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A Comparison of Peracetic Acid and Hydrogen
Peroxide Bleaching on Cotton Fabric
By: Dr. A. Farhan Khan
Department of Textile Science, Textile Institute of Pakistan, Karachi
Abstract
Bleaching tests were conducted to study the efficacy of peracetic acid as a
replacement of hydrogen peroxide in bleaching processes of 100% cotton fabric.
The criteria chosen for assessing bleaching performances of peracetic acid and
hydrogen peroxide were whiteness index, tensile strength, absorbency and fluidity
values. The CIE whiteness index value of fabrics was measured by a
spectrophotometer using appropriate computer software. Universal Strength
Tester (Titan) was used to measure tensile strength. Ostwald – Fenske Cuen
viscosimeter was used to determine chemical degradation of cotton fabric by
measurement of its fluidity and embroidery hoop was used to determine
absorbency. The results of this research showed that the peracetic acid is more
effective as a bleaching agent than hydrogen peroxide. An acceptable degree of
whiteness (CIE whiteness index 80) can be obtained with minimum loss of tensile
strength. This study has also provided valuable information for industrial
application of the developed bleaching systems.
Key words: Cotton, Bleaching, Peracetic acid, Hydrogen peroxide
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Introduction:
The art of bleaching has been practiced since beginning of civilization [1,2].
Bleaching is the process of removing colored impurities from the griege fabric as
efficiently as possible, with minimum or no damage to the fiber and leaving in a
perfect white state [3,4].
Nowadays, consumers increasingly demand more environmentally friendly
products. This also effect the textile industry, and thus, aspects such as control of
water, energy and chemicals consumption should be taken into account in wet
textile processes. Hydrogen peroxide (H2O2) is the most widely used bleaching
agent for textiles and came into use around 1878 [1]. Hydrogen peroxide is suitable
for most fibers and it can be used in a wide range of machines under different
conditions. Reaction products are non-toxic and non-dangerous but hydrogen
peroxide is a highly corrosive compound and degrades to oxygen and water.
Hydrogen peroxide is however, damaging to fiber, because it is applicable in
strongly alkaline medium and it requires a high temperature to give the most
effective bleaching [5,6 ].
Paracetic Acid (PAA) as a bleaching agent has many advantages compared to
hydrogen peroxide. It does not produce any toxic by product in bleach reaction, it is
less corrosive, it is biologically totally degradable and it causes no AOX (absorbable
halogenated organic compounds) load in the waste water [7].
Paracetic acid can be prepared in situ in solution from hydrogen peroxide and
acetic anhydride.
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H2O2 + (CH3CO)2O → CH3COOOH + CH3COOH
Commercial peracetic acid, which is available, for example, in 5% and 15%
solutions, is a colorless liquid with a pungent smell & both solutions are water
soluble [8].
Experimental:
Materials:
Fabric:
The characteristic parameters of the 100% pure scoured cotton fabric used for all
the experiments, purchased from the market are presented in Table-1.
Table-1: Basic characteristics of 100% cotton scoured fabric
Area Warp Weft CIE Tensile
Fabric Weave Weight Yarn Yarn Whiteness Strength Absorbency Fluidity
Composition Count count Index (N)
(g/m2) (tex) (tex) (WI) Warp Weft (Sec) (Rhe)
Scoured
Taffeta
100% Cotton weave 168.5 40 31 26.9 542.0 240.4 4.2 1.3
Water:
The water used during all bleaching and washing operations had the following
qualities.
Table-2: The Quality of Water
pH Total Hardness Total Dissolve Solids
(ppm) (ppm)
7.8 42.0 145
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The Total Hardness was measured in terms of calcium carbonate. The pH, Total
Hardness and Total Dissolve Solids (TDS) of water suitable for all textile processing
are 6.5-7.5, 0-50 ppm and 65-150 ppm respectively [9].
Equipments/ Methods:
Bleaching Machine:
Bleaching runs were carried out in an SDL ‘ECO’ Infra Red Lab Bleaching/Dyeing
machine with automatic temperature programming and agitation.
Digital pH Meter:
A digital pH/Temperature meter was used with a combination of glass electrode.
Whiteness Measurement:
The CIE Whiteness Index value (CIE WI) was determined for the bleached fabric
using AATCC Test method (110–1995) [10]. The whiteness was measured using a
DataColorSpectra flash SF 600X with the following setting; illuminants D-65, large
area view, specular included and CIE 1964 supplemental standard observer (100
observer). Each sample was folded twice to give an opaque sample with four piles
and the whiteness was measured four times at different fabric surface. The average
value of (CIE WI) was recorded.
Absorbency:
Absorbency was determined as per AATCC Test Method (79-1986) [11].
Absorbency is one of the several factors that determine the suitability of a fabric for
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a particular use wet ability or absorbency of textiles or fabric can be determined by
the this test method.
Fluidity:
Ostwald Cannon-Fenske (Cuen) (Cupriethylene Diamine Hydroxide) viscosimeter
was used to determine the chemical degradation of cotton by measurement of their
fluidity as per AATCC Test Method (82-1989) [11].
Tensile Strength:
The tensile strength was measured by Universal Strength Tester (Titan) according
to EN (ISO. 13934-1: 1999) [12].
Chemicals:
Hydrogen Peroxide:
Hydrogen Peroxide (35% wt/wt) supplied by MERCK (Germany).
Wetting Agent:
Sandozin Niti.in liq (non ionic) wetting agent supplied by Clariant (Pakistan).
Sodium Hydroxide:
Sodium Hydroxide (NaOH) pellets supplied by MERCK (Germany).
Peracetic Acid:
Peracetic acid supplied by Tianjin Xinyuan Chemical, CO., Ltd (China).
Stabilizer EDTA:
Stabilizer EDTA supplied by MERCK (Germany).
For comparing the hydrogen peroxide and peraectic acid bleaching effects, the
recipes used are shown in Table-3.
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Table-3: Bleaching recipes of hydrogen peroxide and peracetic
acid
Hydrogen peroxide Bleaching Peracetic acid Bleaching
H2O2 35% (wt/wt) 5% (owf) PAA (8% solution) 10g/l
NaOH 100% 2.5% (owf) for pH 10-10.5 Wetting agent 1.5% (owf)
Pellets (non ionic)
Wetting agent 1.5% (owf) Stabilizer EDTA 2% (owf)
(nonionic)
Stabilizer EDTA 2% (owf) Treatment 65°C
temperature
Treatment temperature 95°C Treatment time 45 min
Treatment time 60 min pH 6.5-7.0
Fabric Scoured Cotton Fabric Scoured
Cotton
Liquor to fabric ratio 15:01 Liquor to fabric 15:01
ratio
*owf: On the weight of fabric
The hydrogen peroxide and peracetic acid bleached samples were then hot
washed at 95°C for 15 minutes followed by cold wash and air dried.
Results and Discussion:
The purpose of this comparative study was to explore the possibility of bleaching
cotton fabric by peracetic acid and to achieve an acceptable degree of whiteness
(CIE whiteness index 80) with minimum loss of tensile strength and maximum
absorbency.
The results of CIE whiteness index, tensile strength, absorbency and fluidity are
shown in Table- 4.
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Table-4: Comparison of properties of cotton fabric bleached by
hydrogen peroxide and peracetic acid
Kind of treatment CIE whiteness index Tensile strength Absorbency Fluidity
(WI) (N) (Sec) (Rhe)
Warp Weft
H2O2 81.1 435.1 198.9 1.0 2.3
PAA 83.6 450.7 205.1 1.0 2.1
The colouring matter present in cotton is characterized by the presence of
conjugated double bonds and these double bonds are attacked by the oxidizing
species during bleaching [13,14].
Bleaching was carried out with PAA (10g/l) on scoured cotton fabric at pH- 6.5-7 for
45 minutes. The PAA bleached sample was compared with sample bleached by
hydrogen peroxide. It was observed that PAA bleaching increased the CIE
whiteness index from 26.9 (non bleached cotton fabric) to 83.6, this whiteness index
was about 3% higher than of hydrogen peroxide bleaching. Which is considered as
acceptable whiteness index, so that the material would be ready for dyeing/printing.
This acceptable degree of whiteness was decided in consultation with processing
mills. The same results are shown in graphical form in Fig. 1.
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Fig.1: Comparison of degree of
whiteness for samples bleached by
Hydrogen peroxide & Peracetic acid.
90
80
70
CIE Whiteness Index (WI)
60
50
40
30
20
10
0
Non bleached H2O2 PAA
On the other hand when the tensile strength and fluidity values of hydrogen
peroxide and peracetic acid bleached samples were examined, it was noticed that the
tensile strength of PAA bleached sample was (3.5% warp direction; 3.1% weft
direction) higher than hydrogen peroxide, also the fluidity values were changed
from 1.3rhes (non bleached) to 2.1rhes in the case of PAA bleached sample and
2.3rhes in the case of hydrogen peroxide bleached samples. The fluidity value of
PAA 2.1rhes shows the marginal degradation of cellulose than those of bleached
sample by hydrogen peroxide. A report by Hickman.W.S and Andrianjafy.H showed
that the value of fluidity below 5rhes is considered acceptable for bleached fabric
and Vaeck showed direct relationship between fluidity values and loss of tensile
strength [15,16]. The results of tensile strength and fluidity are also exhibited in
graphical form. Fig.2,3.
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Fig.2: Comparison of tensile strength for
samples bleached by Hydrogen peroxide
& Peracetic acid.
600
500
Tensile strength (N)
400
300
200
100
0
(warp)(weft)non bleached (warp)(weft)H2O2 (warp)(weft)PAA
Fig.3: Comparison of fluidity for samples
bleached by Hydrogen peroxide &
Peracetic acid.
3.5
3
2.5
Fluidity (Rhe)
2
1.5
1
0.5
0
Non bleached H2O2 PAA
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A big improvement in the absorbency (time required for the specular reflection of
the water drop to disappear) (4.2sec to 1.0sec) were also observed in all cases of
bleaching. The results of these figures are represented in Fig.4.
Fig.4: Comparison of absorbency for
samples bleached by Hydrogen peroxide
& Peracetic acid.
4.5
4
3.5
Absorbency (sec)
3
2.5
2
1.5
1
0.5
0
Non bleached H2O2 PAA
All the above results of CIE whiteness index, tensile strength, fluidity and
absorbency obtained by PAA bleaching indicate that the main advantage of
bleaching with PAA instead of peroxide is that a satisfactory degree of whiteness
can be obtained at 65ºC in 45 minutes at neutral pH. This results in lower energy
and water consumption in both during bleaching and rinsing of the fabric.
Neutralization of the fabric after bleaching is not required, unlike bleaching with
hydrogen peroxide, where large amount of alkali must be removed before dyeing.
This is also much less damaging to the cotton fabric when PAA is used.
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Conclusion:
In this study PAA has been studied as an alternative to hydrogen peroxide for the
bleaching of cotton. It has been demonstrated in this work that scoured cotton
fabric can be bleached by PAA and it is possible to achieve an acceptable degree of
whiteness in a shorter time than is required for hydrogen peroxide bleaching
process.
Furthermore, bleaching can be carried out at 65ºC with neutral pH without
producing any harmful chemicals.
PAA, as an industrial chemical is easily available and can be safely introduce to an
existing process design.
References:
1) Peters,R.H., Textile Chemistry, Elsevier Publ., 1967,vol.2.
2) Easton,B.K., Ciba Geigy Rev., 1971, 3, 3.
3) Shenai,V. A., Technology of Bleaching and Mercerizing, Sevak Publications.,
New Dehli, 1991, p.10-60.
4) Cates, D.M; Cranor,W.H., Textile Res. J, 1960, 30, 848.
5) Conzelmann, F; Wurster, P; Zahn, A., Textil Praxis International, 1989, p.644.
6) Schulz, G., Textil Praxis International, 1990, p.40.
7) Parch, M.et al., Fette Wachse, 1990, 77.
8) John, Shore., Colorant & Auxiliaries, Hobbs The printers., Hampshire, UK,2002,
vol.2, p.602-607.
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9) Athur,D. Broadbent., Basic Principles of Textile Coloration., Society of Dyers &
Colourists, UK, 2001, p.132.
10) AATCC Technical Manual, Vol.75, Research Triangle Park: AATCC, 2000.
11) AATCC Technical Manual, Vol.66, Research Triangle Park: AATCC, 1991
12) British Standard, BS EN ISO 13934-1: 1999.
13) Jones,B.M; Langlois,G.W; Sakaji,R.H., Environ. Prog., 1985, 4, 252.
14) Rounsaville, J; Rice,R.G,. Ozone.sci.eng., 1997, 18, 549.
15) Hickman,W.S; Andrianjafy,H., J.S.D.C., 1983, 99, 88.
16) Vaeck., J.S.D.C.,1966, 82, 374.
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