Appl Phys A (2013) 112:1063–1071

DOI 10.1007/s00339-012-7489-y

Effect of microwave radiation on the macromolecular,

morphological and crystallographic structures of sisal fiber
Annapurna Patra · Dillip K. Bisoyi · Prem K. Manda ·
A.K. Singh

Received: 31 July 2012 / Accepted: 29 November 2012 / Published online: 14 December 2012
© Springer-Verlag Berlin Heidelberg 2012

Abstract Experiments have been performed to find out the reinforced polymer composite (NFRPC) has become an at-
effectiveness of the microwave radiation on the modification tractive active area of research [1]. As NFRPC are recy-
of the sisal fiber. The idea of taking the high frequency mi- clable, renewable, less abrasive and having low density and
crowave for modification of the sisal is fueled by the present high specific strength, they are superior to their synthetic
environmental and energy crisis. Physical properties of the counterparts like glass, aramid and carbon fiber reinforced
fiber have been modified significantly after microwave ir- polymer composites [2]. NFRPC is found to be suitable in
radiation under different conditions in terms of power and many electrical applications like in suspension insulators,
time. Macromolecular parameters of the fiber are charac- switch boards, and antistatic applications. Therefore, it is
terized by the Small angle X-ray Scattering characteriza- generating a new potential market for environment friendly
tion (SAXS) technique. These parameters have been found composites [3, 4]. Among all the natural fibers, sisal fiber,
to be changed significantly after the microwave heat treat- which is widely used as yarns, ropes, twines and carpets,
ment as compare to the raw fiber. The fibers that are irradi- has been found to be most suitable for the applications in
ated for 4 min under 320 W microwave power (320W4) are polymer composites because of its superior properties like
found to have least distortion, defect, enhanced density, sur- high cellulose content, high tensile strength and yet cheaper
face roughness, improved crystallinity, and hydrophobicity. in price [5]. However, the inherent hydrophilic nature of
However, the degradation of the structural component and the sisal fiber like most of the other natural fiber leads to
crystallinity of the fiber are observed at higher power and poor moisture resistance. This in turn results in poor wet-
higher treatment period. The chemical structure of the mi- ting of the fiber with the hydrophobic polymeric matrix [6].
crowave treated fiber does not change much except at higher The inherent hydrophilicity of the fiber is found to be re-
power and prolong treatment period. duced by chemical and physical methods. This also results
in good wetting of the fiber with that of the matrix [7]. How-
ever, the use of hazardous chemicals for modifying the fiber,
1 Introduction polymer, and its disposal have become health and environ-
mental issues. Hence, the interest in nonhazardous chemi-
Impressive attention on the development of environment cal and physical modification of the fibers and polymers are
friendly products have been observed from the last few becoming an attractive area of research. In this regard, mi-
decades. Due to this, the development on the natural fiber crowave irradiation on the natural fiber is gaining substan-
tial attention. Microwaves are electromagnetic waves that lie
between radio and infrared frequency regions in the elec-
A. Patra () · D.K. Bisoyi tromagnetic spectrum. The majority of the microwave fre-
Department of Physics, NIT Rourkela, Rourkela 769008, India quencies are dedicated for communications and radar pur-
e-mail: annapurna.patra@gmail.com poses, while the following frequencies are designated for in-
dustrial, scientific, and medical uses: 915 MHz, 2.45 GHz,
P.K. Manda · A.K. Singh
Material Science Division, DMRL Hyderabad, Hyderabad 5.8 GHz, and 20.2–21.1 GHz [8, 9]. Kitchen microwave
500058, India ovens operate at a frequency of 2.45 GHz frequency due to
1064 A. Patra et al.

the fact that the water molecules present in food show good has been made to analyze the modification of the fiber in
microwave absorption at this frequency. The relative avail- terms of macromolecular parameters.
ability of 915 MHz and 2.45 GHz microwave ovens resulted
in their applications to the processing of materials [8]. Mi-
crowaves interact with materials in different ways. Depend- 2 Materials and methods
ing on the materials, microwaves are generally reflected,
transmitted, or absorbed. The ability of certain materials to The sisal fibers used in this work were obtained from the
convert microwaves into heat makes these materials suitable Sisal Research Station, Indian Council of Agricultural Re-
for microwave processing [10]. In conventional heating, the search, Bamara, Odisha, India, having a diameter of 170–
heating elements supply heat to the sample; the majority of 300 µm.
heat is concentrated along the surface of the body rather than
the interior of the sample. In microwave heating, the mate- 2.1 Treatment of the fiber
rial will absorb microwave energy and then convert it into
heat. In recent years, many materials are dried and modi- The basic purifications of the sisal fibers were done by de-
fied under microwave irradiations [11, 12]. A significant po- waxing, which is described elsewhere [4]. The microwave
tential for the development of novel, lightweight, low-cost, treatment of the fiber was carried out in a microwave oven
flexible, and highly efficient microwave absorbing materials (LG electronics) having adjustable power of (160–640) W
are studied by Guo et al. [13]. Xue et al. [14] have studied with a microwave frequency of 2450 MHz. This frequency
the structural and physical properties of microwave irradi- falls under ISM band (industrial, scientific, medical use)
ated wool fabric. They have found that microwave heating showing how the microwave industry is immerging as a
is more efficient than conventional heating. Silk degumming potential market for these above mentioned areas. The de-
using microwave irradiation was done by Mahmoodi et al. waxed fibers were treated with microwave irradiation at var-
[15]. Their finding supports the potential production of new ious power setting (160, 320, 640 W) for different treatment
environment friendly textile fibers using microwave heating. periods (2, 4, 8 min). The fibers were removed from the
Microwave irradiation is also found to be suitable on joining oven and cooled under vacuum for 24 hours. Now the MT
of green composite [16]. Microwave heating of cotton fibers fibers were designated as 160W2, 160W4, 160W8, 320W2,
during mercerization reduces the values of concentration of 320W4, 320W8, 640W2, 640W4, 640W8. The prefixes of
NaOH in the aqueous solution and the time of treatment that “W” denote the power setting whereas the suffixes of “W”
are needed for the complete transformation of cellulose lat- represent the microwave irradiation time on the fiber in min-
tice type I into cellulose lattice type II without any heat- utes. The untreated fiber was designated as UT.
ing [17].
In order to enhance the data transfer, the dominant fre-
quency range of communication has been shifted toward 3 Characterizations
the higher range. Therefore, microwave absorbing materi-
als are gaining attention. In this regard, researchers have The room temperature, smeared out, small angle x-ray scat-
developed an effective, lightweight microwave absorbing tering (SAXS) data for the pristine and MT sisal fiber were
material by the synthesis of size tuneable silver nanoparti- obtained from the SAXS 896986 Anton Paar, which was
cle/collagen fiber composites [18]. The conductivity study mounted on PANalytical X-ray generator (PW3830). The
of the bioinspired, size controlled Ag nanoparticle on skin sample to detector distance “a” was 310 mm.
collagen fiber shows its semiconductive nature and higher
dielectric loss [19]. Theory and computation analysis of SAXS techniques The
The above findings show that microwave irradiation is incident X-rays scatter due to the difference in the elec-
as an alternative processing method for the fiber as well tron density inside the sample.The electron density map tells
as composite due to their beneficial effects on processing about the defects in the crystal system of the sample. There
time, mechanical, and thermal properties. However, there is is little difference in the electron density (η) between crys-
hardly any report on the effect of the microwave irradiation talline phase and amorphous phase in the fiber; hence these
on the macromolecular structure of the sisal fiber. two are taken as one phase, i.e., matter phase whereas void
Dewaxing of the sisal fiber is found to be beneficial from is another phase. The electron density difference between
both mechanical and electrical point of view [4]. So, the these two phases is high. The idea of considering sisal fiber
present analysis aims at the study of effectiveness of the mi- as a two phase system is due to the large difference in elec-
crowave radiation on sisal fiber modification. Special em- tron density of matter phase and void phase. The raw sisal
phasis is made on the study of macromolecular parameter of fiber was studied by Khan [20] considering it as a non-ideal
the pristine and microwave treated (MT) fiber. An attempt two-phase system as the electron density difference between
Effect of microwave radiation on the macromolecular, morphological, and crystallographic structures 1065

the matter phase and void phase does not change suddenly, phase and void phase are thought to be arranged in terms of
which is a realistic approach. For this case, η = ∞. Ac- lamellar stack and each lamellar having some periodicity,
cording to Ruland [21] and Vonk [22], the information about displays information about the specific inner surface area
the non-ideal two-phase system can be obtained from the pa- (S/V ) of those lamellar stacks. It is also defined as phase
rameter defined as “R,” which was later modified by Mishra boundary per unit volume of the dispersed phase.
et al. [23] is as follows:
  ∞ S/V = 2/D (4)
3 2π 2 0 x 3 I˜(x) dx
R= ∞ (1)
2 λa 0 x I˜(x) dx Another important parameter that is derived from the c(r)
is the length of coherence (lc ), which gives the information
where “R” is the corrugation at the phase boundary, “x” is about the distribution of electron across the boundary of the
the position coordinate of the scattered intensity from the particle.
center of the primary beam; “a” is the sample to detector  ∞
distance. If R goes to ∞, the system is the ideal, but if it has lc = 2 c(r) dr (5)
some finite value, i.e., the system is a non-ideal two phase. 0
The expression for the correlation function c(r), which The sum of the volume fraction of matter phase (ϕ1 ) and
contains the valuable information regarding macromolecular void phase (ϕ2 ) is taken as unity inside the fiber.
structural parameters is defined as the ratio of the average of
According to Vonk, the electrodensity and the specific in-
the product of the electron density across the two ends of
ner surface area are related by the following equation:
a virtual rod moving inside the particle to the average of
the product when the length reduces to zero at the origin. It  2
η /η2 = ϕ1 ϕ2 − (ES/6V ) (6)
gives the information about the nature of the phases present
in the particle. The above function c(r) is governed by the This can be used to determine the individual values of ϕ1
following relation. and ϕ2 .
∞ It is assumed that in an irregular two-phase system, if
x I˜(x)J0 (2πrx/λa) dx imaginary arrows are shot in all possible directions, the aver-
c(r) = 0 ∞ (2)
0 x I˜(x) dx age intersectional length in matter and void phases are called
the transversal lengths of matter (l¯1 ) and void phase (l¯2 ) re-
It normalizes to the unit at the origin and decreases to zero spectively. These parameters can be found out by the rela-
when r attains the boundary of the particle, i.e. r = R, cor- tion (7).
responding to the maximum displacement. This correlation
function contains the information about the particle in three l¯1 = 4ϕ1 (V /S), l¯2 = 4ϕ2 (V /S) (7)
dimensions, hence known as 3D correlation function.
In the non-ideal two-phase system, there is corrugation and
at the boundary of matter phase and void phase over a cer-
tain range. This is known as width of the transition layer. It 1/l¯r = 1/l¯1 + 1/l¯2 (8)
can be computed in two ways, i.e., Ruland [21] and Vonk
methods [22]. where l¯r is the range of inhomogeneity which has same
The one-dimensional correlation function C1 (y) can be meaning with that of reduced mass in mechanics [26].
visualized as a measuring rod of length “y” perpendicular to In order to identify the effect of treatment on the crys-
the layers, which moves along the y-direction. In the present tallographic structures of the sisal fiber, wide angle X-ray
study, there is significant contribution of C1 (y) as sisal is diffraction (WAXD) spectra were collected by PHILIPS
having the lamellar structure [24]. The expression for the PAN analytical PW1830 with Cu-Kα radiation from 5◦ to
one-dimensional correlation function C1 (y) introduced by 45◦ with a scan speed of 0.04 degree sec−1 . The crystallite
Kortleve and Vonk [25] for layer structure is given below: sizes of the fibers were determined by modified Scherer’s
formula whereas the degree of crystallinity was calculated
∞
x I˜(x)[J0 (z) − zJ1 (z)] dx by Segal’s empirical method [27].
c1 (y) = 0 ∞ (3)
x I˜(x) dx
0
Vibrational properties of the raw and dewaxed sisal fibers
were investigated by FTIR using the Perkin Elmer FTIR
where z = 2πxy/λa and J1 is the Bessel function of first spectrometer spectrum RX-1 in the mid IR range, i.e., from
order and of the first kind. According to Vonk [22], the po- 400 cm−1 to 4000 cm−1 . The density of the various sam-
sition of first subsidiary maximum in the one-dimensional ples was measured as per ASTM D3800-99 by employ-
correlation function c1 (y), gives the value of the average pe- ing Archimedes’ principle. The surface morphology of sisal
riodicity transverse to layers (D). Inside the fiber, the matter fibers were examined by SEM (JEOL JSM- 6480 LV).
1066 A. Patra et al.

Fig. 1 Background-corrected,
smeared-out scattering curves
for raw and MT sisal fibers.
Inset: Magnified view of the
initial scattering curves to show
the extrapolated data

4 Results and discussion

Figure 1 exhibits the diffuse scattering curve for the un-

treated and MT fibers. The background corrected intensities
are used for analysis of the SAXS data. Five background
corrected intensities are taken for extrapolation up to x = 0
as it is practically impossible to get the scattering curve up
to x = 0, where x = 2aθ and 2θ is the scattering angle. The
extrapolated points are indicated by hollow symbols in the
inset graph of Fig. 1. The above method of extrapolation
does not disturb the position and height of the first subsidiary
maxima of the one dimensional correlation function c1 (y)
[21]. The small but finite positive values of R (shown in Ta-
ble 1) indicates that the samples are non-ideal two phase.
The c1 (y) of all the fibers for various values of y are com-
Fig. 2 Variation of one-dimensional correlation function c1 (y) against
puted and the plots are given in Fig. 2. The previous works y for the raw and MT fibers. Inset: First subsidiary maximum of the
on the lignocellulosic fiber suggest that the areas of cellu- one-dimensional correlation functions
lose production near the protoplasm are related to each other
in some order; hence, forming the cellulose molecules with
some orientation to each other with a high degree orienta- 320 W; the values of l˜1 and ø1 are increased from 2 min
tion. This leads to the kind of isotropic lamellar structure treatment to 4 min, and after that these parameters start de-
[28]. This justifies taking the one-dimensional correlation creasing. But at a higher power of 640 W, with the increasing
function for all the investigated fiber samples [20]. treating period, these parameters are decreased. The values
The observed maximum value of D corresponding to the of l˜1 and ø1 are found to be highest for 320W4, which may
first subsidiary maxima in Fig. 2 of the 320W4 sample, may be due to the rearrangement of cellulose microfibril. Hence,
be due to the evaporation of water molecule from the fiber this decreases the volume fraction of the void content. The
surface due to the efficient heating produced by the mi- decrease in void content increases the mechanical proper-
crowave irradiation as the microwave rotates the dipoles in ties of the fiber [30]. The decrease in the values of l˜r with
the fiber producing the uniform heating [29]. This also leads the increase in treating period at 160 W and 320 W indicates
to the release of residual stress in the fiber. The expansion the decrease in the disorderness inside the fiber [31]. But the
of matter phase occurs due to heat produced by microwave sample gets more disordered and the void content starts to
irradiation within the fiber. This has caused the expansion increase at a higher treating period, that is, for 8 min and it
of the matter phase and compression of void phase. It can becomes the highest for 640W8. It may be due to the degra-
be observed at the microwave power setting of 160 W and dation of cellulosic material and rupturing of cellulose parti-
Effect of microwave radiation on the macromolecular, morphological, and crystallographic structures 1067

Table 1 Various macromolecular parameters of raw and MT treated sisal fibers derived from SAXS study

Macromolecular parameter UT 160W2 160W4 160W8 320W2 320W4 320W8 620W2 640W4 640W8

−2
R(10−4 Å ) 8.831 9.576 11.7098 10.575 11.986 12.869 8.567 7.986 6.753 6.132
D (Å) 654 665 675 670 683 698 648 620 598 582
−1
S/V (10−3 Å ) 3.058 3.007 2.962 2.985 2.928 2.865 3.086 3.225 3.344 3.436
Ev (Å) 21.081 23.293 23.011 22.844 22.778 22.07 22.902 21.788 23.806 23.297
Er (Å) 19.792 19.14 19.992 19.802 19.24 19.351 19.358 19.667 18.747 19.258
Φ1 82.601 83.123 87.001 84.65 87.593 88.201 81.301 80.153 75.132 70.298
Φ2 17.399 16.877 12.999 15.35 12.407 11.799 18.699 19.847 24.868 29.702
l˜1 (Å) 1080.421 1105.535 1174.513 1134.31 1196.52 1231.285 1053.66 993.8972 898.578 818.268
l˜2 (Å) 227.578 224.464 175.486 205.690 169.479 164.714 242.339 246.102 297.421 345.731
l˜r (Å) 187.982 186.581 152.675 174.116 148.452 145.279 197.024 197.258 223.458 243.042
lc 351.097 320.745 279.345 285.678 271.765 260.567 340.43 345.987 350.768 367.598
2Ev /D (%) 6.446 7.005 6.818 6.819 6.669 6.323 7.068 7.028 7.961 8.005
σ 0.013 0.017 0.023 0.011 0.018 0.028 0.024 0.022 0.015 0.021

Fig. 4 Double logarithmic plots for raw and MT fiber

Fig. 3 Variation of three-dimensional correlation function c(r) against
r for raw and MT fibers. Inset: First subsidiary maximum of the three-
-dimensional correlation functions
Figure 5 displays the typical Ruland plots for all the in-
vestigated fibers. The values of E can be calculated from the
Ruland plot, which is a graph of I˜(x)·x verses x −2 . The Ru-
cles into new dimensional particles at a higher concentration land plots are obtained by taking 40 background corrected
with higher treating period because of the excessive heating. intensities. Linear fitting for each of the curves are carried
The values of c(r) have been computed according to the out on 15 extreme points at the tail region of the correspond-
relation (3) are displayed in Fig. 3. The curve pattern of c(r) ing curve. The functional relationship between I˜(x)·x and
has same nature as that of c1 (y). These computed values x −2 takes the form of
of c(r) are used for the subsequent analysis. The slope of
πC π 3C
c(r) at different points of r has been derived by the central I˜(x) · x = −2
− (9)
2 · (λa) · x
3 3 · (λa) · E 2
difference method taking a constant interval of 1 Å.
The logarithmic plots between the x and I˜(x) for the pris- where C is the probability constant.
tine and treated fiber are compiled in Fig. 4. The negative The values of Er , width of transition layer obtained from
slopes of all the plots are ∼3. This suggests that all the sam- Fig. 5 are tabulated in Table 1.
ples are in non-ideal two-phase systems [30]. In the present The standard deviations (σ ) of the intensities are well
study, the width of transition layers are calculated by two within the permissible range showing the accuracy of the
different methods as described by Ruland and Vonk. data collection. The width of transition layer by the Vonk
1068 A. Patra et al.

Fig. 5 Ruland plots I˜(x)·x vs. x −2 for raw and MT sisal fibers

(Ev ) method is calculated from the plot between − R4 ( dC(r)

dr )
versus r and are shown in Fig. 6. The straight line equidis-
tance from both the axes has been drawn and the point of
intersection with the curve gives the values of Ev [24]. It is
found to be in close agreement with Er justifying the accu-
racy of our analysis.
Figure 7 shows the XRD patterns of the untreated and
MT sisal fibers. Microwave irradiation does not change the
basic crystalline nature of the cellulose, but the crystallinity
and crystallite size of the fiber are greatly affected by the mi-
crowaves. The highest degree of crystallinity for the 320W4
is shown by the maximum increase in the intensity of the
crystalline peak at 22.5◦ followed by 320W2 and is least
for 640W8. The lower and moderate microwave power may
have been able to effectively release the residual stress in the
fiber by the absorption of microwave and rearrangement of
the fine structure of the fiber [32]. The increment in the crys- 4 dC(r)
Fig. 6 The curves showing the variation of R ( dr ) against r for the
tallite size and crystallinity may be due to the decrease in raw and MT sisal fibers
crystal distortion and defects in the crystal, which is further
strengthened by the fact that the 320W4 has least (S/V ),
specific inner surface area. It also leads to the increment
Effect of microwave radiation on the macromolecular, morphological, and crystallographic structures 1069

Table 2 Crystallographic and physical parameters of the investigated

raw and MT treated sisal fibers

Fibre Degree of Crystallite size Density (g/cc)

crystallinity (%) (A◦ )

UT 52.11 29.19 1.32

160W2 59.15 35.00 1.45
160W4 61.07 40.17 1.63
160W8 60.15 39.21 1.58
320W2 63.15 43.33 1.70
320W4 65.25 44.09 1.75
320W8 51.00 29.00 1.25
640W2 50.11 28.00 1.34
640W4 48.21 27.12 1.30
640W8 43.35 26.12 1.21

Fig. 7 XRD patterns of raw and MT sisal fibers gen bond network [33]. It shows that hydrogen bond be-
tween intermolecular and intra-molecular has changed sig-
nificantly. The absorbance peak tends to decrease remark-
ably for 320W4 showing the reduction of the O–H group.
But at a higher treatment power and time, the intensities of
the O–H group tend to increase because of the degradation
of cellulose and incorporation of more polar groups [34].
Hence, at 640W8, the O–H group is highest. The 1650 cm−1
band which corresponds to the absorbed water is found to be
decreased remarkably at 320W4. Sisal is a porous dielectric
medium, which means that sisal has both free and bound
water within the cell. Free water can appear as vapor or liq-
uid in the pores. Bound water is captured in the cell matrix.
With the absorption of electromagnetic energy, temperature
of the sisal will reach the boiling point of water. As the tem-
perature increases, internal pressure will also increase, caus-
ing moisture evaporation that will be forced from the inte-
rior towards the surface of the sisal. It seems that these high
frequency radio waves are efficient in penetrating the wa-
Fig. 8 FTIR spectra of raw and MT sisal fiber ter molecule in fiber causing sufficient heat by synchroniz-
ing oscillation of the water molecule. This causes heat to be
generated through intermolecular friction. All other peaks
in bulk density of the fiber given in the Table 2. The cel- remain unaffected by the MT. It suggests that the chemical
lulose provides mechanical strength to the fibers. However, changes in MT sisal fibers are not significant. It affects the
the degradation of cellulose becomes more prominent due OH group and absorbed water molecules of the fiber. As a
to excessive heating at a higher power and higher irradiation result, the maximum hydrophobicity of the fiber is achieved
period. The fiber becomes brittle and turns to black color. with a proper power setting and treatment period.
The crystallinity and the crystallite size of these fibers seem Surface morphology of UT, 320W4, 640W8 fibers are
to be decreased at a higher power and become the least for shown in Figs. 9(a, b, and c), respectively. The untreated
640W8, which may be due to the rupturing of cellulose par- fiber is shown to have a smoother surface than the MT fibers.
ticles into new dimensions. However, enhanced surface roughness was observed for the
Figure 8 exhibits the FTIR spectra of the untreated and 320W4 fiber. It shows that the surface of the fiber has been
MT sisal fibers. It can be seen that the FTIR curve of the eroded, which may lead to the better wetting of the fiber with
MT sisal fibers are almost similar to each other except the hydrophobic matrix. But the longer period of bombard-
for 640W8 suggesting that the change in the fiber is only ment of the high energy radiation lead to the heavy damage
physical in nature. The broad absorbance peak at 3200– of the surface along with the damage to the strength proving
3400 cm−1 corresponds to the O–H stretching of hydro- cellulose as shown in Fig. 9c.
1070 A. Patra et al.

Fig. 9 (a, b, c) Surface morphology of raw, 320W4 and 640W8 fibers, respectively

5 Conclusions Acknowledgements The authors wish to acknowledge the Director,

Defence Metallurgical Research laboratory, Hyderabad, India, for the
The suitability and the applicability of the microwave radi- provision of the small angle X-ray scattering facility.
ation for the modification of sisal fiber have been investi-
gated. Microwave irradiation could affect the macromolecu-
lar parameters of the fiber along with crystallographic struc- References
tures and morphology of the fiber. The chemical structure
of the fiber remained unaffected. Proper treatment time and 1. X. Li, L.G. Tabil, S. Panigrahi, J. Polym. Environ. 15, 25 (2007)
2. J.C.M. de Bruijn, Appl. Compos. Mater. 7, 415 (2000)
power of microwave effectively reduces the absorbed water
3. A. Patra, D.K. Bisoyi, J. Mater. Sci. 42, 5742 (2010)
and O–H group due to heat generated by the water molecule 4. A. Patra, D.K. Bisoyi, J. Mater. Sci. 46, 7206 (2011)
by the synchronizing oscillation with the frequency of the 5. K. Mylsamy, I. Rajendran, Mater. Des. 32, 4629 (2011)
microwave. The 320W4 fiber is found to have the least dis- 6. F. Corrales, F. Vilaseca, M. Llop, J. Girones, J.A. Mendez, P.
order and void content with an increased degree of crys- Mutje, J. Hazard. Mater. 144, 730 (2007)
7. H.M. Mominul, M. Hasan, M.S. Islam, A.M. Ershad, Bioresour.
tallinity, crystallite size, and density showing the changes Technol. 100, 4903 (2009)
in the physical parameters of the fiber. Adequate surface 8. D.E. Clark, W.H. Sutton, Annu. Rev. Mater. Sci. 26, 299 (1996)
roughness is achieved due to the bombardment of high 9. J. Katz, Annu. Rev. Mater. Sci. 22, 153 (1992)
energy electromagnetic radiation at optimized microwave 10. National Materials Advisory Board, Microwave Processing of Ma-
power and time. The present study optimizes the modifica- terials (National Academy Press, Washington, 1994)
11. R. Murugan, M. Senthilkumar, T. Ramachandran, IIE Part TX,
tion process of the fiber by microwave irradiation. Finally, Text. Eng. Div. 87, 23 (2007)
it is concluded that the microwave irradiation with 320 W 12. J.P. Li, H.F. Lin, W.F. Zhao, G.H. Chen, J. Appl. Polym. Sci. 109,
power for the 4 min treating period is the best to modify the 1377 (2008)
sisal fiber. This also gives a new insight to the microwave 13. J. Guo, X. Wang, P. Miao, X. Liao, W. Zhanga, B. Shi, J. Mater.
Chem. 22, 11933 (2012)
energy as a cleaner and safer modification process for the 14. Z. Xue, H.J. Xin, J. Appl. Polym. Sci. 119, 944 (2011)
sisal fiber as compared to the traditional drying, which gives 15. N.M. Mahmoodi, F. Moghimi, M. Arami, F. Mazaheri, Fiber
non- uniform heating. Polym. 11, 234 (2010)
Effect of microwave radiation on the macromolecular, morphological, and crystallographic structures 1071

16. I. Singh, K.P. Bajpai, D. Malik, A.K. Sharma, P. Kumar, Akade- 26. P. Mittelbach, G. Porod, Colloid. Polym. Sci. 202, 40 (1965)
meia 1, 1 (2011) 27. L. Segal, J. Creely, J.A.E. Martin, C.M. Conrad, Tex. Res. J. 29,
17. M.A. Moharram, O.M. Mahmoud, J. Appl. Polym. Sci. 105, 2978 786 (1959)
(2007) 28. K. Muhlethaler, Papier 17, 546 (1963)
18. J. Guo, H. Wu, X. Liao, B. Shi, J. Phys. Chem. C 115, 23688 29. D. Katovic, in Woven Fabric Engineering, ed. by P.D. Dubrovski
(2011) (Sciyo, Rijeka 2010), p. 297
19. J. Guo, X. Wang, X. Liao, W. Zhanga, B. Shi, J. Phys. Chem. C 30. V. Vilay, M. Mariatti, R.M. Taib, M. Todo, Compos. Sci. Technol.
116, 8188 (2012) 68, 631 (2008)
20. N.M.D. Khan, Small angle X-ray scattering study of sisal fiber us- 31. N. Prasad, J. Patnaik, N. Bohidar, T. Mishra, J. Appl. Polym. Sci.
ing correlation function, pp. 71–72. Ph.D. Thesis, NIT Rourkela, 67, 1753 (1998)
1991 32. M. Tsukada, S. Islam, T. Arai, A. Boschi, G. Freddi, AUTEX Res.
21. W. Ruland, J. Appl. Crystallogr. 4, 70 (1971) J. 5, 40 (2005)
22. C.G. Vonk, J. Appl. Crystallogr. 8, 340 (1975) 33. V.A. Alvarez, A. Vázquez, Composites, Part A, Appl. Sci. Manuf.
23. T. Mishra, D.K. Bisoyi, T. Patel, K.C. Patra, A. Patel, Polym. J. 37, 1672 (2006)
20, 739 (1988) 34. A. Paul, K. Joseph, S. Thomas, Compos. Sci. Technol. 51, 67
24. O. Kartky, G. Miholic, J. Polym. Sci. C 2, 449 (1963) (1997)
25. C.G. Vonk, J. Appl. Crystallogr. 4, 340 (1971)