Investigation of Thermal, Mechanical, Morphological and...
Transcript of Investigation of Thermal, Mechanical, Morphological and...
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 1 (2019) pp. 170-179
© Research India Publications. http://www.ripublication.com
170
Investigation of Thermal, Mechanical, Morphological and Optical
Properties of Polyvinyl alcohol Films Reinforced with Buddha Coconut
(Sterculia alata) Leaf Fiber
Kapil Gulati
Research Scholar, Department of Chemistry, Kurukshetra University, Kurukshetra-136119, India.
Sohan Lal
Assistant Professor, Department of Chemistry, Kurukshetra University, Kurukshetra-136119, India.
P.K. Diwan
Assistant Professor, Department of Applied Science, University Institute of Engineering & Technology (UIET), Kurukshetra University, Kurukshetra-136119. Haryana, India.
Sanjiv Arora*
Professor, Department of Chemistry, Kurukshetra University, Kurukshetra-136119, India.
Abstract
Polyvinyl alcohol (PVA) films reinforced with Buddha
Coconut (Sterculia alata) leaf fiber (SA) were synthesized by
solvent casting method. The influence of fiber addition (2.5-
15.0 %) on the resulted blended films was investigated by
thermogravimetric analysis, IR and UV/Vis spectra. The
kinetic parameters such as activation energy and degradation
temperature range for the first and second decomposition stage
based on thermogravimetric data were determined using single
heating rate models. The film containing 2.5 % fiber showed
the maximum weight loss percentage (41.2 ± 1.1) under soil
burial analysis. At the level of 12.5 % fiber, films showed the
lowest water uptake percentage (56.0 ± 1.9) and maximum
Ultimate Tensile Strength (38.1± 1.1) MPa.
Keywords: polyvinyl alcohol, sterculia alata fiber, buddha
coconut, thermal stability, tensile strength.
INTRODUCTION
The requirement to seek out the alternatives of materials
ensuing from non-renewable sources is strongly extending the
necessity for its replacement by renewable sources [1]. Among
the potential substitutes, the progress of composites using
lignocellulosic materials as strengthen filler and thermoplastic
polymer as the matrix is presently the focal point [2]. Natural
fiber polymer composites (NFPCs) have a class of renewable
and sustainable materials as they are created from natural fibers
set in a polymer matrix [3]. There are diverse categories of
natural fibers that are plentifully available from both naturally
and agricultural industries such as jute, banana, bamboo, rice
husk, bagasses etc. [4] In comparison to synthetic fibers,
natural fibers are cheap, light weight, biodegradable,
renewable, showing good mechanical properties, and non toxic
[5-7]. Jayaramudu et al. [8] documented a novel uniaxial bark
fabric obtained from the tree of Sterculiaurens (Roxb).
Mohanty et al. [9] made the use of pineapple leaf fibers by
implanting them with polyacrylonitrile to modify their
properties. The usage of pineapple leaf waste in the form of
short fiber for the synthesis of polypropylene composites was
also made by Nanthaya and Taweechai [10].
The creation of polymer composites by means of polymer
matrix that can offer high tensile strength and non-toxicity will
be appropriate for food packaging and biomedical applications
[11]. Polyvinyl alcohol (PVA) offers the property of
biocompatibility, non-toxicity, water solubility, superior tensile
strength and is gradually replacing other non-biocompatible
plastics like polyethylene, polypropylene, HDPE etc. in many
fields [12]. Certain drawbacks of PVA are its high hydrophilic
character [13] and slow degradation process particularly under
anaerobic conditions [14]. The possible solution to advance the
biodegradation rate and to lower the hydrophilic nature and cost
of PVA, demand the synthesis of its composites with
biodegradable fillers. The requirement of stronger interfacial
adhesion and superior mechanical strength is crucial when
synthesizing such type of composites which can be achieved
using some cross-linking agents such as boric acid, borax and
glutaraldehyde [15-17]. PVA/rice husk composites using boric
acid as cross linking agent [18], PVA fly ash composite cross-
linked with glutaraldehyde solution [19] and plasticized starch
PVA blends cross linked with epichlorohydrin [20] are some
examples, exhibiting the effect of cross-linking agents in
polymer composites. The aim of this work was to synthesize
the PVA based composite films reinforced with Buddha
Coconut (Sterculia alata) leaf fiber (SA). The tree from which
this fiber was extracted belongs to the sterculiacea family.
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 1 (2019) pp. 170-179
© Research India Publications. http://www.ripublication.com
171
MATERIALS AND FABRICATION
Materials
Buddha Coconut (Sterculia alata) leaves were picked from its
plant (Kurukshetra University, Kurukshetra). Polyvinyl alcohol
(PVA) (Mw = 85,000-1,24,000, degree of hydrolysis = 86.0-
89.0 %) was supplied by SDFCL (s d fine-chem limited). Poly
(ethylene glycol) (PEG-6000) and boric acid were supplied by
Himedia (India). Deionised water was used for the preparation
of composite films.
Fabrication of Polymer composite Films
Synthesis of polymer composite thin films of polyvinyl alcohol
(PVA) based matrix, reinforced with different loadings of 2.5,
5.0, 7.5, 10.0, 12.5 and 15.0 % of SA fiber was carried out by
solvent casting method. The plant leaves were washed with
water to remove any greasy materials, dried in the shade for 10
to 15 days and ground to powder. The fiber obtained was
treated with 5% aqueous NaOH solution to remove
hemicellulose and other greasy materials [21, 22]. The dried
fiber was passed through 18 mesh sieve. The calculated amount
of PVA [23] was added to hot deionised water at 80 °C and kept
under stirring for about an hour to dissolve it completely,
followed by the addition of polyethylene glycol (PEG-6000) as
plasticizer (33% of PVA) and cross-linking agent boric acid
(3% of PVA). The addition of homogenised solution of SA
fiber in water was carried out. When completely suspended, the
mixture was kept under stirring for 3h at 60 °C avoiding
frothing. The resultant mixture was sonicated in Ultra cleaner
sonicator for 15 min. and allowed to cool at room temperature.
Films were casted into clean and dry glass dishes 15cm x 5cm.
All the films were dried in vacuum oven at 65 °C for about 40
h to ensure the complete removal of absorbed moisture and
stored in airtight polyethylene bags until further testing. The
thickness of obtained films was 0.5 mm and named according
to the fiber loadings initiating from SA-0 to SA-6 (Table 1).
Table 1: Composition of PVA, PEG-6000, Boric acid and
SA-fiber
Sample
Index
PVA
(g)
PEG-6000
(g)
Boric acid
(g)
Fiber
content (g)
PVA 7.5 - - -
SA-0 7.5 2.5 0.225 -
SA-1 7.5 2.5 0.225 0.187
SA-2 7.5 2.5 0.225 0.375
SA-3 7.5 2.5 0.225 0.562
SA-4 7.5 2.5 0.225 0.750
SA-5 7.5 2.5 0.225 0.937
SA-6 7.5 2.5 0.225 1.125
Characterisation of Polymer Composite Films
FTIR Spectroscopy
FTIR spectra were used to characterize the presence of specific
groups in the neat PVA and composite films showing the
effectiveness of the developed method for different polymer
composites. FTIR spectra were recorded on a MB-3000 ABB
spectrophotometer in transmission mode over the frequency
range of 4000-600 cm-1.
Water Uptake Test
The film cuts (30 mm x 30 mm) dried to the constant weight
(wi) were submerged in the 50 ml water for 24 h at room
temperature which then were taken out and the final weight of
the absorbed films was recorded (wf) after removing the water
left at surface by absorbing it with filter paper. There were three
samples of each composition and the average readings were
taken. The water uptake (%) of each film was determined by
using the following formula [24]:
Water uptake (%) =[wf−wi
wi x 100 ]
Soil Burial Test
The soil collected from Kurukshetra University campus,
Haryana, India after drying in the shade for three days was
complemented with urea (6g/kg) to encourage an active
microbial flora. This blend of soil was then placed in a large
tray and kept wet by spraying water at the regular time interval
to keep the growth of microorganisms dynamic to degrade the
samples. Polymer films to be analyzed for biodegradation
dehydrated at 50 °C under vacuum to acquire constant weight
(wi) were covered in synthetic net and then buried fully into the
wet soil of test medium at 25 °C under aerobic conditions at
relative humidity of 50%. The degradation of the samples was
observed by withdrawing the samples from the soil on every 15
days for two months. Samples were then washed to get rid of
the soil particles. At each time interval atleast three samples of
the films were analyzed. The samples were dehydrated under
vacuum until they obtained a constant weight (wf). The %
degradation of the composite films was calculated using the
following equation [24-26]:
% degradation of the polymer film = [wi−wf
wi x 100 ].
Thermal Study
Thermogravimetry analysis (TGA) of composite films was
carried out using STAH instrument at the heating rate of 10 °C
min-1 from ambient temperature to 600 °C in the nitrogen
atmosphere. Non isothermal single heating rate methods used
for the computation of kinetic parameters are given in Table 2.
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 1 (2019) pp. 170-179
© Research India Publications. http://www.ripublication.com
172
Table 2: Single heating rate methods for the activation energy evaluation
Method Considerations Expression Plots
Coats-Redfern [27] α =w0 − wt
w0 − w∞
is the fraction of
number of molecules
decomposed
ln [g(α)
T2] = −
Ea
RT+ constant
Here, g(α) = −ln(1 − α)
ln [g(α)
T2] vs
1
T
Horowitz-Metzger [28] α =w0 − wt
w0 − w∞
ln {ln (1
1 − α)} = −
Ea θ
RTs2
+ constant
Here Ts is the temperature at which
1
(1−α)=
1
exp= 0.368 and θ is the difference
between the peak temperature and temperature
at particular weight loss (θ =T-Ts)
ln {ln (1
1 − α)} vs θ
Mechanical Properties
The mechanical analysis of the films was studied by tensile
testing on Universal Testing Machine (UTM). The test samples
were according to ASTM D882 standards. The cross head
speed was 10 mm/min. Three samples were tested in each
category and the average value is reported.
Optical Property
Each film specimen was cut into a rectangular piece and placed
directly in a UV-Vis spectrophotometer (MODEL Shimadzu
Double Beam Double Monochromator, UV-2550) test cell and
measurements were made using air as the reference [29]. A
spectrum of each film was obtained at wavelength between 200
and 800 nm and expressed as absorbance.
Scanning Electron Microscopy (SEM) analysis
SEM analyses were performed on JEOL JSM-6510LV to
observe the morphology of composite films. Films were coated
with gold particles to prevent any damages by the electron
beam.
RESULTS AND DISCUSSION
FTIR Spectroscopy
FTIR spectra shown in Figure 1a correspond to the
characteristic peaks of SA fiber. The vibrational bands of SA
fiber observed at 3321 and 1627 cm-1 correspond to the OH
stretching and bending mode respectively. Peak obtained at
2916 cm-1 was due to the C-H stretching in cellulose and
hemicellulose present in fiber. The band observed at 1728 cm-
1 can be due to the C=O group present in hemicellulose.
Asymmetric C-O-C stretching band obtained at 1108 and 1034
cm-1 is an indication towards the presence of the chain of
anhydroglucose ring [25] i.e. cellulose.
FTIR spectra of pure PVA and SA-0 are shown in Figure 1b.
The broad absorption bands observed at 3310 in PVA and at
3350 cm-1 in SA-0 are assumed to arise from OH stretching
frequency of PVA and absorbed moisture. The vibration bands
observed at 2939, 2857 cm-1 (PVA) and 2939, 2830 cm-1 (SA-
0) correspond to the C-H stretching from alkyl groups. The
peaks at 1720 cm-1 are related to the C=O stretching of carbonyl
groups that remain after the synthesis of PVA by the hydrolysis
of polyvinyl acetate or oxidation during its synthesis [30]. A set of bands obtained at 1545-1330 cm-1 were due to the C-H/O-H
bending. The bands obtained at 1095 cm-1 (PVA) and 1102 cm-
1 (SA-0) corresponds to the C-O-H stretching.
The FTIR spectra of PVA composite films from SA-1 to SA-6
are shown in Figure 1c. The values of characteristic peaks
observed in PVA-SA composite films are almost similar to that
of PVA and SA-0. However, the intensity of the peak obtained
at 1111-1103 cm-1 was found to be more in comparison to that
of PVA and SA-0. The decrease in intensity of OH group with
fiber loading can be an indication towards the fact that OH
group of PVA is involved in intermolecular hydrogen bonding
giving rise to the polymeric association of OH group [25].
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 1 (2019) pp. 170-179
© Research India Publications. http://www.ripublication.com
173
(A) (B)
(C)
Figure 1: FTIR spectra of: (A) SA powder and (B) PVA, SA-0 and (C) SA-1 to SA-6
Water Uptake Test
The water uptake percentage of PVA and its composite films
are shown in Figure 2. The virgin polyvinyl alcohol film due to
its high hydrophilic nature showed the highest percentage of
water uptake (79.9 ± 1.6). In case of SA-0, the addition of PEG
and cross linking agent boric acid [31] decreased the
hydrophilic nature of PVA film and hence decreased the water
uptake percentage. On the addition of fiber this value was
further decreased with the lowest value of 56.0 ± 1.9 for SA-5.
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 1 (2019) pp. 170-179
© Research India Publications. http://www.ripublication.com
174
It may be due to the fact that with the addition of SA fiber the
hydroxyl groups in PVA were involved in intermolecular
hydrogen bonding which led to decrease in number of hydroxyl
groups [32] ; responsible for the overall decrease in water
uptake percentage up to SA-5. However, in SA-6 due to the
super saturation of fiber the cross linking between fiber and
polymer matrix could not be made possible entirely; which led
to an increase in number of free hydroxyl groups and hence
increased the water uptake percentage (60.5 ± 0.7).
PVA SA-0 SA-1 SA-2 SA-3 SA-4 SA-5 SA-6
45
50
55
60
65
70
75
80
85
Wa
ter
Up
tak
e (
%)
Polymer Films
Figure 2: Water Uptake percentage of the polyvinyl
alcohol films
Soil Burial Test
The weight loss profile of the polymer films is shown in Figure
3. All the tested specimens had the same dimensions to avoid
the effect of films shape on the weight loss percentage and
hence biodegradability [24, 33]. The biodegradability of the
polymer films was analyzed by calculating the weight loss of
the films at regular interval of 15 days for two months. The soil
burial degradability of the polymer films found to show a slight
rise in its degradation rate with addition of fiber. The virgin
PVA film exhibited the highest resistance against degradation.
The possible reason can be due to the fact that the C-C
backbone linkage of PVA itself caused the low
biodegradability [34]. The maximum weight loss percentage
after 60 days for PVA and SA-0 films were 23.9 ± 1.1 and
28.1 ± 1.0 respectively. This value of weight loss percentage
was found to show a decrease from SA-1 to SA-5. The
maximum weight loss percentage at the end of 60 days was
observed in case of SA-1 (41.2 ± 1.1). This degradation pattern
can be explained on the basis of degree of cross linking. Highly
cross linked films do not favour the degradation, takes long
time to degrade and hence show the lower degradation rate
[35]. The low weight percentage observed for SA-5 (30.1
± 1.0) showed that maximum cross linking was obtained in it,
as established by tensile testing also (Maximum value of UTS
obtained in SA-5). The high degradation percentage observed
in SA-6 (35.0 ± 0.3) showing the presence of free volume/
voids [36] in composite film favouring the attack of
microorganisms and hence led to more degradation in
comparison to SA-5.
PVA SA-0 SA-1 SA-2 SA-3 SA-4 SA-5 SA-6
5
10
15
20
25
30
35
40
45
50
We
igh
t L
os
s %
Polymer Films
15 days
30 days
45 days
60 days
Figure 3: Plot of weight loss % as a function of polymer films
Thermal Study
Thermogravimetric Analysis (TGA)
The thermograms (TG and DTG) of some selected samples viz.
PVA, SA-0 and its composites (SA-2, SA-4 and SA-6) at the
heating rate of 10 °C/ min in the nitrogen atmosphere are shown
in Figure 4.
100 200 300 400 500 600
0
20
40
60
80
100
We
igh
t (%
)
Temperature (oC)
PVA
SA-0
SA-2
SA-4
SA-6
(a)
100 200 300 400 500 600
-14
-13
-12
-11
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
1
dw
/dt
(% m
in-1
)
Temperature (oC)
PVA
SA-0
SA-2
SA-4
SA-6
(b)
Figure 4: (a) TGA thermograms and (b) DTG curves of
polymer films at the heating rate of 10 °C/ min
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 1 (2019) pp. 170-179
© Research India Publications. http://www.ripublication.com
175
Table 3: Characteristic thermal decomposition data of PVA
and composite films
Sample First degradation stage Second degradation stage
To
(°C)
Tmax
(°C)
Tend
(°C)
MWLR
(%min-1)
To
(°C)
Tmax
(°C)
Tend
(°C)
MWLR
(%min-1)
PVA 268.8 325.6 368.8 7.24 388.9 427.6 448.9 7.24
SA-0 262.1 319.8 362.9 8.41 396.9 413.8 436.8 8.07
SA-2 282.1 323.7 362.8 7.80 392.9 415.9 442.9 10.45
SA-4 290.0 331.5 370.9 5.45 390.0 415.9 450.9 13.21
SA-6 288.1 325.6 368.8 6.78 398.9 411.8 438.9 9.90
where To, Tmax and Tend stands for onset, maximum
degradation and endset temperature respectively.
The weight loss in all the samples, up to about 150 °C results
from the evaporation of absorbed water. Degradation of PVA
occurs in two steps [37]. For pure PVA and SA-0, weight loss
during first degradation stage can be due to the formation of
polyethylene resulting from the dehydration and
depolymerization of PVA. During the second step after 385 °C
the residue resulting from the first stage undergoes the process
of intramolecular cyclization and producing some organic
volatiles [38]. After 500 °C weight loss percentage was
constant (Figure 4a) due to the carbonaceous mass formed
during the degradation of polymer which creates layer on the
polymer surface and hence prevents its further decomposition
[39]. The SA reinforced PVA composites exhibited two stage
decomposition like PVA and SA-0. The onset temperature for
PVA-SA composites was found to increase with incorporation
of fiber in the matrix. A shift of around 20 °C was realized in
the first degradation stage of SA-4 with the highest value of
onset degradation temperature (To) around 290 °C in
comparison to PVA. The maximum degradation temperature
(Tmax) and maximum weight loss rate (MWLR) for
PVA/composites showed a slight variation during the first
degradation stage (Figure 4b). However, these values were
found to be significant in the second degradation stage (Table
3).
All the observations apparently showing that the mechanism of
thermal decomposition differs for PVA, SA-0 and its
composites. The improvement in thermal stability of SA-0 with
the addition of fiber is indicated by a shift in its onset
degradation temperature to the higher side. The increase in
thermal stability can be explained in terms of interaction of
fiber with the hydroxyl group of PVA forming a complex as
confirmed from the IR spectra of PVA/SA composite films.
Moreover, boric acid played an important role as a cross linking
agent between PVA and fiber, resulting in the high thermal
stability of PVA/SA composite films [31]. Among the
composite films, SA-4 showed the highest thermal stability;
followed by SA-6 and SA-2. The reason for observing a
decrease in thermal stability from SA-4 to SA-6 can be
explained in such a way that at high fiber loading the
homogeneous dispersion of fiber could not take place and
resulting adhesion between fiber and matrix reduced and hence
decreased the thermal stability. The above statement can be
generalized by saying that with increase in the fiber loading
thermal stability increases up to 10% and the order is SA-4 >
SA-6 >SA-2.
Kinetic Study
Kinetic parameters comprising of degradation temperature
range and activation energy (Ea) for both the stages were
calculated and are summarized in Table 4. It can be inferred
that in case of most thermally stable composite SA-4, the
activation energy value was less during first degradation stage
and high during second degradation stage in comparison to SA-
0. This shows that although the degradation of SA-4 occurs at
high temperature but once it starts, it degrades much faster in
comparison to SA-0 during first degradation stage.
Table 4: Kinetic parameters in the thermal decomposition of
PVA and composite films
Sample
index
Degradation
temperature
range (°C)
Activation Energy (kJ/mol)
and Regression Coefficient
Coats-
Redfern
R2 Horowitz-
Metzger
R2
PVA 268-368 53.94 0.984 62.79 0.986
388-448 41.78 0.987 37.10 0.995
SA-0 262-362 67.48 0.979 76.80 0.976
396-436 54.12 0.980 45.51 0.985
SA-2
282-362 63.46 0.983 66.60 0.967
392-442 57.20 0.968 49.23 0.976
SA-4 290-370 60.65 0.995 66.99 0.986
390-450 77.92 0.975 73.08 0.986
SA-6 288-368 58.52 0.981 64.37 0.977
398-438 58.87 0.973 49.74 0.978
Optical Property
The light absorbance of composite films at wavelengths from
200 and 800 nm were recorded [40] and shown in Figure 5.
Virgin PVA and composite films showed the absorbance in the
range of 200-300 nm with maximum at 248 for pure PVA and
252 for SA-0. On increasing the fiber loading the absorption
region shifted towards the higher wavelengths. At the same
wavelength, SA-5 showed the highest absorbance with
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 1 (2019) pp. 170-179
© Research India Publications. http://www.ripublication.com
176
maximum obtained at 272 nm. An increase in
absorbance/intensity of absorption with addition of fiber is an
evidence of occurring electronic interactions in composite films
[41]. The enhancement in intensity of composite films showed
the localization of SA fiber between PVA chains [13].
However, no significant changes were observed in the
absorption spectrum of SA-6 showing that with further loading
of fiber homogeneous dispersion could not take place and
hence not any observable change in its absorbance value.
300 400 500 600 700 800
0.0
0.5
1.0
1.5
2.0
2.5
3.0
Ab
so
rba
nc
e (
a.u
.)
Wavelength (nm)
PVA
SA-0
SA-1
SA-2
SA-3
SA-4
SA-5
SA-6
Figure 5: Absorbance spectra of composite films as a
function of wavelength (nm)
Mechanical Properties
Table 5: Mechanical Properties of Polymer Composite Films
Sample
Index
Percentage
Elongation
Ultimate Tensile
Strength (MPa)
Young’s
Modulus (MPa)
PVA 161.6± 2.0 30.2 ± 1.0 98.2± 3.8
SA-0 168.0± 2.3 25.1 ± 1.1 79.2± 3.2
SA-1 164.6± 2.6 27.2± 1.2 133.6± 4.1
SA-2 162.3± 2.6 29.9± 1.2 149.6± 4.9
SA-3 148.3± 2.3 31.8± 1.0 154.8± 3.6
SA-4 111.6± 1.8 35.0± 1.2 179.8± 4.9
SA-5 82.0± 2.0 38.1± 1.1 204.6± 5.1
SA-6 72.6± 2.6 30.9± 1.1 285.4± 6.6
The Elongation (%), Ultimate Tensile Strength (UTS) and
Young’s Modulus calculated from the stress-strain (%)
relationship diagrams are reported in Table 5. Tensile strength
of polymer composite films was found to improve in
comparison to virgin. An addition of SA fiber increased the
tensile strength of the films up to 12.5% loading (Figure 6a).
PVA SA-0 SA-1 SA-2 SA-3 SA-4 SA-5 SA-6
0
5
10
15
20
25
30
35
40
Te
ns
ile
Str
en
gth
(M
Pa
)
Polymer Films
(a)
PVA SA-0 SA-1 SA-2 SA-3 SA-4 SA-5 SA-6
0
50
100
150
200
250
300
Yo
un
g's
Mo
du
lus
(M
Pa
)
Polymer Films
(b)
Figure 6: (a) Tensile strength (MPa) and (b) Young’s
modulus (MPa) of polymer composite films
This implies that PVA-SA composites can withstand much
greater stress without undergoing any irreversible deformation.
The reason for obtaining high tensile strength can be due to the
hydrophilic nature of PVA which results in a strong interface
bonding between hydroxyl groups of fiber with PVA [42]. A
further addition of fiber (SA-6) led to the significant decrease
in UTS. The decrease in tensile strength was due to the super-
saturation of particles in the composite films, due to which the
enhancement of particle-particle interfacial interaction takes
place rather than particle-PVA interaction [43]. It can also be
said that with increase in further loading of fiber the nature of
adhesion resulted between fiber and matrix was poor which led
to an increase in number of void formation in composite film.
Due to which enhancement in the formation of micro cracks at
the interface of composite film took place and reducing the
tensile strength [44]. The decrease in elongation was also
observed continuously with an increase in the loading. Young’s
modulus of the natural fiber reinforced polymer composites
generally increases with increasing the fiber amount [6, 45]. In
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 1 (2019) pp. 170-179
© Research India Publications. http://www.ripublication.com
177
the present study also, Young’s modulus was found to increase
continuously up to fiber loading of 15% (Figure 6b) and is an
indication of difficulty obtained during stretching the films in
an elastic way. It can be inferred that 12.5% loading of SA fiber
reinforced in PVA matrix gives the optimum results of tensile
strength.
Scanning Electron Microscopy (SEM) Analyses
The SEM photographs of the cross-sections of PVA, SA-0,
SA-3 and SA-5 are shown in Figure 7. It was observed that
surface of pure PVA film was smooth [46] (Figure 7a). An
obvious aggregation of PEG was observed in SEM photograph
of SA-0 (Figure 7b). On the introduction of fiber, contraction
in the surface of the produced film (SA-5) was observed as
shown in Figure 7c. Surface roughness was increased with high
fiber content. It was also observed that fiber dispersed more
homogeneously with its loading up to 12.5% in PVA matrix.
On further addition of fiber (SA-6), roughness level and
cracking of surface was enhanced, showing that the
homogeneous dispersion of fiber can’t take place further with
high loading (Figure 7d).
(a)
(b)
(c)
(d)
Figure 7: SEM photographs of (a) PVA and (b) SA-0 and
(c) SA-5 and (d) SA- 6
CONCLUSIONS
In this work, PVA has been blended with PEG-6000
(plasticizer), boric acid (cross-linking agent) and Sterculia alata leaf fiber to form the polymer composite films and were
characterized by different techniques. FTIR studies confirmed
the presence of interactions involved in PVA matrix with SA
fiber. Polymer films exhibited decrease in water uptake
percentage with fiber loading. Soil burial test confirmed fairly
good biodegradability of PVA/SA composites in comparison of
PVA and SA-0. Addition of fiber enhanced the thermal
stability. Tensile strength with 12.5 % loading was found to be
maximum. Light absorbance of the composite films against UV
light was also found to be improved.
ACKNOWLEDGEMENT
Financial support from the University Grant Commission
(UGC), New Delhi as Junior Research Fellowship, award letter
no. 21/06/2015 (i) EU-V to Kapil Gulati is gratefully
acknowledged. Acknowledgement is also due to Chairman,
Chemistry department, Kurukshetra University, Kurukshetra
for providing necessary laboratory facilities.
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 1 (2019) pp. 170-179
© Research India Publications. http://www.ripublication.com
178
REFERENCES
[1] Winandy J, Williams R, Rudie A and Ross R.
Opportunities for using wood and biofibers for
energy, chemical feedstocks, and structural
applications. Properties and Performance of Natural-
Fibre Composites. Elsevier, 2008, p. 330-55.
[2] Yang H-S, Kim H-J, Park H-J, Lee B-J and Hwang T-
S. Effect of compatibilizing agents on rice-husk flour
reinforced polypropylene composites. Composite
Structures. 2007; 77: 45-55.
[3] Väisänen T, Das O and Tomppo L. A review on new
bio-based constituents for natural fiber-polymer
composites. Journal of Cleaner Production. 2017; 149:
582-96.
[4] Puglia D, Biagiotti J and Kenny J. A review on natural
fibre-based composites—Part II: Application of
natural reinforcements in composite materials for
automotive industry. Journal of Natural Fibers. 2005;
1: 23-65.
[5] Mishra S, Misra M, Tripathy S, Nayak S and Mohanty
A. Potentiality of pineapple leaf fibre as reinforcement
in PALF-polyester composite: Surface modification
and mechanical performance. Journal of Reinforced
Plastics and Composites. 2001; 20: 321-34.
[6] Ku H, Wang H, Pattarachaiyakoop N and Trada M. A
review on the tensile properties of natural fiber
reinforced polymer composites. Composites Part B:
Engineering. 2011; 42: 856-73.
[7] Khan T, Hameed Sultan MTB and Ariffin AH. The
challenges of natural fiber in manufacturing, material
selection, and technology application: A review.
Journal of Reinforced Plastics and Composites. 2018;
37: 770-9.
[8] Jayaramudu J, Guduri B and Rajulu AV.
Characterization of natural fabric Sterculia urens.
International Journal of Polymer Analysis and
Characterization. 2009; 14: 115-25.
[9] Mohanty A, Tripathy P, Misra M, Parija S and Sahoo
S. Chemical modification of pineapple leaf fiber: graft
copolymerization of acrylonitrile onto defatted
pineapple leaf fibers. Journal of Applied Polymer
Science. 2000; 77: 3035-43.
[10] Kengkhetkit N and Amornsakchai T. Utilisation of
pineapple leaf waste for plastic reinforcement: 1. A
novel extraction method for short pineapple leaf fiber.
Industrial Crops and Products. 2012; 40: 55-61.
[11] Paradossi G, Cavalieri F, Chiessi E, Spagnoli C and
Cowman MK. Poly (vinyl alcohol) as versatile
biomaterial for potential biomedical applications.
Journal of Materials Science: Materials in Medicine.
2003; 14: 687-91.
[12] 12. Mallakpour S and Jarang N. Mechanical, thermal
and optical properties of nanocomposite films
prepared by solution mixing of poly (vinyl alcohol)
with titania nanoparticles modified with citric acid and
vitamin C. Journal of Plastic Film & Sheeting. 2016
;32: 293-316.
[13] Mohammad Mahdi Dadfar S, Kavoosi G and
Mohammad Ali Dadfar S. Investigation of mechanical
properties, antibacterial features, and water vapor
permeability of polyvinyl alcohol thin films
reinforced by glutaraldehyde and multiwalled carbon
nanotube. Polymer Composites. 2014; 35: 1736-43.
[14] Pšeja J, Charvátová H, Hruzík P, Hrnčiřík J and Kupec
J. Anaerobic biodegradation of blends based on
polyvinyl alcohol. Journal of Polymers and the
Environment. 2006; 14: 185-90.
[15] Sreedhar B, Sairam M, Chattopadhyay D, Rathnam P
and Rao D. Thermal, mechanical, and surface
characterization of starch–poly (vinyl alcohol) blends
and borax-crosslinked films. Journal of Applied
Polymer Science. 2005; 96: 1313-22.
[16] Uslu I, Daştan H, Altaş A, Yayli A, Atakol O and
Aksu M. Preparation and Characterization of
PVA/Boron Polymer Produced by an Electrospinning
Technique. e-Polymers. 2007; 7.
[17] Yin Y, Li J, Liu Y and Li Z. Starch crosslinked with
poly (vinyl alcohol) by boric acid. Journal of Applied
Polymer Science. 2005; 96: 1394-7.
[18] Arora S, Kumar M and Kumar M. Flammability and
thermal degradation studies of PVA/rice husk
composites. Journal of Reinforced Plastics and
Composites. 2012; 31: 85-93.
[19] Nath DCD, Bandyopadhyay S, Yu A, Blackburn D
and White C. High strength bio-composite films of
poly (vinyl alcohol) reinforced with chemically
modified-fly ash. Journal of materials science. 2010;
45: 1354-60.
[20] Sreedhar B, Chattopadhyay D, Karunakar MSH and
Sastry A. Thermal and surface characterization of
plasticized starch polyvinyl alcohol blends
crosslinked with epichlorohydrin. Journal of Applied
Polymer Science. 2006; 101: 25-34.
[21] Hu G, Cai S, Zhou Y, Zhang N and Ren J. Enhanced
mechanical and thermal properties of poly (lactic
acid)/bamboo fiber composites via surface
modification. Journal of Reinforced Plastics and
Composites. 2018; 37: 841-52.
[22] Jayaramudu J, Reddy DJ, Guduri BR, Rajulu AV.
Tensile properties of polycarbonate coated natural
fabric Sterculia Urens: Effect of coupling agent.
Iranian Polymer Journal. 2209: 693-1.
[23] Jeurissen S, Andersen JH, DiNovi M, Folmer D,
Schlatter J and Wallin H. Polyvinyl alcohol (PVA)–
polyethylene glycol (PEG) graft copolymer. Who
Food Additives Series. World Health Organization,
2016, p. 88-106.
International Journal of Applied Engineering Research ISSN 0973-4562 Volume 14, Number 1 (2019) pp. 170-179
© Research India Publications. http://www.ripublication.com
179
[24] Guohua Z, Ya L, Cuilan F, Min Z, Caiqiong Z and
Zongdao C. Water resistance, mechanical properties
and biodegradability of methylated-cornstarch/poly
(vinyl alcohol) blend film. Polymer Degradation and
stability. 2006; 91: 703-11.
[25] Bana R and Banthia A. Green composites:
development of poly (vinyl alcohol)-wood dust
composites. Polymer-Plastics Technology and
Engineering. 2007; 46: 821-9.
[26] Sarah S, Rahman W, Majid R, et al. Optimization of
Pineapple Leaf Fibre Extraction Methods and Their
Biodegradabilities for Soil Cover Application. Journal
of Polymers and the Environment. 2018; 26: 319-29.
[27] Coats AW and Redfern J. Kinetic parameters from
thermogravimetric data. Nature. 1964; 201: 68.
[28] Horowitz HH and Metzger G. A new analysis of
thermogravimetric traces. Analytical Chemistry.
1963; 35: 1464-8.
[29] Kanatt SR, Rao M, Chawla S and Sharma A. Active
chitosan–polyvinyl alcohol films with natural
extracts. Food Hydrocolloids. 2012; 29: 290-7.
[30] C.A. Finch. Chemical reactions and stereochemistry
of polyvinyl alcohol. Polyvinyl alcohol, Wiley and
Sons, London, 1992, p. 269.
[31] Lum YH, Shaaban A, Mohamad N, Dimin F, Yatim
NM. Boric acid modified starch polyvinyl alcohol
matrix for slow release fertilizer. e-Polymers. 2016
Mar 1;16(2):151-8.
[32] Ooi ZX, Chan KL, Ewe CY, Muniyadi M, Teoh YP,
Ismail H. Evaluation of Water Affinity and Soil Burial
Degradation of Thermoplastic Film Derived from Oil
Palm Ash-filled Polyvinyl Alcohol. BioResources.
2017 Apr 24;12(2):4111-22.
[33] Yang H-S, Yoon J-S and Kim M-N. Dependence of
biodegradability of plastics in compost on the shape
of specimens. Polymer degradation and stability.
2005; 87: 131-5.
[34] Ooi Z, Ismail H, Abu Bakar A and Aziz N. Effects of
jackfruit waste flour on the properties of poly (vinyl
alcohol) film. Journal of Vinyl and Additive
Technology. 2011; 17: 198-208.
[35] Shaini VP, Jayasree S. Isolation and characterization
of lipase producing bacteria from windrow compost.
Int. J. Curr. Microbiol. App. Sci. 2016;5(5):926-33.
[36] Pradhan S, Mohanty S, Nayak SK. In-Situ Aerobic
Biodegradation Study of Epoxy-Acrylate Film in
Compost Soil Environment. Journal of Polymers and
the Environment. 2018 Mar 1;26(3):1133-44.
[37] Zhou X-Y, Jia D-M, Cui Y-F and Xie D. Kinetics
analysis of thermal degradation reaction of PVA and
PVA/starch blends. Journal of Reinforced Plastics and
Composites. 2009; 28: 2771-80.
[38] Gilman J, VanderHart D and Kashiwagi T. Fire and
polymers II: materials and test for hazard prevention.
ACS Symposium Series. 1994, p. 161.
[39] Singh R, Kulkarni SG and Channe SS. Thermal and
mechanical properties of nano-titanium dioxide-
doped polyvinyl alcohol. Polymer bulletin. 2013; 70:
1251-64.
[40] Mallakpour S and Dinari M. Enhancement in thermal
properties of poly (vinyl alcohol) nanocomposites
reinforced with Al2O3 nanoparticles. Journal of
Reinforced Plastics and Composites. 2013; 32: 217-
24.
[41] Aziz SB, Ahmed HM, Hussein AM, Fathulla AB,
Wsw RM, Hussein RT. Tuning the absorption of
ultraviolet spectra and optical parameters of
aluminum doped PVA based solid polymer
composites. Journal of Materials Science: Materials in
Electronics. 2015 Oct 1;26(10):8022-8.
[42] Bhatnagar A and Sain M. Processing of cellulose
nanofiber-reinforced composites. Journal of
Reinforced Plastics and Composites. 2005; 24: 1259-
68.
[43] Nath DC, Bandyopadhyay S, Boughton P, Yu A,
Blackburn D, White C. Chemically modified fly ash
for fabricating super-strong biodegradable poly (vinyl
alcohol) composite films. Journal of Materials
Science. 2010 May 1;45(10):2625-32.
[44] Thwe MM, Liao K. Effects of environmental aging on
the mechanical properties of bamboo–glass fiber
reinforced polymer matrix hybrid composites.
Composites Part A: Applied Science and
Manufacturing. 2002 Jan 1;33(1):43-52.
[45] Malkapuram R, Kumar V, Negi YS. Recent
development in natural fiber reinforced polypropylene
composites. Journal of Reinforced Plastics and
Composites. 2009 May;28(10):1169-89.
[46] Chen Y, Cao X, Chang PR, Huneault MA.
Comparative study on the films of poly (vinyl
alcohol)/pea starch nanocrystals and poly (vinyl
alcohol)/native pea starch. Carbohydrate Polymers.
2008 Jul 4;73 (1):8-17.