1. J Polym Environ
DOI 10.1007/s10924-011-0357-6
ORIGINAL PAPER
Preparation and Characterization of Gamma Irradiated Sugar
Containing Starch/Poly (Vinyl Alcohol)-Based Blend Films
Fahmida Parvin • Mubarak A. Khan • A. H. M. Saadat •
M. Anwar H. Khan • Jahid M. M. Islam •
Mostak Ahmed • M. A. Gafur
Ó Springer Science+Business Media, LLC 2011
Abstract Blends based on different ratios of starch obtained after gamma irradiation on the film. The water up-
(35–20%) and plasticizer (sugar; 0–15%) keeping the take and degradation test in soil of the film were also
amount of poly(vinyl alcohol) (PVA) constant, were pre- evaluated. In this study, sugar acted as a good plasticizing
pared in the form of thin films by casting solutions. The agent in starch/PVA blend films, which was significantly
effects of gamma-irradiation on thermal, mechanical, and improved by gamma radiation and the prepared starch-
morphological properties were investigated. The studies of PVA-sugar blend film could be used as biodegradable
mechanical properties showed improved tensile strength packaging materials.
(TS) (9.61 MPa) and elongation at break (EB) (409%) of
the starch-PVA-sugar blend film containing 10% sugar. Keywords Biodegradable materials Á Blend film Á
The mechanical testing of the irradiated film (irradiated at Gamma irradiation Á Tensile properties Á Plasticizers
200 Krad radiation dose) showed higher TS but lower EB
than that of the non-radiated film. FTIR spectroscopy
studies supported the molecular interactions among starch, Introduction
PVA, and sugar in the blend films, that was improved
by irradiation. Thermal properties of the film were also Plastics are used as packaging materials due to their
improved due to irradiation and confirmed by thermo- excellent thermo-mechanical properties and for economical
mechanical analysis (TMA), differential thermo-gravimet- reasons. But use of these materials has become serious
ric analysis (DTG), differential thermal analysis (DTA), problems because of lack of recycling facilities or infra-
and thermo-gravimetric analysis (TGA). Surface of the structure, non-recyclability, non-renewability, non-biode-
films were examined by scanning electron microscope gradability or incorporation of toxic additives [1, 2].
(SEM) image that supported the evidence of crosslinking However, most of these plastics are petroleum-based syn-
thetic polymers, so the increase in their production results
in an increase of petroleum use and causes serious envi-
F. Parvin Á M. A. Khan (&) Á J. M. M. Islam Á M. Ahmed ronmental pollution, due to wasted and un-degraded
Institute of Radiation and Polymer Technology, Bangladesh
polymers [3]. One of the possibilities to solve the problems
Atomic Energy Commission, Dhaka, Bangladesh
e-mail: makhan.inst@gmail.com related to fossil resources and global environment is thor-
ough recycling wasted polymeric materials. The recycling
F. Parvin Á A. H. M. Saadat of wasted plastics is limited, whether materials recycling or
Department of Environmental Sciences, Jahangirnagar
chemical recycling consumes a considerable amount of
University, Savar, Dhaka, Bangladesh
thermal energy, and plastics cannot be recycled forever,
M. A. H. Khan i.e., wasted plastics are eventually destined to be burnt or
Department of Geography, University of California Berkeley, buried in landfills [4]. The use of biodegradable polymers
Berkeley, CA 94720, USA
for packaging offers an alternative and partial solution to
M. A. Gafur the problem of accumulation of solid waste composed of
PP and PDC, BCSIR, Dhaka, Bangladesh synthetic inert polymers [5]. These materials provide
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2. J Polym Environ
environmentally advantageous biodegradable alternatives Materials and Methods
to conventional non-biodegradable materials such as
polyethylene for many applications. Materials
Starch is a widely used material for making biode-
gradable plastics. Starch is an abundant, inexpensive, Starch (pH 6–7, sensitivity: complying, sulfated ash: maxi-
renewable and biodegradable material [6], but pure starch mum 0.5%) was supplied from Sigma–Aldrich Chemie
lacks the strength, water resistibility, processability, and Gmbh, Germany. Poly Vinyl Alcohol (Physical state: White
thermal stability. To overcoming these drawbacks, blend- flake, Density: 1.19–1.31 g/cm3, Specific Gravity: 1.19–1.31)
ing of starch or its derivatives with various thermoplastic was obtained from Merck, Germany. Sugar (Sucrose, white
polymers [7, 8] and adding plasticizers have been investi- crystalline disaccharide, C12H22O11) was purchased from
gated enormously. Among the existing synthesized poly- local market (Fresh Company Ltd, Bangladesh). The water
mers, Poly(vinyl alcohol) (PVA) possesses many useful used to prepare starch/PVA blend films was distilled after
properties, such as excellent chemical resistance, good film deionization.
forming capability, having emulsifying and adhesive
properties, water solubility, high thermal stability, and an Preparation of Starch/PVA/Sugar Film
excellent biocompatibility [5]. Due to its excellent optical
and physical properties, PVA is successfully used in a wide Films were prepared by the casting method. At first, starch
range of industrial fields [2, 9–13]. The strength, flexibility with PVA and sugar were blended in hot water at 150 °C
and water resistance of starch productions improved when for 1 h to form a homogeneous gel like solution. This
PVA was added [14]. solution was used to prepare several formulations with
Starch and PVA can be successfully used to form edible varying starch and sugar concentration keeping PVA con-
or biodegradable film [15]. A major component of edible centration constant. The mixing composition is shown in
films is the plasticizer. The addition of a plasticizing agent Table 1. The solutions were then poured up to a thickness
to edible films is required to overcome film brittleness, of 4 mm on the silicon paper covered glass plate. Water
caused by high intermolecular forces. Plasticizers reduce was evaporated from the moulds in an oven at 50 °C for
these forces and increase the mobility of polymer chains, 10 h. After cooling the dried films at room temperature for
thereby improving flexibility, processability and extensi- 72 h, they were peeled from the silicon cloth and cut into
bility of the film. On the other hand, plasticizers generally small pieces of length 70 mm and width 10 mm. The
decrease gas, water vapor and solute permeability of the average thickness of the dried films was about 0.3 mm. The
film and can decrease elasticity and cohesion [4, 16, 17]. In films were stored 24–48 h in a dessiccator at room tem-
recent years large number of researches have been per- perature (30 °C) and at RH 65% prior to performing the
formed on the plasticization of starch/PVA blends using measurements.
glycerol [18, 19], sorbital [20, 21], urea [22], citric acid
[20, 23], as well as complex plasticizers [24]. However, Gamma Irradiation of the Film
few works have been performed on sugar, especially
sucrose, which acts as a plasticizer [25]. After making films from different formulations, the film
Commercially, biodegradable starch/PVA plastics, ‘Mater- having best mechanical property (e.g., tensile strength and
bi’ (physically blended 60% starch, 40% modified PVA and elongation at break) was chosen for irradiation by gamma
plasticizers), have been produced in Japan [26]. Due to the rays (60Co gamma source, Inter Professional Investment
chemical reaction between PVA and starch molecules in PVA/ Ltd, UK). The film was irradiated with 350 krad/h dose
starch blend systems induced by irradiation, the tensile strength rate at different doses of 0, 25, 50, 100, 200, 500 krad and
of PVA hydrogels was improved significantly. Radiation after 24 h, mechanical, thermal and water absorption
technology has already been successfully used to improve the properties of the films were studied.
properties of plastic products in many occasions [27, 28].
Starch/PVA grafted hydrogels have also been prepared by
irradiation technology [11]. In this study, we prepared starch/ Table 1 Composition of starch/PVA/sugar blends (%, w/w)
PVA based plastic sheets by inducing chemical reaction Formulation Percentage of Percentage of Percentage of
between starch and PVA molecules under the action of ion- starch PVA sugar
izing radiation. The aim of this study was to evaluate the effect
F1 35 65 0
of sugar (as a plasticizer) in starch/PVA based films. The
F2 30 65 5
effects of gamma radiation on the mechanical, thermal and
F3 25 65 10
water absorption properties of the prepared films were also
studied in the study. F4 20 65 15
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3. J Polym Environ
Characterization Methods Electron Microscope (SEM) at an accelerating voltage of
2 kV. The SEM specimens were sputter-coated with gold.
Tensile Properties Testing
Soil Burial Test
Tensile strength (TS) and elongation at break (EB) of the
films (both irradiated and non-irradiated) were measured The degradation tendency of the films (both irradiated and
with universal Testing Machine (Hounsfield Series S, UK). non-irradiated) in the soil was studied. The films were
Each piece of the film had a length of 20 mm and width of buried in soil for (1, 2, 3, 4, 5, 6) weeks. Moisture content
10 mm. Crosshead speed was 2 mm/min and gauge length of the soil was maintained at around 15–18%. In every
was 20 mm with load capacity of 500 N. ASTM D882 was week, samples were taken out from the soil. After cleaning
followed for the tensile test and five replicates were tested carefully with water and drying at room temperature, their
for each sample to assess the precision of the method. All weight changes were measured [29]. Weight changes (%)
the tests were carried out at 20 °C and 50% RH. were determined using the following equation:
Wg ¼ ðWa À Wo Þ=Wa  100;
Fourier Transformed Infrared Spectroscope (FTIR)
where, Wa and Wo were the weights of the sample before
The IR spectra of the films were measured by FTIR Spec- and after soil burial treatment.
trophotometer (Perkin Elmer, UK). The FTIR spectrum was The changes in physical appearance were also deter-
taken in a transmittance mode. The spectra were obtained at mined by comparing the photographs of the films taken
a resolution of 8 cm-1 in the range of 650–4,000 cm-1. before and after soil burial treatment.
Swelling Degree
Results and Discussion
The swelling degree of the irradiated and non-irradiated
films was monitored (up to 120 min) to find the profile of Effect of Sugar and Starch on Tensile Properties
water uptake. Water uptake was determined using the of the Film
following equation.
As polymeric films may be subjected to various kinds of
Wg ¼ ðWa À Wo Þ=Wo  100
stresses during being used, the study of the mechanical
where, Wg and Wa were the weights of the sample after and properties (tensile strength, elasticity, etc.) is of primary
before soaking in water. importance for determining the performance of the mate-
rials [5]. Figure 1 and 2 show the tensile strength and
Thermal Analysis elongation at break of the starch/PVA/sugar blend film as a
function of both starch and sugar contents, respectively.
The thermal test of the films was performed using computer Starch and sugar content show the contrary effects on the
controlled TG/DTA 6300 system controlled to an EXSTAR tensile properties of the films. The tensile strength (TS) and
6000 STATION, Seiko Instrument Inc., Japan. The TG/ the elongation at break (EB) of the film increased initially
DTA module used a horizontal system balance mechanism. with the increase of sugar content and decrease of starch
All the experiments were performed under nitrogen atmo- content and after reaching a maximum value, TS and EB
sphere. Sample weights were 8–10 mg, and heating rate was values began to decrease. Previous study [30] suggested
10 °C/min within the temperature range of 50–600 °C. that TS of the film decreased with increasing starch content
of the polymeric film. In this study, the TS of the films
Thermo-Mechanical Analysis (F3, 10% sugar and F2, 5% sugar) were found to be higher
than that of the film (F1, without sugar). The increased
Glass transition temperatures were measured for all the sugar content in both F3 and F2 usually tends to reduce the
materials using thermo-mechanical analyzer (TMA) Lien- tensile strength of the film. But the strength of both of the
sis 200 with an instrumental precision of ±3 °C. The films has increased in the study due to the decrease of
temperature range was 60–220 °C. starch content. The EB of the films (F2, 5% sugar and F1,
without sugar) was found to be lower than that of the films
Morphological Study (F3, 10% sugar and F4, 15% sugar) because of increasing
of the sugar content. The increase of the sugar content in
The morphological studies of the (irradiated and non-irra- the film favors the plasticizing effect that increases the
diated) blend films were done using a JEOL 6400 Scanning flexibility and elongation at break of a polymer [25, 31].
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4. J Polym Environ
Fig. 3 Effect of gamma irradiation on the tensile strength and
elongation at break of the starch/PVA/sugar blend (F3) film
Fig. 1 Effect of sugar and starch on the tensile strength of the starch/
PVA/sugar blend film blend films with different irradiation doses (25, 50, 100,
200, 500 krad) are shown in Fig. 3. Tensile strength of the
starch/PVA/sugar blend film (F3) was found to be lower
(9.02 MPa at 25 krad and 9.47 MPa at 50 krad) than that of
the untreated film (9.61 MPa). The film showed poor
mechanical properties at low radiation dose, as the amor-
phous part of the starch degraded for the weak intra-
molecular bonds [32]. The highest TS (12 MPa) of the
irradiated film was observed at 200 krad radiation dose. A
higher radiation dose produces a denser network structure
because of the increased crosslinking or chain scission that
leads to the enhancement of mechanical properties such as
TS, modulus of elasticity, hardness and softening temper-
ature. A further increase of radiation dose ([500 krad)
causes a decrease of TS (9 MPa) because of the degrada-
tion of the polymeric film at higher radiation dose. Previ-
ous studies [32, 33] reported similar trends in where the
Fig. 2 Effect of sugar and starch on the elongation at break of the tensile strength of the film decreased at low irradiation
starch/PVA/sugar blend film dose; then increased with an increase of the irradiation
dose, but when the dose was further increased, the TS
The maximum EB was found at a value of 409% for the decreased with increasing irradiation dose.
film (F3, 10% sugar). The TS and EB of the film (F4, 15% Percent elongation indicates the flexibility of the film. In
sugar) began to decrease with further increasing the sugar this study, the EB value of the irradiated film (e.g., 222% at
content. An increase in the plasticizer concentration 25 krad) was found to be significantly lower than that of
resulted in decreasing the cohesive force of attraction the non-radiated film (409%). The higher radiation dose
between PVA and plasticizer or starch and plasticizer. The (500 krad) also showed the lowest EB (130%). High-
plasticizers are expected to reduce the modulus, tensile energy radiation (usually gamma radiation) causes chain
strength and hardness of the polymer [31]. Since F3 com- scission of polymer that leads to the decrease of the EB
position exhibited the optimum performance for both ten- values [32].
sile strength and elongation at break, this composition was
used for further investigation.
FTIR Analysis of the Film
Effect of Gamma Irradiation on the Mechanical
Properties of the Film Figure 4 represents the comparison of FTIR spectra of
pure PVA, non-radiated starch/PVA/sugar film and irra-
The effects of gamma irradiation of 350 krad/h dose rate diated starch/PVA/sugar film. In this analysis, it was
on the mechanical properties of the starch/PVA/sugar attempted to characterize the incorporation of sugar and
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5. J Polym Environ
Fig. 4 The FTIR spectrum of
film: a pure PVA, b starch/
PVA/sugar blend (F3) film,
c gamma- irradiated starch/
PVA/sugar blend (F3) film
starch into the PVA-based film without radiation and Scanning Electron Microscope Image analysis
under gamma radiation and then distinguish the IR bands
and vibrations shifts related to sugar and starch interac- The surface topography of pure PVA, non-radiated and
tions with PVA and molecular interaction due to gamma gamma–irradiated starch/PVA/sugar blend (for formula-
irradiation. tions F3) films were studied with SEM (See Fig. 5). The
Starch and PVA molecules are in general associated surface of pure PVA film was found quite smooth and
with inter- and intra-molecular hydrogen bonding in the homogeneous. The surface of starch/PVA/sugar blend film
blends. The cross-linking of these blends results in a (F3) appeared to be slightly rougher and more condensed
decrease in the intermolecular hydrogen bonds. The pure due to the incorporation of the starch and the sugar in film
PVA spectrum are mainly assignable to the hydrogen formulation. The surface of gamma-irradiated starch/PVA/
bound O–H vibration at 3400 cm-1, stretching vibration of sugar blend film (F3) appeared to have stripes or fibrous
C–H or C–H2 at 2,900 cm-1, bending vibration of C–H or like in the surface. The SEM observations seem to support
C–H2 (asymmetric) at 1,542 cm-1, bending vibration of the FTIR structural analysis and provide evidence for the
CH or CH2 (symmetric) at 1,427 cm-1, stretching vibration enhanced properties by crosslinking obtained after gamma
of C–O at 1,047 cm-1 and bending vibration of C–H (out irradiation on the starch/PVA/sugar blend film.
of plane) at 917 cm-1, 830 cm-1 and 674 cm-1, respectively.
In the spectra of non-radiated starch/PVA/sugar film, the Thermal Analysis of the Films
absorption band at 3,380 cm-1 was broadened after starch
and sugar addition, related to the increase of typical Thermomechanical Analysis of the Film
hydrogen bound O–H vibration of semi-crystalline starch
and sugar indicating the formation of strong H-bond. The Thermomechanical analysis (TMA) was used to determine
shifting of the bending vibration of C–H2 from 1427 cm-1 gel-melting temperature of the film. The comparison of
to 1334 cm-1 and the broadening of the peak also con- onset of melting, glass transition (Tg) and offset of melting
firmed the formation of strong H-bond. In the FTIR spectra of the pure PVA, 35%starch/65%PVA, non-radiated and
of gamma-irradiated starch/PVA/sugar blend film, the irradiated 25%starch/65%PVA/10%sugar blend (formula-
absorption bands for most of the functional groups were tions F3) film are shown in Fig. 6. The onset of melting,
disappeared or weakened because the cross-linking of the glass transition, and offset of melting temperatures of the
film resulted in a decrease of the intermolecular hydrogen pure PVA film were found to be 198, 200 and 205 °C,
bonds. Only the peak at 3,622 cm-1 was broadened for the respectively. After blending starch with PVA the onset,
gamma-irradiated film because of the increasing number of glass transition and offset of melting temperature has
H-bonded OH vibration. decreased. As starch acting as filler in PVA based film, it
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6. J Polym Environ
Fig. 5 Scanning electron microscopic images: a pure PVA film, b non-radiated starch/PVA/sugar blend (F3) film, c gamma-irradiated starch/
PVA/sugar blend (F3) film
Fig. 6 The onset, glass point
and offset of melting
temperature of pure PVA,
starch/PVA, non-radiated and
gamma-irradiated starch/PVA/
sugar blend (F3) films
lowers the glass transition temperature of the blend film. gamma-irradiated film making a compact structure which
However, the incorporation of sugar into starch/PVA, the increased the thermal stability of the film.
onset, glass transition and offset of melting temperatures
(130, 137 and 143 °C, respectively) of the starch/PVA/ Thermo Gravimetric Analysis
sugar blend film decreased significantly. When sugar was
incorporated into the thermally stable starch/PVA, the Figure 7 shows the Thermo Gravimetric Analysis (TGA) of
melting temperature of the blend film was decreased, as pure PVA, 35%starch/65%PVA, non-radiated and irradi-
sugar work effectively to lower the glass transition tem- ated 25%starch/65%PVA/10%sugar blend (formulations
perature of the host polymer [31]. After irradiation of the F3) film. Pure PVA curve showed a two-step decomposition
film by gamma radiation, the onset, glass transition and pattern. The first step began at approximately 199 °C and
offset of melting temperatures of the starch/PVA/sugar the second one began at about 347 °C. The final temperature
blend film were regained (149, 166 and 177 °C, respec- of the decomposition was at 450 °C. The first step of weight
tively) slightly. This may be due to crosslinking in the loss could be attributed to the loss of loosely bound water,
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7. J Polym Environ
Fig. 8 Comparison of DTG of pure PVA, starch/PVA, non-radiated
Fig. 7 Comparison of TG of pure PVA, starch/PVA, non-radiated and gamma-irradiated film starch/PVA/sugar blend (F3) films
and gamma-irradiated starch/PVA/sugar blend (F3) films
non-radiated and irradiated 25%starch/65%PVA/10%sugar
accompanied by the formation of volatile disintegrated blend (formulations F3) film. Differential curves also indi-
products. The second step was mainly caused by the thermal cated similar effects of thermal stability (Fig. 7) of the films.
decomposition of the molecules and the products were The DTG curve of pure PVA film depicted one predominant
composed of small molecular carbon and hydrocarbon. peak at 378 °C in where the maximum degradation rate was
Starch/PVA film shows two major degradation stages. 2.17 mg/min. The DTG curve of the starch/PVA based film
The first degradation occurred at approximately 209.1 °C. depicts two peaks at 370 °C and 437 °C, where the maximum
This first degradation process could be attributed to the loss degradation rate was 0.621 mg/min. The DTG curve of non-
of water. The second degradation was started at about radiated starch/PVA/sugar blend (formulations F3) film
314.5 °C and this was attributed to the thermal degradation showed several broad peaks because of the incorporation of
of semi-crystalline starch. Nearly 50% degradation of the starch and sugar into the PVA film and the maximum deg-
film occurred at approximately 369.0 °C. The starch/PVA radation rate was found to be better than that of PVA and
blend film lost its 90.5% weight at 423.5 °C. starch/PVA film (0.79 mg/min at 363 °C). The DTG curve of
The TGA curve of non-radiated and irradiated starch/ gamma-irradiated starch/PVA/sugar blend (F3) films also
PVA/sugar blend (F3) films show higher rate of thermal showed several broad peaks in where the maximum degra-
degradation compared to pure PVA and starch/PVA film. dation rate was found to be 1.18 mg/min at 355 °C.
As sugar is sensitive to thermal degradation, the incorpo-
ration of sugar into starch/PVA film intensifies its thermal Differential Thermal Analysis (DTA)
degradation. However, irradiation of the film by gamma
radiation slightly decreases the rate of thermal degradation. Figure 9 shows the DTA curves of pure PVA, 35%starch/
This may be due to the crosslinking of the film, which 65%PVA, non-radiated and irradiated 25%starch/65%PVA/
increases the resistant to thermal degradation. The starch/ 10%sugar blend (formulations F3) film. The pure PVA
PVA/sugar blend (F3) film showed a two-step decompo- shows two endothermic peaks at 140 and 222 °C indicating
sition pattern as shown in Fig. 7. The first weight loss was the melting point of pure PVA and the loss of moisture,
at approximately 197 °C due to the loss of water. The respectively. Another endothermic peak at 361 °C indi-
second weight loss was started at approximately 296 °C cated the decomposition of the PVA chain. The curve of
due to the thermal degradation of starch/PVA/sugar blend the starch/PVA blend film depict two endothermic peaks at
(F3) and 50% degradation took place at approximately 138 °C and at 333 °C, indicating the melting point and
360 °C. At 420 °C, the starch/PVA/sugar blend (F3) films decomposition point of the starch/PVA containing film.
lost its 90% weight. The curve of the non-irradiated starch/PVA/sugar blend
(F3) film showed a new endothermic broad peak appeared
Differential Thermo Gravimetric Analysis in the temperature range of 120–330 °C due to the lower
melting temperature of the starch-PVA-sugar molecules.
Figure 8 shows the comparative Differential Thermo Gravi- Homogeneous polymer mixtures with a crystallizable
metric (DTG) studies of pure PVA, 35%starch/65%PVA, component usually show a decrease in experimental
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8. J Polym Environ
loss of the starch/PVA/sugar blend films (both irradiated
and non-irradiated) at room temperature (25 °C) for dif-
ferent periods of time (1, 3, 5, 10, 20, 40, 60 and 120 min).
The water absorption capacity of the irradiated Starch/
PVA/Sugar film showed lower than that of the non-radiated
Starch/PVA/Sugar film. The non-radiated film absorbed
water in a typical manner, i.e., initially gained very rapidly,
then steadily absorbed and finally lost its weight into the
medium. In contrast, the radiated film was more stable in
water and absorbed water slowly up to 120 min. Sufficient
intermolecular hydrogen bonding between the hydrocar-
bons groups of starch and PVA and sugar side chain favors
the water absorption in the film. The maximum degree of
swelling for the non-radiated film for 20 min is 160%
while that attained by radiated film for the same amount of
Fig. 9 Comparison of DTA of pure PVA, starch/PVA, non-radiated time is 95% as shown in Fig. 10. This large difference in
and gamma-irradiated film starch/PVA/sugar blend (F3) films the degree of swelling between irradiated and non-radiated
could be due to the increased degree of cross-linking
melting points with the addition of the amorphous com- between polysaccharide chain of starch and OH- groups of
ponent, because the interaction of the two polymers PVA and sugar that creates a three-dimensional compact
reduces the crystallite size. Significant changes of DTA structure. The compact irradiated film had a less chance for
curves of the blend films suggested the strong interactions the water molecule to be associated or absorbed within the
among starch, PVA and sugar molecules. The curve of the film.
gamma-irradiated starch/PVA/sugar blend (F3) film
showed a new exothermic peak appeared at 428 °C due to Soil Burial Test
the crosslinking of starch, PVA and sugar molecules.
Non-radiated and irradiated starch/PVA/sugar blend (for-
Water Absorption Test mulations F3) films were buried into the soil for comparative
degradation study of the film. The weight change of the film
As starch and sugar is sensitive to water, it affects the in soil burial test is presented in Fig. 11 and the picture of
mechanical properties of thermoplastic starch materials; the degraded films (42 days) is shown in Fig. 12. The non-
hence, any improvement in reducing water sensitivity and radiated film exhibit slightly higher weight change com-
enhancing water resistance of thermoplastic starch mate- pared to the gamma–irradiated starch/PVA/sugar blend
rials is highly important. Figure 10 shows the % weight (formulations F3) film. At initial stage the biodegradation
Fig. 10 Comparison of water uptake between gamma-irradiated and Fig. 11 Comparison of weight loss between gamma-irradiated and
non-radiated starch/PVA/sugar blend (F3) films at different soaking non-radiated starch/PVA/sugar blend (F3) films at different soil burial
times times
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9. J Polym Environ
Fig. 12 Photographs of the
gamma-irradiated and non-
irradiated starch/PVA/sugar
blend (F3) films after 42 days
of degradation
rate was higher, as the interaction of microorganism on Acknowledgments We thank the staff of Institute of Radiation and
starch and sugar molecule increased, the degradation was Polymer Technology, Bangladesh Atomic Energy Commission for
technical support and advice throughout the work.
accelerated. When the starch and sugar was almost fully
degraded, the PVA was further degraded, but the degra-
dation rate of PVA was slower than that of the starch and
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