CHAPTER 3 MATERIALS AND METHODS -...

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CHAPTER 3

MATERIALS AND METHODS

3.1 INTRODUCTION

This Chapter presents the details of materials and methods utilized for analysing

the performance of yarns and fabrics along with the description of apparatus, procedures

and techniques. The methodology adopted for this study is presented in the form of a

flow diagram, as given in Figure 3.1.

Figure 3.1: Flow Diagram of Methodology Adopted for the Study

I. Staple Fibres

Bamboo/Cotton (50:50)

Ring Spinning

Modal (100%)

Viscose (100%)

Bamboo (100%)

II. Production of Spun Yarns (40 Ne)

100% Modal Yarn 100% Viscose Yarn Bamboo/Cotton (50:50) Blended Yarn

Cotton (100%)

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III. Fabric Production (Production of Weft Knitted Fabrics with Variations in Loop Length)

Bamboo/Cotton (50:50)

Modal (100%) Viscose (100%)

1x1 Rib Interlock

0.31cm

0.29cm

0.27cm

1x1 Rib Interlock 1x1 Rib Interlock

0.31cm

0.29cm

0.27cm

0.31cm

0.29cm

0.27cm

0.31cm

0.29cm

0.27cm

0.31cm

0.29cm

0.27cm

0.31cm

0.29cm

0.27cm

IV. Preparation of Weft Knitted Fabrics

Desizing + Scouring + Bleaching

Dyeing With Cold Brand Reactive Dye

Relaxation Treatments Given for Weft Knitted Fabrics

Dry Relaxation

Wet Relaxation

Full Relaxation

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V. Objective Evaluation

Yarn Testing Fabric Testing

Physical Properties Physical Properties

Count and Twist Strength and Elongation Evenness and Imperfections Hairiness and Yarn Quality Index (YQI)

Loop Length Tightness factor Fabric Weight Fabric Thickness

Mechanical Properties

Mechanical Properties

Yarn to Yarn Dynamic Friction Yarn to Metal Dynamic Friction Yarn Abrasion Yarn Flexural Rigidity Yarn to Needle Static Friction

Bursting Strength Abrasion Resistance Bending Length Flexural Rigidity Surface Friction

Comfort Properties Related to Moisture Management

Yarn Wicking

Comfort Properties Related to Moisture Management

Wettability Sinking Time Absorptive Capacity Vertical Wicking

Aesthetic Properties

Fabric Drape

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VI. Instrumentation

Fabric Analysis Yarn Analysis

Simple Low Cost Manual

Drape Elevator

Fabric Surface Friction Tester

Yarn Friction Tester

Yarn Flexural Rigidity Tester

VII. Investigating the Drape Formation of Weft Knitted Fabrics (with three different loop lengths,

relaxation stages and with two types of stitches and linings variation)

Conventional Method

Simple Low Cost Manual Drape

Elevator Method

Image Analysis Method

Samples without variation

Samples with variation

Stitch Variation

Lining Variation

Type I Type II 40s

80s



Stitch Variation

Lining Variation



Stitch Variation

Lining Variation

Type I Type II 40s 80s

Type I Type II 40s 80s

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3.2 MATERIALS AND METHODS

The materials and methods selected for the research work are discussed below.

Bamboo, cotton, modal and viscose staple fibres of cellulosic origin were selected for the

study. Fifty percent of bamboo and fifty percent of cotton fibres were blended together in

the blow room and were ring spun into blended yarn of 40 Ne. Similarly 100 percent

modal and 100 percent viscose fibres were individually ring spun into 40 Ne yarn. The

physical and mechanical properties of fibres used in the study are given in the Table 3.1.

Table 3.1

Properties of Bamboo, Cotton, Modal and Viscose Fibres

Fibre Type

Average Fibre

Length (mm)

Fibre Fineness (dTex)

Initial Modules (cN/Tex)

Dry Tenacity (cN/Tex)

Wet Tenacity (cN/Tex)

Elongation at Break

(%)

Moisture Regain

(%)

Bamboo 38 1.21 780 22-25 13-17 14-24 13

Cotton 28 1.23 799 20-43 27-56 6-10 7-8

Modal 38 1.23 880 24-36 12-24 13-25 8-9

Viscose 38 1.19 785 18-26 9-15 15-25 12-13

3.3 YARN PRODUCTION

The step by step process followed for producing 40 Ne yarn of 50:50

bamboo/cotton blend, 100% modal and 100% viscose yarns is given in the form of a flow

chart as shown in Figure 3.2.

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Figure 3.2 Flow Diagram of Yarn Production

In the process of yarn production, the fibres were passed through a Platt’s blow

room consisting of two blended hopper bale opener, type 490 air stream cleaner and MB

23 single scutcher lap unit equipped with Kirschner beater. The scutcher lap from the

blow room was processed on 40 inch cards. Normal speeds and settings were used for

bamboo/cotton, modal and viscose fibres. All the samples were processed through two

passages on LR high speed draw frame model Do/2 with polar drafting system followed

by LR can fed inter model G.S. After two passages of drawing, slivers of bamboo/cotton,

modal and viscose were processed in Lakshmi Rieter, Simplex and spun into yarns of

number 40 Ne on ring spinning machine using a spindle speed of 10,500 RPM. Three

types of yarns namely (50:50) bamboo/cotton blend, (100%) modal and (100%) viscose

Fibres (Bamboo/Cotton, Modal and Viscose)

L.R. Blow Room (Opening, Blending and Cleaning)

Carding

Draw Frame

Draw Frame

Simplex

Ring Spinning

40 Ne Yarn

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were produced. The nomenclature of yarn samples are presented in the following

Table 3.2.

Table 3.2

Nomenclature of Yarn Samples

Sample No. Description of Samples Sample Code Yarn Count (Ne)

1 Bamboo/cotton yarn (50 : 50) BCY 40 (14.76 tex)

2 Modal Yarn (100%) MY 40 (14.76 tex)

3 Viscose Yarn (100%) VY 40 (14.76 tex)

3.4 FABRIC PRODUCTION

In this study, spun yarns of bamboo/cotton blend, modal and viscose were utilized

to produce weft knitted fabrics of 1x1 rib and interlock. The weft knitting machinery

details, loop length and tightness factor selected, are given in Tables 3.3 and 3.4

respectively. Figures 3.3 (a) and (b) show the graphical representation of weft knitted

structures.

Table 3.3

Weft Knitting Machinery Details

S.No Particulars Rib Interlock

1 Machine Pailung,Taiwan Pailung,Taiwan

2 Model Pl.xd2.5ba/c Pl.xd2.5ba/c

3 Diameter (inches) 18 30

4 Gauge 16 24

5 Number of feeders 36 60

6 Number of needles 3616 4520

7 Speed (rpm) 15 10

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Table 3.4

Loop Length and Tightness Factor Selected for Weft Knit Structures

S.No. Weft Knitted Fabrics

Sample Code of Knitted Structures

Tightness Factor

(Tex0.5 cm-1)

Loop Length

(cm) 1×1 Rib Interlock

1. Bamboo/

cotton Blend (50:50)

BCR 1 BCI 1 12 0.31

BCR 2 BCI 2 13 0.29

BCR 3 BCI 3 14 0.27

2. Modal (100%)

MR1 MI1 12 0.31

MR2 MI2 13 0.29

MR3 MI3 14 0.27

3. Viscose (100%)

VR1 VI1 12 0.31

VR2 VI2 13 0.29

VR3 VI3 14 0.27

The numbers 1, 2 and 3, indicated in the sample codes represent the large,

medium and small loop lengths such as 0.31cm, 0.29cm and 0.27cm.

1×1 Rib Interlock (a) (b)

Figure 3.3: Graphical Representation of Weft Knitted Structures

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3.5 FABRIC PREPARATION

As a preparatory step to remove the foreign matters, the weft knitted fabrics were

desized, scoured and bleached by making use of the recipe given below:

Sodium hydroxide – 3%

Sodium silicate – 3%

Hydrogen peroxide – 3%

Wetting agent -0.1%

Material liquor ratio – 1:20

Time duration – 1 hour

Temperature – 600c

The measured amount of sodium hydroxide and sodium silicate were taken and

wetted with wetting agent followed by hydrogen peroxide. Water was added as per the

material liquor ratio; the temperature was maintained at 60oc and was kept for one hour.

After pre-treatments, the fabric samples were subjected for dyeing and conditioning.

3.6 DYEING

Reactive dye was chosen due to its good colour fastness properties, brilliancy,

easy dyeability and which are more suitable for dyeing natural and regenerated fabrics of

cellulosic origin. Fabric dyeing was carried out based on normal industrial parameters

and by following the dyeing recipe given below,

Reactive dyes – Yellow F4G- 0.35%

Turquoise blue H2GB – 0.5%

Sodium chloride – 40%

Soda ash – 10%

Material liquor Ratio – 1:20

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Temperature – 600c

Time duration – 1 hour

Shade – 5%

After the process of dyeing, the fabric samples were soaked in water consisting of

soap oil of 5ml per liter for 12 hours at 30°C, and then hydro extracted and flat dried at

60°C. The fabric samples were then conditioned at a standard atmosphere of 27° ± 2°C

and with a relative humidity of 65% ± 2% for 24 hours.

3.7 YARN TESTING

Prior to yarn testing, yarn samples of bamboo/cotton, modal and viscose were

kept in the standard atmospheric conditions of 65% ± 2% relative humidity and

temperature of 27° ± 2°C for 48 hours.

3.7.1 Physical Properties

After conditioning the yarn samples, their physical properties such as yarn count,

twist, strength, elongation, evenness, imperfections and hairiness were subsequently

measured. Table 3.5 gives the details of instruments and standards used for assessing the

physical properties of yarns.

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Table 3.5

Instruments and Standards Used for Assessing the Properties of Yarns

S.No. Yarn Properties Instruments Testing Standards

I Physical properties i. Yarn Count Statex Yarn Count System ASTM D – 1907 – 01

ii. Yarn Twist Electronic Yarn Twist Tester ASTM D – 1422

iii. Yarn Strength & Elongation Uster Tensojet Tester ASTM D – 2256 – 95a

iv. Yarn Evenness Imperfections & Hairiness

Uster – 5 Evenness Tester ASTM D – 0425 – 96

II Mechanical properties

i. Yarn to Yarn Dynamic Friction

Lawson-Hemphill Friction Tester ASTM D 3412/041

ii. Yarn to Metal Dynamic Friction

Lawson-Hemphill Friction Tester ASTM D -3108-07

iii. Yarn Abrasion CTT Yarn Abrasion Tester

(Constant Tension Transport) ASTM LH-403 CTT-

YAT

3.7.1.1 Measurement of Yarn Count and Twist

Yarn count was determined by using Statex yarn count system, which consisted of

a combination of electronic balance and computer. Using this system, twenty readings

were taken and the mean value and CV percentage were calculated. Yarn twist was

assessed on electronic yarn twist tester under a standard tension of 0.5 cN/tex and an

average of fifty readings were taken.

3.7.1.2 Measurement of Yarn Strength and Elongation

The tensile properties of yarns namely breaking strength and elongation were

measured by Uster Tensojet Tester using the single strand method. The tenacity and mean

elongation, along with respective CV percentage were calculated.

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3.7.1.3 Measurement of Yarn Evenness, Imperfections and Hairiness

Yarn evenness was determined by Uster-5 evenness tester equipped with a

quadratic integrator. The imperfection indicator was used in conjunction with the

evenness tester for recording the thin places, thick places and neps per kilometre.

Average values of twenty observations were reported along with the total imperfections

per kilometre of each yarn sample. Yarn hairiness was carried out on Uster yarn hairiness

tester with path setting at 3mm.Twenty readings were taken and mean values were

calculated.

Yarn Quality Index (YQI) was calculated using Barella’s (1976) equation as

shown below,

%UElongationTenacity Yarn YQI ×= ……… (3.1)

3.7.2 Mechanical Properties

The yarn samples were also tested for yarn flexural rigidity and frictional

properties. For the above tests, ten readings were taken and the mean values were

calculated and recorded.

3.7.2.1 Measurement of Yarn to Yarn Dynamic Friction

Coefficient of yarn to yarn dynamic friction was measured using Lawson-

Hemphill friction tester according to ASTM D 3412/01 standard. The speed was

maintained at 0.02m/min, input tension at 9.81 mN/tex, apex angle at 35° and the speed

at 0.02 m/min. From the measured tension, the coefficient of friction was calculated by

using the formula given below,

µθ= eTT

2

1 ……… (3.2)

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Taking logarithms on both the sides, this equation reduces to

2

1

TTlog733.0=µ ……… (3.3)

Where,

µ = Coefficient of friction.

θ = Angular contact in radians (θ = π = 3.14 radians)

T1 = Output tension

T2 = Input tension

3.7.2.2 Measurement of Yarn to Metal Dynamic Friction

Coefficient of yarn to metal friction was measured using Lawson-Hemphill

friction meter as per ASTM D-3108-07 standard. The speed of yarn was maintained at

100 m/min, with wrap angle of 180°.The standard friction surface of 12.7 mm diameter

chrome-plated steel of 4-6µm roughness. The coefficient of friction was calculated from

the measured input and output tensions as the yarn runs at constant speed over the rod.

3.7.2.3 Measurement of Yarn Abrasion

In this test method, the yarn was made to run over a standard abrasion wire. When

the wire breaks, the test stops. The amount of yarn that is required to break the wire is

noted and compared with other sample yarns abrasion test results. In this comparison test,

the higher number indicates less abrasive yarn.

3.7.2.4 Measurement of Yarn Flexural Rigidity

Flexural rigidity is the resistance of yarn to bending. There is no affordable and

standard method available for measuring the flexural rigidity of yarns. This property has

been measured by making use of custom built yarn flexural rigidity tester developed for

this study which is shown in Figure 3.4 (a) and its schematic diagram in Figure 3.4 (b).

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Figure 3.4 (a): Custom Built Yarn Flexural Rigidity Tester

Figure 3.4 (b): Schematic Diagram of Yarn Flexural Rigidity Tester

A – Sample Yarn B – Rider C – Measuring scale

D – Yarn loop Holder Pin E – Measuring Scale Holder

F– Transparent Glass Chamber G –Glass Tube to form Yarn loop

F

A B

E C G

D

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The sample yarn was formed into a loop with a radius of 0.8 cm and hung on a

yarn loop holder pin situated near the measuring scale. A known load(w) of 0.03gf in the

form of a rider was applied and the deflection value(d) was measured and the mean

values of average of ten samples were recorded. The yarn flexural rigidity was calculated,

using the formula given below,

……… (3.4) Where, K = Constant value (0.0047)

W=Applied load (gf)

L= 2πr and θ = 493 d/L

d = Deflection value in cm

Specific flexural rigidity is obtained by dividing flexural rigidity by tex2.

3.7.2.5 Measurement of Yarn to Needle Static Friction

Coefficient of yarn to needle static friction was measured using a simple custom

built yarn friction tester as shown in Figure 3.5(a) and its schematic diagram in Figure

3.5(b).

Figure 3.5(a): Custom Built Yarn to Needle Static Friction Tester

Flexural Rigidity = kWL2 (cosθ/tanθ ) (mN.mm2)

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Yarn samples of 250mm (25cm) in length were taken. A metal needle with a

constant weight of 0.176 gm was threaded on the sample yarn and the ends of yarn was

tied on to metallic hooks provided at both ends of the sliding beam. The friction of yarn

was measured similar to inclined plane method.

Figure 3.5 (b): Schematic Diagram of Yarn to Needle Static Friction Tester

A – Sliding Beam B1 and B2 – Metallic Hooks

C – Metal Needle (Traveller) D – Protractor

E – Protractor Holding Stand

The deflection angle at which the traveler starts to slide is noted from the

protractor. For each yarn sample of bamboo/cotton blend, modal and viscose, ten

readings were taken, mean values were calculated and the coefficient of yarn friction was

calculated by making use of the formula given below,

µ = tan θ ……… (3.5)

Where, µ = coefficient of yarn friction

θ = angle This method is based on the method used by Howell and Mazur (1953).

A B2 C D

E

B1

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3.7.2.6 Yarn Wicking

Wicking behaviour of yarn samples was assessed by making use of an apparatus

developed for measuring the vertical wicking of weft knitted fabric samples, which is

shown in Figure 3.6, based on DIN 53924 standard.

Figure 3.6: Instrument Developed for Measuring Vertical Wicking of Fabrics

The yarn samples of bamboo/cotton blend, modal and viscose of 15cm in length

were suspended with its lower end immersed in a reservoir of distilled water and wicking

height was monitored at a regular time interval of every minute upto a maximum of 10

minutes. The readings of ten samples were recorded and the mean values were calculated.

3.8 RELAXATION TREATMENTS GIVEN FOR WEFT KNITTED FABRICS

Rib and interlock structures of bamboo/ cotton, modal and viscose of three

different loop lengths which were dyed and subjected to three stages of relaxation such as

dry, wet and full by following BS 4931 and BS 4923 standard methods respectively.

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3.8.1 Dry Relaxation

Weft knitted fabrics, knitted in tubular form were laid free from constraints on a

flat surface to relax in dry state in a standard testing atmosphere of 270 ± 20C and a

relative humidity of 65% ± 2% for 24 hours.

3.8.2 Wet Relaxation

Fabric samples were put into a large stainless steel tub containing water

maintained at a constant temperature of 40°C for twelve hours. Then the material was

hydro extracted and then allowed to dry for three days and conditioned in a standard

testing atmosphere of 65% ± 2% relative humidity and 25° ± 2°C for 24 hours. The

samples were subjected to relaxation treatments as recommended by STAR FISH

method.

3.8.3 Full Relaxation

In order to achieve fully relaxed state, the wet relaxed samples were further

subjected for full relaxation. This was achieved by soaking the fabric samples at 40°C for

24 hours followed by hydro extraction and tumble drying for 1 hour at 70°C.

This treatment cycle was repeated for three times and finally the samples were

conditioned in a standard testing atmosphere of 65% ± 2% relative humidity and 25° ±

2°C for 24 hours.

The nomenclature of weft knitted fabric samples is presented in Table 3.6.

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Table 3.6

Nomenclature of Weft Knitted Fabric Samples

S.No. Description of Samples Sample Code Loop Length (cm)

1 Bamboo/Cotton Rib 1 BCR1 0.31



4 Bamboo/Cotton Interlock 1 BCI 1 0.31



7 Modal Rib 1 MR1 0.31



10 Modal Interlock 1 MI1 0.31



13 Viscose Rib 1 VR3 0.31



16 Viscose Interlock 1 VI1 0.31



The numbers 1, 2 and 3 indicated in the sample codes represent the large, medium

and small loop lengths such as 0.31 cm, 0.29 cm and 0.27 cm.

3.9 FABRIC TESTING

Prior to objective evaluation, the dry, wet and full relaxed 1x1 rib and interlock

structures of bamboo/cotton, modal and viscose were conditioned in a standard testing

atmosphere of 27o ± 2oC and 65% ± 2% relative humidity to facilitate accuracy in

physical testing.

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3.9.1 Measurement of Physical Properties 3.9.1.1 Loop Length

To compute the loop length of dry, wet and full relaxed weft knitted fabrics, ten

samples from each with a size of 100mm x 100mm were cut. Ten courses were then

unraveled from each sample and measured for course length using Shirley crimp tester

under a pre-determined tension of 0.1gf/tex. The mean values of course length were

calculated and this was divided by the number of needles of the respective cylinder

yielding the loop length of the respective sample.

The actual loop length and the corresponding measured values of yarn linear

densities were used to calculate the actual tightness factor according to the formula given

below,

……… (3.6)

Where,

l = Loop length in centimetre

K= Tightness Factor (Tex0.5 cm-1)

A number of ten observations were made for each fabric sample.

3.9.1.2 Fabric Weight

Weft knitted fabric samples of 10cm in diameter were cut using Techno GSM

cutter based on ASTM 3776 standard and were weighed using Samsung Electronic

precision balance. The mean weight in grams was multiplied by 100 to obtain the fabric

weight in grams per square metre.

3.9.1.3 Fabric Thickness

MAG thickness tester was used to measure the thickness. Samples with 100mm

x100mm in size were cut and each specimen was placed between the anvil and presser

ltexK =

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foot of the thickness tester gauge. The fabric thickness was then noted from the dial

readings of the tester. The mean values were calculated and expressed in millimetres.

3.9.2 Measurement of Mechanical Properties

The mechanical properties related to fabric stiffness, bursting strength, abrasion

resistance and surface friction were determined for dry, wet and full relaxed weft knitted

fabric samples. The mean values of ten samples were calculated.

3.9.2.1 Bursting Strength

MAG bursting strength tester based on IS 1966-1975 was used to determine the

bursting strength. Ten readings from each fabric sample were taken. A specimen with

30mm in diameter was clamped over an expandable diaphragm. The diaphragm gets

expanded by fluid pressure to the point as the specimen ruptures.

The difference between the total pressure required to rupture the specimen and the

pressure required to inflate was reported as bursting strength. The mean values were

calculated and expressed in kg/cm2.

3.9.2.2 Abrasion Resistance

The abrasion resistances of weft knitted fabrics of bamboo/cotton, modal and

viscose subjected for dry, wet and full relaxed states were assessed using Martindale

abrasion tester based on BS 5690 standard. A standard size of 38mm diameter sample

was held by a modified specimen holder by a pinned ring. A flattened rubber ball pushes

the samples as the holder was tightened thus stretching it. The holder was then mounted

on the Martindale tester with a 12kPa pressure and the test was carried out. The sample

was inspected at suitable intervals until the material develop an unacceptable level of

thinning. The sample weight was then measured in gm/1000 rubs and mean values were

calculated respectively.

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3.9.2.3 Bending Length and Flexural Rigidity

Shirley stiffness tester based on BS 3356 standard was used to measure the

bending stiffness of fabrics. The test specimens with 25mm in width and 200mm in

length were cut both in wale and course directions. The bending stiffness was determined

by allowing the samples to bend to a fixed angle under its own weight. The length of the

fabric required to bend to that angle was measured as the bending length. Four readings

were taken from each sample, one face up and one face down on first end and then the

same for the second end. Finally the mean bending length was calculated using the

formula,

……… (3.7)

Where, C = bending length

l = length of the fabric

θ = angle of inclination

and ……… (3.8)

Flexural rigidity of the fabric was calculated from bending length (C) and weight using

the formula,

……… (3.9)

Where, W = fabric weight in gm/cm2

C = bending length in cm

3.9.3 Measurement of Aesthetic Properties

Aesthetic properties are one among the broad classification of fabric properties, in

which fabric drape is closely associated with it. It is difficult to categorize exclusively

different properties under each category because they are related to one another. The

)(1lfC θ=

5.03/1

tan82/1cos

1f =

θθ

=θ

Flexural rigidity (G) = WC3 x 103 mg.cm

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property of drape is one such property that falls under the psychological comfort as well

as aesthetic properties of fabrics.

The DC values of weft knitted fabrics were assessed by Conventional Method

(CM), Simple Low cost Manual Drape Elevator Method (SLMDEM) followed by Image

Analysis Method (IAM). A comparison between the DC values of these three methods

has been done without any variation and with two type of stitches and linings variation.

Apart from the assessment and comparison of DC values, various non-standard drape

parameters were also measured.

3.9.3.1 Measurement of Fabric Drape by Conventional Method

In the conventional method the drape coefficient was measured according to BS

EN 20139 standard using MAG drape tester. It consists of a draping chamber (I) and an

exposing chamber (II) as shown in Figure 3.7 (a) and its schematic diagram in Figure 3.7

(b) respectively. A circular weft knitted fabric specimen of 25cm in diameter was

concentrically sandwiched between two smaller horizontal discs with a diameter of

12.5cm and the unsupported annular ring of fabric sample was allowed to hang down

under the action of gravity. A circular light sensitive ammonia paper with a diameter

similar to that of fabric specimen was placed under acrylic sheet just below the circular

specimen support present in the draping chamber. A planner projection of the draped

image shadow gets recorded on the circular light sensitive ammonia paper due to the

influence of 2000 watts mercury light, ammonium vapours from the concentrated

ammonium solution kept in a bowl in the exposing chamber. The light sensitive circular

ammonia paper with the exposed draped profile was folded and weighed to give the

initial weight (W1).

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Figure 3.7 (a): Conventional MAG Drape Tester

Figure 3.7 (b): Schematic Diagram of Conventional MAG Drape Tester

A – Mercury Light F – Transparent Acrylic Sheet

B – Smaller Specimen Supporting Disc (a) G – Thick Wire Mesh

C – Smaller Specimen Holding Disc (b) H – Glass Bowl

D – Fabric Sample I – Switch and Cord with Plug Pins

E – Circular Specimen Support

G

I. Draping Chamber

II. Exposing Chamber

A

B

D

C

E

H

I

F

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The paper was then cut along the outline of the shadow of the draped profile and

was weighed to give the final weight (W2). Drape coefficient was calculated using the

equation given below,

Drape Coefficient (%) = W2 / W1 x 100 ……… (3.10)

Where,W1 = Initial weight of the circular ammonia sheet W2 = Weight of the ammonia sheet after cutting it along the outline of the

draped profile.

The folds present along the contour of the draped profile are referred to as nodes.

The numbers of nodes formed were recorded for each sample.

3.9.3.2 Measurement of Fabric Drape by Image Analysis Method

In image analysis method, the instrument set up consisted of a simple low cost

manual drape elevator, a digital camera to capture the draped image of the mounted

fabric specimen, a computer to analyse the captured image and translate it into suitable

output. Image analysis set up for the measurement of fabric drape is shown in Figure 3.8.

Figure 3.8: Schematic Diagram of Drape Measurement Using Image Analysis

Method

Digital Camera

Computer

Simple Low cost Manual Drape Elevator

UPS

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A circular fabric sample with a diameter of 25cm is mounted and executed similar

to that of conventional method. The difference is that, after allowing the sample to fall,

the image of the draped configuration was captured using a digital camera. Then the

captured image was transferred to the computer and the raw image was cropped,

calibrated by setting the dimension of the circular ring for 25cm and then the draped

configuration of the image was selected using “Magnetic Lasso” tool in Adobe

Photoshop, which attaches a boundary to select the dark region based on pixel value,

reducing the variation in the selection process.

The drape coefficient of the fabric was calculated using the image pixels and the

image resolution of the draped specimen. The following equation given below was used

to determine the drape coefficient values.

Total selected Pixels ÷ Pixels per cm2 - Area of supporting disc (cm2) DC % = x 100 Area of the specimen (cm2) - Area of supporting disc (cm2)

OR

As - A1 DC % = x 100 ……… (3.11) A2 - A1

Where, As = the area of draped fabric image

A1 = the area of supporting disc

A2 = the area of circular fabric sample

Apart from measuring the drape coefficient values of original samples without

variation, two types of stitches and linings were introduced to measure and assess the

influence of stitches and linings in measuring the drape coefficient of weft knitted fabrics.

Details concerning sewing requirements with stitches and lining materials are given in

Tables 3.7 and 3.8 respectively.

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Table 3.7

Details of Sewing Requirements and Stitches

S.No Machine Details Single Needle Lock Stitch Machine

3-Thread Flat Lock Machine

1. Brand Name Juki Siruba 737 E

2. Made Taiwan Taiwan

3. Feed Mechanism Drop feed Differential feed

4. Needle System Db×1 Db×1

5. Machine Power ¼ HP ¼ HP

6. Sewing Thread Cotton Cotton

7. Thread ticket No. 120 120

8. Thread ply No. 2 2

9. Needle Medium ball point Medium ball point

10. Needle size 11 11

11. Sewing thread type ‘Z’ Twist ‘Z’ Twist

12. Number of spools 3 1

13. Sewing thread size T27 T27

14. Thread ply 2ply 2ply

15. Stitches per inch 12 12

16. Stitch tension Medium Medium

17. Stitch size 3mm 3mm

18. Stitch classes Class 301

Class 503

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Table 3.8

Details of Lining Materials

S.No Sample Code Count Warp (cm)

Weft (cm) GSM Thickness

(mm)

1. Lining-1 (Bleached 100% Cotton)

40s 68 64 115 0.55

2. Lining-2 (Bleached 100% Cotton)

80s 66 63 105 0.40

Unlike conventional method in the image analysis technique using simple low

cost manual drape elevator, the drape coefficient values of weft knitted fabrics with

stitches and lining variation were also measured.

The simple low cost manual drape elevator fabricated for the study was utilized to

capture the draped image. By making use of digital camera, the image was grabbed and processed by using “Magnetic Lasso” tool in Adobe Photoshop software, as explained in image analysis method. In analysing the drape profile of series of weft knitted fabrics, image analysis enabled to assess further more non standard drape parameters such as Drape Distance Ratio (DDR), Fold Depth Index (FDI) and Amplitude to Average Radius Ratio (ARR) apart from DC and NN.

For estimating the digital image and to make it clear, the image was converted

into binary image, which was then utilized to calculate the non-standard drape

parameters, as shown in Figure 3.9. These new parameters were determined based on the

theoretical equations suggested by Behera and Pattanayak (2008), in their study on

measurement and modeling of drape using digital image processing. Figure 3.9 shows

that draped fabric image indicating the angle and radius needed for the estimating the

non-standard drape parameters.

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(Source: Behera and Pattanayak 2008) Figure 3.9: Draped Fabric Image indicating the Angle and Radius Needed for

Estimating the Non-standard Drape Parameters

From the Figure 3.9, xi = ri cos θi and yi = ri sin θI …… (3.12)

Average radius is ra = (1/n) Σri …… (3.13) Area for the triangle (A) of (0, 0), (Xi, Y1) and (X2, Y2)

points can be denoted by following relationship:

…… (3.14) and the total area for the boundary curve(s) can be given by the following

relationship;

…… (3.15)

Where, r1 and r2 are the radii of the supporting disc and undraped fabric sample

respectively. The angle and radius at different points are needed to measure the area. For

this, all the centre point of the binary image is located and then it is rotated by a constant

∑=

=+ θ×=

1n

1i1ii sinrr

21S

θ××= sinrr21A 21

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angle and radius is calculated at all points. For the calculations, boundary of the fabric

image is approximated by 1° and so that there are 360 points on the boundary of the

image.

Therefore, θ = 1° and n = 360, with these parameters the various drape parameters

such as DC, NN, average radius (ravg), maximum radius (rmax), minimum radius (rmin),

Drape Distance Ratio (DDR), Amplitude to Average Radius Ratio (ARR) and Fold Depth

Index (FDI) were determined using the following relationships given below,

100AAAA(%)DC

12

1s ×−−

= ……… (3.16)

100rr

rr(%)DDR

12

avg2 ×−

−= ……… (3.17)

100rrrr(%)FDI12

minmax ×−−

= ……… (3.18)

cm2

rrARR minmax −= ……… (3.19)

Where, As – the area of draped fabric image

A1 – the area of fabric supporting disc

A2 – the area of undraped fabric sample

r1 – the radius of fabric supporting disc

r2 – the radius of undraped fabric sample

rmax – the maximum radius of draped fabric image profile

rmin – the minimum radius of draped fabric image profile

ravg – the average radius of draped fabric image profile

3.9.4 Determination of Comfort Properties Related to Moisture Management

Fabrics meant for apparel manufacturing must possess good moisture transmission

property which influences the comfort properties. Clothing worn next to skin should

absorb the moisture from the body as well as transmit it to the atmosphere. Apart from

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absorption behaviour, there are other moisture related properties that impart thermo

physiological comfort of fabrics like drying time, air permeability and wicking

behaviour.

3.9.4.1 Wettability

A series of weft knitted 1×1 rib and interlock fabrics of bamboo/cotton (50:50),

modal (100%) and viscose (100%) of cellulosic origin was examined for absorbency tests

such as wettability, sinking time, absorptive capacity, vertical wicking and air

permeability to assess the comfort properties related to moisture management by

following standard test methods. Finally, a comparison was made between yarn and

fabric wicking. The arrangement setup for measuring the property of wettability is shown

in Figure 3.10.

Figure 3.10: Wettability Test

The wettability test was carried out based on BS 4554 standard method. The test

specimen was clamped on to an embroidery frame of 150mm in diameter so that it was

held taut and away from any surface. A burette with a standard tip size was clamped

6mm above the horizontal surface of the sample. The fabric was illuminated at an angle

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of 45° and was viewed at 45° from the opposite direction. At the start of the test, a drop

of liquid was allowed to fall from the burette and the timer started. When the diffuse

reflection from the liquid vanishes the timer was stopped. Five areas on each specimen

were tested and then the average values were determined.

3.9.4.2 Sinking Time

This is a simple test for assessing the water absorption capacity of the textile

materials. The arrangement setup for measuring the sinking time is shown in the Figure

3.11.

Figure 3.11: Sinking Time Test

A fabric specimen of 25 mm x 25 mm in size was taken and was dropped from a

height of 25mm, onto the surface of distilled water and the length of time taken by the

fabric to sink was measured. Ten readings were taken and the mean values were

calculated.

3.9.4.3 Absorptive Capacity

Absorptive capacity provides a measure of the amount of liquid held within a test

specimen after specified times of immersion and drainage, report Das et al., (2009). The

test for absorptive capacity was conducted by following the principles of test described in

ASTM D1117-80 standard. Ten specimens of 76mm x 76mm from each fabric sample

were weighed and immersed in distilled water at 20oC for a specified time, taken out and

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the excess water was drained prior to weighing. The liquid absorptive capacity was given

as a percentage of the original mass of the test specimen, by making use of the equation

given below,

Water absorbency (%) = 100xA

)AB( −

…… (7.1)

Where, A = Specimen weight before immersion B = Specimen weight after immersion The mean percentage absorption was then calculated.

3.9.4.4 Vertical Wicking

The vertical wicking of weft knitted fabrics was determined by measuring the

wicking height against gravity along the course and wale directions. The test was

conducted using a vertical wicking tester based on DIN 53924 standard. The apparatus

used for vertical wicking is given in Figure 3.12. A fabric strip of 150 mm x 25 mm was

suspended vertically with its lower end immersed in a reservoir of distilled water.

Figure : 3.12 Vertical Wicking of Weft Knitted Fabrics

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The duration of each test was 10 minutes and the height reached was noted in

centimetres with respect to the clamped scale. Each experiment was carried out for ten

samples and average was calculated.

3.9.4.5 Air Permeability

Air permeability is a property of textile materials of how well it enables the

passage of air through it. It is the volume of air passing through unit per second and is

normally represented as cm3/cm²/ sec. The Prolific air permeability tester was used for

testing based on IS 11056: 1984 standard. The test fabric samples were preconditioned in

a standard atmosphere of 65% ± 2% relative humidity and 27° ± 2°C temperature for 24

hours.

The air permeability tester consists of an arrangement to hold the test specimen

between two flat faces so as to expose a known area to the flow of air through it, a

vacuum system to draw air through the exposed area of the test specimen, arrangement to

measure the volume of air flowing through the test specimen and arrangement to measure

the pressure drop between the two faces of the test specimen as a result of flow of air.

The test specimen is held between two annular ring shaped grips. The grips are

lined with rubber gaskets to reduce flow of air through the edges. The two grips can be

brought in contact with each other with the help of a hand operated screw arrangement.

The test area can be altered by placing adaptor discs of different openings in the grips.

The vacuum needed to draw air through the exposed area of the test specimen is created

with the help of a vacuum pump supplied with the equipment. The volume of air passing

through the test area is measured with the help of a set of rotameters. The mean values

were then calculated.

3.10 STATISTICAL ANALYSIS

The test results were analysed statistically with the view to finding out the

samples having better correlation, significant differences and for analysing the deviations

between the three different types of weft knitted fabrics.

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Regression analysis was used to analyse the relationship between wickability of

yarns and time in respect of weft knitted fabrics.

Correlation coefficient was employed to find out the relationship between drape

coefficient and mechanical properties of weft knitted fabrics.

ANOVA was used to check the significant difference of fabric friction.

Standard deviation was used for analysing the deviation of drape coefficient

values measured by conventional and simple low cost manual drape elevator methods

followed by image analysis.

CHAPTER 3 MATERIALS AND METHODS -...

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