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CHAPTER 3

MATERIALS AND METHODS

3.1 INTRODUCTION

A knitted fabric can have desired properties such as insulation and

fashion. Often these properties are not enough for daily use in bad weather

conditions. Consumers have become much more demanding when it comes to

the properties of clothing, particularly those of leisure and sportswear.

Nowadays, the fashion aspects play an important role in selection. Consumers

also increasingly want clothing to be comfortable. The fact is that there is an

increasing demand for highly comfortable modern sportswear clothing.

One of the textile properties that have speedily gained importance

among increasingly well informed consumers is moisture management of the

materials, because this property is directly linked to comfortable wear of the

garment. Moisture management fabrics constitute one of the major

components of individual protective clothing used in sports wear. Fabrics

having water vapour permeable characteristics are commonly referred to as

moisture management fabrics. To avoid the condensation of perspiration in a

garment, it has to be made with breathable fabrics through which water

vapour can escape. Thermo physiological comfort is a complex phenomenon

and relates to the thermodynamics, heat and moisture transfer in the human

body and clothing. The heat balance of the system is a function of skin,

clothing and amount of air entrapped between skin and clothing. This heat

balance varies with the change in wind velocity, atmospheric temperature

(external factor) or the activity of the individual (internal factor), causing

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change in heat or moisture production of the body. The individual will feel

comfortable till the amount of heat produced is equal to the amount of heat

lost.

3.2 MATERIALS

In general, polyester continues filament yarns of 150 denier were

taken to produce knitted fabrics. The yarns were kintted on a circular single

jersey machine of 28 gauge with speed of 30rpm.

3.2.1 Novel Agents for the Moisture Management Finish

The following novel finishing agents have been introduced to

impart moisture management finish to the microdenier polyester knitted

fabrics.

i.) Amino Silicone Polyether Copolymer

ii.) Hydrophilic Polymer

Amino silicone polyether copolymer: It is used as a softener on textile

materials giving durable soft handle to fabrics. It gives good water

absorbency properties and improves wickability on knitted fabrics. It is light

yellow in appearance and has good pH stability in acidic regions.

Silicones have wide applications in the textile industry, from fiber,

yarn and fabric production to final product finishing. Their distinctive

chemistry imparts a range of characteristics, including improved softness,

dimensional stability, fabric physical properties, wrinkle recovery, stretch and

recovery. Silicones can also be used to provide hydrophilicity or

hydrophobicity, static control, lubrication, antimicrobial treatments and anti-

slip properties. A variety of silicone technologies have applications in the

textile industry. They include: polydimethylsiloxanes, amino- / amido-

functional silicones, silicone elastomers, methyl hydrogen silicones, silicone

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polyethers, epoxy-functional silicones, epoxy polyether silicones and

hydroxy-functional silicones. Silicone families can be especially useful in

bringing benefits to fabrics when they are incorporated into rinse cycle fabric

softeners or laundry detergents.

Three silicone families are particularly useful in laundry care

applications: polydimethylsiloxanes, amino-functional silicones and amido-

functional silicones softener formulations dramatically improves the water

absorbency of fabric.

Chemical Structure of the Amino-Functional Silicone Polymer

Amino-functional silicones as shown above, have structures similar

to the amino polymers and they have a limited range of viscosities and

nitrogen content. The benefits associated with amino polymers include highly

effective softening properties and water absorbency.

Hydrophilic Polymer: It improves the wetting action and moisture

absorbency on polyester fabrics thus enhancing wearer comfort. It interacts

readily with water imparting a hydrophilic finish to the fabrics. It is white in

appearance.

The term “hydrophilic” is used only to refer to the surface

characteristics of the polymer. i.e. it is wet by aqueous solutions. Hydrophilic

polymers are very important class of polymer materials and the critical

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properties are sorption, desorption and swelling. The addition of one or more

surfactants to the nets of thermoplastic polymers is to impart hydrophilicity.

Hydrocyallylacrylates and the acrylic or methacrylic esters of

polyalkylene oxide or polyalkalenimides are examples of monomers with

hydrophilic group. Examples are polyacrylic acid, polyvinyl pyrrolidone,

polyvinyl alcohol, polyacrylamide, poly hydroxyl butyl acrylate etc.

Hydrophilic polymers are prepared by copolymerization of two hydroxyethyl

mathacrylate (HEMA) with ethylone glycon dimethyacrylate (EGDMA) and

PolyC2-hydroxy-ethyl methacrylate (PHEMA) with diphenyl methane-4.4-

diisocyanate (MDI). In this reaction one type of hydrophilic polymer is

formed.

3.2.2 Novel Wetting Agent

A Novel Wetting agent has been introduced for the preparatory wet

processing of the fabrics as given below.

Fatty Alcohol is made of Stearyl alcohol (1-Octadecanol) with 18

carbon atoms made from natural vegetable oils. It gives a powerful detergent

activity during medium foaming. Common raw materials for the production

of fatty acid or methyl ester are coconut, palm and palm kernel oils, tallow or

lard. While fatty acid is produced through high-pressure fat splitting, methyl

ester for fatty alcohol applications is obtained by transesterification. Some of

the common fatty alcohols used are Myristyl alcohol (1-tetradecanol) – 14

carbon atoms, Cetyl alcohol (1 – hexadecanol) – 16 carbon atoms, Stearyl

alcohol (1-octadeanol) -18 carbon atoms.

Ethylene Oxide (C2H4O) is produced with ethylene and oxygen

reacting on a silver catalyst at 200o-300

oC. It is highly reactive in the

presence of water and alcohols. It acts as a intermediate agent in detergent

activity. Ethylene oxide is a flammable, colorless gas. In industry ethylene

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oxide is produced which ethylene and oxygen reacting on a silver catalyst at

200–300 °C.

Formula for this reaction is CH2=CH2 + ½ O2 C2H4O

Propylene Oxide is an organic chemical in a colourless liquid

form. It is highly reactive in nature and acts as an intermediate in deteragent

activity. The chemical formula and name is as follows.

It is prepared by epoxypropane of propylene chrlorohydrin.

Chlorohydrin is obtained from the reaction of the butyl hypochlorite with

propylene and water.

All the above three chemicals are mixed together in equal

proportion to produce ethoxylated alcohol. The process of blending the

different chemicals is called “ethoxylation”. It is hazy gel in appearance.

3.3 METHODS

The Moisture Management finishing treatment method and

interaction between amino silicone and polyester fiber have been discussed as

given below.

3.3.1 Method for Moisture Management Finishing

The polyester knitted fabrics were hot washed and bleached. The

five fabric samples were treated with a wetting agent consisting of a

synergetic blend of ethoxylated alcohol (a fatty alcohol, ethylene oxide, and

propylene oxide) at 2% concentration for half an hour at 60–70°C temperature

CH3 – CH - CH2

1,2-epoxypropane

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and dried in a stentering machine at 140°C. These fabrics were treated for

moisture management finish with a chemical combination of Amino Silicone

Polyether Copolymer (ASPC) and Hydrophilic Polymer (HP) in the ratio of

1:2 with pH value of 5.5 at 60–70°C temperature. The samples were treated in

the finishing bath and padded using a padding mangle. Then it was dried and

cured in a stenter at 160–170°C and subjected to relaxation for 48 hours.

3.3.2 Interaction between Amino Silicone and Polyester Fibre

Domains of polyglycol (polyether copolymer) side chains act as

channels into which water can diffuse and be directed to the fiber surface. The

polyglycol side chains on the fiber surface form a hydrophilic layer, no matter

if the fiber is hydrophilic or hydrophobic. The upshot of this is that amino

glycol silicones can render hydrophobic fibers hydrophilic.

Figure 3.1 Amino Glycol Silicone Fluids Produce a Hydrophilic Layer on

the Fiber Surface. The Hydrophilic Polyglycol Chains are

Shown in Green

Hydrophilic anchoring groups with silicone polyglycol (polyether

copolymer) ensure that the silicone chains are firmly anchored and spread

across the entire fabric surface. The polymer molecule is constructed such that the

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hydrophilic polyglycol chains lie on the fiber surface. Interacting with the

anchoring groups, they generate a hydrophilic layer directly on the fiber surface.

Figure 3.2 The Hydrophilic Polyglycol Chains (Green) Lie on the Fiber

Surface. Together with the Anchoring Groups (Blue), they

thus form a Hydrophilic Layer Directly on the Fiber Surface

3.4 RESEARCH METHODOLOGY

The methodology adopted for this research work is given below.

3.4.1 Influence of Individual Filament Fineness on Comfort

Characteristics

In this study five different polyester continuous filament yarns of

150 denier were taken. It contained 34 filaments, 48 filaments, 108 filaments,

144 filaments, and 288 filaments. The selected polyester filament yarns were

knitted on a circular knitting machine of 28 gauge with speed of 30 rpm to

produce five different fabrics of single jersey structure containing 2.9mm

stitch length. The five different fabrics were then treated for moisture

management finish. In order to study the influence of individual filament

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fineness on comfort characteristics such as wetting, vertical wicking,

transverse wicking, moisture vapor transfer and drying rate were analyzed for

the moisture management finished polyester knitted fabrics. The detailed

flow chart is given in chapter 4.

3.4.2 Influence of Stitch Length and Knit Structure on Comfort

Characteristics

In this study microdenier polyester filament yarn of 150 denier

containing 108 filaments was used. The yarn was knitted on a circular

knitting machine to produce three different structures such as single jersey,

single airtex and honeycomb structure containing three different stitch length

lengths of 2.6 mm, 2.9 mm and 3.2 mm. All the nine fabrics were then treated

for moisture management finish. In order to study the influence of stitch

length and knit structure on comfort characteristics such as wetting, vertical

wicking, transverse wicking, moisture vapor transfer and air permeability

were analyzed for the moisture management finished fabrics. The influence of

laundering on wicking height was also analyzed. The comfort characteristics

were compared between MMF treated and untreated fabrics. The detailed

flow chart is given in chapter 5.

3.4.3 Influence of Laundering on Comfort Characteristics

Microdenier polyester filament yarn of 150 denier containing 288

filaments was taken as the study. The yarn was knitted on circular knitting

machine of 28 gauge to produce knitted fabric of single jersey plain structure

with 2.9 mm stitch length. The fabric was then treated for Moisture

Management Finish (MMF). In order to investigate the durability of MMF on

the fabrics when subjected to washing the comfort characteristics such as

wetting, vertical wicking, transverse wicking, moisture vapor transfer, air

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permeability and drying rate were analyzed after one, five, ten and twenty

laundry cycles. The results were compared with those obtained prior to

washing. The detailed flow chart is given in chapter 6.

3.4.4 Influence of Moisture Management Finish on Comfort

Characteristics

Five types of yarns namely Microdenier polyester, spun polyester,

polyester/cotton blend yarn, filament polyester and 100% cotton were taken

for the study. All the yarns were of the same count or denier (i.e.) spun

polyester, polyester/cotton and cotton were 35s count, whereas Microdenier

polyester (containing 108 filaments) and filament polyester (containing 34

filaments) were of 150 denier average fineness. The selected yarns were

knitted on the circular knitting machine of 28 gauge to produce five different

fabrics of single jersey plain structure containing 2.9 mm stitch length. The

five different fabrics were then treated for moisture management finish. The

influence of MMF on comfort characteristics such as wetting, vertical

wicking, transverse wicking, moisture vapor transfer, air permeability and

drying rate of five different MMF fabrics were analyzed. The comfort

characteristics were compared between MMF treated and untreated fabrics.

The detailed flow chart is given in chapter 7.

3.4.5 Influence of Moisture Management Finish on Thermal Comfort

Characteristics

Five different types of yarns namely Microdenier polyester, spun

polyester, polyester/cotton blend yarn, filament polyester and 100% cotton

were used for the study. All the yarns were of the same count or denier (i.e.) spun

polyester, polyester/cotton and cotton were 35 s

count, whereas Microdenier

polyester (containing 108 filaments) and filament polyester (containing 34

filaments) were of 150 denier average fineness. The selected yarns were

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knitted on the circular knitting machine of 28 gauge to produce five different

fabrics of single jersey plain structure containing 2.9 mm stitch length. The

five different fabrics were then treated for moisture management finish. The

influence of MMF on thermal comfort characteristics of five different fabrics

were analyzed. The thermal characteristics include thermal conductivity,

thermal resistance, thermal absorptivity, relative water vapor permeability and

water vapor resistance. The thermal comfort characteristics were compared

between MMF treated and untreated fabrics. The detailed flow chart is given

in chapter 8.

3.5 TESTING METHODOLOGY

The process of moisture transport in textile materials takes place in

three district steps viz. wicking, absorption and evaporation if the material is

hydrophilic, or wicking, spreading and evaporation if the material is

hydrophobic. Rate of wicking and rate of evaporation are the key variables in

moisture management. Higher the rate of wicking and evaporation better is

the fabric performance. Another factor which affects moisture management in

fabrics is absorbency. Optimum absorbency is desirable because while greater

absorbency increases the ability for moisture to be drawn into the fabric, the

tendency of absorbent fibres to retain such moisture affects comfort levels, as

the garment becomes saturated and wearer feels clammy. Hence the need for

various tests.

The fabrics treated with moisture management agents and untreated

fabrics were tested to assess the following characteristics.

3.5.1 Wetting Test

As per Saville (2000),this property was evaluated by measuring the

time required for a piece of fabric to sink completely from the surface layer of

water in a beaker. The fabric was measured by cutting a sample of 3 x 3 cm

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and placing it on the surface layer of water. The time taken for the sample to sink

completely in water was measured. The samples were dropped on the surface of

distilled water from a standard height and the time taken to sink the specimen in

water was noted. This reading varies according to the way and pressure of putting

the fabric. So utmost care has been taken for putting the fabric into water in a

horizontal form..

3.5.2 Vertical Wicking Test

As per BS 3424 this property was evaluated. To assess the wicking

characteristics of the fabric, a strip of 20 cm x 2 cm test fabric was

suspended vertically with its lower end (2 cm) immersed in a reservoir of

distilled water. In this method the vertical movement of water by capillary

action was observed at different time interval wicking rate which is used to

evaluate the sweating transfer rate from the body to fabric) and after 30 min (for

wicking height which is to assess the saturated level of sweat transfer). The

wicking tests were conducted with 10 samples each.

3.5.3 Moisture Vapour Transfer Test

This property was evaluated using ASTM E 96 –cup method.

Moisture vapour transmission rate is the speed or rate at which moisture

vapour moves through a fabric. Moisture vapour transfer test (open cup test)

is used for measuring the moisture vapour transmission rate. The rate of

water vapour that passes through the fabric was determined by two different

methods. The same are explained in detail below.

Reduction in the Height of Water in the Cup

Water was poured into cups upto 6cms from base level. The cups

were marked for every half centimeter. The fabric samples are placed tightly

on top of the cups where the water, the air above the water and the room

environment are at the same temperature and pressure. After 48 hrs the level

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of water decreased in the cups and the reduction in height of water was noted

down. The moisture vapour transfer rate is the difference between the initial

height of water and the actual height of water in the cups.

Reduction in the Weight of Water in the Cup

After measuring the height of water in the cups after 48 hours, the

fabrics were taken out from the top of the cups and the cups with water were

weighed in an electronic balance and the reduced weight was noted down.

The moisture vapour transfer rate is the difference between the initial weight

of water and the actual weight of water in the cups after 48 hours.

3.5.4 Air Permeability Test

This test was evaluated as per IS 11056 : 1984. The test gave the

rate of air flow through a material under a differential pressure between the

two faces of a fabric. It is expressed as the quantity of air, in cubic centimeter

passing per second through a square centimeter of fabric.

3.5.5 Drying Rate Test

Drying capability was evaluated by the drying rate of the fabric.

Two methods were adopted as detailed below.

As per Robert Miller et al (2006) this property was evaluated.

A 10x10cm fabric sample was taken. The sample was soaked in distilled

water and excess water was removed with a paper towel. The dry and wet

samples were weighed. Then the samples were put in a hot-air oven at 80°C

and allowed to dry. The samples were taken out and weighed at intervals of two

minutes each, till the sample weight reached dry weight of fabric. This method was

adopted in chapter 4 and chapter 6.

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As per Raul Fanguerio et al (2009) this test was conducted. The

specimen was cut as a 200 mm × 200 mm square, put on the plate of the

balance and the drying weight was recorded as wf (g). The water weight

added to the fabric, equal to 30% of the dry sample weight before testing was

designated wo (g). Record the change of water, wi (g) at regular intervals

continuously for some time observation. The “Water Evaporating Rate”

(WER) expresses the change of water weight remained in the specimen over

time. The evaporating curve was drawn from 100% to 0% at 33±2°C and

65±5% relative humidity. The mass of water wi (g) was recorded continually

every 2 minutes till dry fabric weight was reached.

WER (%) = (w0 – wi) × 100 / (w0 – wf)

This method was adopted in chapter 7.

3.5.6 Laundry Test

The durability of moisture management finish was assessed by the

laundry test. As per Lee Sumin et al (2009) this test was conducted.

The influence of laundering on moisture management finished

fabrics was measured by the wicking height for each set of samples twice

(i.e.) after 5 washes and after 10 washes respectively. The fabric samples were

laundered in a home washing machine and one laundry cycle took 15 minutes

which included washing and drying of samples. After 5 washes the samples

were tested for wicking characteristics and results noted down. Similarly the

samples obtained after 10 washes were tested for wicking characteristics. This

method was adopted in chapter 5.

The influence of laundering on moisture management finished

fabrics was analyzed for the comfort characteristics (i.e.) after one wash, 5

wash, 10 wash and 20 wash respectively. The fabrics were laundered in a

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home washing machine and one laundry cycle took 15 minutes which

included washing and drying of the fabrics. After one wash the fabrics were

tested for comfort characteristics and the results noted down. Similarly the

fabrics obtained after 5,10 and 20 washes were tested. This method was

adopted in chapter 6.

3.5.7 Alambeta Instrument

As per Nida Oglakcioglu et al (2009) this test was conducted.

Alambeta instrument was used to measure thermal conductivity, dry thermal

resistance and thermal absorptivity values. The Alambeta basically simulates

the dry human skin and its principle depends in mathematical processing of

time course of heat flow passing through the tested fabric due to different

temperatures of bottom measuring plate (22°C) and measuring head (32°C).

The specimen is kept between the two plates and a pressure of 200 pa is kept

in the hot plate while contacting the specimen. With the heat flux sensors, the

flow of heat is measured, while hot plate touches the specimen. One

observation time is 30 - 50 seconds.

Thermal conductivity is a property of materials that expresses the

heat flux (energy per unit area per unit time) that will flow through the

material if a certain temperature gradient (temperature difference per unit

length) exists over the material.

Thermal resistance is an indication of how well a material insulates

(Dry thermal resistance in transient state and wet thermal resistance in

isothermal state). It is based on the equation:

R = h / (m2K/W) (3.1)

where, R = Thermal resistance,

h = fabric thickness (m) and

= thermal conductivity (W/mK).

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Thermal absorptivity is the objective measurement of warm-cool

feeling and determines the contact temperature of two materials. It can be

expressed as:

B = ( p c)1/2

, (Ws1/2

/m2K) (3.2)

where,

= thermal conductivity (W/mK),

p = fabric density (kg/m3),

c = specific heat of fabric (J / kg K)

3.5.8 Sweating Guarded Hot Plate

Wet thermal resistance and water vapour resistance were measured

using sweated guarded hot plate as given by ISO 11092:1993 (E).

The sweating guarded hot plate determines the evaporative heat

resistance (Ret) and wet thermal resistance (Rct) of a material. The fabric

samples are conditioned in the chamber for 24 hours prior to testing. Water is

supplied through holes in the guarded hot plate and distributed onto a wet

membrane (Sontara®), which is placed on the hot plate to simulate sweating

skin. The test fabric (5” x 5”) is placed on the membrane, and the energy

required maintaining the simulated skin at 35°C after the system reaches

equilibrium is recorded and used to calculate the evaporative heat resistance in

steady state condition. This device simulates the sweat pulse produced by a

sweating human. It consists of a controlled environmental chamber, guarded hot

plate, diffusion cell, and data acquisition system. The guarded hot plate,

maintained at 35°C is used as a heat source, and housed in a chamber where

ambient conditions (21°C, 65% RH) and an air velocity of 50 cm/s are maintained.

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3.5.9 Permetest Instrument

Relative water vapor permeability was measured on ‘Permetest’

instrument working on similar skin model principle as given by the ISO 11092.

A slightly curved porous measuring surface is wet (either

continuously or on demand) and exposed to parallel air flow of velocity

(1.5 or 3.0 m/s). The tested sample is located in the distance of 1 to 1.5 mm

from the wet area of diameter 80 mm and characterized by high thermal

conductivity. The heat flow is generated by evaporation of water from the

surface and is measured by a special heat flow sensor integrated into the

porous layer. The time required is 2 minutes for measuring the permeability

of synthetic and blend fabrics. This instrument provides the relative water

vapor permeability of the fabric in the steady state isothermal condition. The

temperature of the measuring head is maintained at room temperature for

isothermal conditions. The heat supplied to maintain the temperature of the

measuring head, from where the supplied water gets evaporated, is measured.

The heat supplied to maintain a constant temperature with and without the

fabric mounted on the plate is measured.

Relative water vapor permeability is the rate of water vapor

transmission through a material. Relative water vapour permeability (%)

Heat lost when the fabric is placed on the measuring head

X 100 (3.3)

Heat lost from the bare measuring head

3.5.10 Scanning Electron Microscope (SEM) Test

SEM analysis was done using Japan Electron Optics Limited

(JEOL) model JSM-6360 microscope. It was done to study the fibre

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characteristics and determining the changes that have occurred in the fibre due

to the application of moisture management finish on the different woven

fabric samples. A fabric sample of size 1x1 inch was taken. It was placed

over a strip of carbon tape to improve the conductivity and then put under the

microscope for observations. Secondary electrons were focused on the

surface of the fabric to form an image known as Secondary Electron Image

(SEI). A two kilovolt electrical current was applied to obtain a 1000 times

image magnification of the sample fabric.

3.5.11 Geometrical Characteristics

The average wales per centimeter and courses per centimeter were

measured with the help of counting glass, The average stitch length was

measured by using a crimp tester. The average stitch density was measured

according to method IS : 1963 : 1981. The fabric areal density was measured

using an electronic scale according to method ASTM D 3776. The fabric

thickness was measured with the aid of thickness gauge according to method

ASTM D 1777 – 96. Fabric geometrical characteristics were measured at ten

different places in the fabric in each case.

3.6 DEVELOPMENT OF NOVEL METHOD FOR

TRANSVERSE WICKING BEHAVIOUR

A novel method has been developed through this research work to

measure the water spreading area on the fabric, to find out the transverse

wicking behavior of the fabrics.

3.6.1 Transverse Wicking

Analysis of transverse wicking characteristics of the fabric is more

important than longitudinal wicking because the perspiration (sweat) transfer

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from skin involves its movement through the lateral direction of the fabric. It

is the water transfer through the thickness of the fabric. Two methods have

been developed for evaluating transverse wicking behavior of the fabrics.

3.6.2 Area of Water Spread for One Drop of Water

It is the ability of the fabric to transfer the water by spreading

action. It helps to measure the lateral wicking area on fabrics while avoiding

directional effect. A total of 10 samples were tested. Each fabric sample of

10 cm diameter was mounted on an embroidery frame. A burette is placed

6mm above the surface of the fabric. One ml of water was allowed to fall

from the burette and the area spread on the fabric was measured. This was

done by placing a graph sheet beneath the fabric surface and tracing the

boundary of the water spread area by using a pin as illustrated in Figure 3.3.

3.6.3 Saturation Method

Similar to earlier method, ten fabric samples each measuring 20 cm

diameter were mounted on an embroidery frame. For every 3 seconds, one ml

of water was allowed to fall on the sample from a standard height of 6mm

through a burette. The drops of water falling on the fabric were continuously

absorbed by the sample. When the sample could not absorb any more water,

the excess water droplets fell down through the fabric. This is called the

saturation point. The time taken to reach saturation point was noted and the

area spread was also measured using a graph sheet similar to the earlier test as

shown in Figure 3.3.

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(a) Determination of transverse

wicking of fabric (front view)

(b) Determination of transverse

wicking of fabric (plan view)

(c) Marking of water spreading

area using pin

d) Pin marking impression on

graph sheet (graph sheet placed

below the fabric)

(e) darkening of pin marks using pen

Figure 3.3 Determination of Water Spreading Area on the Fabrics

The given materials and methods are common for all the chapters

from 4 to 8. The detailed specifications of the materials, machines and processes

are discussed under each objective mentioned in the respective chapters.