20320130406008

International Journal of Advanced JOURNAL OF ADVANCED RESEARCH ISSN 0976 –
INTERNATIONAL Research in Engineering and Technology (IJARET), IN
6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 7, November – December (2013), © IAEME

ENGINEERING AND TECHNOLOGY (IJARET)

ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 4, Issue 7, November-December 2013, pp. 60-70
© IAEME: www.iaeme.com/ijaret.asp
Journal Impact Factor (2013): 5.8376 (Calculated by GISI)
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IJARET
©IAEME

EFFECT OF UREA AND THIOUREA ON PHYSICO-CHEMICAL AND
THERMAL CHARACTERISTICS OF POLYURETHANE FILAMENT
B. H. Patel1,

S. B. Chaudhari2,

A. A. Mandot2

1

Department of Textile Chemistry, Faculty of Technology & Engineering, The M. S. University of
Baroda, Vadodara, India
2
Department of Textile Engineering, Faculty of Technology & Engineering, The M. S. University of
Baroda, Vadodara, India

ABSTRACT
This article reports modification of polyurethane filament by urea and thiourea. Change in
physical and chemical properties of treated filament were evaluated and compared with the untreated
filament which indicate that the nitrogen content was increased with minor loss in physical properties
of the filament. The treated polyurethane dyed with reactive dyes show improvement in percentage
exhaustion with improved fastness properties. Structural transformation in polyurethane filament was
further confirmed by using IR spectroscopy and Differential Scanning Colorimeter (DSC) analysis.
Keywords: Dyeing, Physical property, Polyurethane filament, Reactive dye, Thermal property,
Urea.
1. INTRODUCTION
The urethane polymer forming system has received intensive attention especially in plastics,
rubber, surface coating, adhesive and fibre due to its unique structural property [1-4]. Chemical
structure of polyurethane filament contains soft section (polyether or polyester) and hard section
(polyurethane) which tie the chains together and the resulting polymer is called segmented
polyurethane. Such fibres are generally called spandex fibres, which are defined as manufactured
fibres in which the fibre forming substance is a long chain synthetic polymer comprised of at least
85% of segmented polyurethane [4, 5].
The unique structure of polyurethane, in contrast to any other polymeric fiber possesses
different chemical composition of amorphous and crystalline regions. Polar groups, which could
preferentially take part in secondary non-ionic bonding, are the ether groups in polyether urethanes
and the ester groups in polyester urethanes. The urethane and urea groups are found only in the
60

International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –

crystalline, interfaced segments, which do not participate in the bonding dyestuffs [5-7]. The dyestuff
is adhered only on the surface of the crystalline regions. It is plain enough that polyurethane filament
can be dyed with various classes of dyestuff, still the dyestuff uptake is limited and the fastness
properties are often unsatisfactory [7, 8].
Polyurethane filament has been in practical use for decades now, and so one would think that
there should no longer be any problems and that even theoretically everything should be perfectly
clear. Nevertheless new insights can always being attained. In this paper an attempt has been made to
study the effect of urea and thiourea: typical chemicals used for dyeing and finishing of fabric
containing polyurethane. Their effects on physical, chemical and thermal characteristics as well as on
the dyeing performances along with fastness properties of polyurethane filaments have been studied.
2. MATERIAL & METHODS
2.1 Material
2.1.1 Fiber: Single filament polyurethane fiber (40s Denier; 70 µ Diameter) was used for the study.
The fiber was supplied by Bharat Vijay Mills, Ahmedabad, Gujarat.
2.1.2 Chemicals: Urea and thiourea used for the study were of analytical grade and were purchased
from Suvidhanath Chemicals. All others chemicals and auxiliaries used in this work were of LR
grade.
2.1.3 Dyestuffs: Three commercial reactive dyes namely RDI- Corazole yellow 7GL, RDIICoractive yellow H4G, RDIII- Procion yellow HE4R were used without any further purification.
2.2 Experimental Methods
2.2.1 Pretreatment with urea and thiourea: The polyurethane filament (1 gm filament in hank form)
samples were treated at 10, 20 and 30 gpl concentration of urea and thiourea at room temperature (40
±1 °C) for 15 min. The samples were dried in an oven at 80o C, cured in the curing chamber at 115o
C for 3 min. without tension. Finally, the samples were washed thoroughly and air-dried.
2.2.2 Dyeing polyurethane fibers with reactive dyes: Purified polyurethane fiber was dyed with
commercial reactive dyes on a laboratory constant temperature water bath (Model: Paramount
Instrument Pvt. Ltd.), using 1, 3, and 5% (owf) concentrations of the dye. A required quantity of
dyestuff solution was taken in dyebath and 30 gpl Glauber’s salt was added to dyebath at room
temperature using liquor ratio 50:1 and 3 % shade (owf). Material was then entered in dyebath and
worked for 5 minutes. A further addition of 30 gpl glauber’s salt was made in two lots in interval of
10 minutes. Temperature was gradually raised upto required level depending on reactive dye. After
30 minutes alkali was added to the bath and temperature was maintained for another 15 min. Then,
material was taken out, washed with water and soaped with a good non-ionic detergent (Lissapol N)
at room temperature for 10 min, then washed and air-dried.
2.3 Testing and Analysis
2.3.1 Measurement of physical properties
2.3.1.1 Tensile properties: The treated as well as untreated samples were tested for breaking load
and elongation at break on Instron 1121 Tensile Tester (UK) using 200 mm/min extension rate and
500 mm gauze length. An average of 10 readings was taken.
61


2.3.1.2 Shrinkage behavior: The shrinkage due to the pretreatment was determined by measuring
the length before and after the pretreatment. Consequently, the percentage shrinkage was calculated
using the following equation (1);
ܲ݁‫ ݁݃ܽ݇݊݅ݎ݄ݏ ݐ݊݁ܿݎ‬ൌ

ଡ଼ିଢ଼
ଡ଼

ൈ 100

…….Equation (1)

Where; x and y are the initial and final lengths of the samples before and after the pretreatment
2.3.1.3 Weight analysis: The change in weight due to the pretreatment was also measured in the
same manner as shrinkage by taking weights of the samples before and after the pretreatment. The
percentage change in weight was calculated as follow (2):
ܲ݁‫ ݁݃ܽ݇݊݅ݎ݄ݏ ݐ݊݁ܿݎ‬ൌ

୵ଵି୵ଶ
୵ଵ

ൈ 100

…….Equation (2)

Where; w1 and w2 are the initial and final weights of the samples before and after the pretreatment.
2.3.1.4 Determination of percentage exhaustion: The optical density of initial dyebath and the final
left-over liquor was measured spectrophotometrically using UV-vis Spectrophotometer 117
(Systronic Pvt. Ltd.) at λmax of a particular dye. The percent exhaustion of the dye on the fiber was
calculated using following equation (3).
ܲ݁‫ ݁݃ܽ݇݊݅ݎ݄ݏ ݐ݊݁ܿݎ‬ൌ

୍୬୧୲୧ୟ୪ ୓.ୈ.ି୊୧୬ୟ୪ ୓.ୈ.
୍୬୧୲୧ୟ୪ ୓.ୈ.

ൈ 100

…….Equation (3)

Where, Initial O.D. = Optical density of dye liquor before dyeing.
Final O.D. = Optical density of dye liquor after dyeing.
2.3.2 Analysis of chemical composition
2.3.2.1 IR Analysis: The chemical analysis of the fiber, before and after the treatment, was
recorded on Shimadzu FTIR Spectrometer 8300 using KBr Palatte technique.
2.3.3 Determination of nitrogen content
Nitrogen content of the treated and untreated samples was determined on C, H, N Analyzer (Coleman
Elemental Analyzer).
2.3.4 Evaluation of thermal properties
The thermal analysis of the treated and untreated samples was performed on Differential Scanning
Colorimeter (METTLER (Λexo) by METTLER TOLEDO STARe system). The analysis was
performed on the system at a heating rate of 10oC/min under nitrogen atmosphere.
2.3.5 Evaluation of dyed samples
2.3.5.1 Colour measurement: Dyeing performance of various dyed samples was assessed by
measuring the relative colour strength (K/S value) spectrophotometrically. These values are computer
(on Spectra Scan 5100 (RT) spectrophotometer; Premium Colourscan Instruments, India) calculated
from reflectance data according to Kubelka - Munk equation.
62


2.3.5.2 Assessment of fastness properties: All the dyed samples were evaluated for fastness to
various agencies like washing, light and rubbing using standard methods.
Fastness to washing: Wash fastness of different dyed samples was assessed on Launder-ometer using ISO standard Test No. 3. The change in shade was visualized using grey scale and
graded from 1 to 5, where 1 indicates poor and 5 excellent fastness to washing.
Fastness to light: Colour fastness to light was evaluated by exposing the dyed samples to
sunlight according to AATCC test method 16B-1977. They were graded from 1 to 8; where 1
indicates poor and 8 excellent fastness to light.
3

RESULT & DISCUSSION

3.1

Effect of treatment on physical properties of polyurethane filament
Polyurethane single filament was pretreated with urea and thiourea at various concentration
levels. The changes in various physic-mechanical characteristics due to the pretreatment have been
analyzed. The tensile strength (dry) and elongation at break of untreated as well as pretreated
polyurethane single filament are mentioned in Table 1. '
Table 1 Change in physical properties of polyurethane due to urea and thiourea
Sample
Concentration
Breaking
Shrinkage
Weight
Breaking
(gpl)
strength
(%)
reduction
elongation (%)
(gmf)
(%)
Untreated

--

47.00

412.42

--

--

10

45.00
(-4.25)

463.23
(+12.32)

1.14

2.18

20

40.20
(-14.89)

501.12
(+21.51)

2.82

2.13

30

35.40
(-25.68)

545.66
(+32.31)

4.07

1.60

10

38.00
(-19.14)

479.8 (+16.33)

3.08

3.60

20

38.40
(-18.29)

522.6 (+26.72)

4.63

3.44

30

36.25
(-22.87)

566.2 (+37.29)

6.11

3.34

Treated with
urea

Treated with
thiourea

Note: Data in the parenthesis indicates percent loss or gain in respective property

63


From the table 1, it can be visualized that the treatment with urea and thiourea reduces the
tensile strength of the fiber. The tensile strength of the untreated fiber was 47.00 gmf, while that of
samples treated with 10 gpl urea and 10 gpl thiourea were 45.00 and 38.00 gmf respectively. The
reduction in the tensile strength may be due to the structural transformation of polyurethane filament.
The loss in strength was further enhanced with increase in the concentration of the treating
chemicals. The elongation at break for untreated was 412.12 %. On treatment with 10 g/l urea and
thiourea, the respective values of elongation at break were 463.23% and 479.80%, which was
comparatively higher than the parent sample. The increased in the values of elongation at break also
becomes more prominent with the increase in the concentration of urea and thiourea. The probable
reason for the change in the tensile properties of the polyurethane fiber due to the pretreatment
largely depends on the chain length of the macromolecule and also on the intermolecular hydrogen
bonding in the soft segments. The hydrogen bond (a non-covalent, weak bond) plays a major role in
bolstering the strength of the polyurethane fiber. Thus, the decline in the tensile strength of the
filament may be attributed to the breaking of weak hydrogen bonds formed in between the soft
segments of the polyurethane macromolecule.
The changes in the length of the filament due to pretreatment were also indicated in Table 1.
The shrinkage incurred due to the treatment was quite negligible, which indicates that the treatment
with urea and thiourea chemicals was not sufficient enough to cause significant swelling of the fiber.
However, the concentration of treating chemical influences the shrinkage behavior; as the
concentration of urea or thiourea was increased in the treating liquor, the percent shrinkage also
increased to a small extent. The results mentioned in the Table 1 clearly indicated the extent of
weight loss due to variation in the concentration of both urea and thiourea chemicals.
3.2

Effect of treatment on chemical composition of polyurethane filament

3.2.1 Infrared spectral analysis
The polyurethane filament pretreated with urea and thiourea was analyzed by IR
spectroscopy. The IR spectrum of pure polyurethane filament and filament treated with urea are
illustrated in fig. 1 and 2 respectively.

Figure 1 IR Characterisation absorption peaks of (a) untreated polyurethane filament
64


Figure 2 IR Characterisation absorption peaks of (b) polyurethane filament treated with urea
The characteristic absorption peak of 3325 cm-1 demonstrates the -NH stretching vibration,
and the -CH2- was observed at 2839 cm-1, The characteristic absorption of C=O was observed at
1705 cm-1; the aromatic -NH at 1600 cm-1 ; C-O at 1257 cm-1. Moreover, the peak for polyurethane
treated with urea appears at 1512.1 cm-1. These confirm the presence of C=O and NH2 groups on the
polymer structure. The probable reaction between the fibre and urea can be anticipated in fig. 3.

Figure 3 Modified structure of polyurethane filament with urea

The infrared spectrum of polyurethane treated with thiourea is shown in fig. 4. It can be
clearly seen that all the characteristic groups present in the untreated fibre; similar trend is also
observed in the infrared spectrum of polyurethane pretreated with thiourea. One additional
characteristic absorption peak was observed at 1068.5 cm-1 represent C=S stretching vibration
indicates modification of polyurethane by the treatment with thiourea. In case of fibre treated with
thiourea, the probable reaction is shown in fig. 5.
65


Figure 4 IR Characterisation absorption peaks of (c) polyurethane filament treated with thiourea

Figure 5 Modified structure of polyurethane filament with thiourea
3.2.2 Nitrogen content analysis
The results given in Table 2 show that, as the nominal concentration of urea in the treatment
bath increases, there is minor increase in nitrogen content. Similar trend is observed in case of
samples treated with thiourea.
Table 2 Nitrogen content in untreated and treated polyurethane filament
Sample
Concentration (gpl)
Nitrogen content (%)
Control
12.12
Treated with Urea
10
13.86 (+14.35)
20
17.15 (+41.50)
30
19.28 (+58.91)
Treated Thiourea
10
12.63 (+4.21)
20
12.90 (+6.44)
30
13.06 (+7.75)
NOTE: Data in the parenthesis indicate percentage gain in nitrogen content compared to (Control) untreated sample.

66


3.3 Effect of treatment on thermal property of polyurethane filament
The thermal properties of untreated as well as pretreated polyurethane fibre, which were
measured by differential scanning colourimetry (DSC) are listed in Table 3 and shown in fig. 6, 7
and 8.
Table 3 Thermal analysis of untreated and treated polyurethane filament
Sample
On set temperature
T peak
∆H° (Enthalpy)
°
(mj)
range ( °C)
(°C)
°
Untreated (a)
204.41 - 254.12
220.35
437.53
Treated with 30 gpl Urea (b)

201.39 - 244.63

215.19

630.22

Treated with 30 gpl Thiourea (c)

204.19 - 253.66

223.11

292.83

Note- 3U : Treated with 30 gpl urea, 3T : Treated with 30 gpl thiourea

Figure 6 Thermal analysis curve of (a) untreated polyurethane filament

Figure 7 Thermal analysis curve of polyurethane filament treated with urea

67


Figure 8 Thermal analysis curve of polyurethane filament treated with thiourea
From the table 3 and fig. 6, 7, 8; it has been found that the melting point as well as the
decomposition temperature of polyurethane was highly affected by the treatment. The melting point
of untreated fibre was found to be 220°C, but when the substrate was treated with urea (30 gpl), the
melting point was decreased to 215°C. On the other hand, treatment with thiourea increased the
melting point to 223°C. The thermal decomposition of the untreated sample occurred at about 258°C,
but treatment with urea as well as thiourea slightly lowered down the thermal degradation
temperature. The treatment probably increases the length of chain in soft segment and the larger soft
segment domain leads to a lower decomposition temperature. It has been also seen from Table 3, that
the melting temperature of polyurethane fibre treated with urea was decreased and the filament
treated with thiourea was increased by 2-3°C temperature. This may be attributed due to the fact that
the polyurethane consisted of copolymer with the hard and the soft segment. The melting
temperature of copolymer decreases with the increase of hard segment content. Besides, it was not
clearly seen in the DSC fig. 6, 7, 8 for the melting temperature of the hard and soft segment.
3.4 Dyeing behavior of pretreated polyurethane
The exhaustion percentage of untreated and treated polyurethane filament dyed with reactive
dyes is shown in Table 4. The untreated polyurethane filament hank dyed with RDI, RDII and RDIII
dyes exhibits 11.70, 10.95, and 32.31% exhaustion percentage respectively. On the other hand, when
the samples pretreated with urea or thiourea subsequently dyed with reactive dyes at 3% shade (owf).
The exhaustion percentage vary widely with the pretreatment chemical and its concentration used for
pretreatment. As visualised from Table 4, with thiourea the increase in exhaustion percentage was
considerably lower than that of urea, still it was higher than the sample dyed without pretreatment.
The maximum increase in the exhaustion percentage was observed with the urea pretreatment. The
probable reason for the increase in exhaustion may be due to the increase in -NH2 groups on the
fibre. This was further confirmed by quantitative nitrogen analysis of pretreated polyurethane
filament.
Table 4 also represents the washing, light and perspiration fastness (acidic and alkaline)
grades of polyurethane dyed with and without pretreatment by reactive dyes. These grades were
compared with those of control samples dyed without pretreatment with all three dyes used for the
study. The wash fastness grading were in the range of 2 to 3 indicating that washing fastness ranges
68


from poor to satisfactory. A washing fastness grade of 3/4 is particularly observed for pretreated
samples. The light fastness grades are in the range of 3 to 4 for untreated fibre. The pretreated fibre
having light fastness grades of 3/4 to 4 from the results, it is clear that due to the pretreatment the
light fastness was improved by one or two points.
Table 4 Effect of pre-treatment on the dying performance of polyurethane filament with reactive dye
Pre-treatment Concentration Dye
(3%,
Exhaustion
Fastness ratings
Chemical
of treatment
owf)
(%)
WF FL
PF
chemical (gpl)
APF
BPF
Untreated
RD I
11.70
2/3
3
2/3
3
RD II
10.95
3
3/4
2/3
3
RD III
32.31
3
4
3
¾
Urea
10
RD I
12.52 (+7.0)
2/3
3/4
2/3
3
20
14.5 (+20.0)
3
3/4
3/4
2/3
30
15.23 (+30.1)
3
4
3/4
3
10
RD II
11.63 (+6.2)
2/3
3/4
3
2/3
20
12.26 (+11.9)
3/4
3/4
3
3
30
12.97 (+18.4)
3/4
3/4
3/4
3
10
RD III
33.02 (+2.2)
3
3/4
3
3
20
34.50 (+6.7)
3
4
3/4
3
30
36.54 (+13.1)
3
4
3/4
3
Thiourea

10
20
30
10
20
30
10
20
30

RD I

11.99 (+2.4)
12.78 (+9.2)
13.61 (+16.3)
11.32 (+3.4)
11.63 (+6.2)
12.35 (+12.8)
32.38 (+0.2)
32.68 (+1.15)
33.02 (+2.2)

RD II

RD III

2/3
2/3
3
2/3
2/3
2/3
2/3
3
3

3/4
3/4
3/4
3
3/4
3/4
3/4
3/4
4

3
3
3/4
3
3
3/4
3
3/4
3/4

2/3
2/3
3
2/3
2/3
3
2./3
2/.3
3

Note: Data in the parenthesis indicate percentage increase in exhaustion compared to untreated dyed samples. RD I - Corazole Yellow 7GL, RD IICoractive Yellow H4G, RD III- Procion yellow HE4R, WF - Wash fastness, LF- Light fastness, PF- Perspiration fastness, APF- Acidic Perspiration
fastness, BPF- Alkaline perspiration fastness.

The perspiration fastness (acidic and alkaline) grades were in the range 2/3 to 3 and 3 to 3/4
for untreated sample. The treatment in some cases lowered the perspiration fastness grade by one
point. The perspiration fastness ranges from good to very good in both the cases i.e. acidic and
alkaline perspiration fastness property.
4

CONCLUSIONS

Pretreatment with urea and thiourea can be used to modify the physico-chemical properties.
Due to the pretreatment the tensile strength was reduced to 4-28.72%, depending upon the pretreatment chemical and its concentration. The melting point of polyurethane was increased in case of
thiourea, i.e. 222.43 °C. But in case of urea it was decreased to 215.19°C. The nitrogen is also
increased by the pretreatment, which can influence the exhaustion of the dye.
69


The polyurethane filament can be dyed uniformly with reactive dyes. The pretreatment with
urea and thiourea not only improves the exhaustion of reactive dye (30% at 3% shade) but also
improves washing, light and perspiration (both alkaline as well as acidic) fastness properties by 1-2
points.
Now-a-days the polyurethane fibre and its blends are gaining importance in the global
market, so, to produce higher quality goods it can be dyed with reactive dyes. Reactive dye can be
successfully applied on pretreated polyurethane with improved exhaustion so, the pretreatment with
urea and thiourea can be adopted to economise the dyeing process.
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