ijftr 38(2) 202-206
TRANSCRIPT
Indian Journal of Fibre & Textile Research
Vol. 38, June 2013, pp. 202-206
Optimization of polyester printing with
disperse dye nanoparticles
H Osman1,a
& M Khairy2
1Textile Printing, Dyeing & Finishing Deptartment,
Faculty of Applied Arts, Benha University, Benha, Egypt 2Chemistry Department, Faculty of Science,
Benha University, Benha, Egypt
Received 13 April 2012; revised received and
accepted 25 July 2012
A nanoparticle size disperse dye treated with ultrasound has
been applied on polyester fabric without using a carrier. Various
dyeing and process parameters used are studied in detail, such as
K/S values, dye particle size, dye exposure to ultrasound waves,
printing paste pH, steaming conditions of prints, morphological
study using SEM and TEM of dye particles and fastness
properties of the prints. The use of nanosized dye particles
enormously improves the colour depth of the prints without the
addition of extra chemicals to the printing paste.
Keywords: Ball miller, Dye nanoparticles, Fastness properties,
Polyester fabric, Printing, Ultrasound waves
A disperse dye is defined as a substantially water
insoluble dye having an affinity for one or more
hydrophobic fibres1. Disperse dyes are essentially non-
ionic dyes2, they are the most commonly employed
dyes in the textile industry to colour synthetic fibers
such as polyester, acrylic and acetate3. Disperse dyes
have extremely low water solubility and for application
from this medium, they must be milled to a very low
particle size and dispersed in water using a surfactant
(dispersing agent)4 or else a carrier must be added
during textile coloration.
The actual mechanism by which a carrier used in
dyeing accelerates textile coloration has been widely
debated. Polyester fibres absorb the carrier and swell.
This swelling can impede liquor flow in packaging
causing unlevelness. The overall effect leads to
lowering of the polymer glass transition temperature
(Tg), thus promoting polymer chain movements and
creating free volume. This speeds up diffusion of the
dye into the fibres. Alternatively, the carrier may form
a liquid film around the surface of the fibre in which
the dye is very soluble, thus increasing the rate of
transfer into the fibre5.
Power ultrasound (US) can enhance a wide variety
of chemical and physical processes; mainly due to
the phenomenon known as cavitations in a liquid
medium that is the growth and explosive collapse of
microscopic bubbles. Sudden and explosive collapse
of these bubbles can generate hot spots6, i.e. localized
high temperature, high pressure, shock waves and
severe shear forces capable of breaking chemical
bonds. Many efforts have been made explore this
technique in the textile coloration as it is a major
wet process, which consumes much energy and
water and releases large effluent to the environment.
Improvements observed in ultrasound assisted coloration
processes are generally attributed to cavitations
phenomena7 and, as a consequence, other mechanical
and chemical effects are as shown below:
• Dispersion (breaking up of aggregates with high
relative molecular mass);
• Degassing (explussion of dissolved or entrapped
air from fibre capillaries);
• Diffusion (accelerating the rate of diffusion of dye
inside the fibre);
• Intense agitation of the liquid;
• Destruction of the diffusion layer at dye/fibre
interfaces;
• Generation of free radicals; and
• Dilation of polymeric amorphous regions.
In the present work, 100% polyester fabric is
printed using a disperse dye having nanosized
particles. The dye is milled and treated with
ultrasound for different durations in order to obtain
tiny dye particles able to disperse in the printing paste
without adding a dispersing agent, since the size of
nanoparticles is small enough to diffuse into the
hydrophobic fibres properly.
All materials used were of analytical grade. The
100% plain weave polyester fabric of 185 g/m2,
purchased from El-Mahalla El Kobra, Egypt, was
used. The disperse dye Dianix Yellow-Brown HRSL-
SE 150, supplied and manufactured by Dystar Textile
Farben, Germany, was used. A thickening agent (an
acrylic synthetic polymer of low concentration),
having the commercial name Alcoprit PTF, supplied
—————— aCorresponding author.
E-mail: [email protected]
SHORT COMMUNICATIONS
203
and manufactured by Ciba Speciality Chemicals,
Switzerland, was used.
Preparation of Dye Nanoparticles
The disperse dye was ground using an energy Ball
Mill with a speed of 50 cycles/min. The dye powder
was sealed in a hardened steel vial (AISI 44°C
stainless steel) using hardened steel balls of 6 mm
diameter. Milling was performed using a ball :
powder mass ratio of 4:1. The dye was milled at
different intervals, such as 4, 6, 9 and 25 days. After
each milling interval, the particle size of the resulted
dye powder was measured. The smallest particle size
of 23 nm chosen to be used in the present study was
obtained from milling the dye powder for 25 days.
Two stock solutions were prepared using the
milled nanoparticle dye powder of 1% and 3%,
where 1 and 3 g of dye powder was dispersed in
99 and 97 mL of distilled water respectively. Each
dispersion was irradiated with ultrasound waves (720
kHz) and stirred at 80 °C for different periods of time,
such as 4, 6 and 8 h.
Printing Procedure
To investigate each factor, two printing pastes were
prepared for each parameter containing the two
different dye concentrations. The printing paste has
the following recipe:
Stock dye solution : 300 mL
Alcoprint PTF thickener : 50 g
Water : X mL
Total weight of paste : 1000 g
The pH was adjusted at 6 using sodium dihydrogen
phosphate. The printing paste was applied to fabric
through flat screen printing technique and then
samples were left to dry at room temperature. Fixation
of dye was carried out with two methods, namely
steaming at 130 °C for 30 min and thermofixation at
140 °C for 10 min to determine the optimal fixation
method that results in best K/S values. The samples
were finally washed off using a 2g/L non-ionic
detergent (Sera Wash M-RK) at a liquor ratio of 1:50.
Soaping was carried out at 60 °C for 10 min.
Effect of Ultrasonic Irradiation and Particle Size
The two stock solutions, having a different
nanoparticle dye concentration, are exposed to
ultrasound irradiation for 4, 6 and 8h respectively.
The K/S values of the prints, both steamed and
thermofixed, are given in Fig. 1.
It is obvious that ultrasound treatment of both stock
dye solutions has a great influence on the colour yield
of the printed polyester fabrics. To determine the best
dye fixation method, steaming and thermofixation are
applied on the prints separately using both dye
concentrations. For steamed prints, optimum K/S
enhancement reaches 85.4% and 53.9 % for polyester
prints with 1% and 3 % stock solutions respectively
compared with the untreated dye solution with
ultrasound waves. These great results are due to the
fact that ultrasound enhances the dye molecule's
diffusion into the fibres8,9
. Also, ultrasound has a
significant effect on the reduction of particle size of
the disperse dye10,11
.
On the other hand, the figure shows that
thermafixation has a negative influence on the K/S
values of the prints. These results show that
thermofixation in the absence of a carrier fixes only
50-70 % dye while in the steaming process, steam
condenses on the cold fabric, raising its temperature
to 100 °C and swelling the thickener film. The
condensed water is largely evaporated again during
the exposure to steam but the thickener is not bount
into the fabric as in dry fixation, subsequently handle
of the fabric becomes softer. The absorption capacity
(build-up) increases in proportion to the steam
pressure and corresponding temperature. The colour
depth obtained at high pressures cannot be obtained
by using longer times at lower pressures. Figure 1
shows that steaming is the best method for dye
fixation and subsequently, it is chosen to be applied in
the proceeding work.
Printing Paste pH
Disperse dyes are sensitive to alkalis and so
polyester is generally dyed under acidic condition12
.
Sodium dihydrogen phosphate is recommended
Fig. 1—Effect of ultrasound exposure duration on K/S values of
steamed and thermofixed polyester prints
INDIAN J FIBRE TEXT. RES., JUNE 2013
204
because, unlike some organic acids, it has no
corrosive effect on nickel screens and is compatible
with natural thickeners. Figure 2 illustrates the effect
of printing paste pH using the nanotreated dye with
ultrasound exposure for 8 h on the K/S of polyester
fabrics. The printing process is carried out using
two stock dye solutions having 1% and 3% disperse
dye concentrations printed on polyester fabric and
followed by steaming at 130°C for 30min. The best
K/S values are obtained for both stock dye solutions at
pH 6. It means that the use of a nanoparticle disperse
dye enables the dye to penetrate the fibres more easily
at more neutral pH value.
Steaming Conditions It is well established that with saturated steam at
100° C the fixation is incomplete unless a carrier is
used. Also, the colour depth obtained at high pressures
cannot be obtained by using longer times at lower
pressures13
. Fibres of the most common polyester are
quite crystalline, very hydrophobic and have no ionic
groups. Hot water does not swell them and large
dye molecules (that have lower diffusion coefficients)
do not easily penetrate into the fibre interior.
For the samples used in this study, the effect of
steaming temperature and time on the K/S of polyester
fabrics printed with disperse dye nanoparticles of the
two different concentrations is investigated and the
data is plotted in Fig. 3.
It is observed that the best K/S values are obtained
by increasing both steaming temperature and time that
reach their maximum values on steaming at 130 °C
for 40 min. Despite that, steaming for 30 min is
chosen as the best steaming time since a small K/S
difference is observed on steaming for longer durations.
It is also noted that these results are considered
satisfying since no carrier is added to the printing
paste and are referred to both the nanosize of dye
particles as well the as ultrasound treatment of dye.
SEM and TEM Studies
The surface morphology, structure and particle size
of dye samples milled at different durations prior to
their exposure to ultrasound are shown in Figs 4 & 5.
Figure 4 shows the SEM images of dye particles
which have different shapes like breaking dishes
shape, spherical shape and tiny sprinkled dots. The
TEM micrographs of the samples milled at 9 and 25
days compared with the unmilled sample are shown in
Fig. 5. The micrographs indicate uniform spherical
dye nanoparticles. The micrographs also indicate that
an average size of the nanosized dispersed dyes is
200–23 nm in diameter. It is found that, the particle
size decreases as the period of grinding increases. The
difference in particle size after grinding is referred to
their dissociation due to the impact of shear forces
that act on dye particles in the ball mill that converts
gradually the particle size from 200 nm (before
milling) to 60nm (after 9 days of milling) and 23 nm
(after 25 days of milling).
Fig. 2—Effect of printing paste pH on the colour strength of
polyester prints
Fig. 3—Effect of steaming temperature (a) and time (b) on K/S of
polyester prints
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205
Fastness Properties
The durability of printing on polyester fabrics with disperse dye nanoparticles with and without exposure to ultrasound waves (using overall optimum conditions) is evaluated in terms of washing, perspiration, rubbing, light, tensile strength (tenacity and elongation) (Table 1).
Table 1 shows negligible differences in properties on comparing printing polyester fabrics using disperse dye nanoparticles with or without pretreatment with ultrasound waves.
Fig. 4—SEM images of disperse dye (a) before milling, and after
(b) 4 days, (c) 6 days, (d) 9 days, and (e) 25 days of milling
Table 1—Properties of polyester fabrics printed with disperse dye nanoparitcles (exposed to ultrasound waves for 8 h) using overall
optimum conditions
Perspiration Wash
fastness Acidic Alkaline
Rub
fastness
Tensile strength Sample
St. Alt. St. Alt. St. Alt. Dry Wet
Light
fastness
Tenacity, kg Elongation, %
Untreated
1% dye
4-5
5
4
4
4
4
3-4
4
6
124
40
3% dye 4-5 5 4 4 4f 4 3-4 4 6 118 36
Treated
1% dye
4-5
4-5
4-5
4
4-5
4
4
4-5
6
120
33
3% dye 4-5 4 4-5 4 4-5 4 3-4 4 5-6 122 45
Fig. 5—Representative TEM images of disperse dye (a) before
milling, and after (b) 9 days, and (c) 25 days of milling
INDIAN J FIBRE TEXT. RES., JUNE 2013
206
In this study, a disperse dye is ground to a nanosize
of 23 nm and is exposed afterwards to ultrasound
treatment, in the form of a solution of two dye
concentrations for 8 h. The nanoparticle suspension
is directly added to the stock thickener and printed
on a polyester substrate. All measurements as well
as various parameters affecting dye fixation are
investigated. The results indicate that grinding and
ultrasound exposure of the dye results in minimizing
particle size which facilitates dye penetration in the
hydrophobic substrate. This result is obtained without
the incorporation of a carrier in the printing paste
and only pH is adjusted at 6. Steaming at 130° C
for 30min used for dye fixation of the prints show
very good fastness properties and no differences can
be observed from prints of untreated dye with
ultrasound. SEM measurement illustrates the effect of
grinding on dye particle size.
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