Sangappa et al., J Fashion Technol Textile Eng 2015, 3:2
http://dx.doi.org/10.4172/2329-9568.1000119
Journal of Fashion
Technology & Textile
Engineering
Research Article
A SCITECHNOL JOURNAL
Influence of Electron Irradiation
on Tassr Non-mulberry Silk Fibers
Y Sangappa1*, S Asha1, B Lakshmeesha Rao1, Mahadeva Gowda1
and R Somashekar2
1Department
of Studies in Physics, Mangalore University, Mangalagangotri,
Mangalore 574 199, India
2Department
of Studies in Physics, University of Mysore, Manasagangotri, Mysore
570 006, India
*Corresponding author: Y Sangappa , Department of Studies in Physics,
Mangalore University, Mangalagangotri, Mangalore 574 199, India, Tel: +91
9845205065; E-mail: [email protected]
Rec date: September 2, 2014 Acc date: February 17, 2015 Pub date: February
21, 2015
the field of characterization of silk (non-mulberry) to understand the
properties in terms of its structural features and find ways of
improving the quality of silk fibers by treatment. In recent days, there
is a spurt of activities involving the exposure of silk fibers to high
energetic beams, such a study was carried out by us on silk C108 and
NB4D2, belonging to bivoltine race of the Bombyx mori family
indicated significant changes in the microcrystalline parameters [9,10].
Takeshita et al have studied the physical, chemical and thermal
properties electron beam irradiated Bombyx mori silk fibers [11].
Effects of gamma radiation on biodegradation of Bombyx mori silk
fibers have been studied by Kojthung group [12]. All these studies
were related mulberry silk. So far only few studies have reported the
properties of wild silk fibers and no reports on irradiation effects on
wild silk.
Here we have irradiated silk fiber samples with 8 MeV electron
beams of various doses and studied the structural changes, chemical
and thermal properties of virgin and electron irradiated tassar nonmulberry silk fibers.
Abstract
In this work the effect of electron irradiation on the structural,
chemical and thermal properties of tassar non-mulberry silk
fibers was investigated. Tassar silk fiber (Antheraea mylitta)
samples were irradiated in air at room temperature using 8
MeV electron beam in the range 0 to 100 kGy. Various
properties of the irradiated fibers were characterized by X-ray
diffraction (XRD), Fourier transform infrared spectroscopy
(FTIR) and differential scanning calorimetry (DSC). The wide
angle X-ray scattering (WAXS) study shows the crystallite size
(L) increases with increasing radiation dosage. It was found
that the thermal stability of the fibers improved after electron
irradiation.
Keywords: Fiber; Electron irradiation; XRD; Chemical properties;
Thermal properties
Introduction
Silk is semicrystalline biopolymer which is produced by
Lepidoptera such as silk worm and species like spider, scorpions and
mites which belong to Araneae and pseudoscorpionida respectively
under class Archnida which belongs to Artropoda phylum [1,2].
Silkworm silk are classified as Mulberry (Bombyxmori) and NonMulberry (Tassar, Muga and Eri).
In radiation chemistry, polymers were classified into two types:
scission polymers and cross-linking polymers, and most biopolymers
were placed into the scission polymers [3]. Recent developments in
this field proved, that a variety of biopolymers could be cross-linked by
irradiation of high energy radiation and tassar natural polymer tends
to radiation cross-linking. Among the natural fibers, silk has a
profound place in industrial applications. Silk has excellent intrinsic
properties utilizable in biotechnological and biomedical fields as well
as the importance of silkworm in the manufacture of textiles [4].
Sargunamani have studied the Ozone treatment on the properties of
tassar silk fibers [5]. Yutaka Kawahara has studied micro voids in wild
silk fibers using stannic acid treatment [6]. Divakar have studied the
microstructure and micro rheological parameters of various wild silk
fibers [7]. Gulrajani have studied structural variants of mulberry and
tassar silk filaments [8]. In this context, there is a continued interest in
Experimental
Sample preparation
Tassar silk is belongs to Antheraea mylitta family. Tassar silk
cocoons were collected from the germplasm stock of the Department
of Sericulture, University of Mysore, India. The fiber samples were
obtained using the method mentioned in earlier work [9,10].
Electron irradiation
Irradiation work was carried out at Microtron Center; Mangalore
University, India, using 8 MeV Microtron accelerator. The electron
beam feature is mentioned elsewhere [10].
X-Ray diffraction measurements
Wide – angle X-ray diffraction patterns of the samples were
recorded on a Rigaku Miniflex- II, X-ray diffraction instrument using
CuKα radiation of wavelength λ=1.5406 Å at 40 kV and 100 mA with a
scan rate of 1° /min. The diffraction angle ranged from 5° to 60 °.
FT-IR spectroscopic analysis
Fourier transform infrared (FT-IR) spectra of the unirradiated and
EB irradiated tassar non-mulberry silk fiber samples was recorded in
transmission mode using Thermo Nicolet, Avatar 370, FTIR
spectrophotometer having a resolution 4 cm-1 in the wave number
range 500-4000 cm-1.
Differential scanning calorimetry (DSC)
Thermal analysis of the tassar silk, with and without electron
irradiation of natural polymer fibers were carried out using Mettler
Toledo DSC 822 apparatus. The thermograms were obtained from the
heating cycle run in a temperature range of 30-450°C at a constant
heating rate of 10°C / min. under nitrogen atmosphere.
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Sangappa Y, Asha S, Rao BL, Gowda M, Somashekar R (2015) Influence of Electron Irradiation on Tassr Non-mulberry Silk Fibers. J Fashion
Technol Textile Eng 3:2.
Citation:
doi:http://dx.doi.org/10.4172/2329-9568.1000119
Results and Discussion
X-ray diffraction study
X-ray diffraction curves of pure and electron irradiated fiber
samples are given in Figure 1. The average crystallite size of the
crystallites was calculated from the Scherrer equation [13] with the
method based on the width of the diffraction patterns obtained in the
X-ray reflected crystalline region.
The lattice strain and its variation for various values of the radiation
doses (kGy) in polymer samples are very small and insignificant.
Sample
2-theta
(deg.)
β (deg.)
Crystallite size
(nm)
Lattice strain
0 kGy
20.86
1.76
4.8
0.04
25 kGy
19.91
1.30
6.48
0.03
50 kGy
20.24
1.18
7.15
0.02
100 kGy
20.68
1.45
5.48
0.03
Table 1: Structural parameters of non-mulberry pure and electron
irradiated silk fibers for (020) reflection
Fourier transforms infrared spectroscopy
FT-IR measurements were carried out to investigate the nature of
the chemical modifications caused by electron irradiation on the
natural polymer tassar non-mulberry silk fiber. FT-IR spectra of tassar
non-mulberry silk fiber pure and 8 MeV electron irradiated are shown
in Figure 2 and corresponding band assignments are tabulated in
Table 2.
Figure 1: XRD scans of pure and 8 MeV electron irradiated fiber
samples.
In this study, the crystallite size (L in nm) was determined with the
diffraction pattern obtained from the lattice planes at a 2θ of ~20;
kλ
L = β cosθ
(1)
where k is Scherrer constant, λ is X-ray wavelength, β is the full
width at half maximum of the measured reflection and θ is peak value.
The determined structural parameters such as crystallite size (L),
lattice strain are given in Table 1. From the Table 1, it is very clear that
the crystallite size (L) increases as radiation dose increases.
Irradiation of polymers mainly causes two important changes. (1)
Degradation of the polymer, wherein main chain scission takes place,
leading to low molecular weight polymer. (2) Cross-linking which is
chemical bonding between polymeric chains to form network
polymers. Both of these effects cause changes in physical properties.
Degradation of polymer leads to loss in mechanical strength, whereas
cross linking improves the physical properties. Quite often these
effects may occur simultaneously. The final result depends on the
nature of the material, on the amount radiation, dosage rate and
energy of the radiation. From the Table 1 it is evident that the
crystallite size increases as radiation dose increases. It is known that
the strength of the fibers irrespective of natural or man-made increases
with increase in crystallite size [14]. This indicates that the electron
irradiated fiber has higher tenacity than virgin fibers.
Volume 3 • Issue 2 • 1000119
Figure 2: FTIR spectra of pure and electron irradiated fibers.
The shift in frequency is correlated with force constant and bond
length. The force constant values can be calculated from the
expression [16]
1
ν = 2Πc
k
μ
(2)
where ν is the wave number, c the velocity of light, k the force
constant and μ is the reduced mass. From the Table 3, it is interesting
to note that the force constant decreases for C=O stretching band with
increasing irradiation dosage. This decrease in force constant is due to
interaction of high energy radiation with polymer matrix.
From the Table 2, the observed IR band assignment for unirradiated
tassar non-mulberry silk fiber is similar to earlier researcher [15].
From the infrared spectra it can be noticed that increasing irradiation
dosage causes some observable changes in the spectrum of silk fiber in
the wavenumber range 4000 – 600 cm-1. It induces some new
• Page 2 of 4 •
Citation:
Sangappa Y, Asha S, Rao BL, Gowda M, Somashekar R (2015) Influence of Electron Irradiation on Tassr Non-mulberry Silk Fibers. J Fashion
Technol Textile Eng 3:2.
doi:http://dx.doi.org/10.4172/2329-9568.1000119
absorption bands and slight changes in the intensities of some
absorption bands.
Wavenumber (cm-1)
Peak assignments
0 kGy
25
kGy
50
kGy
100
kGy
N-H deformation
3440
3445
3444
3438
C=O stretching (amide I)
1632
1640
1633
1634
N-H bending
1540
1535
1527
-
N-H in plane bending (amide II)
1231
1230
1231
1232
O-H bending
1162
1160
1157
1164
N-H rocking
960
962
960
960
N-C=O in plane bending (amide IV)
697
695
695
694
electron irradiated samples the decomposition temperature was
slightly increased and the values are given in Table 4.
The shifting of decomposition temperature (td) from 345-349 for
irradiated fibers indicates that improvement of thermal stability of
electron irradiated fibers. All the measurements were taken in an inert
atmosphere of nitrogen and a temperature ranging from 30-400°C.
The heating rate was 10°C/min. The unirradiated fiber showed
enthalpy 124.56 J/g and it slightly goes on increasing as irradiation
increases. In case of 25 kGy irradiated sample enthalpy is 145.32 J/g
and in 100 kGy irradiated sample it was 147.14J/g. Increase in
decomposition temperature and enthalpy suggests the requirement of
higher amount of energy for breaking the bands compared to virgin
samples.
Table 2: IR peak assignments for unirradiated and electron irradiated
samples
The absorption band observed at 1632 cm-1 (amide I), 1540 cm-1
(amide II), 1231 cm-1 (amide III) and 697 cm-1 (amide IV) observed
for the unirradiated sample. The significant alterations after 8 MeV
electron beam irradiation one can see in the positions of amide I, II
and III. The position of amide I that is C=O stretching peak at 1632
cm-1 has shifted to 1648 cm-1, amide II (N-H bending) are shifted to
1525 cm-1 and amide III shifting are very small namely 1-3 cm-1. Apart
from these various shifts in the peak positions for the irradiated
samples (Table 2), new peak start appearing around 3440 cm-1. The
observed shifts in the wavenumber along with change in the peak
intensify in the FTIR spectra indicate the occurrence of chemical
modifications within the silk fiber due to electron irradiation which
starts from the dose of 25 kGy. These results are understood by
invoking the conformational changes introduced within the polymer
due to electron irradiation.
Sample
C=O band variations
N-H band variations
Wavenumber
(cm-1)
Force
Constant
(N/cm)
Wavenumber
(cm-1)
Force
Constant
(N/cm)
0 kGy
1632
10.77
3440
6.56
25 kGy
1640
10.88
3445
6.58
50 kGy
1632
10.78
3445
6.58
100
kGy
1637
10.81
3438
6.55
Table 3: FTIR modes of C=O and N-H band variations in Pure and
Electron irradiated Tassar fibers
Differential scanning calorimetric analysis
Figure 3 shows the DSC thermograms of the pure and 8MeV
electron irradiated silk fibers. The endothermic peak nearly at 70°C
which is corresponding to the water evaporation appeared in all the
cases except in 100 kGy irradiated sample [17].
The other strong endothermic transition is observed at 346 oC for
pure is attributed to decomposition (td) of the fiber. In the case of
Volume 3 • Issue 2 • 1000119
Figure 3: DSC thermograms of (a) pure, (b) 25kGy, (c) 50kGy and
(d) 100 kGy electron irradiated fibers.
Sample
td (°C)
Enthalpy (J/g)
0kGy
345.53
124.56
25kGy
347.76
145.32
50kGy
348.00
145.98
100kGy
348.33
140.14
Table 4: Thermal properties of pure and electron irradiate Tassar silk
fibers
Conclusions
The main intension of this study was to investigate the influences of
the electron irradiation on the structural, chemical and thermal
properties of tassar non-mulberry silkfibers. From the wide angle Xray scattering (WAXS) study of electron irradiated silk fiber (Nonmulberry) samples; we have observed that even though there is not
much change in the position of the X-ray reflections, an increasing
trend in the value of microstructural parameters occurs. The
significant change in microstructural parameters in polymer is due to
• Page 3 of 4 •
Citation:
Sangappa Y, Asha S, Rao BL, Gowda M, Somashekar R (2015) Influence of Electron Irradiation on Tassr Non-mulberry Silk Fibers. J Fashion
Technol Textile Eng 3:2.
doi:http://dx.doi.org/10.4172/2329-9568.1000119
the effect of electron irradiation. FT-IR study reveals the structural
changes occur due to electron irradiation. From the DSC study td the
decomposition temperature slightly increases with irradiation. This
reveals that a variety of biopolymer (tassar) could be cross-linked by
the application of high energy electron beam irradiation (ionizing
radiation).
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