ABSTRACT BILGEN, MUSTAFA. Wrinkle Recovery for Cellulosic Fabric by Means of Ionic Crosslinking. (Under the direction of Peter Hauser and Brent Smith.) When treated with formaldehyde-based crosslinkers, cellulosic fabrics show improved mechanical stability, wrinkle recovery angles and durable press performance, but N-methylol treatment also causes fabrics to lose strength and later to release formaldehyde, a known human carcinogen. We have discovered that ionic crosslinks can stabilize cellulose using high or low molecular weight ionic materials which do not release hazardous reactive chemicals, but at the same time provide improved wrinkle recovery angles as well as complete strength retention in treated goods. We have varied polyelectrolyte, the ionic content of fabrics, and various features of the application procedure to optimize the results and to develop an in-depth fundamental physical and chemical understanding of the stabilization mechanism.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
ABSTRACT
BILGEN, MUSTAFA. Wrinkle Recovery for Cellulosic Fabric by Means of Ionic Crosslinking. (Under the direction of Peter Hauser and Brent Smith.)
When treated with formaldehyde-based crosslinkers, cellulosic fabrics show
improved mechanical stability, wrinkle recovery angles and durable press performance,
but N-methylol treatment also causes fabrics to lose strength and later to release
formaldehyde, a known human carcinogen. We have discovered that ionic crosslinks can
stabilize cellulose using high or low molecular weight ionic materials which do not release
hazardous reactive chemicals, but at the same time provide improved wrinkle recovery
angles as well as complete strength retention in treated goods. We have varied
polyelectrolyte, the ionic content of fabrics, and various features of the application
procedure to optimize the results and to develop an in-depth fundamental physical and
chemical understanding of the stabilization mechanism.
WRINKLE RECOVERY FOR CELLULOSIC FABRIC BY MEANS OF IONIC CROSSLINKING
by
MUSTAFA BILGEN
A thesis submitted to the Graduate Faculty of North Carolina State University
in partial fulfillment of the requirements for the Degree of
Master of Science
TEXTILE CHEMISTRY
Raleigh
2005
APPROVED BY:
Dr. Peter Hauser (Chair) Dr. Brent Smith (Co-Chair)
Dr. Charles Boss (Minor)
ii
DEDICATION
This thesis is dedicated to my family and my wife, Nicole, who supported me with
constant love and caring and inspired my interest in studying textile chemistry.
iii
BIOGRAPHY
Mustafa Bilgen was born in December 1, 1978 in Erdemli, Turkey. He graduated
from Erzurum Science High School in June 1995. He received the Bachelor of Science
degree in Textile Engineering from Department of Engineering and Architecture, Uludag
University, Bursa, Turkey in July 1999.
After he graduated he worked as a dyeing and finishing supervisor in Akay Textile
Dyeing & Finishing Company for one year before he started to help his father for taking
care of the family business.
He came to North Carolina State University in January 2004, to continue his education
and started his master program in Textile Chemistry under the direction of Dr. Brent
Smith and Dr. Peter Hauser.
iv
ACKNOWLEDGEMENTS
I would like to thank to the National Textile Center and North Carolina State University
for their financial support. I also would like to thank to my advisors, Dr. Hauser and Dr.
Smith, for their crucial help and patience during my research and preparation of my thesis.
v
LIST OF CONTENTS
LIST OF TABLES ------------------------------------------------------------------------------- viii LIST OF FIGURES --------------------------------------------------------------------------------x 1. INTRODUCTION -------------------------------------------------------------------------------1 2. LITERATURE REVIEW ----------------------------------------------------------------------3
2.1 Cellulose chemistry ---------------------------------------------------------------------------3 2.2 Cellulosic fabric’s nature of wrinkling -----------------------------------------------------5 2.3 Durable Press finishing of cotton -----------------------------------------------------------6
2.3.1 Urea-Formaldehyde derivatives--------------------------------------------------------7 2.3.2 Melamine-Formaldyhe derivatives ----------------------------------------------------7 2.3.3 Methylol derivatives of cyclic ureas --------------------------------------------------8 2.3.4 Effects of formaldehyde based DP finishes on cellulose ---------------------------9
2.6.1 Chitosan and its reaction with CHTAC --------------------------------------------- 16 2.6.2 Reaction of Cellulose with CHTAC------------------------------------------------- 18
2.7 Carboxymethylation of cellulose---------------------------------------------------------- 20 2.8 Proposed Research-------------------------------------------------------------------------- 21
3.5 Reaction of cellulose with chloroacetic acid -------------------------------------------- 29 3.6 Reaction of Cellulose with CHTAC------------------------------------------------------ 32 3.7 Synthesis of compounds ------------------------------------------------------------------- 35
3.7.1 Molecular weight determination of chitosan --------------------------------------- 35 3.7.2 Depolymerization of chitosan and characterization ------------------------------- 37 3.7.3 Reaction of chitosan with CHTAC -------------------------------------------------- 39 3.7.4 Reaction of glycerin and ethylene glycol with CHTAC -------------------------- 51
vi
3.7.5 Reaction of cellobiose and dextrose with CHTAC -------------------------------- 53 3.8 Preparation of fabric samples-------------------------------------------------------------- 53 3.9 Crosslinking of carboxymethylated cellulosic fabric----------------------------------- 54
3.9.1 Treatment with cationic chitosan ---------------------------------------------------- 54 3.9.2 Treatment with cationic glycerin ---------------------------------------------------- 54 3.9.3 Treatment with cationic cellobiose, cationic dextrose and cationic ethylene glycol------------------------------------------------------------------------------------------- 55 3.9.4 Treatment with calcium chloride and magnesium chloride ---------------------- 55
3.10 Crosslinking of cationic cellulosic fabric----------------------------------------------- 57 3.10.1 Treatment with PCA and BTCA --------------------------------------------------- 57 3.10.2 Treatment with EDTA, NTA and HEDTA --------------------------------------- 59 3.10.3 Treatment with oxalic acid, citric acid and malic acid -------------------------- 59
4.2.1 Wrinkle recovery angles of cationic chitosan treated fabrics -------------------- 60 4.2.2 Application of paired t-test analysis on cationic chitosan treatments ----------- 68 4.2.3 Wrinkle recovery angles of cationic glycerin treatments ------------------------- 71 4.2.4 Wrinkle recovery angles of cationic cellobiose and cationic dextrose treated fabrics ------------------------------------------------------------------------------------------ 76 4.2.5 Wrinkle recovery angles of calcium chloride and magnesium chloride treated fabrics ------------------------------------------------------------------------------------------ 76 4.2.6 Discussion of wrinkle recovery angles for polycation treatments --------------- 79
4.3 Wrinkle recovery angles of polyanion treated cationic cellulosic fabrics ----------- 82 4.3.1 Wrinkle recovery angles of PCA and BTCA treated fabrics--------------------- 82 4.3.2 Wrinkle recovery angles of EDTA, NTA and HEDTA treated fabrics --------- 87 4.3.3 Wrinkle recovery angles of oxalic acid, citric acid and malic acid treatments 89 4.3.4 Discussion of wrinkle recovery angles for polyanion treatments---------------- 90
4.4 Strength data--------------------------------------------------------------------------------- 92 4.4.1 Tensile strength of conventional durable press finished fabric ------------------ 92 4.4.2 Strength data of polycation treated anionic cellulosic fabrics-------------------- 93 4.4.3 Strength data of polyanion treated cationic cellulosic fabrics-------------------- 96 4.4.4 Discussion of strength data of untreated and treated fabrics --------------------- 98
4.5 CIE whiteness index data -----------------------------------------------------------------101 4.5.1 CIE whiteness index of conventional durable press treated fabric -------------101 4.5.2 CIE whiteness index of polycation treated anionic cellulosic fabrics----------102 4.5.3 CIE whiteness index of polyanion treated cationic cellulosic fabrics----------104 4.5.4 Discussion of whiteness index of untreated and treated fabrics ----------------106
4.6 Stiffness data -------------------------------------------------------------------------------108 4.6.1 Stiffness of conventional durable press treated fabrics --------------------------109 4.6.2 Stiffness data of polycation treated anionic cellulosic fabrics ------------------109 4.6.3 Stiffness data of polyanion treated cationic cellulosic fabrics ------------------111 4.6.4 Discussion of stiffness data of untreated and treated fabrics--------------------113
vii
5. CONCLUSIONS ------------------------------------------------------------------------------116 6. RECOMMENDATIONS FOR FUTURE WORK--------------------------------------118 7. LIST OF REFERENCES--------------------------------------------------------------------121 8. APPENDIX-------------------------------------------------------------------------------------126
Table 3.2 Results for carboxymethylation of cellulosic fabrics ------------------------------ 32 Table 3.3 Scheme of intrinsic viscosity measurement for the low viscosity chitosan ----- 36 Table 3.4 Properties of the Low Viscosity chitosan.------------------------------------------- 37 Table 3.5 The intrinsic viscosity and Mv of depolymerized chitosans----------------------- 39 Table 4.1 Paired t-test results for dry wrinkle recovery angles of cationic chitosan treated
fabrics ------------------------------------------------------------------------------------------ 69 Table 4.2 Paired t-test results for wet wrinkle recovery angles of cationic chitosan treated
fabrics ------------------------------------------------------------------------------------------ 70 Table 4.3 Paired t-test results for dry/wet wrinkle recovery angles of Ca++ and Mg++
treated fabrics --------------------------------------------------------------------------------- 79 Table 4.4 Paired t-test results for dry/wet wrinkle recovery angles of PCA and BTCA
treated fabrics --------------------------------------------------------------------------------- 87 Table A.1 Dry and wet wrinkle recovery angles for molecular weight of 3.2 x 104g/mole
cationic chitosan treated fabrics -----------------------------------------------------------126 Table A.2 Dry and wet wrinkle recovery angles for molecular weight of 1.4 x 105g/mole
cationic chitosan treated fabrics -----------------------------------------------------------127 Table A.3 Dry and wet wrinkle recovery angles for molecular weight of 6.11 x 105g/mole
cationic chitosan treated fabrics -----------------------------------------------------------127 Table A.4 Dry and wet wrinkle recovery angles for molecular weight of 1.4 x 105g/mole
cationic chitosan treated fabrics by exhaustion method --------------------------------128 Table A.5 Dry and wet wrinkle recovery angles for cationic glycerin treated fabrics----128 Table A.6 Dry and wet wrinkle recovery angles for cationic glycerin treated fabrics by
exhaustion method---------------------------------------------------------------------------129 Table A.7 Dry and wet wrinkle recovery angles for cationic cellobiose and cationic
dextrose treated fabrics ---------------------------------------------------------------------129 Table A.8 Dry and wet wrinkle recovery angles for calcium chloride and magnesium
chloride treated fabrics ---------------------------------------------------------------------130 Table A.9 Dry and wet wrinkle recovery angles for PCA treated fabrics------------------130 Table A.10 Dry and wet wrinkle recovery angles for BTCA treated fabrics --------------131 Table A.11 Dry and wet wrinkle recovery angles for EDTA treated fabrics --------------131 Table A.12 Dry and wet wrinkle recovery angles for NTA treated fabrics ----------------132 Table A.13 Dry and wet wrinkle recovery angles for HEDTA treated fabrics ------------132 Table A.14 Dry and wet wrinkle recovery angles for oxalic, malic and citric acid treated
fabrics -----------------------------------------------------------------------------------------133 Table A.15 Breaking strength data for molecular weight of 3.2 x 104g/mole cationic
chitosan treated fabrics ---------------------------------------------------------------------134 Table A.16 Breaking strength data for molecular weight of 1.4 x 105g/mole cationic
Table A.17 Breaking strength data for molecular weight of 6.11 x 105g/mole cationic chitosan treated fabrics ---------------------------------------------------------------------135
Table A.18 Breaking strength data for cationic glycerin treated fabrics -------------------135 Table A.19 Breaking strength data for calcium chloride and magnesium chloride treated
fabrics -----------------------------------------------------------------------------------------136 Table A.20 Breaking strength data for PCA treated fabrics ---------------------------------136 Table A.21 Breaking strength data for BTCA treated fabrics -------------------------------137 Table A.22 Whiteness index data for molecular weight of 3.2 x 104g/mole cationic
chitosan treated fabrics ---------------------------------------------------------------------138 Table A.23 Whiteness index data for molecular weight of 1.4 x 105g/mole cationic
chitosan treated fabrics ---------------------------------------------------------------------138 Table A.24 Whiteness index data for molecular weight of 6.11 x 105g/mole cationic
chitosan treated fabrics ---------------------------------------------------------------------139 Table A.25 Whiteness index data for CG treated fabrics-------------------------------------139 Table A.26 Whiteness index data for calcium and magnesium chloride treated fabrics -140 Table A.27 Whiteness index data for PCA treated fabrics -----------------------------------140 Table A.28 Whiteness index data for BTCA treated fabrics---------------------------------141 Table A.29 Stiffness data for molecular weight of 3.2 x 104g/mole cationic chitosan
treated fabrics --------------------------------------------------------------------------------142 Table A.30 Stiffness data for molecular weight of 1.4 x 105g/mole cationic chitosan
treated fabrics --------------------------------------------------------------------------------142 Table A.31 Stiffness data for molecular weight of 6.11 x 105g/mole cationic chitosan
treated fabrics --------------------------------------------------------------------------------143 Table A.32 Stiffness data for cationic glycerin treated fabrics ------------------------------143 Table A.33 Stiffness data for calcium chloride and magnesium chloride treated fabrics 144 Table A.34 Stiffness data for PCA treated fabrics --------------------------------------------144 Table A.35 Stiffness data for BTCA treated fabrics ------------------------------------------145 Table A.36 Nitrogen analysis data for molecular weight of 3.2 x 104g/mole cationic
chitosan treated fabrics ---------------------------------------------------------------------146 Table A.37 Nitrogen analysis data for molecular weight of 1.4 x 105g/mole cationic
chitosan treated fabrics ---------------------------------------------------------------------146 Table A.38 Nitrogen analysis data for molecular weight of 6.11 x 104g/mole cationic
chitosan treated fabrics ---------------------------------------------------------------------147 Table A.39 Nitrogen analysis data for cationic glycerin treated fabrics--------------------147
x
LIST OF FIGURES
Figure 2.1 Molecular structure of a cellulose polymer chain -----------------------------------4 Figure 2.2 Crystalline and amorphous structure of cellulose -----------------------------------4 Figure 2.3 Molecular structure of DMDHEU-----------------------------------------------------8 Figure 2.4 Molecular structure of BTCA-------------------------------------------------------- 12 Figure 2.5 Reaction of chitosan with CHTAC in alkaline conditions ----------------------- 17 Figure 2.6 Reaction of cellulose with CHTAC in alkaline conditions----------------------- 19 Figure 2.7 Molecular structure of carboxymethyl cellulose ---------------------------------- 20 Figure 3.1 Reactions of cellulose with CAA that impart an anionic character ------------- 30 Figure 3.2 Reactions of cellulose with CHTAC that impart a cationic character ---------- 34 Figure 3.3 Huggins plot of ήsp/c versus c for the cationic chitosan -------------------------- 37 Figure 3.4 Reaction of chitosan with CHTAC-------------------------------------------------- 41 Figure 3.5 Conductometric titration curve of cationic chitosan ------------------------------ 43 Figure 3.6 FTIR spectrum of deacetylated chitosan ------------------------------------------- 46 Figure 3.7 FTIR spectrum of cationic chitosan------------------------------------------------- 47 Figure 3.8 1H-NMR spectrum of deacetylated chitosan --------------------------------------- 48 Figure 3.9 1H-NMR spectrum of O-substituted and N-substituted cationic chitosan ----- 50 Figure 3.10 Reaction of glycerin with CHTAC ------------------------------------------------ 52 Figure 3.11 Crosslinked anionic cellulose with calcium -------------------------------------- 56 Figure 3.12 Crosslinked cationic cellulose with BTCA --------------------------------------- 58 Figure 4.1 Effect of carboxyl content and concentration on dry wrinkle recovery angles of
cationic chitosan treated fabrics ------------------------------------------------------------ 62 Figure 4.2 Effect of carboxyl content and concentration on wet wrinkle recovery angles of
cationic chitosan treated fabrics ------------------------------------------------------------ 62 Figure 4.3 Effect of carboxyl content and concentration on %Nitrogen content of cationic
chitosan treated fabrics ---------------------------------------------------------------------- 64 Figure 4.4 The relationship between %Nitrogen content of the fabrics and dry/wet wrinkle
recovery angles ------------------------------------------------------------------------------- 65 Figure 4.5 Effect of molecular weight of chitosan and concentration on dry wrinkle
recovery angles of cationic chitosan treated fabrics ------------------------------------- 67 Figure 4.6 Effect of molecular weight of chitosan and concentration on wet wrinkle
recovery angles of cationic chitosan treated fabrics ------------------------------------- 67 Figure 4.7 Effect of carboxyl content and concentration on dry wrinkle recovery angles of
cationic glycerin treated fabrics ------------------------------------------------------------ 72 Figure 4.8 Effect of carboxyl content and concentration on wet wrinkle recovery angles of
cationic glycerin treated fabrics ------------------------------------------------------------ 72 Figure 4.9 Effect of carboxyl content and concentration on %Nitrogen content of cationic
glycerin treated fabrics----------------------------------------------------------------------- 74 Figure 4.10 The relationship between %Nitrogen content of the fabrics and dry/wet
Figure 4.11 Effect of carboxyl content on dry wrinkle recovery angles of calcium and magnesium treated fabrics------------------------------------------------------------------- 77
Figure 4.12 Effect of carboxyl content on wet wrinkle recovery angles of calcium and magnesium treated fabrics------------------------------------------------------------------- 78
Figure 4.13 Effect of %Nitrogen fixed and concentration on dry wrinkle recovery angles of PCA treated fabrics ----------------------------------------------------------------------- 83
Figure 4.14 Effect of %Nitrogen fixed and concentration on wet wrinkle recovery angles of PCA treated fabrics ----------------------------------------------------------------------- 84
Figure 4.15 Effect of %Nitrogen fixed and concentration on dry wrinkle recovery angles of BTCA treated fabrics --------------------------------------------------------------------- 85
Figure 4.16 Effect of% Nitrogen fixed and concentration on wet wrinkle recovery angles of BTCA treated fabrics --------------------------------------------------------------------- 86
Figure 4.17 Effect of %Nitrogen fixed and concentration on dry wrinkle recovery angles of EDTA treated fabrics --------------------------------------------------------------------- 88
Figure 4.18 Effect of %Nitrogen fixed and concentration on wet wrinkle recovery angles of EDTA treated fabrics --------------------------------------------------------------------- 89
Figure 4.19 Effect of treatment on dry wrinkle recovery angles ----------------------------- 91 Figure 4.20 Effect of treatment on wet wrinkle recovery angles ----------------------------- 92 Figure 4.21 Effect of carboxyl content and concentration on breaking strength of the
cationic chitosan (molecular weight of 1.4 x 105g/mole) treated fabrics-------------- 94 Figure 4.22 Effect of carboxyl content and concentration on breaking strength of the
cationic glycerin treated fabrics ------------------------------------------------------------ 95 Figure 4.23 Effect of carboxyl content and concentration on breaking strength of the
calcium and magnesium treated fabrics --------------------------------------------------- 95 Figure 4.24 Effect of %Nitrogen content and concentration on breaking strength of the
PCA treated fabrics--------------------------------------------------------------------------- 97 Figure 4.25 Effect of %Nitrogen content and concentration on breaking strength of the
BTCA treated fabrics ------------------------------------------------------------------------ 97 Figure 4.26 Effect of treatment on breaking strength------------------------------------------ 99 Figure 4.27 Correlation between wet wrinkle recovery angles of cationic chitosan
(molecular weight of 1.4 x 105g/mole) treatment and tensile strength ---------------100 Figure 4.28 Correlation between wet wrinkle recovery angles of PCA treatment and
tensile strength -------------------------------------------------------------------------------101 Figure 4.29 Effect of carboxyl content and concentration on whiteness index of the
cationic chitosan (molecular weight of 1.4 x 105g/mole) treated fabrics-------------103 Figure 4.30 Effect of carboxyl content and concentration on whiteness index of the
cationic glycerin treated fabrics -----------------------------------------------------------103 Figure 4.31 Effect of carboxyl content and concentration on whiteness index of the
calcium chloride and magnesium chloride treated fabrics -----------------------------104 Figure 4.32 Effect of %Nitrogen fixed and concentration on whiteness index of the PCA
Figure 4.33 Effect of %Nitrogen fixed and concentration on whiteness index of the BTCA treated fabrics --------------------------------------------------------------------------------106
Figure 4.34 Effect of treatment on whiteness index ------------------------------------------108 Figure 4.35 Effect of carboxyl content and concentration on stiffness of the cationic
chitosan (molecular weight of 1.4 x 105g/mole) treated fabrics -----------------------110 Figure 4.36 Effect of carboxyl content and concentration on stiffness of the cationic
glycerin treated fabrics----------------------------------------------------------------------110 Figure 4.37 Effect of carboxyl content and concentration on stiffness of the calcium
chloride and magnesium chloride treated fabrics----------------------------------------111 Figure 4.38 Effect of %Nitrogen fixed and concentration on stiffness of the PCA treated
fabrics -----------------------------------------------------------------------------------------112 Figure 4.39 Effect of %Nitrogen fixed and concentration on stiffness of the BTCA treated
fabrics -----------------------------------------------------------------------------------------113 Figure 4.40 Effect of treatment on stiffness----------------------------------------------------115
1
1. INTRODUCTION
The textile market has shown an interest in the demand for easy care, wrinkle-
resistant for cellulosic fabrics over the years. Untreated cellulose has poor recovery,
because cellulose is stabilized by hydrogen bonds within and between cellulose chains.
Moisture between the polymer chains can invade the cellulose structure and can
temporarily release the stabilizing hydrogen bonds and hydrogen bonds in cellulose
experience frequent breaking and reforming when extended and newly formed hydrogen
bonds tend to hold cellulose chain segments in new positions when external stress is
released. Preventing wrinkling of cellulosic fabric can be accomplished by the
crosslinking of polymer chains, thus making intermolecular bonds between chains that
water cannot release. In a typical durable-press (DP) treatment, some hydrogen bonds are
replaced with covalent bonds between the finishing agent and the fiber elements. Because
covalent bonds are much stronger than hydrogen bonds, they can resist higher external
stress. Hence, treated cellulose has a higher initial modulus and better elastic recovery.
After the external force is released, the energy stored in the strained covalent bonds
provides the driving force to return chain segments back to their original positions.
Formaldehyde-based cellulose crosslinking was a very important textile chemical
breakthrough of the 1930's, and is still the basis for a vast array of modern finished cotton
products today. N-methylol crosslinkers have the biggest use in durable press finishing.
They give fabrics crease resistance, shrinkage control, anti-curl, and durable press, but
2
they also impart strength loss and release formaldehyde, a known human carcinogen. [1]
Today’s textile industry has for a long time been searching for durable press finishes that
can give same results as formaldehyde based finishes, but cause less strength loss and no
formaldehyde release. For example, polycarboxylic acids and citric acid have been used
with varying degrees of success. [2, 3]
We have developed multiple methods of forming ionic crosslinks to give non-
wrinkle effects to cellulosic fabric. [4] These includes, (1) treatment of cellulose with an
anionic material and reacting with a polycation, (2) treatment of cellulose with a cationic
material and then application of a polyanion, (3) treatment of cellulose with a
precondensate of an ionic reactive material and a polyelectrolyte of the opposite charge.
The performance of crosslinkers can be measured by dry and wet wrinkle recovery angle
(WRA). Dry WRA is important for outerwear clothing to help resist dry wrinkling during
wearing, but wet WRA is more important for bedding which is almost never ironed and
must resist wrinkling during laundering. We observed simultaneous enhancements of both
wet and dry WRA as well as significant strength gain and excellent washing durability.
Polyelectrolytes are strongly bond and thus do not desorb during laundering. The
chemicals are common industrial reactants and do not have unusual safety or
environmental issues. Processes use existing equipment and no high temperature curing is
necessary. In addition, ionic crosslinks may have other important advantages, such as
antimicrobial activity and enhanced dyeability.
3
2. LITERATURE REVIEW
2.1 Cellulose chemistry
We can only understand chemical as well as physical properties of cellulose by the
knowledge of both chemical nature of the cellulose molecules and their structural and
morphological arrangement in the solid, mostly fibrous, state. For example reactivity of
the functional sites in the cellulose molecules and structural characteristics of polymers
such as; inter- and intramolecular interactions, and size of crystallites and fibrils. These
structural characteristics of the cellulosic polymers influence the physico-mechanical
properties utilized in the textile industry. The largest part of the cellulosic polymers used
for textile substrates comes from cotton.
Cotton is a soft fiber that grows around the seeds of the cotton plant. The fiber is
most often spun into thread and used to make a soft, breathable textile. Cotton is a
valuable crop because only about 10% of the raw weight is lost in processing. [5] Once
traces of wax, protein, etc. are removed, the remainder is a natural polymer of pure
cellulose. This cellulose is arranged in a way that gives cotton unique properties of
strength, durability, and absorbency. After scouring and bleaching, cotton is 99% pure
cellulose. [6] Cellulose is a macromolecule made up of anhydroglucose units united by 1,
4, oxygen bridges as shown in Figure 2.1. The anhydroglucose units are linked together as
beta-cellobiose; therefore, anhydro-beta-cellobiose is the repeating unit of the polymer
chain. The number of these repeat units that are linked together to form the cellulose
polymer is referred to as the degree of polymerization and is between 1000 and 15000. [7]
4
O
O
OH
HH
H
H H
OHOH
OH
OO
OH
HH
H
H H
OH
OH
O
O
OH
HH
H
H H
OH
OH
O
OHOH
HH
H
H
HOH
OH
nCellulose
Figure 2.1 Molecular structure of a cellulose polymer chain
The cellulose chains within the cotton fibers tend to be held in place by hydrogen
bonding. These hydrogen bonds occur between the hydroxyl groups of adjacent molecules
and are more prevalent between the parallel, closely packed molecules in the crystalline
areas of the fiber as shown in Figure 2.2. [8]
Figure 2.2 Crystalline and amorphous structure of cellulose
The chemical characters of the cellulose molecules are determined by the
sensitivity of the three-hydroxyl groups, one primary and two secondary, in each repeating
cellobiose unit of cellulose, which are chemically reactive groups. These groups can
undergo substitution reactions in procedures designed to modify the cellulose fibers such
5
as esterification and etherification or in the application of dyes and finishes for
crosslinking. The hydroxyl groups also serve as principal sorption sites for water
molecules. Directly sorbed water is firmly chemisorbed on the cellulosic hydroxyl groups
by hydrogen bonding. [8] Of particular interest in the case of cellulosic fibers is the
response of their strength to variations in moisture content. Generally, in the case of
regenerated and derivative cellulosic fibers, strength decreases with increasing moisture
content. In contrast, the strength of cotton generally increases with increased moisture.
The contrast seen between the fibers in their response to moisture is explained in terms of
intermolecular hydrogen bonding between cellulose chains and their degree of
crystallinity. [8]
2.2 Cellulosic fabric’s nature of wrinkling
The textile market has shown an interest in the demand for easy care, wrinkle-
resistant for cellulosic fabrics over the years. Improvements in crease angle recovery
property are obtained by chemical treatments, which improve the ability of fibers to
maintain configurations in which they are treated. [9] Untreated cellulose has poor
recovery, because hydrogen bonds in cellulose experience frequent breaking and
reforming when extended, and newly formed hydrogen bonds tend to hold cellulose chain
segments in new positions when external stress is released. In a typical durable-press
treatment, some hydrogen bonds are replaced with covalent bonds between the finishing
agent and the fiber elements. Because covalent bonds are much stronger than hydrogen
bonds, they can resist higher external stress. Hence, treated cellulose has a higher initial
6
modulus and better elastic recovery. After the external force is released, the energy stored
in the strained covalent bonds provides the driving force to return chain segments back to
their original positions. However, chemical treatment on cellulose also causes the loss of
mechanical properties. [10] The classical explanation to this problem is that traditional
crosslinks are too rigid to allow cellulose chain segments to move.
2.3 Durable Press finishing of cotton
Durable press is shaping a garment and then treating it in such a way that after
wearing and washing it will return to its pre-set shape. In order to produce non-wrinkle
cellulosic fabrics the durable press finishing has been developed.
The original process for the production of crease resistant fabrics was developed in 1928.
[11] DP finishes have been marketed ever since. Durable press is accomplished by resin
treatments. The main purpose of resin treatments is to overcome a serious drawback of
cellulosic fabrics, for example their ease of wrinkling, which requires ironing after
washing. [12] Ideally, a DP finished fabric will wash and dry to a completely smooth
state. The usual method of production of crease resistant fabric consists of padding fabric
trough a crosslinking agent along with a catalyst and other additives, drying at 100-110oC
followed by curing at 155-175oC for 2-3 minutes. [13] The resulting fabric has the ability
of recovering from creases both when fabric is wet and dry. The selection of crossslinking
agents for DP finishing is important. There are a large number of cross linker available.
Some of the most common reagents are urea-formaldehyde derivatives, melamine-
7
formaldehyde derivatives and methylol derivatives. All of these reagents used for DP of
cellulosic fabric with varying degrees of success.
2.3.1 Urea-Formaldehyde derivatives
The first widely used crosslinking agent for DP finishing was urea-formaldehyde
adducts. These products are mostly prepared at the finishing plant; also precondensate are
available in the market. The treatment of fabrics with urea-formaldehyde resin involves
padding the fabric through precondensate and an acid catalyst, drying, curing and
washing. The advantages of urea-formaldehyde resins are the low cost and high
efficiency. The disadvantages are poor stability of the agent, poor durability and imparting
chlorine retention to the fabric. The chlorine retention is due to the presence of the –NH
groups which react with chlorine from the bleach or laundry bath. [14, 15, 16] The
reaction of –NH groups and chlorine produces hydrochloric acid and it is a strong acid
that causes tendering and yellowing of cellulose.
2.3.2 Melamine-Formaldyhe derivatives
The most commonly used melamine product is trimethylol melamine. It has good
stability and durability. Trimethylol-melamine is more expensive than urea-formaldehyde.
It picks up and retains chlorine, it also yellows the bleached fabric but the fiber
degradation due to strong acid is avoided because of basicity of the compound. [17, 18]
8
2.3.3 Methylol derivatives of cyclic ureas
These compounds are also referred to as fiber reactants, because they only react
with the cellulose instead of themselves. As a result insoluble resin on the surface of the
fabric is absent hence the finished fabric have a softer hand. The members of this group
are:
(a) Dimethylol ethylene urea (DMEU) has high reaction efficiency and low price. [19] It
can produce high wrinkle recovery angles at low add-ons. The finish with DMEU is
sensitive to acids and can be destroyed by acid treatment during laundering. (b)
Dimethylol propylene urea (DMPU) is suitable for white goods, since it does not produce
yellowing on heating. [20] Another advantage of it is that not giving any odor. But the
finish is not susceptible to chlorine retention damage. It is more expensive than others in
the group. (c) Dimethylol dihydroxy ethylene urea (DMDHEU) as shown in Figure 2.3. It
is the most commonly used DP finish agent and gives excellent crease angle recovery.
[21, 22]
NN
O
OHOH
OHOH
DMDHEU
Figure 2.3 Molecular structure of DMDHEU
9
It shows some chlorine retention therefore it is not recommended for white goods. It does
not effect the lightness of the dyes hence it is dominating the colored garments durable
press finishing.
2.3.4 Effects of formaldehyde based DP finishes on cellulose
Formaldehyde-based N-methylol reagents are the most common DP reagents. But
these reagents produce losses in tensile strength of cotton due to depolymerization of
cellulose chains. Cellulose depolymerization occurs with a polycarboxylic acid or a Lewis
acid, which are catalysts for formaldehyde based resins. As a result they cause a high
degree of depolymerization. A direct correlation between tensile strength loss of the
treated cotton and the molecular weight of cellulose was found. [23] Severe tensile
strength loss is a major disadvantage of DP finished cotton fabrics, and it continues to be
the major obstacle for DP applications. Most of the studies of mechanical strength of
durable press finished cotton fabrics in the past have focused on changes in the gross
properties of cotton fabrics, such as tensile strength and abrasion resistance. Another
disadvantage of N-methylol reagents is later formaldehyde release. In recent years there
have been extensive efforts to find non-formaldehyde alternatives due to increasing
concern with health risks associated with formaldehyde. On the other hand, the final
textile products not only have to be eco-friendly, but also have to be produced by clean
technologies. Crosslinking of cellulose with N-methylol crosslinking agents to impart
wrinkle-resistance, shrink proofing, and smooth drying properties by virtue of chemical
reaction with cellulosic hydroxyl groups to form covalent crosslinks in the interior of
10
cellulosic fibers have successfully been done. However, at the present time, presence of
formaldehyde in the finished product, working atmosphere, as well as in wastewater
streams is considered as highly objectionable due to the mutagenic activity of various
aldehydes, including formaldehyde. [24]
2.4 Recent developments in non-formaldehyde DP applications
Extensive research has attempted to develop nonformaldehyde crosslinking agents
to replace N-methylol compounds that release formaldehyde during production and
storage, which is proven to be carcinogenic. [25] Durable press finishing, used to
overcome wrinkling problems in cotton fabric for some years, involves chemical
crosslinking agents that covalently crosslink with hydroxyl groups of adjacent cellulose
polymer chains within cotton fibers. This crosslinking not only results in the fabric's
wrinkle resistance, but also in discoloration and impairment of fabric strength and of other
mechanical properties. The early chemical agents used for crosslinking with cellulose
were mostly formaldehyde and formaldehyde derivatives, which can form ether bonds
with cellulose. DMDHEU is the most widely used crosslinking agent because it provides
good durable press properties at a lower cost and an acceptable level of detrimental effects
on fabric strength and whiteness compared to other N-methylol agents. However, fabric
treated with DMDHEU tends to release formaldehyde vapors during processing, storage,
and consumer use. Because formaldehyde is toxic to human beings, several attempts have
been made to replace it with formaldehyde-free crosslinking agents.
11
Several polycarboxylic acids have served as durable press agents. Carboxylic
groups in polycarboxylic acids are able to form ester bonds with hydroxyl groups in
cellulose. The main advantages of polycarboxylic acids are that they are formaldehyde-
free, do not have a bad odor, and produce a very soft fabric hand. BTCA (1.2,3,4-
butcnetetracarboxylic acid) is the most effective polycarboxylic acid for use as a durable
press agent as shown in Figure 2.4. In the presence of sodium hypophosphite monohydrate
as catalyst, BTCA provides almost the same level of durable press performance and finish
durability with laundering as the conventional DMDHEU reactant, but its high cost may
be an obstacle to a mill's decision to use it as a replacement for the conventional durable
press reactant. As with DMDHEU, fabrics treated with polycarboxylic acids generally
lose their strength, [26] probably due to excess crosslinking with cellulose chains. This
may be tackled by using long-chain polycarboxylic acids, which can be obtained through
copolymerization of two unsaturated polycarboxylic acids.
BTCA satisfies many desirable requirements such as durability to laundering and
durable press performance. Crosslinking of cellulose molecules with BTCA increases
fabric wrinkle resistance at the expense of mechanical strength. [27]
12
COOH
COOH
COOH
COOH
BTCA
Figure 2.4 Molecular structure of BTCA
Severe tensile strength loss diminishes the durability of finished cotton garments.
The factors involved in strength loss of cotton fabric treated with BTCA include acid
catalyzed degradation of cellulose molecules and their crosslinking. The common
catalysts for polycarboxylic acids are phosphorous-containing compounds, although their
use has disadvantages such as high cost, strength loss and raises some environmental
concerns. In order to decrease strength retention other catalysts have been proposed;
among these is boric acid, [28] which was added to increase strength of the treated fabrics.
With this treatment, durable press properties were similar to those obtained with sodium
hypophosphite; moreover the mechanical resistance improved.
A previous study [29] indicated that cellulosic fabric treated with a copolymer
made with maleic and acrylic acids possesses the same level of wrinkle resistance as with
BTCA, while tensile strength retention improves slightly. Another disadvantage of
polycarboxylic acid finishing is yellowing of the treated fabric. It is proposed that the use
of a copolymer between acrylic and maleic acids as a durable press finishing agent can
improve crease angle recovery for cotton fabric. [29] However, the copolymer treatment
does not provide as good tensile strength and whiteness as DMDHEU.
13
Chitosan citrate has been evaluated as non-formaldehyde durable press finish to
produce wrinkle-resistance and antimicrobial properties for cotton fabrics. [30] The
carboxylic groups in the chitosan citrate structure were used as active sites for its fixation
onto cotton fabrics. The fixation of the chitosan citrate on the cotton fabric was done by
the padding of chitosan citrate solution onto cotton fabrics followed by a dry - cure
process. The factors affecting the fixation processes were systematically studied. The
antimicrobial activity and the performance properties of the treated fabrics, including
tensile strength, wrinkle recovery, wash fastness and whiteness index, were evaluated. The
finished fabric shows adequate wrinkle resistance, sufficient whiteness, high tensile
strength and more reduction rate of bacteria as compared to untreated cotton fabric.
A non-polluting system of applying an easy-care finish to cotton fabrics has been
proposed. [31] The new formulation is based on an aqueous system of BTCA-chitosan-
sodium hypophosphite and was applied by the traditional pad-dry-cure method to an
Egyptian poplin. The variables studied were the concentrations of BTCA and chitosan, the
time and temperature of polymerisation. The study also included a comparison with other
traditional or recommended systems. The treated fabric was tested for crease recovery
angle, resistance to traction, elongation to breakage, rigidity, wetability, whiteness,
nitrogen content and dyeability. It was concluded that the new formulation gave
comparable if not better results than the traditional treatments.
14
2.5 Ionic crosslinking
Ionic crosslinking has been used in the polymer industry for various applications.
It is an alternative to covalent crosslinks. It is well known that the thermal resistance,
durability, abrasion resistance, chemical resistance, etc., of a polymer are improved by
crosslinking. For example, acrylic copolymer sizes have been used for improving the
weaving properties of polyester filament warps. [32] Acrylic sizes produce good abrasion
resistance, high strength, good adhesion and easy removability. But when exposed to high
humidity many of the acrylics absorb water and cause blocking on the beam. In order to
improve the stability of acrylic sizes divalent cations are used for reduction of the
moisture regain. Calcium and magnesium ions were used [32] for reducing the water
sensitivity of sizes. These cations form ionic crosslinks between the polymer chains and
stabilize the structure against moisture. Also these crosslinks improved the strength
properties of the polymer film.
The copolymer of propylene and maleic anhydride is also crosslinked by ionic
bonding. It is considered that the ionic crosslinking by maleic anhydride groups is
possible by using not only of magnesium hydroxide but also of other metal compounds.
Magnesium 12-hydroxy stearate, zinc oxide, and zinc sulfide were chosen for ionic
crosslinking. Accordingly, by changing the kind and content of the metal compounds, the
viscosity can be freely controlled. Considering also other rheological characteristics, these
ionically crosslinked compounds are assumed to show ideal flow processabilities except
for the extrudate appearance [33,34]
15
A series of siloxane-based liquid-crystalline elastomers were synthesized by using
ionic crosslinking agents containing sulfonic acid groups. The ions aggregated in domains
forces the siloxane chains to fold and form an irregular lamellar structure. Ionic
aggregates and liquid crystalline segments may be dispersed among each other to form
multiple blocks with increasing ionic crosslinking content. [35]
In a previous work [36] a vulcanized carboxylated nitrile rubber compound was
prepared using a mixed crosslinking system employing a mixture of zinc peroxide and
sulphur accelerators as vulcanizing agents to produce ionic and covalent structures.
Because of the existence of carboxyl groups in the polymeric chain, crosslinked polymers
of ionic nature can be obtained when a bivalent metal oxide, such as zinc oxide, is used as
a crosslinking agent. Ionic vulcanized compounds with properties equal to or better than
those produced using sulphur accelerators can also be obtained in the same way using
metal peroxides.
Polyurethanes are a versatile class of materials; their end applications dictate the
structure and morphology during synthesis. From the prepolymer stage through chain
extension and in the required cases of final crosslinking, there are many ways to influence
the final characteristics of the polyurethanes. Crosslinked networks are obtained through
ionic crosslinking and the different approaches produce cationic, anionic and Zwitter ionic
polyurethanes. These networks find a variety of applications as coatings, adhesives,
shoe soles, and vibration damping materials. [37]
16
2.6 Preparation of quaternized polymers
Conversion to quaternary ammonium salts gives products whose degree of
ionization is pH-independent. Such polymers can be prepared by reaction of polymers
with 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHTAC).
2.6.1 Chitosan and its reaction with CHTAC
Chitosan is the deacetylated form of chitin, poly [β-(1→4)-2-deoxy-D-
glucopyranose], is the second most abundant natural polymer next to cellulose. Chitosan
is a linear copolymer composed mainly β-(1→4)-2-amino-2-deoxy-D-glucopyranose and
partially β-(1→4)-2-acetamido-2-deoxy-D-glucopyranose residues. [38] Chitosan can be
dissolved in diluted acids by being protonated to soluble polyammonium salt. Hydroxyl
and amino groups of chitosan can react with epoxides by a ring opening reaction in either
present of a base or neutral conditions. These reactions were performed previously. [4, 39]
Kim at al performed the reaction between chitosan and CHTAC at neutral conditions.
They proved by FTIR and H1-NMR that the product they produced had a degree of
substitution larger than 60% and substitutions formed at NH2 sites. Because the hydroxyl
groups of chitosan are not sufficiently nucleophilic under neutral conditions, N-substituted
cationic chitosan can be obtained under neutral conditions.
On the other hand; in alkali conditions the hydroxyl groups of chitosan are
nucleophilic therefore reaction of chitosan and CHTAC produce O-substituted cationic
chitosan. Hasem at al performed the reaction under highly alkaline (pH=11-12) conditions
and they believe that the product was O-substituted cationic chitosan and soluble at
17
neutral conditions. Both of the products have cationic properties and can be used as a
cationic polyelectrolyte to form ionic crosslinks and anti-microbial finish for cellulosic
fabrics. [30, 40] Figure 2.5 shows the reaction of chitosan with CHTAC in alkaline
stirred in 1L of 12%(with volume) NaOH solution for 16 hours, filtered over a glass filter
and thoroughly washed with distilled water until neutral. The resin was stirred in 1L of
3M HCl solution for 3 hours and washed with deionized water until pH of 7. This fresh
ion exchange resin was charged into a 500mL burette.
Using the dialysis method, a known amount of cationic chitosan sample was
purified and dried as follows: 10mL of cationic chitosan mixture was charged into a 20cm
of cellulose acetate membrane with a molecular weight separation of 6000-10000 and
stirred in 3L of deionized water for 72 hours, water was changed every 12 hours, followed
by precipitating the chitosan in 1L of acetone. Then a small amount of pure cationic
chitosan was dried at 70oC for 24 hours in a vacuum oven. The pure cationic chitosan was
then transferred into a glass beaker and dissolved in 200mL of deionized water. The
cationic chitosan solution was allowed to flow down through the column. It was collected
in a beaker, precipitated in 1L of acetone and dried in a vacuum oven at 70oC for 16
hours. The DS of cationic chitosan was obtained by titration of the halide (Cl-) with
aqueous silver nitrate (AgNO3) solution. [50] The process was as follows: 0.1344g from
43
the dried cationic chitosan was dissolved in 100mL of deionized water and
conductometrically titrated with 0.017N AgNO3 solution. Titration was conducted at a
constant temperature (23.5oC). The titration curve for cationic chitosan is shown in Figure
3.5.
360
400
440
480
520
0 4 8 12 16 20 24 28 32
Volume of silver nitrate (mL)
Con
duct
ivity
(uS/
cm)
Figure 3.5 Conductometric titration curve of cationic chitosan
The amount of silver nitrate used at the bending point (22.3mL) equals to the amount of
Cl- ions on the cationic chitosan derivative. 1mL of 0.017N AgNO3 is equal to 1mg NaCl,
therefore 0.1g of the cationic chitosan contains 3.81588 X 10-4 moles of Cl- ions. The
percentage degree of substitution was calculated by the equation below:
DS = 100 Χ (MW Χ NCl-) / m
44
Where MW is the molecular weight of each repeating unit of the cationic chitosan when
the DS is 1 (314.89 g/mol), NCl- is the number of moles of Cl- ions in the cationic chitosan
(2.6523 Χ 10-4), and m is the mass of cationic chitosan sample in grams (0.1344g). Finally
the DS of cationic chitosan was calculated as 89%.
3.7.3.2 Characterization of cationic chitosan by FTIR analysis
In order to characterize the products, we obtained Fourier Transform Infrared
Spectroscopy (FTIR) spectrums. For the IR measurements pure cationic chitosan samples
were prepared by using the dialysis method as described previously. The samples were
prepared as KBr pellets and scanned against a blank KBr pellet background. Deacetylated
chitosan shows medium to strong absorption peaks in the range of 1650 to 1580 cm-1. The
major IR functional group frequencies relevant to chitin and chitosan are shown in Table
3.6.
45
Table 3.6 Major IR functional group frequencies relevant to chitin and chitosan [46] Frequencies Intensity Functional group Assignment 3420-3250 s Alcohol –OH OH stretch (solid & liquid)
3460-3280 m Primary amine –NH2 NH stretch; broad band, may have
some structures
350-3050 vs Ammonium, NH4+ NH stretch; broad band
3200-3000 v br Amino acid –NH3 NH3+ antisym stretch
2990-2850 m-s Aliphatic alkyl CH antisym stretch
2830-2810 m Primary amine –NH2 CH stretch
2750-2350 m-s, br Amine hydrohalides -
NH3+
NH3+ stretch, several peaks
1680-1630 vs Secondary amide C=O Carbonyl stretch (Amide I)
1650-1580 m-s Primary amine –NH2 NH2 deformation
1610-1560 vs Carboxylic acid slat –COO- COO- antisym stretch
1565-1475 vs Secondary amide –NH- NH deformation (Amide II)
1440-1260 m-s, br Alcohol C-OH in plane bend
1430-1390 s Ammonium, NH4+ NH2 deformation ; sharp peak
1400-1310 s Carboxylic acid salts –
COO-
COO- sym stretch; broad band
1310-1250 m Trans amide linkage C-N stretch (Amide III)
treatments. The flexural rigidity values are between 45mg x cm and 165mg x cm. On the
other hand, the calcium chloride treated fabrics showed flexural rigidity between 80mg x
cm and 200mg x cm, while it was between 90 to 240mg x cm for magnesium chloride
treatments.
110
0
50
100
150
200
250
300
0 30 60 90 120
Carboxyl content (mmole/100g)
Flex
ural
rigi
dity
(mg
x cm
)
0%1%CC3%CC6%CC
Figure 4.35 Effect of carboxyl content and concentration on stiffness of the cationic
chitosan (molecular weight of 1.4 x 105g/mole) treated fabrics
0
50
100
150
200
250
300
0 30 60 90 120
Carboxyl content (mmole/100g)
Flex
ural
rigi
dity
(mg
x cm
)
0%1%CG3%CG6%CG
Figure 4.36 Effect of carboxyl content and concentration on stiffness of the cationic glycerin treated fabrics
111
0
50
100
150
200
250
300
0 30 60 90 120
Carboxyl content (mmole/100g)
Flex
ural
rigi
dity
(mg
x cm
)
0%0.5M Ca++0.5M Mg++
Figure 4.37 Effect of carboxyl content and concentration on stiffness of the calcium
chloride and magnesium chloride treated fabrics
4.6.3 Stiffness data of polyanion treated cationic cellulosic fabrics
The results of stiffness measurements of PCA and BTCA treated fabrics are given
in Tables A.34 and A.35 of the appendix. The effect of %Nitrogen content of the fabrics
and polyelectrolyte concentrations on stiffness of the treated fabrics are presented in the
Figures 4.38 and 4.39. The cationized cellulosic fabrics also showed significantly higher
flexural rigidity values compared to the untreated fabric. The rigidity of the fabrics
increased while increasing the cationic level of the fabrics. The maximum rigidity was
obtained with 0.57 %Nitrogen fixed fabric. The treatments with polyanions reduced the
rigidity of the cationized fabrics. The crosslinked fabrics’ rigidity values are slightly
higher than that of the untreated fabric. Both the PCA and BTCA treatments produced
112
similar flexural rigidity values. For the PCA treatments, the flexural rigidity values are
between 22 and 73mg x cm, while for BTCA treatments they were between 23 and 72mg
x cm.
0
50
100
150
200
250
300
0.2 0.6 1 1.4
%Nitrogen fixed
Flex
ural
rigi
dity
(mg
x cm
)
0%1%PCA3%PCA6%PCA
Figure 4.38 Effect of %Nitrogen fixed and concentration on stiffness of the PCA treated
fabrics
113
0
50
100
150
200
250
300
0.2 0.6 1 1.4
%Nitrogen fixed
Flex
ural
rigi
dity
(mg
x cm
)
0%1%BTCA3%BTCA6%BTCA
Figure 4.39 Effect of %Nitrogen fixed and concentration on stiffness of the BTCA treated fabrics
4.6.4 Discussion of stiffness data of untreated and treated fabrics
The summary of the stiffness data of treated fabrics is shown in Figure 4.40. The
flexural rigidity of the DMDHEU treated fabric was measured as 39.04mg x cm while it
was 21.4mg x cm for untreated fabric. The stiffness of resin treated fabric is lower than
most of the ionic crosslinked fabrics. But in some cases, for example the PCA and BTCA
treated cationic fabrics having 0.19% and 0.28% fixed nitrogen showed lower flexural
rigidity than DMDHEU treated fabric.
The ionic crosslinking process increases the stiffness of the treated fabric. After
the fabric is carboxymethylated or cationized it shows significantly high flexural rigidity
114
values compared to the untreated fabric, because ionic cellulose molecules have
substitutions on their molecules either with chloroacetic acid or CHTAC. Cellulose
molecules are most extended at low concentrations of ionic groups but at higher
concentrations the molecules overlap and coil up and then, at high concentrations, they
form entangled structures. Increasing ionic strength causes the polymer to become more
coiled. This new molecular structure makes the fabric stiffer. Following application, ionic
crosslinking in this case, reduces the rigidity of the ionic cellulosic fabric by some degree.
The end product, crosslinked cellulosic fabric, shows rigidity values that are still higher
than the initial fabric. The increase in the flexural rigidity is higher for higher cationic or
anionic content of the fabrics. Increases in the concentration of the crosslinker also make
the fabrics stiffer. In the case of anionic fabrics treated with polycations, the cationic
chitosan treatments produced the highest increase in stiffness. Calcium and magnesium
treated fabrics also produced high rigidity values, though are not as high as cationic
chitosan treated fabrics. Cationic glycerin treatments also showed significantly high
flexural rigidity values, but are still lower than cationic chitosan treatments. On the other
hand, the polyanion treated cationic fabrics showed flexural rigidity values that are
slightly higher than the initial fabric. The flexural rigidity values are almost identical for
PCA and BTCA treated fabrics. These treatments resulted with significantly low rigidity
values compared to polycation treated anionic fabrics.
115
Figure 4.40 Effect of treatment on stiffness
116
5. CONCLUSIONS
Ionic crosslinking of cellulose for durable press finish can be a potential solution
for today’s textile industry, which is searching for durable press finishes that can give the
same advantages as formaldehyde based finishes without causing strength loss and
formaldehyde release. There are many alternatives for forming ionic crosslinks, for
example, making cellulose anionic with chloro acetic acid and reacting with a polycation
or producing cationic cellulose with 3-chloro-2-hydroxypropyl trimethyl ammonium
chloride and then reacting with a polyanion. In both ways, the polymer chains are bound
at as many sites as possible with having an excellent washing durability. These treatments
produce improvements in both dry and wet wrinkle recovery angles with significant
increases in tensile strength. Increases up to 140o were obtained in wet wrinkle recovery
angles and up to 100o in dry wrinkle recovery angles, while including a considerable
strength gain in treated fabrics. The DMDHEU treatment decreased the tensile strength of
the fabrics more than 50%, a considerable strength loss and a major problem. On the other
hand the ionic crosslinked fabrics improved tensile strength of treated fabrics up to 58%, a
very significant strength gain. The whiteness index of resin treated fabric was 51.04, an
approximately 12% decrease compared to untreated fabric. Treatments with cationic
glycerin, calcium and magnesium did not cause significant decrease in whiteness index of
treated fabrics. The difference was between 2% and 20%. Cationic chitosan treatments
showed over 25% decreases in whiteness of the treated fabrics. The stiffness values of the
treated fabrics were significantly higher than initial fabric. The BTCA and PCA
117
treatments showed similar stiffness values to that of the DMDHEU treatment. The other
polyelectrolyte treatments produced significantly higher stiffness values than DMDHEU
treated fabric.
In addition, ionic crosslinks may have other important advantages, such as
antimicrobial activity and enhanced dyeability. The chemicals are common industrial
reactants and do not have unusual safety or environmental issues. The processes use
existing equipment that are widely used in the textile industry and have no need for high
temperature curing.
118
6. RECOMMENDATIONS FOR FUTURE WORK
This research focused on effects of altering polyelectrolyte types, ionic content of
the fabrics and application process on wrinkle recovery angles, tensile strength, whiteness
and stiffness of the treated fabrics.
In terms of polyelectrolyte types, we observed that small molecular weight
molecules such as cationic glycerin could give same advantages as high molecular weight
polyelectrolyte without causing significant decreases in whiteness of the treated fabrics. In
addition, it is expected that smaller molecules have higher mobility between the cellulose
polymer chains; therefore they could form ionic crosslinks either in the same cellulose
chain or between two different chains. The nitrogen analysis after several laundry
washings showed there was no significant difference in loss of polyelectrolyte between
cationic chitosan treatment and cationic glycerin treatment. Thus treatments with small
molecular weight polyelectrolyte are recommended for future work.
In the case of ionic content of the fabrics, four ionic levels have been tested and an
optimum level was observed. The wrinkle recovery angles and strength data of the treated
fabrics were not significantly different for levels 3 and 4. Meanwhile, treated fabrics
having lower levels of ionic contents produced higher whiteness and lower stiffness
values than the fabrics having higher ionic contents. Therefore, it is recommended to work
with just three different levels of ionic contents. Working with different fabric and fiber
types may also vary the results. For example, a tight fabric structure can produce lower
improvements than a loose fabric, as the tight weave inhibits movements causing the
119
fibers to take on more pressure, and therefore more wrinkling occurs. Fiber thickness also
affects the crease angle recovery of the fabric. For example, a fabric made of thicker fibers
may show lower crease angle recovery improvements, as the cellulose chains have greater
force difference due to stretching under an applied force and they wrinkle more.
The application process consisted of producing anionic and cationic cellulose
followed by the application of a polyelectrolyte of the opposite charge. The treatments of
anionic cellulosic fabrics with various polycations showed greater improvements.
Therefore, polycation application is preferable. A one-step treatment can also be applied,
such as making a precondensate by adding an ionic material to a polyelectrolyte of the
opposite charge and then reacting this precondensate with the fabric. This method is much
easier and faster, as it avoids the production of ionic fabric prior to ionic crosslinking and
is similar to conventional durable press finishes. In order to accomplish higher dry wrinkle
recovery angles, a solvent system can be used instead of water to apply polyelectrolytes.
The selected solvent should easily dissolve the polyelectrolytes and open the structure of
cellulose.
The ionic crosslinking process may have some effects on the microstructure of the
cellulose polymer chains, such as changes in the crystalline structure of the polymer
chains and internal structure of the cellulose. A further understanding of the molecular
changes after the ionic crosslinking process is recommended. Ionic crosslinking may
increase the crystalline part of the cellulose structure. The strength data obtained from
treated fabrics showed significant strength gain. This strength gain may be due to an
increase in the amount of crystalline part of cellulose structure. There are instrumental
120
techniques to determine the crystallinity level of the polymer. X-Ray diffraction analysis
can be performed to identify the changes in the crystallinities and the internal structures as
a result of ionic crosslinking.
121
7. LIST OF REFERENCES
1. Wei C., Gary C. L., Charles Q. Y. Molecular modeling of cellulose in amorphous state part II: effects of rigid and flexible crosslinks on cellulose. Polymer 2004 Sep; 45(21):7357-7365. 2. Xu W. and Li Y. Cotton fabric strength loss from treatment with polycarboxylic acids for durable press performance. Textile Research Journal 2000 Nov;70(11):957-961. 3. Kittinaovarut S. Acrylic and citric acid in nonformaldehyde durable press finishing on cotton fabric. AATCC Review 2003 Jan;3(8):62-64. 4. Hasem M., Hauser P. and Smith B. Wrinkle Recovery for Cellulosic Fabric by Means of Ionic Crosslinking. Textile Research Journal 2003 Sep;73(9):762-766. 5. Hebeish A., El-Rafie M.H., El Alfy E., El Sheltawi S.T. and El Sisy F.F. Chemical desizing and development of a one-stage process for desizing and scouring of starch-sized cotton fabrics. Cellulose Chemistry and Technology 1987 July;21(4):401-418. 6. Hebeish A., El Rafie M.H. and El Sisy F. Combined desizing, scouring and bleaching of starch-sized cotton fabric. Cellulose Chemistry and Technology 1987 March;21(2):147 158. 7. Islomov S., Bobodzhanov P.K., Marupov R.M., Likhtenshtein G.I. and Zhbankov R.G. Study of the structure of cotton cellulose during biosynthesis by the spin-label method. Cellulose Chemistry and Technology 1986 May;20(3):277-287. 8. Venkataraman A., Subramanian D.R. and Jacob S. Effect of low-concentration alkali on modified and decrystallized cotton cellulose structures. Cellulose Chemistry and Technology 1987 Sep;21(5):475-482. 9. Kamel M.M., El Kharadly E.A. and Youssef B.M. Dyeing of chemically modified cellulose with methylolated acrylamide derivatives. Cellulose Chemistry and Technology 1984 Sep;18(5):459-468.
10.Wei Chena, Gary C. Lickfielda and Charles Q. Yangb. Molecular modeling of cellulose in amorphous state part I: model building and plastic deformation study. Polymer 2004 Feb;45(3) 1063-1071.
122
11. Butnaru R., Muresanu A. and Mitu S. Influence of crease resist finish treatments upon the comfort indices in cotton-type textiles. Cellulose Chemistry and Technology 1986 May;20(3):349-355. 12. Ibrahim N.A. and El Alfy EA. Concurrent dyeing and finishing II. Combined dyeing and easy-care finishing of aminized cotton with acid dyestuffs and N-methylol compounds. Cellulose Chemistry and Technology 1987 Sep;21(5):507-512. 13. Vaidya A.A. and Trivedi S.S. Textile Auxiliaries and Finishing Chemicals. Ahmedabad: R.C. Vora; 1975. 90-100. 14. Bajaj P., Chakrapani S. and Jha N.K. Flame retardant durable-press finishes for cotton and polyester/cellulose blends. Textile Research Journal 1984 Sep;54(9):619-630. 15. Shin Y., Hollies N.R.S. and Yeh K. Polymerization-crosslinking of cotton fabric for superior performance properties. I. A preliminary study. Textile Research Journal 1989 Nov;59(11)635-642. 16. Hamalainen C., Mard H.S. and Cooper A.S. Comparison of application techniques for deposition of resins in cotton fibres. American Dyestuff Reporter 1972 ;71(2):30-38. 17. Vail S.L. and Verburg G.B. Chemical and physical properties of cotton modified by N-methylol agents. III. Observations on polymerization and crosslinking of melamine- based reagents with cotton. Textile Research Journal 1973 Jan;43(2):67-74. 18. Nair P. Resin finishing of polynosic/cotton blended fabric by poly-set process. Cellulose Chemistry and Technology 1982 Sep;16(5):491-502. 19. Reinhardt R.M. and Harper R.J. Comparison of aftertreatments to lower formaldehyde release from cottons crosslinked with various finishing agents. Journal of Coated Fabrics 1984 April;13(4):216-227. 20. Sarma G.V., Gupta R.C. and Verma B.C. Performance report of BIL-treated all cotton durable press shirts in a pilot service test. Journal of the Textile Association 1973 May;34(3):115-122. 21.Turner J.D. Articles with durable press produced by low temperature treatment. Textile World 2001 March;151(3):50-53. 22. Yang C.Q., Qian L. and Lickfield G.C. Mechanical strength of durable press finished cotton fabric Part IV: Abrasion resistance. Textile Research Journal 2001 June;71(6):543-548.
123
23. Charles Q. Yang and Weishu Wei. Mechanical Strength of Durable Press Finished Cotton Fabric Part II: Change in Cellulose Molecular Weight. Textile Research Journal 2000 Oct;70(10):910-915. 24. Ibrahim N. A., Abo Shosha M. H., Elnagdy E. I. and Gaffar M. A. Eco Friendly Durable Press Finishing of Cellulose Containing Fabrics. Journal of Applied Polymer Science 2002 June;84(12):2243–2253. 25. Day M.P. and Collier B.J. Prediction of formaldehyde release from durable press treated fabrics. Textile Chemist and Colorist 1997 Jan;29(1):33-36. 26. Xu W. and Li Y. Cotton fabric strength loss from treatment with polycarboxylic acids for durable press performance. Textile Research Journal 2000 Nov;70(11):957-961. 27. Charles Q. Yang and Weishu Wei. Mechanical strength of durable press finished cotton fabric. Part II: Comparison of crosslinking agents with different molecular structures and reactivity. Textile Research Journal 2000 Feb;70(2):143-147. 28. Srichharussin W., Ryo Aree W., Intasen W. and Poungraksakirt S. Effect of Boric Acid and BTCA on Tensile Strength Loss of Finished Cotton Fabrics. Textile Research Journal 2004 June;74(6):475-480. 29. Udomkichdecha W., Kjttinaovarat S., Tianasoonthornroek U. and Potlyaraj P. Acrylic and maleic acids in nonformaldehyde durable press finishing of cotton fabric. Textile Research Journal 2003 May;73(5):401-406. 30. Aly A.S., Hashem A. and Hussein S.S. Utilization of chitosan citrate as crease-resistant and antimicrobial finishing agent for cotton fabric. Indian Journal of Fiber & Textile Research 2004 June;29(2):218-222. 31. Achwal W.B. Chitosan and its derivatives for textile finishing. Colourage 2003 ;50(8): 51-76. 32. Gary A. Ungefug and Stephan B. Cello. Ionic Crosslinking of Acrylic Sizes. Textile Chemist and Colorist 1983 Oct;15(10):193-196. 33. Fujiyama M., Kondou M., Ayama K. and Inata H. Rheological Properties of Ionically and Covalently Crosslinked Polypropylene Type Thermoplastic Elastomers. Journal of Applied Polymer Science 2002 July;85(4):762–773. 34. Mitsuyoshi F., Kazuhiro Y., Kazuhiko A. and Hitoshi I. Rheological Properties of Ionically Crosslinked Poly(propylene)-Type Thermoplastic Elastomers. Journal of Applied Polymer Science 2002 Dec;86(11):2887–2897.
124
35. Fanbao M., Baoyan Z., Lumei L. and Baoling Z. Liquid-crystalline elastomers produced by chemical crosslinking agents containing sulfonic acid groups. Polymer 2003 June;44(14):3935–3943. 36. Ibarra L. and Alzorriz M. Vulcanization of carboxylated nitrile rubber (XNBR) by a mixed zinc peroxide–sulphur system. Polymer International 2000 Jan;49(1):115-121. 37. Sriram V., Aruna P., Naresh M. D. and Radhakrishnan Ganga. AB Crosslinked Polyurethanes Through Ionic Crosslinking: Influence of Crosslinking Networks on Physico Chemical properties. Journal of Macromolecular Science Part A: Pure Application Chemistry 2001 Sep;38(9):945–959. 38. Roberts G.A.F. Chitin Chemistry. London: Macmillan Press Ltd.; 1992. 94-112. 39. Kim, Y., Choi, H., and Yoon, J. Synthesis of a Quaternary Ammonium Derivative of Chitosan and Its Application to a Cotton Antimicrobial Finish. Textile Research Journal 1998 June;68(6):428. 40. El Hilw Z.H. Development of an ecological system for the easy-care finishing of cotton. Tinctoria 2004 March;101(3):29-35. 41. Kittinaovarut S. Acrylic and citric acid in nonformaldehyde durable press finishing on cotton fabric. AATCC Review 2003;3:62-64. 42. Hasem M., Hauser P. and Smith B. Reaction Efficiency for Cellulose Cationization Using 3-Chloro-2-Hydroxypropyl Trimethyl Ammonium Chloride. Textile Research Journal 2003 Nov;73(11):1017-1023. 43. Shore John, editor. Colorants and Auxiliaries Organic chemistry and application properties. Hampshire: Hobbs The Printers; 2002. 664-666. 44. Timell T.E. editor. Proceedings of the Eighth Cellulose Conference. II. General Papers. New York: John Wiley & Sons; 1975. 811-830. 45. Tae K., Kim S., Han Y. and Young A.S. Effect of reactive anionic agent on dyeing of cellulosic fibers with a Berberine colorant. Dyes and Pigments 2004 March;60(3):121-127. 46. Lamber J.B., Shurrel H.F., Lightner D.A. and Cooks R.A. Introduction to Organic Spectroscopy. New York: Macmillan Publishing Company; 1987. 22-70.
125
47. Wang W., Bo S., Li, S. and Qin W. Determination of the Mark-Houwink equation for chitosans with different degree of deacetylation. International Journal of Biological Macromolecules 1991 Oct;13(5):281-285. 48. Kasaai R.M. Depolymerization of chitosan. Doctoral Dissertation. Quebec: Laval Quebec University; 1999. 49. Shugar G.J. and Ballinger J.T. Chemical technicians’ ready reference handbook. New York: McGraw Hill Inc; 1990. 626-635. 50. Muzzarelli R. A. A. and Parisher E.R., editor. Characterization of chitosan. II: The determination of the degree of acetylation of chitosan and chitin in “Proceedings of the First International Conference on Chitin/Chitosan. 1978. 306-314. 51. Rao P.V. Statistical Research Methods in the Life Sciences. Pacific Grove:Duxbury Press; 1998. 140-148.
126
8. APPENDIX
8.1 Wrinkle recovery angles
The wrinkle recovery angles of the untreated fabric, carboxylated fabrics,
cationized fabrics, conventional durable press finished fabric and polyelectrolyte treated
fabrics and their relationships with ionic content of the fabrics and polyelectrolyte
concentration are given in the tables below.
Table A.1 Dry and wet wrinkle recovery angles for molecular weight of 32000g/mole cationic chitosan treated fabrics (dry/wet)
CC treatment > pad batch concentration Resin treatment 272/266
COO- content
(mmol/100g)
0%(Blank) 1% 3%
6%
6.2 138/125 184/168 172/172 178/168
30.2 160/149 212/236 242/250 226/255
60.7 163/145 220/244 234/246 222/257
87.1 162/153 224/248 232/248 230/242
114.5 166/159 220/250 234/254 208/268
127
Table A.2 Dry and wet wrinkle recovery angles for molecular weight of 140000g/mole cationic chitosan treated fabrics (dry/wet)
CC treatment > pad batch concentration Resin treatment 272/266
COO- content
(mmol/100g)
0%(Blank) 1% 3%
6%
6.2 138/125 186/185 172/182 183/193
30.2 160/149 204/234 208/246 211/256
60.7 163/145 212/244 218/258 214/256
87.1 162/153 228/246 222/260 209/260
114.5 166/159 212/260 207/264 215/266
Table A.3 Dry and wet wrinkle recovery angles for molecular weight of 611000g/mole cationic chitosan treated fabrics (dry/wet)
CC treatment > pad batch concentration Resin treatment 272/266
COO- content
(mmol/100g)
0%(Blank) 1% 3%
6%
6.2 138/125 170/172 164/166 168/164
30.2 160/149 208/246 212/252 212/250
60.7 163/145 210/249 215258 218/256
87.1 162/153 222/252 218/262 230/258
114.5 166/159 233/242 234/237 230/244
128
Table A.4 Dry and wet wrinkle recovery angles for molecular weight of 140000g/mole cationic chitosan treated fabrics by exhaustion method (dry/wet)
CC treatment > batch concentration Resin treatment 272/266
COO- content
(mmols/100g)
0%(Blank) 6%
30.2 160/149 135/216
87.1 162/153 123/191
114.5 166/159 120/232
Table A.5 Dry and wet wrinkle recovery angles for cationic glycerin treated fabrics (dry/wet)
Cationic glycerin treatment > pad batch concentration Resin treatment: 272/266
COO- content
(mmol/100g)
0% (Blank) 1% 3%
6%
6.2 138/125 188/185 174/183 185/192
30.2 160/149 216/250 206/256 207/257
60.7 163/145 201/256 208/262 212/265
87.1 162/153 215/259 215/258 204/265
114.5 166/159 214/269 227/266 224/273
129
Table A.6 Dry and wet wrinkle recovery angles for cationic glycerin treated fabrics by exhaustion method (dry/wet)