1. business and industrial
2. chemicals industry
3. dyes and pigments

DEVELOPING EASY WASH-OUT EFFECT ON COTTON KNITTED FABRICS DYED
WITH REACTIVE DYES VIA FOAM MEDIA
TSOI SHAN SHAN
BA (Hons) Scheme in Fashion and Textiles
(Fashion Technology Specialism)
INSTITUTE OF TEXTILES & CLOTHING
THE HONG KONG POLYTECHNIC UNIVERSITY
2010
DEVELOPING EASY WASH-OUT EFFECT ON COTTON KNITTED FABRICS DYED
WITH REACTIVE DYES VIA FOAM MEDIA
A Thesis Submitted
in Partial Fulfillment of the Requirements
for the Degree of
Bachelor of Arts (Honours)
in
Fashion & Textiles
(Fashion Technology Specialism)
under the Supervision of
Dr. Songmin SHANG
by
Tsoi Shan Shan
Institute of Textiles & Clothing
The Hong Kong Polytechnic University
April 2010
ACKNOWLEDGEMENTS
I would like to express my sincere gratitude to my supervisor,
Dr. Songmin SHANG, Assistant Professor of Institute of Textiles
and Clothing at the Hong Kong Polytechnic University, for his
constant guidance, invaluable advice, sustained interest, and
encouragement throughout my planning and preparation of the
project work.
I would like to express my thanks to Mr. E.L.HU, Research
Assistant of Institute of Textiles and Clothing at the Hong
Kong Polytechnic University, for his useful suggestion and
encouragement to the project.
I
also
thanks
to
all
Laboratory
Technicians,
including
Institute of Textile and Clothing and Department of Applied
Physical and Chemical Technical, for their thoughtful help and
guidance in operating the laboratory equipments.
Last but not least, special thanks to my family, friends and
classmates give their encouragement and spiritual support to
me during this endeavor.
CERTIFICATE OF ORIGINALITY
I hereby declare that this thesis is my own work and that, to the best of my knowledge and belief, it
reproduces no material previously published or written, nor material that has been accepted for the
award of any other degree or diploma, except where due acknowledgement had been made in the
text.
_____________________________________________________________(Signed)
______________________________________________________(Name of Student)
ABSTRACT
The wash-out effect on cotton knitted fabrics is getting more
and more popular. Foam dyeing technique is advantageous to
obtain the fading effect easily, since it is a low penetrating
dyeing method, to enhance surface dyeing effect, preventing
dyes to totally penetrate into the inner parts of the fibre.
After the United Nations Climate Change Conference held in
Copenhagen of Denmark in 2009, textile industries are aware
of lowering the emission of carbon dioxide in order to try and
delay the rate of global warming.
Foam dyeing, a ‘green’
technology, can meet today’s environmental requirements, such
as
low
carbon
emission,
reduction
of
water
and
energy
consumption, etc. due to the low wet pickup.
In this study, foam technique is used to develop a unique fading
effect on the cotton knitted fabrics dyed with reactive dyes.
Cationization on cotton will be conducted first, to enhance
surface dyeing effect and promote dyeing ability. The optimum
cationization process, concentration of cationic agents and
sodium carbonate, curing temperature and time, will be examined.
Moreover, concentration of surfactants, dosage of hydroxyethyl
(HEC) will be studied to evaluate foam stability.
Wet pickup
of fabrics and build-up property will be examined to know how
they affected the color shade.
After dyeing, fastness testing will be conducted to examine
the color fastness of the dyed cotton fabrics and the surface
temperature of fabrics in the drying process will be carried
out to evaluate the degree of energy saving.
CONTENTS
Page
ACKNOWLEDGEMENTS
ABSTRACT
CONTENTS
LIST OF TABLES
LIST OF FIGURES
CHAPTER1
GENERAL INTRODUCTON
1.1 Background of Study
1
1.2 Objectives
7
1.3 Scope of Study
10
1.4 Methodology
11
CHAPTER 2
LITERATURE REVIEW
2.1. Introductions
2.1.1 Wash-out effect
14
2.1.2 Background of wash-out effect
14
2.1.3 Main methods for developing
the wash-out effect
15
2.2 Foam technology
2.2.1 The background of foam technology
19
2.2.2 The history of foam technology
Development
2.2.3 The advantages and limitations
20
22
2.3 Foam properties
2.3.1 Background of foams
27
2.3.2 The collapse of the foam
28
2.3.3 Factors affecting the stability of
foams
30
2.4 Dyeing process with reactive dye
2.4.1 Introduction
32
2.4.2 Dyeing Principle of Reactive Dye
32
2.4.3 Factors Affecting Dyeing Reactive
Dye
33
2.4.4 Dyeing process for cationized
cotton fabrics
2.5 The application of foam technology
37
2.5.1 Preparation of foam combined with
finishing agent or colorants
39
2.5.2 Methods of Foam Application
41
2.5.3 Pre-drying and curing process
42
2.6. Washing process
CHAPTER 3
2.6.1 Introduction
43
2.6.2 Washing process
44
METHODOLOGIES
3.1 Cationization on cotton fabric
3.1.1 Introduction
46
3.1.2 Apparatus
47
3.1.3 Fabric used
48
3.1.4 Chemical used
48
3.1.5 Experiment procedures
49
3.2 Studied in foam system
3.2.1 Introduction
50
3.2.2 Apparatus
50
3.2.3 Chemical used
51
3.2.4 Experiment procedures
3.3
Foam-padding
dyeing
and
52
liquid-padding
dyeing
3.3.1 Introduction
53
3.3.2 Apparatus
53
3.3.3 Chemical used
54
3.3.4 Experiment procedures
56
3.4 Color strength (K/S) and dye
fixation (F%) measurement
3.4.1 Introduction
57
3.4.2 Apparatus
57
3.4.3 Experiment procedures
58
3.4.4 Calculation
59
3.4.5 Dye fixation (Fixation %)
measurement
59
3.5 Fastness Testing (Colorfastness to washing)
3.5.1 Introduction
60
3.5.2 Apparatus
60
3.5.3 Sample preparation
64
3.5.4 Experiment procedures
64
3.6 Fastness Testing (Colorfastness to rubbing)
3.6.1 Introduction
66
3.6.2 Apparatus
67
3.6.3 Experiment procedures
68
3.7 Energy saving evaluation
3.7.1 Introduction
69
3.7.2 Apparatus
69
3.7.3 Experiment procedures
70
3.8 Washing method
CHAPTER4
3.8.1 Introduction
71
3.8.2 Apparatus
71
3.8.3 Chemical used
74
3.8.4 Experimental procedures
75
RESULTS AND DISCUSSION
4.1 Optimization of Cationization on Cotton
76
4.1.1 Effect of cationic agent
concentration on color shade
77
4.1.2 Effect of sodium carbonate
concentration on color shade
79
4.1.3 Effect of curing conditions
on color shade
4.2 Studies on Foaming System
81
82
4.2.1 Effect of several surfactants
on foam abilities
83
4.2.2 Effect of hydroxythyl cellulose (HEC)
dosage on foam stabilities
85
4.2.3 Compatibility of foaming system
for dyeing
87
4.3 Evaluation of color shade
4.3.1 Effect of wet pickup property
89
4.3.2 Effect of build-up property
91
4.4 Evaluation of colorfastness
4.4.1 Effect of fixation condition
on colorfastness
94
4.4.2 Effect of Colorfastness of fabrics
dyed with reactive dyes
96
4.5 Evaluation of energy saving
97
4.6 Effect of wash-out
100
CHAPTER5
CONCLUSION AND RECOMMENDATIONS
5.1 Conclusions
103
5.2 Recommendations for future research
107
REFERENCES
110
LIST OF TABLES
Page
4.1
Effect of curing conditions on
relative K/S value
82
4.2
Compatibility of foaming system
88
4.3
Effect of fixation condition on color
fastness (Super Black G)
4.4
4.5
95
Colorfastness of fabrics dyed with reactive
dyes
97
Drying time for wetted fabrics
99
LIST OF FIGURES
Page
1.1
Schematic of catoinization on cotton
and its dyeing effect. (a) Original
cotton; (b) Cationized cotton; (c) Dyed
cationized cotton.
1.2
4
Schematic of enzyme wash on dyed cationied
cotton. (a) Dyed cationized cotton;
(b) Wash-out effect on cationized cotton
dyed; (c) Cross section of cationized cotton
dyed after wash.
7
3.1
Horizontal padding mangles
47
3.2
Mathis lab dryer
48
3.3
Dynamic foam generator
51
3.4
Foam dyeing on horizontal padders
56
3.5
Spectrophotometer
58
3.6
Launderometer
61
3.7
Stainless steel balls
62
3.8
Stainless steel lever lock canisters
63
3.9
AATCC Grey scale
64
3.10
AATCC crockmeter
67
3.11
AATCC Tumble washer
72
3.12
Hydro-extractor
73
3.13
Tumble dryer
74
4.1
Effect of cationic agent concentration
on color shade
78
4.2
Effect of Na2CO3 concentration on color shade
80
4.3
Foaming abilities of several surfactants
85
4.4
Effect of HEC dosage on foam half-life
87
4.5
Effect of wet pickup on colour strength
91
4.6
Effect of reactive dye amount on colour shade
93
4.7
Wash-out effect of cherry blouse made by
cotton knitted fabrics
102
To my
parents,
brother
&
sisters
Chapter 1 – General Introduction
Chapter 1
General Introduction
1.1
Background of Study
The wash-out effect on cotton fabric is getting more and more
popular in the market and in the fashion market. It is because
the fading effect is an aesthetic finishing, which can add value
to the clothing, giving more choices for customers to choose
from. The important reason is that the wash-out effect on the
cotton fabrics is very rare in the market; the most well known
end-use is to be applied in denim.
This fading effect is originally and generally made in the denim
products such as jeans. Because of its deep color and material
property, which is relatively stiff, it can easily achieve the
wash-out effect through abrasion using mechanical wash. Some
dye particles of materials are washed out and the fabrics will
expose the white areas on the inside of fiber to make a contrast
1
Chapter 1 – General Introduction
on the surface of fabrics. But, only using the wash method to
obtain the wash-out effect of the cotton knitted fabric is
inadequate, and it is also required the dyes to support
achieving the fading effect.
The dyeing process is also critical in achieving the wash-out
effect. In the traditional dyeing process, most of the cotton
knitted fabrics is conventionally dyed with overflow dyeing
machines and reactive dyes are completely penetrated into fibre,
thus the ring dyeing effect cannot be achieved and the wash-out
effect cannot be obtained either. Furthermore, another dyeing
process is not applicable to the cotton knitted fabrics. It
is the continuous slasher dyeing method (a kind of pad dyeing
method), which is applied in the denim. The cotton knitted
fabrics cannot use this method on account of the loose structure
and easy-to-curl property on opened knitted fabrics.
Aiming at achieving the fading effect and developing more
colorful fashion cotton fabrics, a novel technology of dyeing
2
Chapter 1 – General Introduction
cationized cotton with reactive dyes via foam media was studied.
Cationization on cotton is usually applied to improve dyeing
ability with reactive dyes on cellulosic fabrics, especially
cotton [1-3]. In the traditional dyeing process, high dosage
of sodium chloride or sodium sulfate is added in the dyebath
to enhance the dye affinity to cotton, which causes serious
water pollution for a large amount of salt including wastewater
discharged. However, the dyeing ability can be enhanced rapidly
by the means of cationization on cotton, which reduce the usage
of sodium chloride or sodium sulfate. This is because the
reactive dyes in dyebath have higher affinities to cationic
sites on cotton for their negative property. While cotton
without cationization appears negatively (Figure 1.1, a), some
polarity as soluble dyes in dyebath, it has fewer appetence
to reactive dyes. In this research, cotton is treated with
Indosol E-50 as a cationic agent to form cationic sites.
Generally speaking, compared to the inner part of fibre, there
are more cationic sites on the cotton surface, as the polymeric
cationic agent cannot penetrate into inner part of the fibre
3
Chapter 1 – General Introduction
easily. Therefore, most of the Indosol E-50 bonds to the surface
of the fibre or yarn, which forms a special layer with positive
polarity (Figure 1.1, b). When the reactive dyes are padded
on to the fabrics, dyes are absorbed to this special positive
layer by electrostatic interactions, which partly prevent the
dyes to penetrate into the inner part of the fibre in the
pre-drying or curing process. In other words, this layer acts
as a filter on the fibre surface which makes most of the dyes
attached to the fibre superficially (Figure 1.1, c).
Figure 1.1 Schematic of catoinization on cotton and its dyeing effect. (a) Original
cotton; (b) Cationized cotton; (c) Dyed cationized cotton.
4
Chapter 1 – General Introduction
However, although the inner part of the fibre has few Indosol
E-50, it does not mean that there are no affinities between
dyes and fibres at all. A few dyes can still penetrate into
the fibre core in property conditions. Since the wet pickup
in padding dyeing process is varied from 60% to 80%, a pre-dyeing
process required. In the drying process, the activities of dyes
increases as the temperature rises, dye-penetration happened.
To decrease this penetration, shortening of the pre-drying time
is very essential. Thus, foam technology is applied in this
research, in which the wet pickup decreases rapidly. Besides,
foam dyeing has other extension advantages, like decreasing
energy
consumption
in
drying
process,
reducing
water
consumption and improving the utility efficiency of the
chemicals, etc.
Both theoretical and practical foam dyeing technology is
beneficial to achieve the wash-out effect knitted cotton fabric.
Theoretically, foam dyeing can reduce the pickup ratio. Since
the lower is the pickup ratio of foam solution (about 30- 45%),
5
Chapter 1 – General Introduction
the higher is the reduction of energy (about 50%), accompany
with the low carbon emission and sustainable development of
dyeing industry. Practically, although foam technology results
in poor penetration and unevenness, it is good for achieving
the wash-out effect of the fabrics. It is because the dye is
not completely penetrated into the fiber of fabrics and it may
stick onto the surface of the fabrics, the parts of dye are
removed on the surface of the cotton knitted fabrics easily
and the fading effect obtained. The slight unevenness is not
important in the wash-out effect fabrics.
In enzyme-stone wash process, some dyes on fabrics are washed
out because of mechanical abrasion by pumice and chemical
degradation by enzyme, which expose white areas on the inside
of fiber to make a color-contrast effect on the surface of
fabrics. The schematic of enzyme wash effect can be seen in
.
6
Chapter 1 – General Introduction
Figure 1.2
Schematic of enzyme wash on dyed cationied cotton.
(a) Dyed cationized cotton; (b) Wash-out effect on cationized
cotton dyed; (c) Cross section of cationized cotton dyed after
wash.
1.2
Objectives
There are several objectives of this study, including achieving
the
wash-out
effect
on
the
cotton
knitted
fabrics,
environmental protection and developing more colorful fashion
cotton and so on.
To begin with, the major objective of this research is to develop
easy wash-out effect on cotton knitted fabrics dyed with
7
Chapter 1 – General Introduction
reactive dyes via foam media. As we know, some wash-out effect
is developed on denims, which is generally, difficult to be
made on the cotton knitted fabrics. This objective is the main
purpose of this study.
The second objective is to test the ability of foam dyeing and
cationization to obtain surface dyeing to achieve wash-out
effect. Whether all dyes on the surface of the fabrics will
be washed out during washing process or parts of dye will be
removed to achieve the fading effect.
The third objective is to find out the optimum cationization
process, such as the concentration of cationized agents, sodium
carbonate (Na2CO3), the drying time and the drying temperature.
Furthermore, it also aims at investigating on a surfactant and
the concentration of that surfactant which is the most suitable
for generating foam and has the highest foam stability, because
foam stability is very critical in foam dyeing.
8
Chapter 1 – General Introduction
Moreover, this study focuses on protecting the environment.
The application of foam technology can decrease the pickup ratio,
finally reducing the energy and water consumption. Besides,
cationization on cotton can improve the dyeing ability and
reduce the usage of sodium chloride or sodium sulfate, which
causes serious environmental pollution wastewater discharged
and so on.
This study does not only emphasize on the achieving of fading
effect on the fabrics, but also on the effects of fabrics are
required to meet the satisfactory application properties, such
as rubbing colorfastness and washing colorfastness, which
should meet the requirements of wash-out effect.
Last but not least, more colorful colors for dyeing of the cotton
knitted fabrics are hoper to be developed, like cherry, yellow,
ocean, navy and super black, etc., to cater for the customers’
needs and meet the fashion market.
9
Chapter 1 – General Introduction
1.3
Scope of Study
In this paper, it will be focused on cationization, reactive
dye, foam technology and stone and enzyme wash.
A. Cationization
Cationization is applied on the cotton before dye, because
it can improve dyeing ability of reactive dyes on cellulosic
fabrics. Moreover, it can reduce the usage of sodium chloride
or sodium sulfate, which leads to the water pollution.
B. Reactive Dye
Reactive dye has been the most common dye in the dyeing
of cotton because of the low price, full shade, easy
application and excellent fastness.
C. Foam Technology
Foam technology is theoretically and practically beneficial
to achieve the wash-out effect knitted cotton fabric. It can
10
Chapter 1 – General Introduction
decrease the pickup ratio, thus leading to the decrease in
energy and water consumption decrease. Though using this
method may result in poor penetration and unevenness dyeing
of fabrics, they do not influence the wash-out effect of the
cotton knitted fabrics.
D. Enzyme and Stone Wash
In enzyme-stone wash process, some dyes on fabrics are washed
out because of mechanical abrasion by pumice stones and
chemical degradation by enzyme, which expose white areas on
the inside of fiber to make a color-contrast effect on the
surface of fabrics.
1.4
Methodology
1. Desk Research
This includes looking through the past lecture notes, reference
books,
internet,
journals
and
so
on.
Introduction
on
cationization, reactive dye, foam technology and washing
11
Chapter 1 – General Introduction
methods studies and literature review were provided, which can
help doing the study very well.
2. Laboratory Test
The cotton knitted fabrics will be dyed and the fading effect
is created on the fabrics in the chemical and coloration
laboratory of ITC. Furthermore, I will do some laboratory tests
will be carried out using standard test methods according to
the ASTM (American Society for Testing and Materials) and AATCC
(American Association of Textile Chemists and Colorists) to
observe physical properties of the cationized cotton fabrics.
The
experiments
are
conducted
in
the
Physical
Testing
Laboratory of ITC.
3. Data analysis
During and after experiments, data are collected to conduct
the result. Data are processed and studied using the standard
formulae, in order to acquire a comprehensive evaluation of
the study. Also, SPSS data analysis system is used to analyze
12
Chapter 1 – General Introduction
the data, and it can show clear presentation of results by means
of graph pictures which aid result analysis.
13
Chapter 2 – Literature Review
Chapter 2
Literature Review
2.1
2.1.1
Introduction
Wash-out Effect
Wash-out effect is to remove dye particles of fabrics to
obtain the desirable abraded, worn out look through washing
process. It is an aesthetic finishing by giving particular
appearance of fabrics, especially denim.
2.1.2
Background of Wash-out Effect
Wash-out effect is an aesthetic finishing adding value on
the clothing, giving more choice for customers to choose.
This fading effect is originally made in the denim products
such as jeans, which is an indigo color. Because of its
deep color and material property, which is relatively stiff,
14
Chapter 2 – Literature Review
it can easily be to achieve the wash-out effect through
abrasion,
using
the
stone
washing
method
at
first,
afterwards, various washing methods such as microsanding,
bleaching and enzyme wash created to attain this effect.
Some dye particles of materials are washed out and expose
white areas on the inside of fiber to make a contrast on
the surface of fabrics. This finishing is very popular in
the textile market and caters for the customers. Therefore,
the development of wash-out effect is more and more in the
textile industry.
2.1.3
Main Methods for Developing Wash-out Effect
There are some main methods for developing wash-out effect,
which can be divided into two types: mechanical and chemical
wash. The mechanical wash contains garment wash and stone
wash. The chemical wash includes acid wash, enzyme wash
and bleaching. These washing methods can remove the dye
particles of fabrics.
15
Chapter 2 – Literature Review
a. Garment Washing
Garment washing is a traditional washing method. It can give
fabrics a soft hand feel and natural clean visually.
In the procedures, the denim is lightly singed and scoured with
a blend of phosphate esters before conducting open-width and
rope washing to ensure that the denim will have desirable handle
and texture. Afterwards, they are washed with detergents at
60 - 90 oC for about 15 minutes in the industrial used washing
machines. At last, the fabric is then softened and lubricated.
b. Stone washing
Stone washing provides a fading look for denim and increases
the softness and flexibility. It is one of the traditional
washing, but it has been improved by using other materials
during the process.
16
Chapter 2 – Literature Review
For the process, the freshly dyed jeans are loaded in large
washing machines and tumbled with pumice stones as abrasion.
The stones have rough surfaces, which remove some of the dye
particles from the surface of the yarns to give jeans a worn-out
effect.
c. Acid Washing
Acid washing is one of the traditional chemical washing method.
It can give the garment a random, shaded look by washing out
indigo dyes to create sharp contrasts in the color and reduces
the stiffness of the denim.
In the procedures, the dry denim cloth is bleached first. Pumice
stones are presoaked in bleaching agents such as sodium
hypochlorite or potassium permanganate. Then, the garments are
tumbled in a rotating drum with the stones to remove the first
layer of color of jeans chemically and mechanically to obtain
the fading effect. Finally, the garments are dried to neutralize
17
Chapter 2 – Literature Review
the hypochlorite left.
d. Enzyme Washing
Enzyme washing is a relatively new technology on denim to
achieve the worn appearance and provide a soft handle for jeans
since the enzyme cellulase removes surface fuzz.
The process can be operated at the low, warm or high temperatures.
Denim is treated in enzyme baths in which organic enzymes loosen
up the indigo dye and eat away cellulose fibers on the surface
of the fabrics. When the jeans get the preferred color,
enzymatic reaction is stopped by altering the alkalinity of
the bath. Special softeners and smoothing agents for softening
cycles are utilized to give the jeans a longer life.
e. Bleaching
Bleaching is a traditional method to remove the colour to create
18
Chapter 2 – Literature Review
special colour for the denim.
During the process, the strong oxidative bleaching agent
like sodium hypochlorite or potassium permanganate (KMnO4)
is sprayed during the washing with or without stone addition.
The addition of stone may further enhance the wash-out
effect. Then, the garment may be exposed some partially
white parts.
2.2
2.2.1
Foam Technology
The Background of Foam Technology
For foam technology, using air replaces water as the transport
medium for the reagents. The application of finishes using foam
technology has great advantages than the conventional finishing
techniques, which can attain economic, technical and ecological
advantages, for example, reduction of the large amounts of water
during processes, energy saving in the drying of fabrics,
19
Chapter 2 – Literature Review
reduction of chemical add-on, improvement in the fabric
physical properties, etc. Because of these benefits, it is more
and more popular in the textile industry, with a higher growth
rate.
2.2.2
The History of Foam Technology Development
Foam technology invented for a long time ago. In 1907, Schmid
used soap lather to improve a batch process for degumming and
weighting silk [4]. After, in the mid-1930s, Faber and Carroll
invented a foam batch process to treat textiles or material
[5]. In 1961, a foam-assisted engraved-roller- printing process
was disclosed for use with various dye classes [6]. It could
achieve the high yields and great economies. A specially
designed enclosed foam applicator could prevent changes in the
foam density in the printing process [6].
In 1972, a low-liquor-ratio dyeing process, that solvent was
emulsified in water, was developed [7]. This process was further
20
Chapter 2 – Literature Review
developed in 1974, by replacing the water-solvent emulsion by
an air-water mixture in a process, which was called the Sancowad
batch-dyeing process that used condensation foam [8]. The major
purpose of this process was water and energy savings. Later,
the Sancowad was used for pre-treatment in the wet processing
of textiles [9]. However, foam technology is frequently
possible to use conventional padders.
Foam technology was rapidly growing in the early 1980s. The
number of textile machine manufacturers developed their own
foam applicators for a wide variety of uses, for instance,
Monforts [10-11] and Dinting [12]. The machine manufacturers
providing foam equipment and foam finishing machinery at ITMA
(International Textile Machinery and Accessories exhibition)
increased from two in 1979 up to more than 30 in 1983 [13].
All chemicals used for the conventional treatment of textiles
can be added with foam applying to textiles such as sizing [14,
15], dyeing [16, 17], finishing and so forth. Moreover, foam
21
Chapter 2 – Literature Review
can be applied on products like durables- press resins,
softening agents, soil-release products, stiffening agents,
flames-retardants, bonding agents and so on. A wide variety
of fabrics from lightweight to heavyweight woven and knitted
fabrics, non-woven fabrics, fusible interlinings, industrial
fabrics, carpets [18-21], etc. can be applied by foams. Even,
yarns can be also applied by foam [22, 23].
2.2.3 The Advantages and Limitations
There are some advantages of using foam technology such
as low pickup percentages, energy and cost savings,
reduction of water consumption and water pollution, etc.
However, it is not a perfect technology because the low
pickup ratio will affect the uniformity and leveling of
fabrics, difficult production of deep shades and both sides
of fabrics and so on.
22
Chapter 2 – Literature Review
A. Advantages
To begin with, using foam application can save the pickup
percentage about 30% - 45%. Normally, the pickup percentage
of reactive dye solutions without foam is 60% - 75%, yet
using foam the pickup percentage is 30%.
Because of the reduction of pickup percentages, it can save
energy and cost. For instance, drying-energy cost is
reduced about 50% because it is low-add-on techniques. Also,
it can reduce drying temperature and shorten the time,
therefore producing products very quickly leading to high
production.
Moreover, the water consumption is reduced. According to
the report, it can be reduced from 30% - 90% [24-27]. It
is also reduced the volume of effluent water and thus the
effluent-treatment costs can be reduced by 50 - 60% [28,
29].
23
Chapter 2 – Literature Review
Apart from the water consumption, chemicals are utilized
more efficiently because of foam application treatment.
The dyestuff can be used less than in the conventional
padding process and the chemical can save up to about 50%
[30-32], so the chemical consumption and costs can be
eliminated. Then, it also improves water pollution because
of reduction of chemicals and certain auxiliaries such as
thickeners.
B. Limitation
To begin with, foam technology should have a well-prepared
fabric for foam processing. It is because variations in fabric
absorbency will result in variations in the wet pickup ratio,
and also affect the application of chemicals. As a result, the
preparation of fabrics is very important to ensure adequate,
uniform and level absorbency.
At very low wet pickup values affect the uniformity and
24
Chapter 2 – Literature Review
application [33, 34]. Fabrics cannot sufficiently wet and they
cannot be stretched to the required width in the stenter [35,
36]. Also, the penetration of the chemicals into fabrics is
not inadequate [37]. Thus, the fabrics cannot be dyed adequately
and evenly.
Because of low wet pickup levels of foam technology, it is
difficult to produce deep shades on the fabrics. Using the low
pickup levels is limited in dyestuff solubility [38, 39]. So
it cannot produce deep or dull shades on the fabrics, just
relatively light colors. For example, the company requires dull
shade on fabrics, but the manufacturers produce light color
because there does not easily control on the dyestuff solubility
of low wet pickup levels, which cannot meet the requirement.
So it will waste time and cost to produce again, and finally
defer the delivery time of products, even breaking the contract.
Also, using foam technology is only dyed on the one side of
fabrics, which is contacted with the dyestuff. It is because
25
Chapter 2 – Literature Review
the dyestuff with the aid of foam is low water inside replaced
by air. So there is no enough liquor to squeeze into the fabrics
by rollers, just for one side. It cannot achieve the fabrics
required dyeing on both sides.
The liquor preparations in any low-add-on application systems
of the foam technology are more crucial than
those in
conventional application systems [40, 41]. The concentrations
of chemicals in the liquors in the low-add-on application are
normally higher than conventional liquors [42, 43], and finally
the chemicals have to be screened for high solubility and
compatibility with the foam agents [44]. Therefore, the fabrics
can be dyed more uniform and even.
Some products and chemicals which are anti-foam formation
cannot be used on the foam technology. For example, many
commercial products including anti-foaming agents may forbid
foam formation. Solvents and mineral oils also inhibit foam
formation because they are used for certain processes that are
26
Chapter 2 – Literature Review
not reacted with foam. Certain optical brightening agents and
softeners and the existing of sulphate ions often reduce foam
stability.
2.3
2.3.1
Foam Properties
Background of Foams
Foam is an agglomeration of gaseous bubbles showing spherical
or polyhedral shape, usually of air, which are dispersed in
a liquid and separated from each other by thin films of liquid
or lamellae [45].
Foams can be solid or gaseous. For solid foams, produced from
gas and solid, are generally used in upholstery and in the
preparation of insulation [46]. Another is gaseous foams
produced from gas and liquid, used in textiles, especially
dispersion foams which are one type of gaseous foams. Dispersion
foams are produced in mixing of gas from an external source
27
Chapter 2 – Literature Review
into a liquid phase. This type of foam is mainly applied in
textiles. The gas phase is air, and the liquid phase is water,
containing surfactants such as foaming agent to produce foam.
However, foam properties are very important, especially foam
stability; otherwise the foam is unstable and easier to
collapse.
2.3.2
The Collapse of the Foam
Foam collapse is affected by foam stability, which will
influence the effect of application in textiles. If the foam
is relatively unstable, it may prematurely collapse, leading
in an uneven distribution of chemicals on the fabrics. On the
contrary, if the foam is too stable, it may be difficult to
obtain uniform collapse of the foam. As a result, the foam
penetrating into fabrics is poor.
Some disturbing influences can hasten the collapse of the foam
28
Chapter 2 – Literature Review
such as vibration, draughts, evaporation, radiant heat,
temperature differences, dust and other impurities.
However, foam stability is very important in measuring the
degree of foam collapse. Foam stability is meant that it is
to measure the time that foam will maintain its initial
properties as generated [47]. And the foam half-life is to
measure the foam stability, which is defined that the time
required for half of the volume of liquid included in the foam
to return to liquid form [47]. When the time is shorter, the
foam stability is lower.
In short, foam collapse is very important in foam application
because
it
will
affect
the
chemical
distribution
and
penetration into fabrics. So, it is required foam stability
to measure the degree of foam collapse.
29
Chapter 2 – Literature Review
2.3.3
Factors Affecting the Stability of Foams
Foam stability is an important factor in foam application, but
required a certain degree of stability. It is attributed to
several factors such as surface viscosity, film elasticity,
and zeta potential of the film and variation of bubble size.
First, surface viscosity is one of major factors affecting foam
stability. Increasing viscosity of the liquid in the walls of
the bubbles can contribute to film strength and durability,
because it increases the resistance to deformation, to increase
the rate of thinning and drainage. However, if the surface
viscosity is too high, it will become too hard to remove the
entrapped air and to break down the foam [48].
Apart from surface viscosity, film elasticity also affects the
stability of foam. It is defined as the ability of the liquid
film to withstand mechanical disturbance. Change in the surface
tension, influenced by time [49] and concentration of the
30
Chapter 2 – Literature Review
surfactant [50], affects film elasticity. When the bubble is
deformed, the surfactant flows form high concentration regions
to lower concentration. It is a self-healing mechanism, which
helps to keep more uniform film elasticity and results in better
foam stability.
Affecting the foam stability contains Zeta potential of the
film. It is an electric effect which can prevent collapse of
the bubble walls, because there is repulsion of ironically
charged surfactants in the film. Ionic surfactants are absorbed
in the bubble wall. The inner and outer bubble walls have similar
charge approaching each other; the electrical double layers
can overlap, so the resultant repulsive forces can avoid bubble
walls to collapse [46].
Besides, variation of bubble size affects the foam stability.
Finer bubble size of foam is more stable than coarse bubbles
of foam with the same density. For textile application, uniform
bubble size ranges from 50 to 100 microns in diameter [46].
31
Chapter 2 – Literature Review
In conclusion, foam stability is a significant element in the
foam properties. If we can get well in foam stability, it will
be very beneficial in the processes, such as dyeing process.
It can let the dyestuff with foam penetrate into fabrics
uniformly and evenly.
2.4
2.4.1
Dyeing Process with Reactive Dye
Introduction
Reactive dye first appeared in 1956, which was very popular.
Up to now, it has been the most common dye in the dyeing
of cotton because of cheap price, full shade, easy
application and excellent fastness.
2.4.2
Dyeing Principle of Reactive Dye
This range of dyes includes a reactive group which will
react with the hydroxyl group in cellulose forming a
32
Chapter 2 – Literature Review
covalent bond [51].
Simultaneously with the reaction of the dye with cellulose,
a certain amount of the dye reacts with water, and it removes
the particular reactive group from the dye, which is called
hydrolyzed dye [51].
The above reactions are under the alkali condition like
soda ash or caustic soda for reaction and fixation with
the fiber.
2.4.3
Factors Affecting Dyeing Reactive Dye
There are some factors influencing the dyeing, exhaustion
and fixation of reactive dye.
1. The pH of the dye bath
2. The temperature of dyeing
3. The time of dyeing
33
Chapter 2 – Literature Review
4. The liquor ratio
5. Effect of Dye Concentration
6. The concentration of electrolyte
7. Surfactants and other auxiliaries
1. The pH of the Dye Bath
The pH does not have significant effect on the exhaustion
of dye into fabric, but it is very important for fixation.
For most of the dye, the optimum pH is 10.8 to 11.0. But,
if the pH value is more than 11, it will reduce the
reaction rate and the efficiency of fixation, contrarily,
increasing hydrolysis. If the pH value is too small, it
will have the incomplete fixation. To attain the
required dyeing pH Is used different types of alkalis
such as caustic soda, soda ash, sodium silicate and a
combination of these alkalis.
2. The Temperature of Dyeing
Increasing in temperatures affects the rate of physical
34
Chapter 2 – Literature Review
and chemical processes in dyeing [51]. The affinity of
the dye for the fiber decreases with increases in
temperature, and at the same time, the rate of hydrolysis
of the dye increases and adversely affects the fixation
of color yield [51]. However, increasing temperature
rise the rate of diffusion of the dye in the fiber, having
better dye penetration, better leveling and easier
shading. If the temperature is lower than 20 oC, the rate
of fixation will be very low [51]. Maximum fixation is
at the optimum temperature.
3. The Time of Dyeing
Generally, increasing time can increase the final
exhaustion and increase levelness. The depth of shade
and the reactivity of dye decide the time of dyeing [51].
Longer time can obtain deeper shades.
4. The Liquor Ratio
Decreasing liquor ratio can increase the exhaustion and
35
Chapter 2 – Literature Review
color strength, so increasing of the liquor ratio lowers
the final exhaustion. But, the rate of fixation of most
of the dyes is not significantly influenced.
5. Effect of Dye Concentration
Increase
of
dye
concentration
reduces
the
final
exhaustion. So, for high dye concentration, the rate of
exhaustion tends to be slow. However, the rate of
fixation of the dyes is not significant affected.
6. The Concentration of Electrolyte
The addition of electrolytes tends to promote the final
exhaustion and the rate of exhaustion, increasing in dye
aggregation and a decrease in diffusion. When salt
concentration reaches a critical concentration, the
effect will stop. If salt is excessive, there will cause
‘salt-out’ of the dye. Using salts are no effects for
fixation of dye to fabrics.
36
Chapter 2 – Literature Review
7. Surfactants and other auxiliaries
Cellulosic fibres with the aid of suitable surfactants
can enhance the dye uptake. For instance, cationic
surfactants can change negatively charged fiber to
positive charge in order to exhaust dyes. Anionic
surfactants can also obtain a high dye uptake. Yet, nonionic surfactants may decrease the dye exhaustion, color
yield and cause a change in the shade.
2.4.4
Dyeing Process for Cationized Cotton Fabrics
Owing to cationic surfactants can promote the dye uptake and
affinity, the cotton fabrics treated with the cationic agent
becomes the cationized cotton fabrics.
As we know, cotton fibre in aqueous solution is negatively
charge because of the ionization of its hydroxyl groups.
Simultaneously, reactive dyes in aqueous solution are also
negatively charged, so they cannot attract each other and the
37
Chapter 2 – Literature Review
reactive dyes cannot penetrate into fiber in the dyebath. Thus,
cotton fiber is required to treat with a suitable cationic agent
to
change
its
polarity,
which
changes
to
uniform
electropositive charge.
After treatment, the dye can be able to penetrate and fix onto
the fiber. The cationization systems used are exhaustion,
pad-batch and pad-dry. This treatment is very good for reactive
dye because it can reduce the dye hydrolyzing and reduce the
wastage of water and energy.
After treatment with the cationic agent, it is required a rinse
to eliminate the cationic surfactants which are not fixed on
the fiber.
For dyeing process, there is used horizontal padding rollers
(mangles) method to impregnate the dyestuff with foam into the
fabric, followed by squeezing, usually by a passage through
a nip, to leave a specific quantity of foam dye into the fabric.
38
Chapter 2 – Literature Review
Pressure between the padding rollers affects the solution
uptake. The capillary effect is emerged through dye process.
It means that the fabrics quickly absorb a certain amount of
foam dye and replace the gas which is originally remained on
the capillary of fabrics. After padding, there is required to
dry and cure the fabrics to fix the dye on the fabrics.
2.5
2.5.1
The Application of Foam Technology
Preparation of Foam Combined with Finishing Agent or
Colorants
For foam preparation, there is required to have the foaming
agent and the foam stabilizer.
To form foam, it is desirably used foaming agent. Foaming agent
is a surfactant to facilitate the foam generation under the
mechanical action. There are several types of surfactants to
be suitable as forming agent such as ionic surfactants including
39
Chapter 2 – Literature Review
anionic and cationic depending on the pH of the system,
amphoteric and non-ionic surfactants.
It is also required foam stabilizer to improve foam stability,
which is not thickener. The typical examples are sodium
polyphosphates and dodecanol [52]. Sodium polyphosphates
increase
the
foam-stabilization
effect
[53].
Dodecanol
increases the viscosity of the film, leading to slow down from
the bubble walls to the drainage of liquid.
For this project, adding finishing agents (foaming agent and
foam stabilizer) required, there also needs to add colorants
in the mixture to create the dye with the aid of foam which
we desire.
After this preparation, these essential ingredients mix and
generate the dyestuff with foam through foam generators. And
then using the foam application methods applies the dye with
foam into the fabrics.
40
Chapter 2 – Literature Review
2.5.2
Methods of Foam Application
There are several types of foam application methods available
for applying finishes to textile fabrics, for instance,
horizontal pad mangle, foam coating methods, knife-over-roller
coating systems, knife-on-air system, screen printing system,
slot applicator system. For this project, we choose the
horizontal pad mangle to apply the foam to the fabrics.
The horizontal padder or pad mangle was one of the first machines
used for foam application. In the horizontal padder, the foam
is applied to both sides of the fabrics, which run vertically
through the foam picked up that is collapsed in the nip of the
padder.
Foam stability is very important in the foam application.
Unstable foam can form an excessive amount of liquor in the
nip, which gives an uneven application of the finish liquor.
More stable foam may tend not to collapse in the nip by the
41
Chapter 2 – Literature Review
action of the pad rollers. The advantages of this method are
relatively simple to control and the wet pickup of the fabric
is controlled by the foam density and the nip pressure. Moreover,
a conventional horizontal padder is easily converted to a foam
padder without a large capital investment. Finishing liquors
can be applied to cotton and cotton/polyester fabrics using
horizontal padder at a wet pickup level of 30% [54-58].
2.5.3
Pre-drying and Curing Process
After the horizontal pad mangle method, the fabrics are dyed
and required to weigh compared with the original weight. Then,
it is required to dry in the baking machine at 100 oC for 5 minutes
first. The objective of drying is to remove water of fabrics.
Afterwards, the fabrics are cured in the curing chambers under
the specific condition. The purpose of curing is to fix the
dye on the fabrics.
42
Chapter 2 – Literature Review
2.6
2.6.1
Washing Process
Introduction
To achieve wash-out effect, it is required to use washing
processes through friction under the standard condition. This
can produce a contrast color on the fabric surface between the
areas attacked by the enzyme in which the white areas on the
inside of the fibre exposed and other areas not attacked by
the enzyme.
In this project, using enzyme stone wash is used to obtain the
worn effect, because it combines advantages of mechanical and
chemical wash. For stone wash, pumice stones are used for
abrasion, which have rough surfaces removing some of the dye
particles from the fabrics to achieve a fading effect.
Cellulases enzyme treatment also gives wash-out effect,
removing the hairiness, prevention of pills, and provides
excellent handle.
43
Chapter 2 – Literature Review
Cotton fibres are made up of ß-cellobiose polymers, forming
highly ordered areas called crystalline and other disordered
areas called amorphous. The enzyme has a high molecular weight,
which acts upon the fiber surface and breaks the cellulosic
chains, attacking the fine threads and opening constructions.
The cellulosic chains in the amorphous areas are attacked by
the enzyme due to the presence of exoglucanase. On the contrary,
the cellulosic chains in the crystalline areas are not attacked
by the enzyme on account of the highly ordered areas.
The enzyme is controlled by the pH and the temperature. Below
is the introduction on the washing process, showing the
preferred pH and the temperature.
2.6.2
Washing Process
In the washing process, it is more preferable to use acid
cellulases more than neutral cellulases because of high
abrasion, high backstaining, high bio-polishing (removing
44
Chapter 2 – Literature Review
hairiness and anti-pilling) and soft handle. Acid cellulases
operate at pH around 4.5 - 5.5 and slightly lower temperature
range from 45 – 60
o
C.
After preparation of the enzyme solution, the specimen was
placed in the washing device together with the pumice stones.
Then, the specimen was rotated with pumice stones at 60 oC for
30 minutes. After the washing process, the specimen was rinsed
at room temperature for 5 minutes to remove residue. Finally,
the fabric was hydro-extracted and dried inside the tumble
dryer.
The surfaces of fabrics show wash-out effect after drying. If
the colors of fabrics are dull or deep, a more worn-out effect
can be created.
45
Chapter 3 - Methodology
Chapter 3
Methodology
3.1
Cationization on Cotton Fabrics
3.1.1
Introduction
Cationization on cotton is to improve dyeing ability of reactive
dyes on cellulosic fabrics, especially cotton [1-3]. As cotton
fibre and reactive dye in aqueous solution both present
negatively charges, they cannot attract each other and the dye
cannot penetrate into fiber in the dyebath. Thus, cotton fiber
is required to be treated with a suitable cationic agent to
change
the
polarity
cellulosic
fiber,
which
is
uniform
electropositive charge, to promote dye uptake and affinity.
46
Chapter 3 - Methodology
3.1.2
Apparatus
1. Horizontal Padding Mangles
It consists of two squeezing bowls (rollers) made by the iron
and covered with rubbers, illustrated in the Figure 3.1. Through
squeezing, usually by passage through a nip, the solution is
impregnated onto the surface of fabrics.
Figure 3.1 Horizontal padding mangles
2. Curing Chamber
Curing chamber is used to dry the fabrics and fix the solution
47
Chapter 3 - Methodology
on the surface of fabrics, shown in Figure 3.2.
Figure 3.2 Mathis lab dryer
3.1.3
Fabric Used
One hundred percent cotton (250 g/m2), bleached and desized was
purchased from Seven Seas Knitting & Dyeing Woks Ltd.,
Guangdong.
48
Chapter 3 - Methodology
3.1.4
Chemical Used
Cationization agent (CA) Indosol E-50 was provided by Clariant
Chemicals (China) Co., Ltd. Sodium carbonate (SC) was also
required for cotton fabrics to be cationized.
3.1.5
Experiment Procedures
Cotton fabric was dip-nipped in the solution containing
cationization agent (CA) Indosol E-50 and sodium carbonate (SC)
at room temperature on Mathis pad mangle. The pressure on the
pad mangle was adjusted to give a wet pickup of 70%. The sample
obtained then curing at the certain temperature for several
minutes.
Afterwards,
the
cationized
fabric
was
cleaned
immediately in distilled water to remove the un-reacted and
excessive actinic agent and loft-dried at room temperature.
The samples were ready for dyeing.
49
Chapter 3 - Methodology
3.2
Studied on foam system
3.2.1
Introduction
Foam is very critical in foam dyeing, which will affect the
dyeing effect and color shade. The initial foam height and foam
half-life is used to measure foam stability. In this study,
different
concentration
hydroxyethyl
cellulose
of
surfactants
were
examined
to
and
dosage
evaluate
of
foam
stability.
3.2.2
Apparatus
1. Dynamic Foam Generator
Dynamic foam generator consists of a liquor-flow pump, air-flow
unit and mixing head. The mixing head consists of a rotor and
stator.
50
Chapter 3 - Methodology
Figure 3.3 Dynamic foam generator
3.2.3
Chemical used
Sodium dodecyl sulfate (SDS), hydroxyethyl cellulose (HEC) and
sodium carbonate (SC) were used. The following was the foam
recipe:
Chemical
Dosage (g/L)
Sodium dodecyl sulfate (SDS)
15
hydroxyethyl cellulose (HEC)
5
Sodium carbonate (SC)
15
51
Chapter 3 - Methodology
3.2.4
Experiment procedures
Foam is generated by injecting air under pressure into liquor,
using the dynamic foam generator. To begin with, a required
amount of dye solutions containing foaming agent and other
auxiliaries were poured into the built-in liquid container.
Air under pressure and the amount of liquor were introduced
into the mixing head. The outflow of foam was near the mixing
head.
The collected foam was weighed to measure the initial foam
height, and the time taken for half of the volume of liquid
to collect was determined as the foam intermediate life [47].
3.3
3.3.1
Foam-padding dyeing and liquid-padding dyeing
Introduction
Foam technology can decrease pickup percentage rapidly,
52
Chapter 3 - Methodology
shortening the drying time, reduction of energy and water
consumption, improving the utility efficiency of the chemical,
finally minimizing the production cost and time. Dyeing is used
horizontal padder with foam, leading to even and uniform
application.
There
was
conducted
different
wet
pickup
percentages of fabrics and build-up property compared with
liquid-padding dye.
3.3.2
Apparatus
1. Horizontal Padding Mangles
It consists of two squeezing bowls (rollers) made by the iron
and covered with rubbers. Through squeezing, usually by passage
through a nip, the foam or a substrate of liquor is impregnated
into the fabrics.
2.
Curing Chamber
Curing chamber is used to dry the fabrics and fix the dye. It
can conduct at the high temperature.
53
Chapter 3 - Methodology
3.3.3
Chemical Used
(a) Reactive dyes via foam media
The reactive dyes used were Novacron Cheery S-D, Novacron Yellow
S-3R, Novacron Ocean S-R, Novacron Navy S-G and Novacron Super
Black G, which were obtained from Huntsman Textile Effects
(China) Co., Ltd. These dyes were chosen because of their
commercial availability and representative of five different
basic colors.
(b) Effect of wet pickup on color shade
Sodium dodecyl sulfate (SDS), hydroxyethyl cellulose (HEC) and
sodium carbonate (SC) and dye was used. The recipe was the
following:
Chemical
Dosage (g/L)
Sodium dodecyl sulfate (SDS)
15
Hydroxyethyl cellulose (HEC)
5
Sodium carbonate (SC)
15
Dye
80
54
Chapter 3 - Methodology
The dyed fabrics were cured at 180
o
C for 1 min.
(c) Effect of build-up property
Sodium dodecyl sulfate (SDS), hydroxyethyl cellulose (HEC) and
sodium carbonate (SC) and dye was used. The recipe was the
following:
Chemical
Dosage (g/L)
Sodium dodecyl sulfate (SDS)
15
Hydroxyethyl cellulose (HEC)
5
Sodium carbonate (SC)
15
Dye
Foam-padding: 80 g/L
(Pickup: 30%)
Liquid-padding: 35 g/L
(Pickup: 70%)
The dyed fabrics were cured at 180
55
o
C for 1 min.
Chapter 3 - Methodology
3.3.4
Experiment Procedures
After foam generation, the fabric was dyed using horizontal
padders. In the horizontal padders, the foam was applied to
one side of the moving fabric at the appropriate rate, which
introduced vertically to the nip of the padders. The foam
collapsed at the nip of the padders, finally fabrics were dyed.
The generation of foams and their dyeing process can be seen
in Figure 3.4.
Figure 3.4 Foam dyeing on horizontal padders
56
Chapter 3 - Methodology
For liquid-padding dyeing, it is similar to the conventional
dyeing method. The dyeing solution was prepared and then poured
directly between the padding rollers in the horizontal padders.
3.4 Color Strength (K/S) and Dye Fixation (F%) Measurement
3.4.1
Introduction
Color strength is a measure of the ability of a dye to impart
color to other materials [59]. It is evaluated by light
absorption in the visible region of the spectrum [59].
3.4.2
Apparatus
1. Spectrophotometer
Spectrophotometer
is
equipped
with
a
Xenon
source
(interchangeable with a tungsten source), which is connected
with the computer system for data processing. It is used to
measure the relative amounts of energy reflected from a specimen
57
Chapter 3 - Methodology
in the visible region of the energy spectrum at 10 nm intervals
in the range 400 - 700 nm.
Figure 3.5 Spectrophotometer
3.4.3
Experiment Procedures
The spectrophotometer is calibrated with the Merck Barium
Sulphate
using
Xenon
source
and
the
specular
component
contained prior to sample measurement. Each sample fabric was
measured
three
times
at
different
areas
and
directions. The data were stored in the computer.
58
different
Chapter 3 - Methodology
3.4.4
Calculation
The color strength expressed as K/S value is calculated from
Kubelka-Munk equation as shown in Equation (1):
K 1  R 

S
2R
2
(1)
where R is the reflectance of the dyed sample, it was determined
on UltraScan XE Color Measuring and Matching Meter (Roaches
Co.) at the wavelength of maximum absorbance of each dyestuff.
3.4.5
Dye Fixation (F %) Measurement
The fixation of adsorbed dye (F %) was calculated using Equation
(2):
F% 
K / S 1
K / S 0
(2)
59
Chapter 3 - Methodology
where the subscripts 0 and 1 indicate values obtained before
and after soaping, respectively.
3.5
3.5.1
Fastness Testing (Colorfastness to Washing)
Introduction
As for Colorfastness to washing, it is to evaluate the
colorfastness of textiles to repeat washing using a soap
solution. The fabric color loss and surface changes are resulted
from detergent solution and abrasion action of laundering. Dyed
fabrics are tested for colorfastness to washing according to
ISO 105-B01:1994.
3.5.2
Apparatus
1. Washing device (launderometer)
A
washing
machine
is
to
rotate
closed
canisters
in
a
thermostatically controlled water bath at 40 ± 2 rpm. The
60
Chapter 3 - Methodology
following machine is launderometer in Figure 3.6.
Figure 3.6 Launderometer
2. Stainless steel balls
Each stainless steel ball is approximately 0.6 cm in diameter,
shown in Figure 3.7.
61
Chapter 3 - Methodology
Figure 3.7 Stainless steel balls
3. Stainless steel lever lock canisters
Each stainless steel lever lock canister is for carrying a
sample, solutions and stainless steel balls to put in the
washing machine for washing.
62
Chapter 3 - Methodology
Figure 3.8 Stainless steel lever lock canisters
4.
Multifibre fabric
The multifiber fabric has bands of acetate, cotton, nylon, silk,
viscose rayon and wool.
5.
Grey scales
The grey scale is for assessing the change in color of the test
specimen and the staining of the adjacent fabrics.
63
Chapter 3 - Methodology
Figure 3.9 AATCC Grey scale
3.5.3
Sample Preparation
The test specimen and the microfiber fabric were cut 50 x 150
mm and sewn them together to form a composite specimen.
3.5.4
Experiment Procedures
Before carrying out the colorfastness, fabrics were dyed with
the following recipe.
64
Chapter 3 - Methodology
Chemical
Dosage (g/L)
Sodium dodecyl sulfate (SDS)
15
Hydroxyethyl cellulose (HEC)
5
Sodium carbonate (SC)
15
Dye
Foam-padding: 80g/L
(Pickup: 30%)
After dyeing, the fabrics were cured 180
o
C for 3 min.
For washing fastness, the composite specimen was placed in the
canister and added total liquor volume 150 mL and 0.15%
detergent of total volume previously heated to a specified
temperature. The washing test conducted at 49 oC ± 2 oC for 45
minutes. Finally, the composite specimen was removed from the
canister and rinse twice for 1 minute in two separate 100 ml
portions of distilled water at 40 oC ± 3 oC. To remove excess
water from the composite specimen, it was opened out by breaking
the stitching on all sides except one of the shorter sides and
dried by hanging it in air at a temperature not exceeding 60
65
Chapter 3 - Methodology
o
C. At last, it was assessed with the grey scales the change
color of the test specimen and the staining of the specified
component
of
the
multifiber
fabric
in
standard
viewing
conditions.
3.6 Fastness Testing (Colorfastness to Rubbing)
3.6.1
Introduction
Colorfastness to rubbing is intended for determining the amount
of color transferred from the surface of colored materials to
other surfaces by rubbing. It is done according to ISO
105-X12:2001using Y (B) 571-II crockmeter. Colored test
specimens are rubbed with white crock test cloth (including
dry and wet) under standard conditions.
66
Chapter 3 - Methodology
3.6.2
Apparatus
1. AATCC crockmeter
Crockmeter with a finger of 1.6 cm diameter is to move forward
and backward in a straight line along a 10 cm track on the
specimen with a downward force of 0.9 kg.
Figure 3.10 AATCC crockmeter
2. 5 cm x 5 cm white crock test cloth
It is undyed bleached cotton rubbing cloth, free from the starch
67
Chapter 3 - Methodology
or other finish.
3. Grey scale for assessing staining
Grey scale is for assessing the staining of the undyed rubbing
cloth pieces (the white crock test cloth).
3.6.3
Experiment Procedures
There were two tests including dry rubbing test and wet rubbing
test.
For dry rubbing test, a test specimen was placed on the base
of the crockmeter resting flat and used specimen holder to
prevent it to slip. It was rubbed with the dry and undyed rubbing
cloth to and from 10 times in 10 seconds, which was in a position
over the end of the finger of the testing device. At last, the
white test cloth square was removed to evaluate with grey scale.
The other test was the wet rubbing test similar to the dry
68
Chapter 3 - Methodology
rubbing test. The only difference was that the white test cloth
was required to wet with water and squeezed or hydro-extracted
to a take-up of 100%. After rubbing, the cloth dried at room
temperature. Finally, the staining of the undyed rubbing cloth
pieces was assessed with the grey scale.
3.7
3.7.1
Energy saving evaluation
Introduction
Foam dyeing technology aims at saving energy and drying time
because of reducing the amount of water used in dyeing. Fabrics
with different wet pickup percentages of water were dried in
the curing chamber to evaluate the energy saving.
3.7.2 Apparatus
1. Horizontal Padding Mangles
It consists of two squeezing bowls (rollers) made by the iron
69
Chapter 3 - Methodology
and covered with rubbers, illustrated in the Figure 3.1. Through
squeezing, usually by passage through a nip, the solution is
impregnated onto the surface of fabrics.
2. Curing Chamber
Curing chamber is used to dry the fabrics and fix the solution
on the surface of fabrics, shown in Figure 3.2.
3.7.3
Experiment procedures
Fabrics were padded to result in different wet pickup of water
including 0%, 20%, 30%, 70%, 80%, 90% and 100%. Afterwards,
the fabrics were dried in the curing chamber. The surface
temperature of the fabrics was monitored as a function of time.
The screen of the curing chamber showed a drying curve depending
on the degree of fabrics dried. The drying temperature and time
were recorded.
70
Chapter 3 - Methodology
3.8
Washing Method
3.8.1 Introduction
The washing method is to remove some dyes on fabrics to expose
white areas on the inside of fiber to make a color-contrast
effect on the surface of fabrics. For this study, using enzymestone wash process, some dye on fabrics are washed down because
of mechanical abrasion by pumice and chemical degradation by
enzyme.
3.8.2
Apparatus
1. Tumble washer
The tumble washer is used to rotate specimens with pumice stones
and enzyme inside to achieve the wash–out effect through
abrasion at the specific condition. It can increase the washing
temperature by adding steam. The machine can determine the
results of the wash-out effect on the fabrics such as uniform,
71
Chapter 3 - Methodology
appearance, etc.
Figure 3.11 AATCC Tumble washer
2. Hydro-extractor
The hydro-extractor is used to dewater fabrics efficiently
after washing and reduce drying time.
72
Chapter 3 - Methodology
Figure 3.12 Hydro-extractor
3. Tumble dryer
It is a steam-heating model, used to dry the fabrics totally.
There are different temperatures and time to select under
specified conditions.
73
Chapter 3 - Methodology
Figure 3.13 Tumble dryer
3.8.3
Chemical used
Acid cellulase was used because of high abrasion, high
backstaining, high biopolishing (removing hairiness and antipilling) and soft handle.
74
Chapter 3 - Methodology
3.8.4
Experimental procedures
In this study, for the washing process, it was required acid
cellulases operating at pH around 4.5 - 5.5 and slightly lower
temperature range from 45 oC - 60 oC. After preparation of the
enzyme solution, the specimen was placed in the washing device
and pumice stones were put inside. Then, the specimen was
rotated with pumice stones at 60 oC for 30 minutes. After the
washing process, the specimen was rinsed at room temperature
for 5 minutes to remove the residue. Finally, the fabric was
hydro-extracted and dried through the tumble dryer.
75
Chapter 4 – Results and Discussion
Chapter 4
Results and Discussion
4.1
Optimization of cationization on cotton
Cationization degree is an important factor that influences
the ring dyeing effect on cotton fibre. The more cationic agent
reacts with fibre, the more sites are on the fibre surface.
Therefore, most of the dyes are attached to the fibre surface
rather than penetrating into inner of the fibre. Research in
this step is looking for the most suitable cationization
situation which can be obtained at the highest cationization
degree. And the relative K/S (%) was calculated as the special
value for characterizing cationization degree. This was because
the more cationic agent reacted with cotton, the higher was
the affinity for dyes and the darker shade obtained on cotton.
76
Chapter 4 – Results and Discussion
4.1.1
Effect of cationic agent concentration on color shade
Aiming at optimizing the cationization conditions, the effect
of the concentration of cationic agent was studied first. The
results could be seen in Figure 4.1. Wherein, the concentration
of sodium carbonate was 50 g/L, curing temperature was 120 oC
and curing time was 2 min.
In Figure 4.1, it showed the variation of the color depth of
dyed sample as a function of cationic agent usage. As the
concentration increased from 0 to 60 g/L, the color depth
increased rapidly. However, when the concentration further
increased, there was no remarkable change in color yield. This
could be explained that the reaction between cationic agent
and cotton reached the saturation point. At this moment, the
reacted cationic agent on fibre acted as an obstacle to the
non-react cationic agent. This was because some electro
properties
between
them
led
to
more
difficulties
for
non-reacted cationic agent approach to fibre. Moreover, the
77
Chapter 4 – Results and Discussion
steric exclusion which prevented the further reaction between
excessive cationic agent and cotton was also an important factor
that should not be neglected. Although there were still a number
of hydroxyl groups on fibre, cationic agent could not react
with them at all.
Thus, in the following research, 60 g/L was selected as the
optimum concentration in cationization process.
Relative K/S
Relative K/S (%)
100
80
60
40
0
40
80
120
160
Concertration of cationic agent (g/L)
Figure 4.1 Effect of cationic agent concentration on color shade
78
Chapter 4 – Results and Discussion
4.1.2
Effect of sodium carbonate concentration on K/S value
Sodium carbonate was really a necessity in cationization. In
this process, the main function was that it led to the formation
of covalent bonds between solution and cotton.
In the Figure 4.2, it showed the influence of sodium carbonate
usage on color yields obtained. Wherein, the concentration of
cationic agent was 60 g/L, curing temperature was 120 oC and
curing time was 2 min.
According to this figure, the relative color shade was lower
than 60% without sodium carbonate in dyes solution. However,
the color depth rose dramatically when the concentration of
sodium carbonate went up. Even at a low concentration of 20
g/L, there obtained more than 20 percent growth of color yield.
Yet, when the concentration continuously rose from 60 g/L to
100 g/L, there was no significant change in color depth. Upon
the further increase in Na2CO3 dosage, the upward trend in pH
79
Chapter 4 – Results and Discussion
value led to acceleration of hydrolysis of cationic agent, which
resulted less color yield being produced.
As a consequence, the optimum concentration was 60g/L, which
could obtain good color yield and achieve higher efficiency
of sodium carbonate utility
Relative K/S
Relative K/S (%)
100
80
60
40
0
40
80
120
160
Concertration of sodium carbonate (g/L)
Figure 4.2 Effect of Na2CO3 concentrations on color shade
80
Chapter 4 – Results and Discussion
4.1.3
Effect of curing conditions on color shade
Both curing temperature and time were important for the
cationization process and the application properties of the
cationic cotton. The reaction between cotton and cationic agent
was happened in this step.
For
the
investigation
of
the
relationship
about
curing
conditions to cationization, the dosage of cationic agent and
the concentration of sodium carbonate were 60g/L and 50 g/L,
respectively.
As shown in Table 4.1, the color depth could not reach to 90%
at a relative lower temperature, no matter how long the curing
time lasted. As the temperature increased, color yield improved
accordingly. Also, the curing time for obtaining maximum color
yield decreased. At 120 oC, when the curing time was 130 s, the
maximum color depth obtained. Furthermore, at 140 oC, the peak
of the color shade was only required 90 s.
81
Chapter 4 – Results and Discussion
Based on the above study, the optimum conditions of the cationic
modification were obtained: cationic agent concentration was
60 g/L, Na2CO3 concentration was 60 g/L, and curing at 130 oC
for 110 seconds.
Table 4.1 Effect of curing conditions on relative K/S value
Temperature (oC)
Time
4.2
(s)
100
110
120
130
140
90
80.6
85.9
90.5
95.0
100
110
83.7
88.4
95.2
97.5
99.3
130
84.9
86.9
98.7
95.5
99.8
150
82.4
88.5
98.6
96.4
97.5
Study on foaming system
Foaming system is very important in the dyeing, because its
ability affects the dyeing results and color shade. Surfactants
generate foam, which affect the initial height of foam and
intermediated life of foam, finally affect the dyeing effect.
82
Chapter 4 – Results and Discussion
In this section, concentration of several surfactants and
dosage of hydroxyethyl cellulose (%) were conducted to examine
which could obtain the highest foam ability.
4.2.1
Effect of several surfactants on foam abilities
Foam ability is very critical in a foam system, initial height
of foam involved. To have high initial height is advantageous
for foam ability. If the initial height is higher, the foam
ability is better. There were several surfactants (including
anion and nonion) using different concentrations to evaluate
the initial height of foam.
The results could be seen in Figure 4.3. For anion, the initial
height of foam of sodium dodecyl sulfate (SDS), ABS and AS
rapidly increased from 0.0 to 1.0 g/L, especially for sodium
dodecyl sulfate, rose sharply between 0.0 to 0.5 g/L from 95
cm of initial height of foam to 170 cm. If the concentration
further increased, they did not cause any remarkably change
83
Chapter 4 – Results and Discussion
in the initial height of foam. For nonion, the initial height
of foam of JFC and JU gradually climbed when the concentration
increased. But, JFC could generate higher initial height of
foam than JU.
The results showed that, for both anion and nonion, sodium
dodecyl sulfate and JFC were the most suitable to be surfactant
to generate high initial height of foam quickly, respectively.
The peak concentration of sodium dodecyl sulfate and JFC was
0.5 g/L and 1.0 g/L respective. From the concentration onwards,
it did not significantly influence in the initial height of
foam. Therefore, for this study, sodium dodecyl sulfate was
selected as the surfactant which was also the foaming agent.
84
Chapter 4 – Results and Discussion
200
SDS
ABS
AS
JFC
JU
Initial height (cm)
160
120
80
40
0.0
0.5
1.0
1.5
2.0
2.5
Concentration of surfactants (g/L)
Figure 4.3 Foaming abilities of several surfactants
4.2.2
Effect of hydroxyethyl Cellulose Dosage on Foam
Stability
Foam stability can be measured by foam half-life, which is the
time required for half of the volume of liquid included in the
foam to change the liquid foam. There were used different
dosages of hydroxyethyl cellulose (%) to examine the foam
half-life or foam stability.
85
Chapter 4 – Results and Discussion
The results showed in the Figure 4.4. When the dosage of
hydroxyethyl cellulose (%) increased, the initial height of
foam decreased. On the contrary, the intermediate life of foam
increased when the dosage of hydroxyethyl cellulose (%)
increased. The results demonstrated that the foam stability
was the best when the dosage of hydroxyethyl cellulose (%) was
0.50. It was because the intermediate life of foam was the
highest for 15 minutes. It meant that the foam did not quickly
collapse during the time required, and it had good foam
stability. The longer the half-life time lasted, the higher
was the foam stability obtained. However, it did not last for
too long time.
Foam stability was an important parameter in
this study. Unstable foam resulted in an excess amount of
liquor in the nip, leading to an uneven application. However,
more stable foam tended not to collapse in the nip by the action
of the pad rollers. The foam density controlled the wet pickup
of the fabrics.
86
Chapter 4 – Results and Discussion
Intermediate life of foam (min)
Intermediate life of foam
Initial Height of foam
12
135
9
90
6
45
3
0
0.00
0.02
0.04
0.06
0.08
0.10
Initial height of foam (mm)
180
15
0.50
Dosage of HEC (%)
Figure4.4 Effect of hydroxyethyl cellulose dosage on foam
half-life
4.2.3
Compatibility of Foaming System for Dyeing
Compatibility between chemicals applied and foaming system is
very critical in foam technology [60]. In the table 4.2, it
demonstrated the relationship between dyes, concentration, and
blow ratio and foam half-life time. For Super Black G, when
the concentration increased, the blow ratio and foam half-life
time
decreased.
For
all
the
87
dyestuffs,
no
remarkable
Chapter 4 – Results and Discussion
instability of foams was observed. The concentration of dye
was at 80g/L which was suitable for the formulation of foams
for dyeing. Therefore, for different dyes including cherry,
yellow, ocean and navy, they used 80 g/L to dye with foam.
Table 4.2 Compatibility of foaming system
Dyes
Con.(g/L)
Blow ratio
T1/2(min)
0
4.75
15.31
20
4.37
15.22
40
4.01
15.37
60
3.79
14.86
80
3.45
14.79
Cheery S-D
80
3.36
15.41
Yellow S-3R
80
3.29
15.64
Ocean S-R
80
3.76
14.91
Navy S-G
80
3.48
13.54
Super Black G
88
Chapter 4 – Results and Discussion
4.3.
4.3.1
Evaluation of color shade
Effect of wet pickup on color shade
Wet pickup of fabrics is an important element affecting the
color shade because of adequate, uniform and level absorbency.
Using foam application can reduce the wet pickup of fabrics,
which can minimize the amount of water used to transmit the
required amount of chemicals to fabrics. However, it is
difficult to determine how much the minimum amount of water
is needed for the fabric. Different wet pickup percentages were
used to evaluate the effect of color shade, the results were
shown in the figure.
In the figure, when the pickup percentage increased, the color
shade also rose. From 15 to 40 % of pickup, the color shade
soared sharply. From the pickup percentage onwards, the color
shade was slowly increased. There showed that the optimum pickup
was around 30 - 40%. As we knew, the optimum wet pickup was
89
Chapter 4 – Results and Discussion
about 30 - 40% for cotton fabrics, leading to an even and uniform
color distribution of fabrics. If the wet pickup of fabrics
was too high, it would result in excess liquor held within
inter-fibre and inter-yarn capillaries of the fabrics. It would
not only result in high drying cost due to the higher energy
and time required, but also left behind an uneven chemical and
color distribution during the migration and evaporation of the
liquor in drying.
On the contrary, a too low wet pickup value affects the
uniformity and the application method [33, 34]. Fabrics could
not sufficiently be wetted and they could not be stretched to
the required width in the stenter
[35, 36]. Also, the
penetration of the chemicals into fabrics would not be
inadequate [37]. Thus, the fabrics could not be dyed adequately
and evenly.
90
Chapter 4 – Results and Discussion
24
K/S
K/S
20
16
12
8
10
20
30
40
50
Pick-up ratio (%)
Figure 4.5 Effect of wet pickup on colour strength
4.3.2
Effect of build-up property
Build-up property is an essential factor, which reflects the
utility efficiency of colorants at different dosage and the
highest color yield that fabrics can obtain. The color shades
of fabrics dyed by foam technology and pad dyeing were compared
in different concentrations in Figure 4.6. It could be seen
that fabrics showed an increase in K/S value upon using the
high dyestuff amounts on fabric weight in both the full-liquid
91
Chapter 4 – Results and Discussion
padding dyeing method and the foam-solution padding dyeing
method.
In the Figure 4.6, it revealed that the build-up property of
foam dyeing and pad dyeing was not significantly different.
Their curves in the figure were similar. Their color shade
increased dramatically between 1 and 2.25%, owf from around
6 to 18. The K/S was sharply risen meaning the color depth was
higher and deeper. With the dosage further increased, it climbed
minimally, even remained constant. This could be explained that
the reaction between dosage and color shade reached the
saturation
point.
Therefore,
the
optimum
dosage
was
approximately 2.25%, owf.
The results revealed that the build-up property of foam-padding
dyeing and liquid-padding dyeing was not remarkably different.
As the penetration of reactive dyes was very good, no matter
what application of reactive dyes used such as foam dyeing and
pad dyeing, the dye would penetrate to another side of fabrics
92
Chapter 4 – Results and Discussion
and both sides of fabrics were dyed. Also, the color depth is
deeper when using reactive dyes, so the color depth increased
when the dosage rose as shown in the figure 4.6. Moreover, the
hydrolyzed dye on the surface of fabrics would rinse when
soaping, so their color shade was not significantly different.
Consequently, the build-up property was not related to the
application of reactive dyes used, and it was related to the
property of reactive dye such as penetration.
Foam-padding
24
Liquid-padding
K/S
18
12
6
0
0
1
2
3
Dyestuff amount (%, owf)
4
Figure 4.6 Effect of reactive dye amount on colour shade
93
Chapter 4 – Results and Discussion
4.4
4.4.1
Evaluation of colorfastness
Effect of fixation condition on color fastness
Curing is aimed to fix the dye on the fabrics, so there are
different curing conditions affecting the fixation. In Table
4.3, it had different curing temperature (160 oC, 170 oC and 180
o
C) and time (30 s, 60 s, 90 s and 120 s) to observe the fixation
of dye on the fabrics and the colorfastness effect.
The result showed that the fixation of dyestuff usually
increased when the curing time and temperature increased.
Generally, the rubbing and washing colorfastness was more and
more satisfactory when the dyestuff fixation was higher. But,
it was not a must. For example, the fixation condition was 180
o
C for 120 s, which could obtain 89.2% of fixation, but the
colorfastness to wet rubbing could not get an acceptable result.
On the contrary, the fixation condition was 170 oC for 60 s and
the fixation was 88.7%, that the rubbing fastness and washing
94
Chapter 4 – Results and Discussion
fastness were satisfactory and met the application requirement.
As a consequence, the recommended fixation condition was 170
o
C for 60 s (Fixation %: 88.7%). For this fixation condition,
not only did it lead to an acceptable result of colorfastness,
but also decrease energy consumption and curing time.
Table 4.3 Effect of fixation condition on color fastness (Super
Black G)
160
Curing
time
F%
o
C
Rubbing
170
Washing
D
W
Ch
St
F%
o
Rubbing
C
180
Washing
D
W
Ch
St
F%
o
C
Rubbing
Washing
D
W
Ch
St
30s
79.6
4
2-3
4
4-5
83.5
4-5
2-3
4
4-5
85.5
4-5
3
4
4-5
60s
80.2
4-5
2-3
4
4
88.7
4
3
4
4-5
85.1
4
3
4-5
4-5
90s
85.1
4-5
3
4-5
4
86.1
4-5
3
4-5
5
87.6
4
3
4-5
4-5
120s
84.3
4
2-3
4-5
4-5
89.1
4
2-3
4-5
4-5
89.2
4-5
2-3
4-5
4-5
D – Dry, W – Wet
Ch – Change, St – Staining
95
Chapter 4 – Results and Discussion
4.4.2
Effect of colorfastness of fabrics dyed with reactive
dyes
Table 4.4 showed colorfastness properties (rubbing and washing
fastness) of all 5 reactive dyes. The dry rubbing fastness was
acceptable, about 4 of the grey scale, except for ocean S-R
being 3 - 4. But, it was also acceptable. In contrast, the wet
rubbing around 2 - 3 of the grey scale was relatively lower
than others. It was because the cationization was removed on
the surface of the fabrics during wet rubbing. However, since
these dyed fabrics were required to develop the wash-out effect
during the garment laundry process, these relative lower wet
fastnesses were also acceptable [61]. The washing fastnesses
of these colors were all appreciated for both the color change
and the color staining around 4 - 5.
96
Chapter 4 – Results and Discussion
Table 4.4 Colorfastness of fabrics dyed with reactive dyes
Rubbing
Washing
Reactive dyes
Dry
Wet
Change
Staining
Cheery S-D
4
2 – 3
4
4
Yellow S-3R
4
3
4 - 5
4 – 5
Ocean S-R
3 - 4
2 – 3
4 - 5
4 – 5
Navy S-G
4
2 – 3
4
4 – 5
Super Black G
4
3
4 – 5
4 – 5
4.5 Evaluation of energy saving
Surface temperature of fabrics in drying process can evaluate
the energy and drying time saving. There were several wet pickup
ratio of fabrics including 24.3%, 32.4%, 72.8%, 78.5%, 90.1%,
105.9%, as shown in Table 4.5.
The table showed the relationship between the pickup ratio of
the fabrics and the drying time. For high wet pickup percentage
of fabrics, the duration of drying was longer than the fabrics
97
Chapter 4 – Results and Discussion
with low wet pickup. For example, the wet pickup of fabrics
was 78.5% and the drying time was required 120 seconds. On the
contrary, the wet pickup of fabrics was 32.4% and its drying
time was only required 60 seconds. The drying duration was
represented the energy consumption. The shorter was the drying
duration; the lower was the energy consumption. For this
example, using low wet pickup fabrics could shorten the drying
time 60 s. The energy could save 50% for 1 minute, calculated
by [(120 - 60)/120] x 100% = 50%.
On the other hand, the high pickup fabrics had low surface
temperature, because of plenty water inside the fabrics. The
higher was the pickup fabrics; the lower was the surface
temperature. The fabrics were required relatively long time
to dry. For example, the fabrics with high wet pickup percentage
such as 72.8%, 78.5%, 90.1% and 105.9% had low surface
temperature because more water was presented inside the fabrics,
and they required long time to evaporate water. In contrast,
low
wet
pickup
fabrics
had
98
relatively
higher
surface
Chapter 4 – Results and Discussion
temperature than that fabric with high pickup, so the drying
time quickly reached to 100 oC. It was because the fabrics just
have less water inside.
The results revealed that the fabrics with low pickup ratio
could save energy and drying time. It was because the initial
surface temperature was higher than others, and it could dry
quickly, thus shortening the drying time in terms of energy
consumption. It not only saved energy consumption, but also
it could save cost, achieving high yield and protect the
environment.
Table 4.5 Drying time for wetted fabrics
Wet pickup ratio (%)
Time (s)
24.30
50
32.40
60
72.80
110
78.50
120
99
Chapter 4 – Results and Discussion
4.6
90.10
170
105.90
180
Wash-Out Effect
In this study, enzyme-stone wash process was used to achieve
the fading effect through mechanical abrasion by pumice stones
and chemical degradation by enzyme.
The result showed that the cherry color of the blouse made by
cotton knitted fabrics could obtain obvious wash-out effect
through washing processes, as shown in Figure 4.7, especially
for seams because of double layers or overlap layers which had
relatively thick and tough surface on the fabrics. The fabrics
had concave-convex surface that it was easily abraded by the
pumice stones to achieve the fading effect, compared with the
flat surface on the fabrics. Therefore, if the fabrics have
some seams that double layers of fabrics are stitched or the
fabrics overlap, the wash-out effect on the fabrics can be
100
Chapter 4 – Results and Discussion
obtained obviously and easily. Moreover, for the washing
process, it was added acid cellulase inside the tumble washer
to enhance the wash-out effect, as the acid cellulase had high
abrasion.
Besides of the high abrasion, acid cellulases had high
bio-polishing (removing hairiness and anti- pilling), thus the
surface of fabrics did not have hairiness and the appearance
of fabrics were acceptable. For handle, the fabrics were soft
because acid cellulose had properties of soft handle on the
fabrics.
However, the accurate time of the tumble washer to abrade with
specimens for obtaining the fading effect is very important.
It will affect the effect of fading, fabric appearance, handle
and so on. For instance, if the washing time is shorter, the
fabrics will have a relatively less abraded effect, even no
any effect. If the washing time is longer than standard, it
will damage the fabrics.
101
Chapter 4 – Results and Discussion
Before
Overlapped fabrics obtained
wash-out effect easily and
obviously
After
Figure 4.7 Wash-out effect of cherry blouse made by cotton
knitted fabrics
102
Chapter 5 – Conclusions and Recommendations
Chapter 5
Conclusions and Recommendations
5.1
Conclusions
Foam dyeing is a promising technology in developing the cotton
knitted fabrics with wash-out effect. It not only achieves the
surface dyeing effect, but also significantly reduces the
energy consumption. Although foam dyeing has some disadvantages,
for this research, it turns to advantages, i.e. the poor
penetration
leading
to
the
surface
dyeing.
Moreover,
cationization on the cotton knitted fabrics can improve the
surface dyeing effect. Therefore, the parts of dyes on the
fabric surface can easily be washed out during washing processes.
This innovative approach to creating a fading effect on cotton
knitted fabrics will become in fashion and well welcomed in
the market.
Besides of achieving surface dyeing effect, foam dyeing is a
103
Chapter 5 – Conclusions and Recommendations
‘green’ technology because of low pickup. Comparing to the
conventional pad dyeing method, foam dyeing can significantly
lower
the
water
consumption,
shortening
the
time
for
pre-drying, minimizing the energy consumption and improving
the utility efficiency of the chemicals, etc. This technology
is
technical,
practical,
economic
and
environmentally
friendly. It is valuable to promote the technique come into
practice.
By studying wash-out effect on cotton knitted fabric dyed with
reactive dyes via foam media, it was shown that this method
was
beneficial
for
achieving
easy
fading
effect
and
environmental protection. The results obtained led to the
following conclusions:
i.
The optimum conditions of the cationic modification were
obtained: cationic agent concentration was 60 g/L, Na2CO3
concentration was 60 g/L, and curing at 130
seconds.
104
o
C for 110
Chapter 5 – Conclusions and Recommendations
ii.
Sodium dodecyl sulfate (SDS) was the most suitable as a
foaming agent to generate foam. It was because that it could
generate the highest initial height of foam, which meant
it had the best foam stability. The dosage of hydroxyethyl
cellulose (%) was 0.50 being the most suitable for the foam
stability, as the intermediate life of foam was the highest
for 15 minutes. The concentration of dye was at 80 g/L being
appropriate for the formulation of foams for dyeing.
iii.
The optimum pickup was around 30 - 40%, leading to even and
uniform color distribution of fabrics. Not only that, but
also it could reduce the water consumption, drying time and
drying energy.
iv.
The K/S values in both the full-liquid padding dyeing method
and the foam-solution padding dyeing method were not
remarkably different. However, the K/S values of reactive
dye could be increased by using a higher dosage that meant
darker shade could be resulted.
105
Chapter 5 – Conclusions and Recommendations
v.
Generally, the fixation of dyestuff increased when the
curing time and temperature rose. The recommended fixation
condition was 170 oC for 60 s, because it had good dyestuff
fixation and acceptable results of colorfastness. Moreover,
it could decrease energy consumption and curing time.
vi.
The dry rubbing fastness is acceptable, while the wet one
is marginal pass. However, as the dyed fabrics were prepared
for developing wash-out effect, this low fastness is also
acceptable [61]. The washing fastnesses of the colours are
all appreciated for both colour change and colour staining.
vii.
Foam dyeing method (30 - 40% wet pickup) was more energy
saving than conventional pad dyeing method (70 - 80% wet
pickup), because less water was presented inside the
fabrics.
viii.
Cotton knitted fabrics could obtain obvious wash-out effect
through the enzyme-stone washing processes, especially for
106
Chapter 5 – Conclusions and Recommendations
double layers or overlap layers which had relatively thick
and tough surface on the fabrics, which had a strong
abrasion.
5.2
Recommendations for future research
In this research, it is shown that the foam dyeing technology
is better than conventional dyeing method, and some objectives
are achieved. However, there are some recommendations for
further research and development.
A. In this study, the dark colors on the fabrics can obtain
the wash-out effect easily, such as black, cherry and navy.
But, the light color like yellow cannot show the wash-out
effect obviously. In summer, light colors on the fabrics are
very welcome because they do not absorb heat much and people
can wear them comfortably. Therefore, the light colors and
other colors can be investigated.
107
Chapter 5 – Conclusions and Recommendations
B. Foam dyeing method can obtain the wash-out effect. In the
study, foam stability is very important. For further study,
foam can be examined to be more stable, even in factories.
C. The colorfastness of the fabrics using the foam dyeing method
is acceptable, but the grey scale in wet rubbing fastness
is low, around 2 – 3. Although it does not influence the effect
in the study, it can also be improved to be better.
D. In this research, the wash-out effect is achieved on the
concave-convex
surface
of
the
fabrics.
However,
the
production cost and production time is relatively high,
because the fabrics are required to stitch to be the tough,
thick
and
concave-convex
surface
first.
Therefore,
achieving the wash-out effect on the flat surface of the
fabrics can lower the production cost and time. This aspect
can be further investigated.
E. Due to the limitation of time, the foam dyed fabrics are not
108
Chapter 5 – Conclusions and Recommendations
evaluated the physical properties. In this study, the fabrics
were treated with cationization first. Cationization on
cotton may influence the fiber structure (Kit-kulnumchsi,
Ajavakom, & Sukwattanasinitt, 2008), and finally it will
affect the wearability of it [62]. So, X - ray diffraction
(XRD), fourier transform infrared spectroscopy (FTIR) and
scanning electron microscope (SEM) are used to investigate
the physical structure properties of the cationic cotton.
Moreover, the bursting test and the pilling test can be
conducted to evaluate the physical properties of the fabrics.
109
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