Incorporating Hybrane H1500 as a nanostructured hyperbranched polyesteramide into polyethylene terephthalate (PET) enhances the dyeability of PET with C.I. Disperse Blue 56. The results show that the disperse dye display much greater substantivity toward the modified PET sheets compared to virgin PET one. DSC tests show that the crystallinity of modified PET sheets has slightly decreased. The main pur-pose of this work was to determine the dyeing mechanism of disperse dye on the modified PET using hy-perbranched polyesteramide by study the adsorption properties in the infinite dyebath at different tem-peratures. In fact, a few of the thermodynamic parameters of dyeing such as the equilibrium adsorption isotherm, standard affinity, enthalpy and entropy changes were studied. The bath containing virgin PET displays the highest negative values of the enthalpy change and entropy change, while the bath containing the modified PET with 2 wt% hyperbranched polyesteramide shows the lowest negative values of them.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3542

Ahani, M.

Khatibzadeh, M.

Kordbacheh, S.H.

Mohseni, M.

Vajar, M.

SocioEconomic Challenges Journal (Sumy State University)

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  
NANOMATERIALS: APPLICATIONS AND PROPERTIES 
Vol. 2 No 3, 03NCNN21 (5pp) (2013) 
 
 
2304-1862/2013/2(3)03NCNN21(5) 03NCNN21-1  2013 Sumy State University 
Blends of Polyethylene Terephthalate (PET) and Nanostructured Hyperbranched  
Polyesteramide for Improvement the Dyeability of PET: Thermodynamics 
 
M. Ahani, M. Khatibzadeh, M. Mohseni M. Vajar, S.H. Kordbacheh 
 
Department of Polymer Engineering and Color Technology, Amirkabir University of Technology P.O. Box 15875, 
Hafez Street, Tehran, Iran 
 
 (Received 29 May 2013; published online 31 August 2013) 
 
Incorporating Hybrane H1500 as a nanostructured hyperbranched polyesteramide into polyethylene 
terephthalate (PET) enhances the dyeability of PET with C.I. Disperse Blue 56. The results show that the 
disperse dye display much greater substantivity toward the modified PET sheets compared to virgin PET 
one. DSC tests show that the crystallinity of modified PET sheets has slightly decreased. The main pur-
pose of this work was to determine the dyeing mechanism of disperse dye on the modified PET using hy-
perbranched polyesteramide by study the adsorption properties in the infinite dyebath at different tem-
peratures. In fact, a few of the thermodynamic parameters of dyeing such as the equilibrium adsorption 
isotherm, standard affinity, enthalpy and entropy changes were studied. The bath containing virgin PET 
displays the highest negative values of the enthalpy change and entropy change, while the bath containing 
the modified PET with 2 wt% hyperbranched polyesteramide shows the lowest negative values of them. 
 
Keywords: Polyethylene terephthalate (PET) sheet, Nanostructure, Hyperbranched polyesteramide, 
Thermodynamic parameters, Dyeing, Disperse dye. 
 
  PACS number: 82.60.Hc 
 
 
1. INTRODUCTION 
 
In textile industry, PET (Polyethylene tereph-
thalate) has widely been used as a raw material for 
woven fabrics and nonwoven because of its excellent 
physical and chemical properties. PET is the most pop-
ular synthetic polymer because of its excellent chemical 
resistance, thermal stability and easy spinnability [1]. 
Disperse dyes are the most important dyes which have 
been used for dyeing PET. The biggest complaint about 
PET is that it absorbs very little dye at boiling temper-
ature without using carriers. Therefore, using carriers 
or high temperature/pressure is necessary for dyeing 
PET with disperse dyes. The high crystallinity, hydro-
phobic nature and compact molecular structure as well 
as does not contain any reactive site in the molecule are 
the reasons that PET cannot be dyed in absence of car-
riers [2]. In order to improve such disadvantage, a vari-
ety of methods have been proposed [3-5]. In one study, 
khatibzadeh et al. used a hyperbranched polymer to 
improve the dyeability of fiber grade PET [6]. 
Hyperbranched polymers have a large number of 
functional groups, low melt viscosities and a globular 
three dimensional structure. Due to these structural 
characteristics, their properties largely deviate from 
linear polymers. They have cavities in their molecule 
which enable them to trap guest molecules by specific 
interactions. Due to their globular structure, den-
drimers and hyperbranched polymers are discussed as 
carrier molecules. Furthermore, the low melt viscosity 
of hyperbranched polymers offers applications as melt 
modifiers or blend components [7-9]. 
Because dyeing is a process, the state of equilibrium 
is reached after a time period. Therefore, determination 
of thermodynamic parameters has a fundamental 
meaning for considering the dyeing mechanism. In this 
study, the results of an investigation into the quantita-
tive evaluation of the dyeing behavior and thermody-
namic parameters of C.I. Disperse Blue 56 on modified 
PET sheets with hyperbranched polymer were studied. 
The results have been then compared with correspond-
ing parameters obtained for the unmodified PET. 
2. EXPERIMENTAL 
 
2.1 Materials 
 
Chips of PET (Zimmer Specification, Germany) 
were supplied by Shahid Tondgoyan Petrochemical 
Company (Iran) and were a fiber grade material with 
an intrinsic viscosity of 0.60 dl g-1, water content 0.25 
%wt and melting point 250ºC. 
Hybrane H1500, a nanostructured hyperbranched 
polyesteramide was provided by DSM, Netherlands. Its 
molecular formula is (C6H15NO2.C8H10O3) x and its mo-
lecular weight is 1500 g mol-1. 
Throughout the experiments, the selected disperse 
dye (C.I. Disperse Blue 56 named as Serilene Blue RL) 
without further purification was purchased from York-
shire Group, UK. The employed disperse dye belongs to 
low energy group of disperse dyes. This dye is an antra-
quinone dye and its molecular weight is 304.69 g mol-1. 
 
2.2 Melt processing 
 
Chips of PET were dried in an oven at 80°C for 24 
hours prior to blending. An internal mixer (Brabender 
Plasticorder W50, Brabender Company, Germany) was 
used for mixing samples including various loads ranging 
from 0.5 to 3.0 wt% of Hybrane H1500 with PET. The 
mixing temperature was set at 250°C at the speed of 60 
rpm for 5 minutes. Sheets of 1 mm thickness were pre-
pared by hot pressing the resultant compounded mix-
tures. Each sample was pressed for 5 minutes at a pres-
sure of 140 bar and a temperature of 250°C. The press 
was subsequently cooled to 100°C using cold water. 
Then, sheets were scoured in a solution containing 2 g/l 
of nonionic surfactant at 60°C for 30 minutes. The liq-
uor-to-goods ratio was 500:1. Sheets were then washed 
completely in cold water and dried in the open air. 
 
  
 M. AHANI, M. KHATIBZADEH, M. MOHSENI PROC. NAP 2, 03NCNN21 (2013) 
 
 
03NCNN21-2 
2.3 Characterization of prepared samples  
 
2.3.1 Atomic Force Microscopy (AFM) 
 
Tapping mode AFM (Ambios Tech (USA)) was used 
to characterize the samples. A scanning probe micro-
scope was operated in tapping mode under ambient 
conditions with commercial silicon microcantilever 
probes. Phase images were obtained using a resonance 
frequency of approximately 300 KHz. 
 
2.3.2 Attenuated Total Reflectance (ATR-FTIR) 
 
ATR-FTIR measurements on samples were carried 
out on a Bomem Hartman & Braun FTIR Spectropho-
tometer. The samples were analyzed in the reflectance 
mode in the range of 400-4000 cm-1. 
 
2.3.3 Differential Scanning Calorimetry (DSC) 
 
Crystallinity and the glass transition temperature 
(Tg) of the samples was calculated by Mettler Toledo 
Differential Scanning Calorimetry (DSC) instrument 
under nitrogen. The sample pan and the reference pan 
were heated from 0 to 300°C at the rate of 10 °C/min.  
 
2.4 Adsorption amount of the dye on to sheet 
 
For determination of the thermodynamic parameters 
dyeing, the dye concentration in the dyebath was meas-
ured using spectrophotometer (Color-Eye 7000A). The 
decrease in the total amount of dye in the dyebath was 
considered as the amount of dye on the sheet. 
 
2.5 Dyeing thermodynamic parameters 
 
Using a laboratory dyeing machine (IR Elite Lab. 
Dyeing Machine, KMS Colortech Service Co., Hong 
Kong), 0.1 g of each sheets were individually dyed in the 
solutions containing 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 
g/l of dye at three temperatures 80, 100 and 130°C with 
the liquor-to-goods ratio 1000:1, until equilibrium ad-
sorption was obtained. Dyeing started at ambient tem-
perature increasing to 80, 100 and 130°C at a constant 
rate of 2 ºC/min and held at these temperatures for 300 
minutes.  
 
2.5.1 Dye adsorption isotherms 
 
Using recording the amount of adsorbed dye on 
sheets ([C]s) versus the amount of remained dye in the 
corresponding dyebaths ([C]b), the adsorption isotherms 
were obtained. 
 
2.5.2 Partition coefficient and standard affinity 
 
The partition coefficient (K) of the dye between the 
sheet ([C]s) and the adsorption solution ([C]b) was ob-
tained from the adsorption isotherms. The standard 
affinity (-∆µ°) of the dye to sheets was determined by 
Eq. (1). 
 
 – ∆µ°  RT ln ([C]s/[C]b)  RT ln K, (1) 
 
where – ∆µ° is the standard affinity (cal mol-1); R is 
the gas constant (1.9872 cal mol-1 K-1); T represents the 
absolute temperature (K); [C]s and [C]b indicate the dye 
concentrations in sheets (mol/kg sheet) and in baths 
(mol l-1) after achieving dyeing equilibrium, respectively 
and K is the partition coefficient. 
2.5.3 Enthalpy change 
 
According to Eq. (2), the enthalpy change (∆H°) 
could be simply determined by plot of ∆µ°/T versus 1/T. 
 
 – ΔH/T  Δμ/T + C, (2) 
 
where ∆H° is heat of adsorption (cal mol-1) and C repre-
sents the integral constant. 
 
2.5.4 Entropy change 
 
The entropy change (∆S°) was calculated using Eq. (3). 
 
 ∆µ°= ∆H°– T∆S, (3) 
 
where ∆S° indicates the change in entropy (cal mol-1 K-1). 
 
3. RESULTS AND DISCUSSION  
 
3.1 AFM results 
 
The evolution of the morphology of the sheet surfac-
es as observed by AFM is illustrated in Figure 1a-d 
which is the original scans without any filtering. The 
phase contrast image for virgin PET shows a relatively 
smooth and uniform surface without any nanoparticle. 
For modified PET sheets using 1 and 2 wt% hyper-
branched polyme, a few number of light-colored parti-
cles were observed which is indicative of the existence 
of hyperbranched polymer. These observations confirm 
that no aggregates were formed and there is a complete 
uniform surface. Some aggregations were observed in 
sample containing 3 wt% hyperbranched polymer. 
Therefore, dyeing on modified PET sheets with 0.5, 1 
and 2 wt% hyperbranched polymer was performed. 
 
 
 
Fig. 1 – AFM images virgin PET (a), PET + 1H (b), PET + 2H 
(c) and PET + 3H (d) 
 
3.2 ATR-FTIR results 
 
In the first step it was necessary to record the ATR-
FTIR spectra of the virgin PET sheet (Figure 2a) and the 
pure hyperbranched polymer (Figure 2b) in order to be 
used for comparison with the ATR-FTIR spectra of the 
modified sheets. The ATR-FTIR spectra of the modified 
PET sheets are shown in Figure 2c-e. The ATR-FTIR 
results showed that the presence of hyperbranched pol-
ymer was detected in all the modified samples. In almost 
all the cases the presence of the hyperbranched polymer 
was proved by the presence of the peaks at 1400-1500 
(c) 
(d) 
(d) 
(b) (a) 
 BLENDS OF POLYETHYLENE TEREPHTHALATE (PET) AND … PROC. NAP 2, 03NCNN21 (2013) 
 
 
03NCNN21-3 
and 1600-1700 cm-1. These peaks belong to the pure hy-
perbranched polymer of the modified PET sheets and it 
just shows the superimposition of the spectra of the vir-
gin PET and pure hyperbranched polymer. So no inter-
action has occurred.  
 
Fig. 2 – ATR-FTIR spectra of virgin PET (a), pure hyper-
branched polymer (b), PET + 0.5H (c), PET + 1H (d) and PET + 
2H (e) 
 
3.3 DSC results 
 
By adding the hyperbranched polymer to the virgin 
PET, the thermal properties of the modified PET sam-
ples may be changed. It can be found from Figure 3 
that as the content of hyperbranched polymer increas-
es, the glass transition temperature decreases. This 
means that samples become more flexible upon addi-
tion of the amorphous hyperbranched polymer. For 
further investigations, the crystallinity for each sample 
was calculated as shown in Figure 3 and it decreased 
with the addition of hyperbranched polymer content in 
the virgin PET. As crystallinity is decreased, the amor-
phous parts are increased, and the dye uptake is in-
creased accordingly. 
 
 
Fig. 3 – Glass transition temperature (Tg) and crystallinity 
(%) of virgin and modified PET sheets. 
 
 
 
 
 
3.4 Thermodynamic parameters 
 
3.4.1 Adsorption isotherm and standard affinity 
 
The standard affinity (-Δμ⁰) of the dye in dyeing so-
lution towards substrate is the most important ther-
modynamic parameter of dyeing. This parameter is 
defined as a difference between the standard chemical 
potential of the dye in the sheet phase (μs) and the 
standard chemical potential of the dye in the solution 
phase (μb) at the equilibrium state [10-12]. This param-
eter is the measure of the tendency of the dye to move 
from its standard state of the dyeing solution to its 
standard state of the sheet [10-12]. In order to calculate 
the standard affinity of C.I. Disperse Blue 56 towards 
virgin PET sheet as well as modified PET ones, the 
adsorption isotherm data of dye were obtained at three 
various temperatures 80, 100 and 130⁰C. Figure 4a-c 
shows the adsorption isotherms for virgin and modified 
PET sheets at various temperatures. Results in Figure 
4a-c suggest a linear trend (Nernst isotherm) for both 
PET and sheets containing hyperbranched polymer. 
According to the type of the isotherm, it can be said 
that in respect of dyeing mechanism, while the dyeing 
sites are not available for samples, the hyperbranched 
polymer provides voids in the modified PET sheets that 
could trap the dye molecules. This phenomenon in-
creases along with increasing hyperbranched polymer. 
 
 
Fig. 4 – Adsorption isotherms of C.I. Disperse Blue 56 on vir-
gin and modified PET sheets at 80(a), 100(b) and 130⁰C(c) 
 
The partition coefficient (K) of the dye between the 
dyeing solution and the substrate is obtained from the 
slope of the adsorption isotherm. It can be seen in Ta-
ble 1 that K values for modified PET sheets are higher 
than that of the virgin PET one. Using K as Nernst 
constant, the standard affinity could be calculated ac-
80.07 ºC 
76.7 ºC 
73.96 ºC 72.49 ºC 
44% 
41.65% 40% 38% 
30
40
50
60
70
80
90
PET PET + 0.5H PET + 1H PET + 2H
Tg Crystallinity
0
1
2
3
4
5
6
0 0.005 0.01
[C
] s
 (
m
g
 d
y
e
/g
 s
h
e
e
t)
 
[C]b (mg/mL) 
PET
PET + 0.5H
PET + 1.0H
PET + 2.0H
(a) 
0
1
2
3
4
5
0 0.005 0.01 0.015
[C
] s
 (
m
g
 d
y
e
/g
 s
h
e
e
t)
 
[C]b (mg/mL) 
PET
PET + 0.5H
PET + 1.0H
PET + 2.0H
(b) 
0
1
2
3
4
5
0 0.01 0.02
[C
] s
 (
m
g
 d
y
e
/g
 s
h
e
e
t)
 
[C]b (mg/mL) 
PET
PET + 0.5H
PET + 1.0H
PET + 2.0H
(c) 
 M. AHANI, M. KHATIBZADEH, M. MOHSENI PROC. NAP 2, 03NCNN21 (2013) 
 
 
03NCNN21-4 
cording to Eq. (1). The values of standard affinity are 
shown in Table 1. As shown in Table 1, the standard 
affinities of dye to modified PET sheets are higher than 
that to virgin PET one. As the content of nanostruc-
tured hyperbranched polymer of samples increased, the 
standard affinity of the modified PET sheets increased. 
This finding explains that the dye has higher tendency 
to move from the dyeing solution to the modified PET 
substrates in comparison with virgin PET one. The 
partition coefficients of C.I. Disperse Blue 56 on all of 
the samples decreased when the temperature in-
creased. The adsorption of dyes on substrate is an exo-
thermic reaction process [10-12], therefore raising the 
temperature of dyeing leads to lower affinity. 
 
Table 1 – Partition coefficient (K) and standard affinity (-Δμ°) 
of C.I. Disperse blue 56 on virgin and modified PET sheets. 
  Temperature 80°C  100°C  130°C 
  Sample K 
(-∆µ⁰) 
(cal mol-1) 
K 
(-∆µ⁰) 
(cal mol-1) 
K 
(-∆µ⁰) 
(cal mol-1) 
   PET 49.67 2739.56 30.36 2529.89 20.73 2427.81 
PET + 0.5H 54.69 2807.10 32.69 2584.70 22.94 2508.94 
PET + 1.0H 57.87 2846.75 34.62 2627.22 25.51 2593.98 
PET + 2.0H 61.23 2886.34 36.30 2662.34 27.74 2661.09 
 
3.4.2 Enthalpy and entropy change 
 
The enthalpy change (ΔH⁰) is regarded as the 
measure of the adsorption strength of dyes [10-12]. The 
entropy change (ΔS⁰) represents the entropy difference 
of the dye molecules within the substrate [10-12]. In 
most dyeing processes, the entropy change indicates 
negative values, because adsorbed dyes stayed inside 
the substrate molecules are more restrained than dyes 
in the solution. Therefore, the value of the entropy 
change could be considered as the measure of immobili-
ty of dyes within the substrate [10-12]. Figure 5 shows 
a linear relationship between Δμ⁰/T and 1/T for enthal-
py change as expected from Eq. (2). From the slope of 
the straight line, the enthalpy change can be calculat-
ed. Meanwhile, from Figure 6 and Eq. (3) showing the 
linear relationship between Δμ⁰ and T, the entropy 
change can be also obtained. The enthalpy and the en-
tropy changes are listed in Table 2. According to Table 
2, virgin PET sheet shows higher negative values of 
ΔH⁰ and ΔS⁰, while modified PET with 2 wt% hyper-
branched polymer shows lower negative values. The 
enthalpy change shows the amount of the released heat  
 
 
Fig. 5 – Relationship between ∆µ⁰/T and 1/T on enthalpy 
change 
Table 2 – Enthalpy change (∆H°) and entropy change (∆S°) of 
C.I. Disperse Blue 56 on virgin and modified PET sheets.  
Parameters PET PET + 0.5H PET + 1.0H PET + 2.0H 
∆H° (cal mol-1) -4908 -4864 -4570 -4386 
∆S° (cal mol-1 K-1) -6.01 -5.69 -4.74 -4.15 
 
 
Fig. 6 – Relationship between ∆µ⁰ and T on entropy change 
 
arising from adsorption of dye molecules into polymer 
chains. The larger negative value indicates that the dye 
molecules are more strongly embedded within the pol-
ymer molecules [10-12]. The entropy change shows the 
extent of the reduced freedom of dye molecules after 
the completion of dyeing. The larger negative value of 
the entropy change represents the fact that the move-
ment of the dye molecules markedly decreases in sub-
strate after dyeing [10-12]. 
 
4. CONCLUSION 
 
In this study, thermodynamic parameters of C.I. Dis-
perse Blue 56 on PET sheets modified using a 
nanostructured hyperbranched polymer were investigat-
ed. Atomic force microscopy (AFM) was performed to 
examine the surface morphology for virgin and modified 
PET samples. According to the observations made by 
AFM, dispersion of the hyperbranched polymer in the 
samples containing 0.5, 1 and 2 wt% hyperbranched pol-
ymer was uniform, but some aggregations were observed 
in sample containing 3 wt% hyperbranched polymer. Fi-
nally, dyeing was performed on modified PET including 
0.5, 1 and 2 wt% hyperbranched polymer. Thermal analy-
sis by Differential scanning calorimetry (DSC) was used to 
probe the effect of hyperbranched polymer on crystallinity 
and glass transition temperature of modified samples. The 
presence of the hyperbranched polymer decreases the 
glass transition temperature as well as the crystallinity of 
the modified samples comparing to the virgin PET. The 
standard affinities of modified PET sheets were higher 
than those of virgin PET one. In the case of enthalpy and 
entropy changes, virgin PET sheet showed higher nega-
tive values of ∆H° and ∆S°, while PET with 2 wt% showed 
the lowest negative values of them. 
 
AKNOWLEDGEMENT 
 
Hybrane H1500 was kindly provided by DSM from 
Netherlands. 
 
  
-8.5
-7.5
-6.5
-5.5
0.0024 0.0026 0.0028 0.003
∆
µ
⁰/
T
 (
c
a
l/
m
o
l 
K
) 
 
1/T (1/K) 
PET
PET + 0.5H
PET + 1.0H
PET + 2.0H
PET
PET + 0.5H
PET + 1.0H
PET + 2.0H
-3000
-2800
-2600
-2400
-2200
340 360 380 400 420
∆
µ
⁰ 
(c
a
l/
m
o
l)
  
T (K) 
PET
PET + 0.5H
PET + 1.0H
PET + 2.0H
PET
PET + 0.5H
PET + 1.0H
PET + 2.0H
 BLENDS OF POLYETHYLENE TEREPHTHALATE (PET) AND … PROC. NAP 2, 03NCNN21 (2013) 
 
 
03NCNN21-5 
REFERENCES 
 
1. E. M. Aizenshtein, Fibre Chem. 41, 1 (2009). 
2. H. W. Partridge, JSDC 75, 373 (2008).  
3. W. Saus, D. Krittel, E. Schollmeyer, Text. Res. J. 63, 135 (1993). 
4. A. Hou, B. Chen, J. Dai, K. Zhang, J. Clean. Prod. 18, 
1009 (2010). 
5. W. M. Raslan, A. Bendak, E. M. Khalil, T. Fawzi, Color. 
Technol. 126, 231 (2010). 
6. M. Khatibzadeh, M. Mohseni, S. Moradian, Color. Technol. 
126, 269 (2010). 
7. C. Gao, D. Yan, Prog. Polym. Sci. 29, 183 (2004). 
8. K. Inoue, Prog. Polym. Sci. 25, 453 (2000). 
9. A. Huit, M. Johansson, E. Malmstrom, Adv. Polym. Sci. 
143, 1 (1999). 
10. T. K. Kim, Y. A. Son, Y. J. Lim, Dyes Pigments 67, 229 (2005). 
11. T. K. Kim, Y. A. Son, Y. J. Lim, Dyes Pigments 72, 246 (2007). 
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BPAS 29, 77 (2010). 
 
 


English

Blends of Polyethylene Terephthalate (PET) and Nanostructured Hyperbranched Polyesteramide for Improvement the Dyeability of PET: Thermodynamics

Electronic Sumy State University Institutional Repository

PROCEEDINGS OF THE INTERNATIONAL CONFERENCE  NANOMATERIALS: APPLICATIONS AND PROPERTIES Vol. 2 No 3, 03NCNN21 (5pp) (2013)   2304-1862/2013/2(3)03NCNN21(5) 03NCNN21-1  2013 Sumy State University Blends of Polyethylene Terephthalate (PET) and Nanostructured Hyperbranched  Polyesteramide for Improvement the Dyeability of PET: Thermodynamics  M. Ahani, M. Khatibzadeh, M. Mohseni M. Vajar, S.H. Kordbacheh  Department of Polymer Engineering and Color Technology, Amirkabir University of Technology P.O. Box 15875, Hafez Street, Tehran, Iran   (Received 29 May 2013; published online 31 August 2013)  Incorporating Hybrane H1500 as a nanostructured hyperbranched polyesteramide into polyethylene terephthalate (PET) enhances the dyeability of PET with C.I. Disperse Blue 56. The results show that the disperse dye display much greater substantivity toward the modified PET sheets compared to virgin PET one. DSC tests show that the crystallinity of modified PET sheets has slightly decreased. The main pur-pose of this work was to determine the dyeing mechanism of disperse dye on the modified PET using hy-perbranched polyesteramide by study the adsorption properties in the infinite dyebath at different tem-peratures. In fact, a few of the thermodynamic parameters of dyeing such as the equilibrium adsorption isotherm, standard affinity, enthalpy and entropy changes were studied. The bath containing virgin PET displays the highest negative values of the enthalpy change and entropy change, while the bath containing the modified PET with 2 wt% hyperbranched polyesteramide shows the lowest negative values of them.  Keywords: Polyethylene terephthalate (PET) sheet, Nanostructure, Hyperbranched polyesteramide, Thermodynamic parameters, Dyeing, Disperse dye.    PACS number: 82.60.Hc   1. INTRODUCTION  In textile industry, PET (Polyethylene tereph-thalate) has widely been used as a raw material for woven fabrics and nonwoven because of its excellent physical and chemical properties. PET is the most pop-ular synthetic polymer because of its excellent chemical resistance, thermal stability and easy spinnability [1]. Disperse dyes are the most important dyes which have been used for dyeing PET. The biggest complaint about PET is that it absorbs very little dye at boiling temper-ature without using carriers. Therefore, using carriers or high temperature/pressure is necessary for dyeing PET with disperse dyes. The high crystallinity, hydro-phobic nature and compact molecular structure as well as does not contain any reactive site in the molecule are the reasons that PET cannot be dyed in absence of car-riers [2]. In order to improve such disadvantage, a vari-ety of methods have been proposed [3-5]. In one study, khatibzadeh et al. used a hyperbranched polymer to improve the dyeability of fiber grade PET [6]. Hyperbranched polymers have a large number of functional groups, low melt viscosities and a globular three dimensional structure. Due to these structural characteristics, their properties largely deviate from linear polymers. They have cavities in their molecule which enable them to trap guest molecules by specific interactions. Due to their globular structure, den-drimers and hyperbranched polymers are discussed as carrier molecules. Furthermore, the low melt viscosity of hyperbranched polymers offers applications as melt modifiers or blend components [7-9]. Because dyeing is a process, the state of equilibrium is reached after a time period. Therefore, determination of thermodynamic parameters has a fundamental meaning for considering the dyeing mechanism. In this study, the results of an investigation into the quantita-tive evaluation of the dyeing behavior and thermody-namic parameters of C.I. Disperse Blue 56 on modified PET sheets with hyperbranched polymer were studied. The results have been then compared with correspond-ing parameters obtained for the unmodified PET. 2. EXPERIMENTAL  2.1 Materials  Chips of PET (Zimmer Specification, Germany) were supplied by Shahid Tondgoyan Petrochemical Company (Iran) and were a fiber grade material with an intrinsic viscosity of 0.60 dl g-1, water content 0.25 %wt and melting point 250ºC. Hybrane H1500, a nanostructured hyperbranched polyesteramide was provided by DSM, Netherlands. Its molecular formula is (C6H15NO2.C8H10O3) x and its mo-lecular weight is 1500 g mol-1. Throughout the experiments, the selected disperse dye (C.I. Disperse Blue 56 named as Serilene Blue RL) without further purification was purchased from York-shire Group, UK. The employed disperse dye belongs to low energy group of disperse dyes. This dye is an antra-quinone dye and its molecular weight is 304.69 g mol-1.  2.2 Melt processing  Chips of PET were dried in an oven at 80°C for 24 hours prior to blending. An internal mixer (Brabender Plasticorder W50, Brabender Company, Germany) was used for mixing samples including various loads ranging from 0.5 to 3.0 wt% of Hybrane H1500 with PET. The mixing temperature was set at 250°C at the speed of 60 rpm for 5 minutes. Sheets of 1 mm thickness were pre-pared by hot pressing the resultant compounded mix-tures. Each sample was pressed for 5 minutes at a pres-sure of 140 bar and a temperature of 250°C. The press was subsequently cooled to 100°C using cold water. Then, sheets were scoured in a solution containing 2 g/l of nonionic surfactant at 60°C for 30 minutes. The liq-uor-to-goods ratio was 500:1. Sheets were then washed completely in cold water and dried in the open air.     M. AHANI, M. KHATIBZADEH, M. MOHSENI PROC. NAP 2, 03NCNN21 (2013)   03NCNN21-2 2.3 Characterization of prepared samples   2.3.1 Atomic Force Microscopy (AFM)  Tapping mode AFM (Ambios Tech (USA)) was used to characterize the samples. A scanning probe micro-scope was operated in tapping mode under ambient conditions with commercial silicon microcantilever probes. Phase images were obtained using a resonance frequency of approximately 300 KHz.  2.3.2 Attenuated Total Reflectance (ATR-FTIR)  ATR-FTIR measurements on samples were carried out on a Bomem Hartman & Braun FTIR Spectropho-tometer. The samples were analyzed in the reflectance mode in the range of 400-4000 cm-1.  2.3.3 Differential Scanning Calorimetry (DSC)  Crystallinity and the glass transition temperature (Tg) of the samples was calculated by Mettler Toledo Differential Scanning Calorimetry (DSC) instrument under nitrogen. The sample pan and the reference pan were heated from 0 to 300°C at the rate of 10 °C/min.   2.4 Adsorption amount of the dye on to sheet  For determination of the thermodynamic parameters dyeing, the dye concentration in the dyebath was meas-ured using spectrophotometer (Color-Eye 7000A). The decrease in the total amount of dye in the dyebath was considered as the amount of dye on the sheet.  2.5 Dyeing thermodynamic parameters  Using a laboratory dyeing machine (IR Elite Lab. Dyeing Machine, KMS Colortech Service Co., Hong Kong), 0.1 g of each sheets were individually dyed in the solutions containing 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 g/l of dye at three temperatures 80, 100 and 130°C with the liquor-to-goods ratio 1000:1, until equilibrium ad-sorption was obtained. Dyeing started at ambient tem-perature increasing to 80, 100 and 130°C at a constant rate of 2 ºC/min and held at these temperatures for 300 minutes.   2.5.1 Dye adsorption isotherms  Using recording the amount of adsorbed dye on sheets ([C]s) versus the amount of remained dye in the corresponding dyebaths ([C]b), the adsorption isotherms were obtained.  2.5.2 Partition coefficient and standard affinity  The partition coefficient (K) of the dye between the sheet ([C]s) and the adsorption solution ([C]b) was ob-tained from the adsorption isotherms. The standard affinity (-∆µ°) of the dye to sheets was determined by Eq. (1).   – ∆µ°  RT ln ([C]s/[C]b)  RT ln K, (1)  where – ∆µ° is the standard affinity (cal mol-1); R is the gas constant (1.9872 cal mol-1 K-1); T represents the absolute temperature (K); [C]s and [C]b indicate the dye concentrations in sheets (mol/kg sheet) and in baths (mol l-1) after achieving dyeing equilibrium, respectively and K is the partition coefficient. 2.5.3 Enthalpy change  According to Eq. (2), the enthalpy change (∆H°) could be simply determined by plot of ∆µ°/T versus 1/T.   – ΔH/T  Δμ/T + C, (2)  where ∆H° is heat of adsorption (cal mol-1) and C repre-sents the integral constant.  2.5.4 Entropy change  The entropy change (∆S°) was calculated using Eq. (3).   ∆µ°= ∆H°– T∆S, (3)  where ∆S° indicates the change in entropy (cal mol-1 K-1).  3. RESULTS AND DISCUSSION   3.1 AFM results  The evolution of the morphology of the sheet surfac-es as observed by AFM is illustrated in Figure 1a-d which is the original scans without any filtering. The phase contrast image for virgin PET shows a relatively smooth and uniform surface without any nanoparticle. For modified PET sheets using 1 and 2 wt% hyper-branched polyme, a few number of light-colored parti-cles were observed which is indicative of the existence of hyperbranched polymer. These observations confirm that no aggregates were formed and there is a complete uniform surface. Some aggregations were observed in sample containing 3 wt% hyperbranched polymer. Therefore, dyeing on modified PET sheets with 0.5, 1 and 2 wt% hyperbranched polymer was performed.    Fig. 1 – AFM images virgin PET (a), PET + 1H (b), PET + 2H (c) and PET + 3H (d)  3.2 ATR-FTIR results  In the first step it was necessary to record the ATR-FTIR spectra of the virgin PET sheet (Figure 2a) and the pure hyperbranched polymer (Figure 2b) in order to be used for comparison with the ATR-FTIR spectra of the modified sheets. The ATR-FTIR spectra of the modified PET sheets are shown in Figure 2c-e. The ATR-FTIR results showed that the presence of hyperbranched pol-ymer was detected in all the modified samples. In almost all the cases the presence of the hyperbranched polymer was proved by the presence of the peaks at 1400-1500 (c) (d) (d) (b) (a)  BLENDS OF POLYETHYLENE TEREPHTHALATE (PET) AND … PROC. NAP 2, 03NCNN21 (2013)   03NCNN21-3 and 1600-1700 cm-1. These peaks belong to the pure hy-perbranched polymer of the modified PET sheets and it just shows the superimposition of the spectra of the vir-gin PET and pure hyperbranched polymer. So no inter-action has occurred.   Fig. 2 – ATR-FTIR spectra of virgin PET (a), pure hyper-branched polymer (b), PET + 0.5H (c), PET + 1H (d) and PET + 2H (e)  3.3 DSC results  By adding the hyperbranched polymer to the virgin PET, the thermal properties of the modified PET sam-ples may be changed. It can be found from Figure 3 that as the content of hyperbranched polymer increas-es, the glass transition temperature decreases. This means that samples become more flexible upon addi-tion of the amorphous hyperbranched polymer. For further investigations, the crystallinity for each sample was calculated as shown in Figure 3 and it decreased with the addition of hyperbranched polymer content in the virgin PET. As crystallinity is decreased, the amor-phous parts are increased, and the dye uptake is in-creased accordingly.   Fig. 3 – Glass transition temperature (Tg) and crystallinity (%) of virgin and modified PET sheets.      3.4 Thermodynamic parameters  3.4.1 Adsorption isotherm and standard affinity  The standard affinity (-Δμ⁰) of the dye in dyeing so-lution towards substrate is the most important ther-modynamic parameter of dyeing. This parameter is defined as a difference between the standard chemical potential of the dye in the sheet phase (μs) and the standard chemical potential of the dye in the solution phase (μb) at the equilibrium state [10-12]. This param-eter is the measure of the tendency of the dye to move from its standard state of the dyeing solution to its standard state of the sheet [10-12]. In order to calculate the standard affinity of C.I. Disperse Blue 56 towards virgin PET sheet as well as modified PET ones, the adsorption isotherm data of dye were obtained at three various temperatures 80, 100 and 130⁰C. Figure 4a-c shows the adsorption isotherms for virgin and modified PET sheets at various temperatures. Results in Figure 4a-c suggest a linear trend (Nernst isotherm) for both PET and sheets containing hyperbranched polymer. According to the type of the isotherm, it can be said that in respect of dyeing mechanism, while the dyeing sites are not available for samples, the hyperbranched polymer provides voids in the modified PET sheets that could trap the dye molecules. This phenomenon in-creases along with increasing hyperbranched polymer.   Fig. 4 – Adsorption isotherms of C.I. Disperse Blue 56 on vir-gin and modified PET sheets at 80(a), 100(b) and 130⁰C(c)  The partition coefficient (K) of the dye between the dyeing solution and the substrate is obtained from the slope of the adsorption isotherm. It can be seen in Ta-ble 1 that K values for modified PET sheets are higher than that of the virgin PET one. Using K as Nernst constant, the standard affinity could be calculated ac-80.07 ºC 76.7 ºC 73.96 ºC 72.49 ºC 44% 41.65% 40% 38% 30405060708090PET PET + 0.5H PET + 1H PET + 2HTg Crystallinity01234560 0.005 0.01[C] s (mg dye/g sheet) [C]b (mg/mL) PETPET + 0.5HPET + 1.0HPET + 2.0H(a) 0123450 0.005 0.01 0.015[C] s (mg dye/g sheet) [C]b (mg/mL) PETPET + 0.5HPET + 1.0HPET + 2.0H(b) 0123450 0.01 0.02[C] s (mg dye/g sheet) [C]b (mg/mL) PETPET + 0.5HPET + 1.0HPET + 2.0H(c)  M. AHANI, M. KHATIBZADEH, M. MOHSENI PROC. NAP 2, 03NCNN21 (2013)   03NCNN21-4 cording to Eq. (1). The values of standard affinity are shown in Table 1. As shown in Table 1, the standard affinities of dye to modified PET sheets are higher than that to virgin PET one. As the content of nanostruc-tured hyperbranched polymer of samples increased, the standard affinity of the modified PET sheets increased. This finding explains that the dye has higher tendency to move from the dyeing solution to the modified PET substrates in comparison with virgin PET one. The partition coefficients of C.I. Disperse Blue 56 on all of the samples decreased when the temperature in-creased. The adsorption of dyes on substrate is an exo-thermic reaction process [10-12], therefore raising the temperature of dyeing leads to lower affinity.  Table 1 – Partition coefficient (K) and standard affinity (-Δμ°) of C.I. Disperse blue 56 on virgin and modified PET sheets.   Temperature 80°C  100°C  130°C   Sample K (-∆µ⁰) (cal mol-1) K (-∆µ⁰) (cal mol-1) K (-∆µ⁰) (cal mol-1)    PET 49.67 2739.56 30.36 2529.89 20.73 2427.81 PET + 0.5H 54.69 2807.10 32.69 2584.70 22.94 2508.94 PET + 1.0H 57.87 2846.75 34.62 2627.22 25.51 2593.98 PET + 2.0H 61.23 2886.34 36.30 2662.34 27.74 2661.09  3.4.2 Enthalpy and entropy change  The enthalpy change (ΔH⁰) is regarded as the measure of the adsorption strength of dyes [10-12]. The entropy change (ΔS⁰) represents the entropy difference of the dye molecules within the substrate [10-12]. In most dyeing processes, the entropy change indicates negative values, because adsorbed dyes stayed inside the substrate molecules are more restrained than dyes in the solution. Therefore, the value of the entropy change could be considered as the measure of immobili-ty of dyes within the substrate [10-12]. Figure 5 shows a linear relationship between Δμ⁰/T and 1/T for enthal-py change as expected from Eq. (2). From the slope of the straight line, the enthalpy change can be calculat-ed. Meanwhile, from Figure 6 and Eq. (3) showing the linear relationship between Δμ⁰ and T, the entropy change can be also obtained. The enthalpy and the en-tropy changes are listed in Table 2. According to Table 2, virgin PET sheet shows higher negative values of ΔH⁰ and ΔS⁰, while modified PET with 2 wt% hyper-branched polymer shows lower negative values. The enthalpy change shows the amount of the released heat    Fig. 5 – Relationship between ∆µ⁰/T and 1/T on enthalpy change Table 2 – Enthalpy change (∆H°) and entropy change (∆S°) of C.I. Disperse Blue 56 on virgin and modified PET sheets.  Parameters PET PET + 0.5H PET + 1.0H PET + 2.0H ∆H° (cal mol-1) -4908 -4864 -4570 -4386 ∆S° (cal mol-1 K-1) -6.01 -5.69 -4.74 -4.15   Fig. 6 – Relationship between ∆µ⁰ and T on entropy change  arising from adsorption of dye molecules into polymer chains. The larger negative value indicates that the dye molecules are more strongly embedded within the pol-ymer molecules [10-12]. The entropy change shows the extent of the reduced freedom of dye molecules after the completion of dyeing. The larger negative value of the entropy change represents the fact that the move-ment of the dye molecules markedly decreases in sub-strate after dyeing [10-12].  4. CONCLUSION  In this study, thermodynamic parameters of C.I. Dis-perse Blue 56 on PET sheets modified using a nanostructured hyperbranched polymer were investigat-ed. Atomic force microscopy (AFM) was performed to examine the surface morphology for virgin and modified PET samples. According to the observations made by AFM, dispersion of the hyperbranched polymer in the samples containing 0.5, 1 and 2 wt% hyperbranched pol-ymer was uniform, but some aggregations were observed in sample containing 3 wt% hyperbranched polymer. Fi-nally, dyeing was performed on modified PET including 0.5, 1 and 2 wt% hyperbranched polymer. Thermal analy-sis by Differential scanning calorimetry (DSC) was used to probe the effect of hyperbranched polymer on crystallinity and glass transition temperature of modified samples. The presence of the hyperbranched polymer decreases the glass transition temperature as well as the crystallinity of the modified samples comparing to the virgin PET. The standard affinities of modified PET sheets were higher than those of virgin PET one. In the case of enthalpy and entropy changes, virgin PET sheet showed higher nega-tive values of ∆H° and ∆S°, while PET with 2 wt% showed the lowest negative values of them.  AKNOWLEDGEMENT  Hybrane H1500 was kindly provided by DSM from Netherlands.    -8.5-7.5-6.5-5.50.0024 0.0026 0.0028 0.003∆µ⁰/T (cal/mol K)  1/T (1/K) PETPET + 0.5HPET + 1.0HPET + 2.0HPETPET + 0.5HPET + 1.0HPET + 2.0H-3000-2800-2600-2400-2200340 360 380 400 420∆µ⁰ (cal/mol)  T (K) PETPET + 0.5HPET + 1.0HPET + 2.0HPETPET + 0.5HPET + 1.0HPET + 2.0H BLENDS OF POLYETHYLENE TEREPHTHALATE (PET) AND … PROC. NAP 2, 03NCNN21 (2013)   03NCNN21-5 REFERENCES  1. E. M. Aizenshtein, Fibre Chem. 41, 1 (2009). 2. H. W. Partridge, JSDC 75, 373 (2008).  3. W. Saus, D. Krittel, E. Schollmeyer, Text. Res. J. 63, 135 (1993). 4. A. Hou, B. Chen, J. Dai, K. Zhang, J. Clean. Prod. 18, 1009 (2010). 5. W. M. Raslan, A. Bendak, E. M. Khalil, T. Fawzi, Color. Technol. 126, 231 (2010). 6. M. Khatibzadeh, M. Mohseni, S. Moradian, Color. Technol. 126, 269 (2010). 7. C. Gao, D. Yan, Prog. Polym. Sci. 29, 183 (2004). 8. K. Inoue, Prog. Polym. Sci. 25, 453 (2000). 9. A. Huit, M. Johansson, E. Malmstrom, Adv. Polym. Sci. 143, 1 (1999). 10. T. K. Kim, Y. A. Son, Y. J. Lim, Dyes Pigments 67, 229 (2005). 11. T. K. Kim, Y. A. Son, Y. J. Lim, Dyes Pigments 72, 246 (2007). 12. G. B. Adebayo, F. A. Adekola, G. A. Olatunji, I. A. Bello, BPAS 29, 77 (2010).   

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Blends of Polyethylene Terephthalate (PET) and Nanostructured Hyperbranched Polyesteramide for Improvement the Dyeability of PET: Thermodynamics

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