 cops

6 Yarn packing coefficient

Projectina microscope

Inhouse test 10 cops 10 test/cop 100 readings

7 Yarn wicking test In house arrangement

In house test 2 cops 6 readings/cop

8 Yarn friction test Lawson-Hemphill constant tension transport-dynamic tension tester

10 cops 10

9 Yarn abrasion test SITRA-MAG yarn abrasion tester.

10 cops 10

10 Yarn compression test

KES-F compression module

12 cops 5 test/cop

11 Yarn bending Loop method 12

12 Yarn surface characteristics

Scanning Electron Microscope

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3.6.1 Tenacity

All tensile measurements namely tenacity, elongation were

measured using Uster Tensojet. 20 readings/cop/sample totalling 200 readings

from 10 cops were taken per sample. All tests were done according to ASTM

D 2256.

3.6.2 Evenness Tests

The yarn evenness measurements were carried out on the Uster

evenness Tester (UT-4). This is based on the capacitance principle. The

measurements were carried out under standard atmospheric conditions, i.e., a

relative humidity of 65 2% and a temperature of 25oC 2oC. The samples

were left overnight in this environment to be fully conditioned. They were

also measured for imperfections at standard and high sensitivity levels. The

diameter and packing density of the yarns were also evaluated. Yarn hairiness

index given by the instrument was also recorded. 10 readings/samples were

taken for assessment. All the tests were done according to ASTM-D-1425-96.

3.6.3 Yarn Hairiness Test

The yarn hairiness was measured using Zweigle yarn hairiness

tester (Zweigle G565 hairiness tester instrument manual). The hairiness of a

yarn characterizes the number of projecting and freely moving fiber ends or

fiber loops. The number of projecting fibres per length unit is assessed. The

measurement technique used by this instrument is based on the photoelectric

principle. The projecting fibres interrupt a light beam and bring about an

alteration in the light density. Photo- transistors register these light density

levels at varying distances and supply test data accordingly. In order to count

the number of hairs over several length zones at the same time, the yarn is

scanned by twelve photo-transistors. Here, the length of fibre protruding from

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one side of the yarn is recorded as shown in the figure. The hairs of length 3

mm and above were measured in the research work. A length of 100

m/sample was carried out for assessing the hairiness of yarns. All the tests

were done according to ASTM-D-5647-01.

3.6.4 Yarn to Metal Friction

The constant tension transport-dynamic tension tester (CTT-DTT)

was used to measure the yarn to metal friction. In this instrument,

manufactured by Lawson-Hemphill (Lawson-Hemphill constant tension

transport-dynamic tension tester (CTT-DTT), instrument manual) the

co-efficient of friction is measured by passing the yarn specimen through two

metal pins in the yarn path as shown in figure.

Then, the co-efficient of friction is calculated using the formula

µ = ln (To/T1) (3.2) 4p (n-0.5) sin β/2

where µ = Co-efficient of friction ln = Natural log

To = Output Tension T1= Input Tension

β = lower apex angle between two yarns n =number of wraps.

Ten tests were carried out for assessing the friction co-efficient of

yarns. The total test length of yarn for the 10 tests is 1000m.

3.6.5 Flexural Rigidity

Flexural rigidity was determined by the loop test based on

Carlene’s (1950) method. The mean of five tests was taken. In this method,

the yarn is made in the form of a loop, and it is distorted by adding a rider.

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Flexural rigidity is calculated from the following formula,

Flexural rigidity (g.cm2) = kWL2 cos θ / tan θ (3.3)

where k is a constant the value of which is around 0.0047

W = applied load in grams

L = circumferential length of in distorted ring in cm

θ = 493d/L

d = deflection of lower end of the ring under action of

applied load.

For greater sensitivity, a value of W is chosen such that θ lies

between 40º and 50º. When W is in grams, L and d are in cm, the filament

rigidity is derived in units of g.cm2 and has the dimensions ML3T-2.

Figure 3.3 Flexural rigidity by ring loop method

Yarn loops of 1.6cm diameter were prepared with the help of a

circular glass tube of known diameter and by putting the reef knot for joining

both ends of yarn. The tube of mounted horizontally on a stand and a stripe of

black paper was introduced into the tube so as to provide an opaque

background for better visibility of loop. The glass tube surface was covered

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with then cellophane sheet wrapped around the glass tube to allow convenient

withdrawal of the loops. This way the circular loops were obtained. A special

care was taken to keep the same tension while putting the reef knot for

preparing the yarn loops. For avoiding the effects of bulk it was desired to

keep the knot at 45o with the vertical in each test. 30 readings were taken for

each sample and the mean was considered. The specific flexural rigidity was

calculated using the formula given below.

Specific flexural rigidity = (couple/curvature)/Lineardensity2 mN, mm2/ Tex

3.6.6 Yarn Compression Properties

Yarn compression property was measured using Kawabata tester.

For compression tests a single yarn was placed on the bottom of the plate of

the instrument and a plunger of 2 cm2 were used to compress the sample at a

constant rate. The following parameter which represents compression

properties, namely LC, WC, RC and EMC % were obtained.

Standard procedures were followed as per the instructions given on

manuals. Parameters of compression are given in Table 3.13.

Table 3.13 Parameters of compression

Parameters Description Unit

Lateral compression

LC - Linearity of compression thickness curve

WC - Compressional energy RC - Compressional resilience

- J/m2 %

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3.6.7 Standardisation of Number of Test for Sample

The number of test to get minimum CV in the estimate of

compression of a single yarn was conducting 5, 10, 15, 20, 25, 30 tests each

time. Table 3.14 shows the levels of CV for different number of test.

Table 3.14 Varying number of tests for compressional energy of yarns

Sl.No Number of tests (N) Coefficient of variation (CV%)

1 5 4.2 2 10 3.68 3 15 3.64 4 20 3.6 5 25 3.4 6 30 3.1

It is clear from the above that coefficient of variation more or less

stabilizes at N = 10 and after wards the improvement in CV is relatively less

with higher number of readings.

Hence 15 tests per sample were carried out for assessing the

compression of yarns.

3.6.8 Fibre Migration

3.6.8.1 Migration studies on microfibre yarns

Towards characterizing the structure of microfibre yarns from ring

and rotor spinning systems, a fibre migration study has been carried out using

tracer fibre technique and microscope with the CCD camera. The

characterization of tracer fibre has been carried out as per Hearle (1965), Huh

(2002) and Primentas (2001).

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In order to investigate fibre migration, dyed cotton fibres were

blended with undyed fibres. These fibres accounted for 0.5% of weight of

undyed fibres and served as tracer fibres, during the structural analysis of ring

and rotor spun yarns. After opening and carding, the materials were subjected

to two passages of drawing, and then taken to the rotor spinner. A small

proportion i.e. 1.0% by weight of above fibres were green dyed and used as

tracer fibres, which were introduced in the carding stage with the remaining

un-dyed material.. The yarn counts 20 Ne (29.5 tex) were selected for the

study. The tracer fibre incorporated sliver was used in rotor spindles to

produce ring and rotor yarns.

The standard tracer-fibre technique was used for the study .The

yarn thus produced using tracer fibres is immersed in liquid medium (methyl

salicylate) having substantially the same refractive index as that of cotton

fibres concerned. Some times the white fibres may no be dissolved optically.

It is because; the refractive index of white fibres and methyl salicylate is

different hence benzaldehyde was mixed with methyl salicylate to match the

refractive index of white fibres and the solution. The yarn was examined

under a microscope; the un-coloured fibres disappeared from view leaving the

path of each tracer-coloured fibre to be clearly visible. The tracer was seen

against the faint background of yarn body as the wavy line representing the

projection in one plane of helix. The present study was confined to the use of

projection microscope.

3.6.8.2 Configuration of tracer fibre

Parameters such as mean fibre position (Y), RMS deviation (D),

migration intensity (I), equivalent migration frequency defined by Hearle

(1965) and migration factor defined by Huh (2002) were used for

characterising migration behaviour of the tracer fibre under microscope.

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3.6.8.3 Mean fibre position

Represents overall tendency of a fibre to be near the surface (or)

near the Centre of yarn and calculated from

z

0

Y1Y YdZz n

(3.4)

where R = Yarn radius

Z = Length along yarn

n = Number of observation

where 2rY

R

r = helix radius

3.6.8.4 Amplitude of migration

The magnitude of deviations from mean position represented by

Root Mean Square Deviation (D).

3.6.8.5 RMS deviation

½½ 2z

2

0

(Y Y)1D (Y Y) dzz n

(3.5)

3.6.8.6 Rate of migration (migration intensity)

This is rate of change of radial position. For this mean migration

intensity is used:

½ ½2 2z

0

1 dY dYI dzz dZ dZ

(3.6)

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The modified form the above formula is

½2Y1 Y2L1I

n

(3.7)

when L1 was the distance between adjacent indications Y1 and Y2.

3.6.8.7 Equivalent migration frequency

I4D 3

(3.8)

For a ideal migration cycle constructed from calculated value of

I and D.

3.6.8.8 Migration factor

Migration factor is derived as:

MF = RMS deviation × migration intensity (3.9)

3.6.8.9 Measurements

Measurements a, b, c and d were made at successive peak and

trough of a tracer fibre image.

Diameter of yarn in scale units is c-a.

Off set of trough / peak from yarn axis given by

(a c)b2

Distance between adjacent trough / peak is ‘d’.

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In order to avoid effects due to change in yarn diameter radial

position of fibres is given by a ratio.

Figure 3.4 Tracer diagram

a c br 2

a cR2

(3.10)

Plot of r/R against length along yarn shows cylindrical

envelope of varying radius around which fibres is following a

helical path as shown in Figure 3.4.

3.6.9 Packing Fraction

Packing fraction was calculated from the following formula

Packing fraction = Volume of fibre / volume of yarn

= Vf / Vy (3.11)

ff

lV

(where f is the density of fibres)

5 2

y10 dV (cc / g)

4Tex

(3.12)

97

where d2 is the yarn diameter in cm.

Therefore packing fraction =

= 5 2

Tex 410 d

(3.13)

3.6.10 Abrasion Resistance

Yarn abrasion resistance was measured by using SITRA-MAG yarn

abrasion tester. In this, a cylinder, which has an oscillating motion, is covered

with the standard emery paper. The yarn specimens held under constant

tensions by weights are pressed against the cylinder under constant pressure

until they break. At the end of every abrading cycle, the cylinder turns slightly

so as to present a clean abrasive surface. The number of strokes required to

break for each yarn is recorded.

A computerized control unit takes care of the complete working of

the tester, once the yarn samples are mounted. It records the number of cycles

required to rupture the yarn individually, and those records can be used for

future applications.

The comparison between the results obtained on different types of

yarns is simplified by the calculation of a “Relative Resistance Index” (RRI)

as given by the following formula:

Mean Resistance (Cycles) x Pretension (cN/tex) RRI = (3.14) (Total Count (Tex)) 1/2

3.6.11 Yarn Wicking

An in-house test method was used to measure the wicking of water

in to the yarn samples. The water transport rate is determined by a vertical

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strip wicking test in which the time in seconds required for the water to reach

a height of 5 cms is measured at intervals of 1 cm.

3.6.12 Scanning Electron Microscope

The ZEISS EVO 50 is a versatile analytical microscope with a

large specimen chamber. The EVO 50 series can handle large specimens at

the analytical working distance of 8.5 mm owing to a combination of the

inclined detectors and the sharp conical objective lens.

Table 3.15 Specifications of Scanning Electron Microscope

Model ZEISS EVO 50

Resolution 2.0 nm@ 30 kV(SE with LaB6 option)

Acceleration Voltage 0.2 to 30 kV

Magnification 5 x 1,000,000x

Field of View 6 mm at the Analytical Working Distance (AWD)

Image processing Resolution: Upto 3072 x 2304 pixel signal acquisition by integrating and averaging.

Image Display Single flicker-free XVGA monitor with SEM image displayed at 1024 x 768 pixel

Sample Requirements for SEM

General Size: Any dimension (Height or Diameter): Less than

10mm. Conductivity (Electrical): Conducting or atleast semi conducting. If

sample is not electrically conducting, it will require silver or gold coating.

Sample preparation

1. Keep the size of the samples to about 5 to 8 mm.

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2. Samples have to be mounted on a circular metallic sample

holder.

3. The samples have to be fixed on to the sample holder rigidly

by using colloidal silver paste or sticky carbon tape.

4. Samples must be arranged in a circular pattern.

5. Since an electron beam is incident on the sample for SEM

analysis, it is essential that the samples are electrically

conducting. If not, the samples have to be coated with 20 to

50 nm thick gold or silver. The SEM is equipped with

BIO-RAD POLARAN sputter coater for this purpose.

3.7 TESTING OF KNITTED FABRICS

Knitted fabrics produced from normal and microfibres were tested

for the following properties.

1. Geometrical properties

2. Dimensional stability

3. Drape

4. Spirality

5. Abrasion resistance

6. Bursting strength

7. Pilling resistance

8. Fabric friction (Instron tensile tester)

9. Fabric hand (Kawabata hand evaluation system)

10. Wicking (in house tester)

11. Moisture vapour transmission (MVTR)

12. Air permeability

13. Surface characterization (scanning electron microscope)

100

The fabric was tested according to standard test procedures which

are shown in Table 3.16.

Table 3.16 Standards of test methods for fabrics

Sl. No.

Test Instrument Standard Sample

size No. of test done

1. CPI, WPI & Stitch density

Pick counting glass IS: 1963: 1981 2 10 readings/sample

2. Dimensional changes

IS: 1963: 1981 2 10 readings/sample

3. Arial density ISO 3801:1983 2 10 readings/sample

4. Fabric drape Drape meter BS 8357 2 10 readings/sample

5. Fabric thickness Thickness gauge IS 7702:1975 2 10 readings/sample

6. Spirality Spirality tester AATCC : 179: 2004

2 10 readings/sample

7. Bursting strength BS 4768 30 mm

2 10 readings/sample

8. Water drop test AATCC : 79: 2000

2 10 readings/sample

9. Abrasion resistance

Martindale abrasion tester

ASTM 4966: 1998

2 10 readings/sample

10. Pilling resistance MAG Pilling tester ASTM D 4970: 2002

2 10 readings/sample

11 Air permeability SDL Atlas air permeability tester

ASTM D 737 2 10 readings/sample

12 MVTR SDL Atlas MVTR ASTM E 96 2 10 readings/sample

11 Fabric friction

Sliding friction apparatus- Model 5569

_ 2 10 readings/sample

12 Surface charecterization

SEM using Japan Electron Optics Limited

_ 2 _

13 Fabric handle

KES-F-Tensile, Shear, Bending Friction

_ 2 4 readings/sample

on each property tested

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3.7.1 Measurement of Fabric Parameters

Courses/cm and wales/cm were counted with counting glass. By

making 1 cm perpendicular to the wales and pulling out the yarns, the number

of courses can be counted. Ten measurements for each dimension were made

at different places on each side of the tubular fabrics. Mean values of

courses/cm and wales/cm were then calculated.

3.7.2 Loop length

In order to find out actual loop length of the knitted fabrics at both

dry and fully relaxed states, the side knitted first of each sample was levelled

out and a cut of approximately 5 cm was carefully made parallel to wale

direction in this tubular form of the fabrics. Six courses were then unroved

from each sample and measured for their lengths on Shirley crimp tester

under pre-determined tensions i.e., 0.1 g/tex.

The mean value course length was calculated and thereafter divided

by the number of needles yielding the loop length. The actual loop length at

both dry and fully relaxed states and the corresponding measured values of

yarn linear densities were used to calculate the actual tightness factor

according to the following formula.

Tightness factor = √tex / l (3.15)

where l = loop length. 10 readings were recorded for each sample.

3.7.3 Determination of Stitch Density, Kc, Kw, Ks, Kc/ Kw and Course

and Wale Spacing

The value of stitch density (S) was calculated by multiplying the

corresponding mean values of courses and wales/cm which were found out as

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explained earlier. The geometrical parameters of the corresponding knitted

samples at both dry and fully relaxed states were calculated according to the

formulae.

Kc = CPC × l (3.16)

Kw = WPC × l (3.17)

Ks = Kc × Kw (3.18)

The loop shape factor of the knitted fabric i.e. the ratio of courses

per cm by the wales /cm. was calculated.

3.7.4 Fabric Thickness (t)

The fabric thickness parameter (t) was measured on “Essdiel”

thickness gauge using the minimum possible load of 20 gf/cm2 which is

equivalent to a pressure of 1.96 kN/m2 (1.96 KPa). Choice of this pressure

was also governed by Postle’s (1971) paper on compression curves for cotton

single jersey fabrics, which shows that around a pressure of 2KPa flattening

of the protruding fibres as well as buckles in the fabric takes place.

The tubular form of the knitted fabrics was cut along the wale line,

and then spread carefully without strain on the gauge tester and then tested for

its thickness. Ten readings at different places of each sample were taken to

calculate the average value of the respective sample thickness.

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3.7.5 Relaxation Treatment

3.7.5.1 Dry relaxation

All the knitted fabrics were laid free from any constraint on a flat

surface and allowed to condition for at least 72 hours in a standard

atmosphere. The desired fabric parameters were then measured and recorded.

3.7.5.2 Full relaxation

The fabrics were washed and tumble dried for 5 times following the

steps suggested by STARFISH project undertaken by the International

Institute of Cotton (IIC), Manchester, UK. The steps involved are given below:

a) Washing in domestic washing machine at 60◦C.

b) Tumble dry until the fabric is dried.

c) Wet-out in washing machine.

d) Repeat steps b and c three times.

e) Condition the sample.

All the knitted fabrics, whether treated or untreated were subjected

to the above treatments to bring them to the stable state before they are taken

up for testing.

3.7.6 Wicking

Wicking tests were carried out on fully relaxed samples. The

fabrics were laid on a flat horizontal surface for at least 24 hours in the

standard atmosphere; the wrinkles were removed without stretching. Strips

(40 × 350 mm) parallel to the wale direction were cut from the samples. All

the samples were marked at intervals of 1 cm along their length using a pen to

make the movement of the water through the fabric more easily measured. A

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pin weighing 1 gm was then inserted through the lower edge of strip to weigh

it to ensure that the end dipped in water. Then the strip was suspended

vertically in the wale direction with one end of the threads clamped into the

clamping bar. The other weighted end dipped 5 mm into the reservoir of water

by using the height adjusted. Each sample was hung freely. Thus the end of

each specimen is put in water (all samples were at the same level). The height

of water that wicked through the fabric at different period of time was

recorded. For each type of sample tests were repeated three times according to

a random sampling order to further reduce any experimental errors due to

slight change in the testing environment, distilled water was used for the

experiment.

3.7.7 Surface Characterisation of Knitted Fabrics

3.7.7.1 Scanning Electron Microscope

A Jeol [Japan Electron Optics Limited] 1989 Model scanning

electron microscope was used to investigate the surface structure of the fabric

knitted from microfiber vis-à-vis normal denier fiber. Samples were sputter

coated with gold and investigated at a magnification level of 100x.

3.7.8 Fabric Friction

The sliding friction apparatus as shown in Figure 3.7 was used to

quantify the smoothness of knitted fabrics using the refined friction

factor, ”R.”

A constant rate of elongation tensile tester (Instron Model 5569)

with the friction adaptation as shown in Figure 3.5 was used to obtain both

static and kinetic friction force values at six different applied loads.

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Figure 3.5 Sliding friction apparatus

3.7.9 Drape Co-efficient

Drape co-efficient of fabrics was measured using Drape Meter

(Drape Co-efficient: BS8357: 1973). A fabric which will deform when it is

allowed to hang under its own weight is defined as fabric drape. A circular

specimen of about 30 cm diameter is supported on a circular disk of about

12.5 cm diameter and the unsupported area drapes over the edge as shown in

figure. If the specimen were, say, a 30 cm gramophone record, no draping

would occur and the area of projection from the periphery would equal the

area of record. With fabrics the material will assume some folded

configuration and the shape of the projected area will not be circular but

something like the shape as shown in the figure.

Drape co-efficient, F is determined by considering areas, Let

AD = the area of the specimen

Ad = the area of the supporting disk and

As = the actual projected area of the specimen

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F is the ratio of the projected area of the draped specimen to its

undraped area, after deduction of the area of the supporting disc.

As - Ad F = (3.19) AD – Ad

10 tests per sample were carried out for assessing the drape

co-efficient of fabrics.

3.7.10 Low Stress Mechanical Properties – Kawabata Evaluation

System for Fabrics

Objective measurement of fabrics replacing subjective

measurement is becoming more accepted as the Kawabata’s evaluation

system of measuring handle of fabrics is more popularly used. Professor

Kawabata developed the KES-FB system mainly for measurement of fabric

hand value in the 1970s. It was also designed to measure basic mechanical

properties of non-woven, papers and other film like materials. The purpose of

developing the KES-FB system was to replace the traditional subjective

method of evaluating fabric hand. The KES-FB system consists of four

instruments to measure the following properties.

KES-FB 1 for Tensile and Shearing

KES-FB 2 for Bending

KES-FB for Compression

KES-FB for Surface Friction and Roughness

and weft direction respectively. The KES-FB system consists of four

instrument blocks as shown in the following Table 3.17.

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Table 3.17 Mechanical properties measured on KES-F

Block Property Description Unit Sample size Tensile Lt

Wt RT EMT

Linearity of stress-strain curve Tensile energy Tensile resilience Strain at 50gf/cm stress

None gf.cm/cm2

% %

5 × 20cm

Bending

B 2HB

Bending stiffness Hysterisis of bending moment

gf.cm2/cm gf.cm/cm

1 × 20 cm

Shear G 2HG 2HG5

Shear stiffness Hysteresis of shear stress at 0.5◦ Hysterisis of shear stress at 5◦

gf/cm/deg gf/cm gf/cm

5 × 20 cm

Compression LC WC RC T0

Tm

Linearity of stress/thickness curve Compression energy Compression resilience Thickness at 0.5 gf/cm2 stress Thickness at 50 gf/cm2 stress

None gf.cm/cm2

% mm mm

Surface MIU MMD SMD

Coefficient of friction Mean deviation of MIU Geometrical roughness

None None micron

20 × 20cm

Weight W Weight mg/cm2

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Mahar (1988) says that characteristics such as stiffness, smoothness,

softness, warmth/coolness, crispness, fullness and drape and descriptive of a

fabric. Handle is related to a series of instrumental measurements based on

fundamental physical properties of a fabric, namely bending length, flexural

rigidity of bending modulus, thickness, compressibility and compression

modulus, density, extensibility and co-efficient of surface friction.

3.7.10.1 Tensile properties

The principle of the instrument is to apply a constant tensile force

to fabric in one direction and to measure the amount of stretch on the fabric.

The stretching deformation can be considered as a kind of biaxial tensile

deformation. The sample is held by two chucks (A and B), chuck B is on a

movable drum connected to a torque detector. The fabric sample is clamped

between chucks A and B and the distance between the chucks is 5cm. A

torque meter is used to measure the tensile stress and by sensing the

movement of chuck B, a potentiometer is used to measure the tensile strain.

Stretching the sample when the tensile force reaches the preset value, it turns

back and recovers to the beginning position. There are two tensile rate

adjustments as 0.2mm/sec or 0.1mm/sec. This is done by changing the gears

at the back of the instrument. The mechanical properties of fabrics under a

tensile and shear stress are very important characteristics. In the tensile testing,

the deformation is a kind of biaxial tensile deformation. To obtain a hand

evaluation objectively, this unit is designed to measure the following:

WT = Tensile Energy

RT = Resilience

LT = Linearity

EMT = Tensile Strain

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Tensile Energy (WT)

WT is the tensile energy or the work done by the extension upto the

maximum force.

Tensile resilience (RT)

RT is the tensile resilience, which can be described as

RT = WT’/WT × 100

where WT’ is the recovered work.

Tensile Linearity (LT)

LT is the linearity of the stress strain curve which can be given as

LT = (WT /WL) × 100 (3.20)

where WT is the tensile energy required for the extension from zero strain to

the maximum strain and WL is the tensile energy when the load extension

curve is linear to zero strain at EMT.

Elongation (EMT)

EMT is the strain at the upper limit The tensile force used was 500 gf / cm

3.7.10.2 Bending Properties

Bending property is an important feature to evaluate fabrics. It is

necessary to assess fabric handle as well as fabric drape. Pure bending test is a

component of the KES-FB system. It is used to determine fabric bending

rigidity. Before the invention of the KES-FB pure bending test, Peirie’s

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cantilever method was used to measure bending rigidity. The pure bending

tester can be used to measure the bending property of thin film materials such

as leather, rubber, film and yarn as well as fabrics (manual bending). Bending rigidity (B) is related to handle and drape.

Bending hysteresis (2HB)

This gives the frictional component of fabrics.

3.7.10.3 Shear Properties

The shear testing using the KES-FB-1 a constant force is applied to

the fabric by attaching a weight to the fabric end on clutch A side. By turning

the clutch off, chuck B is freed and able to move. When the test starts, chuck

B constantly slides to the side until there are 8 degrees of shear angle

(standard condition) and chuck B returns to the original position. During the

test, shear force is detected by a transducer and shear strain is detected by a

potentiometer.

Shear rigidity (G)

This is directly related to the draping quality of the fabrics, which

show the comfort aspects.

Hysteresis of the shear force (2HG)

This is the measure of the hysteresis of shear force on the shear

hysteresis curve at 0.5 degree shear.

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Hysteresis of the shear force (2HG5)

This is the measure of the hysteresis of shear force on the shear

hysteresis curve at 5 degree shear.

Residual shear angle (RS)

It is the rate of 2HG/G and 2HG5/G.

3.7.10.4 Surface properties

The surface test is also necessary to evaluate fabrics. The surface

properties are closely related to the fabric hand, its effect on fabric drape is

not that significant. The KES-FB-4 measures the frictional coefficient

(MIU),the mean deviation of the co-efficient of friction (MMD) and

geometrical roughness (SMD), the measurement is automated and the data

processing is computerized so, data can be read directly after the test. The

parameters obtained are coefficient of friction mean deviation in the frictional

force and geometric roughness. This instrument measures frictional force

generated when the fabric is moved under a metallic friction head. In its

second mode of operation, it measures the vertical movement of probe under

a 10 gf load as it moves over the surface of the fabric.

3.7.10.5 Compression properties

Compressional property of fabrics is another mechanical property

of fabric that is necessary to evaluate fabrics. The KES-FB-3 is a component

of the KES-FB series and is used for measuring the compressional property of

fabrics as well as other materials such as non-woven, leather, rubber and film.

One advantage of the instrument is, it can test fabrics with non-linear

compressional property. This is made possible by the installation of an

integral circuit. It also can be used to measure the bending properties of a

loop-shaped fabric and yarn. The sample should be under the upper-limit

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force and constant rate of compressional deformation. This is a part of the

KES-F series to measure the compressional properties of materials, which is

closely related to the hand-feeling of fabrics. This instrument measures the

compressional deformation property of fabrics with high accuracy and

sensitivity. A constant rate of compressional deformation upto the upper limit

force and its recovery process was applied to the sample.

Compressional work (WC)

This is the work done in compressing the unit area of the fabric.

Compressional resilience (RC)

This is the resilience of the material in compression. It is the ratio

of work of decompression to work of compression, which can be given as

RC (percent) = WC’ /WC × 100 (3.21)

where WC’ is the work of decompression (J/m2) WC is the work of compression (J/m2)

This indicates the hardness of the material.

3.7.11 Air Permeability

Air permeability can be defined as the rate of air flow under a

differential pressure between the two fabric surfaces.

3.7.11.1 Measurement of air-permeability

Air at standard atmosphere is drawn from the laboratory through

the test specimen by means of a suction pump, the rate of flow being

controlled by means of the bypass valve and a series valve. The rate of flow is

adjusted until the required pressure drop across the fabric is indicated on a

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draught gauge, graduated from 0 to 25 mm head of water. When the required

pressure drop which is normally 1 cm of water, is attained and the indicator of

draught gauge is steady, the rate of flow of air is read off one of the four

Rotameters, selected according to the permeability of the test specimen. The

test area is 5.07 cm2, since a 1 inch diameter circle is exposed when the

specimen is clamped in the holder. From the readings on the Rotameter either

the air permeability or resistance can be computed. The average rate of flow

from five specimens is calculated and by dividing this by 5.07 the air

permeability of the fabric can be obtained in cubic centimeters per second at 1

cm head of water.

3.7.12 Measurement of Moisture Vapour Permeability

The moisture vapour permeability of fabrics is an important

property for those used in clothing systems intended to be worn during

vigorous activity. The human body cools itself by sweat production and

evaporation during periods of high activity. The clothing must be able to

remove this moisture in order to maintain comfort and reduce the degradation

of thermal insulation caused by moisture build-up. This is an important factor

in cold environments. The main materials of interest are those fabrics that

incorporate a polymer layer that makes the fabric waterproof but which still

allows some water vapour to pass through. There are two main types of these

materials; those that contain pores through which the moisture vapour can

pass and those containing a continuous layer of hydrophilic polymer. The

mechanism of water vapour transmission through the second type is quite

different from that of the first type. In the British Standard version of this

method, the specimen under test is sealed over the open mouth of a dish

containing water and placed in the standard testing atmosphere. After a period

of time to establish equilibrium, successive weighings of the dish are made

and the rate of water vapour transfer through the specimen is calculated. The

water vapour permeability index is calculated by expressing the water vapour

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permeability (WVP) of the fabric as a percentage of the WVP of a reference

fabric which is tested alongside the test specimen. Each dish is filled with

sufficient distilled water to give a 10 mm air gap between the water surface

and the fabric. A wire sample support is placed on each dish to keep the fabric

level. Contact adhesive is applied to the rim of the dish and the specimen,

which is 96mm in diameter is carefully placed on top with its outside surface

uppermost. The cover ring is then placed over the dish, and the gap between

cover ring and the dish is sealed with PVC tape. A dish which is covered with

the reference fabric is also set up in the same way. All the dishes are then

placed in the standard atmosphere and allowed to stand for at least 1 h to

establish equilibrium.

Measurement of warm/cool feel (qmax), where qmax is defined as the highest

heat flux observed when a hot body comes in contact with a fabric maintained

with a constant temperature. This is determined using Kawabata Thermolabo

system. Thermal conductivity was also determined.

3.8 STATISTICAL TOOL USED FOR DESIGN OF EXPERIMENT AND ANALYSIS IN CARDING

The fibres selected were fixed and the levels of process parameters

were selected based on technical constraints and statistical need.Three levels

were chosen at equivalent distance for predicting the response with a given fit of statistical equation for optimizing the quality response.

Box-Behnken (1960) model of statistical experimental design for 3

variables namely doffer speed, delivery hank and flat speed with 15

combination runs were selected and executed in the carding process for the

study. Regression analysis and ANOVA as described by Mongtomery (2007)

was done using SYSTAT and MINITAB software’s respectively. Design of

experiments with MINITAB was done as described by Mathews (2005).

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Nested analysis of variance was carried out initially in order to find

Variation between various fibres on any quality response.

Significance effect of carding parameters within selected fibres.