ORIGINAL PAPER

Preparation and Characterization of Gamma Irradiated SugarContaining 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

� Springer Science+Business Media, LLC 2011

Abstract Blends based on different ratios of starch

(35–20%) and plasticizer (sugar; 0–15%) keeping the

amount of poly(vinyl alcohol) (PVA) constant, were pre-

pared in the form of thin films by casting solutions. The

effects of gamma-irradiation on thermal, mechanical, and

morphological properties were investigated. The studies of

mechanical properties showed improved tensile strength

(TS) (9.61 MPa) and elongation at break (EB) (409%) of

the starch-PVA-sugar blend film containing 10% sugar.

The mechanical testing of the irradiated film (irradiated at

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,

PVA, and sugar in the blend films, that was improved

by irradiation. Thermal properties of the film were also

improved due to irradiation and confirmed by thermo-

mechanical analysis (TMA), differential thermo-gravimet-

ric analysis (DTG), differential thermal analysis (DTA),

and thermo-gravimetric analysis (TGA). Surface of the

films were examined by scanning electron microscope

(SEM) image that supported the evidence of crosslinking

obtained after gamma irradiation on the film. The water up-

take and degradation test in soil of the film were also

evaluated. In this study, sugar acted as a good plasticizing

agent in starch/PVA blend films, which was significantly

improved by gamma radiation and the prepared starch-

PVA-sugar blend film could be used as biodegradable

packaging materials.

Keywords Biodegradable materials � Blend film �Gamma irradiation � Tensile properties � Plasticizers

Introduction

Plastics are used as packaging materials due to their

excellent thermo-mechanical properties and for economical

reasons. But use of these materials has become serious

problems because of lack of recycling facilities or infra-

structure, non-recyclability, non-renewability, non-biode-

gradability or incorporation of toxic additives [1, 2].

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-

ronmental pollution, due to wasted and un-degraded

polymers [3]. One of the possibilities to solve the problems

related to fossil resources and global environment is thor-

ough recycling wasted polymeric materials. The recycling

of wasted plastics is limited, whether materials recycling or

chemical recycling consumes a considerable amount of

thermal energy, and plastics cannot be recycled forever,

i.e., wasted plastics are eventually destined to be burnt or

buried in landfills [4]. The use of biodegradable polymers

for packaging offers an alternative and partial solution to

the problem of accumulation of solid waste composed of

synthetic inert polymers [5]. These materials provide

F. Parvin � M. A. Khan (&) � J. M. M. Islam � M. Ahmed

Institute of Radiation and Polymer Technology, Bangladesh

Atomic Energy Commission, Dhaka, Bangladesh

e-mail: makhan.inst@gmail.com

F. Parvin � A. H. M. Saadat

Department of Environmental Sciences, Jahangirnagar

University, Savar, Dhaka, Bangladesh

M. A. H. Khan

Department of Geography, University of California Berkeley,

Berkeley, CA 94720, USA

M. A. Gafur

PP and PDC, BCSIR, Dhaka, Bangladesh

123

J Polym Environ

DOI 10.1007/s10924-011-0357-6

environmentally advantageous biodegradable alternatives

to conventional non-biodegradable materials such as

polyethylene for many applications.

Starch is a widely used material for making biode-

gradable plastics. Starch is an abundant, inexpensive,

renewable and biodegradable material [6], but pure starch

lacks the strength, water resistibility, processability, and

thermal stability. To overcoming these drawbacks, blend-

ing of starch or its derivatives with various thermoplastic

polymers [7, 8] and adding plasticizers have been investi-

gated enormously. Among the existing synthesized poly-

mers, Poly(vinyl alcohol) (PVA) possesses many useful

properties, such as excellent chemical resistance, good film

forming capability, having emulsifying and adhesive

properties, water solubility, high thermal stability, and an

excellent biocompatibility [5]. Due to its excellent optical

and physical properties, PVA is successfully used in a wide

range of industrial fields [2, 9–13]. The strength, flexibility

and water resistance of starch productions improved when

PVA was added [14].

Starch and PVA can be successfully used to form edible

or biodegradable film [15]. A major component of edible

films is the plasticizer. The addition of a plasticizing agent

to edible films is required to overcome film brittleness,

caused by high intermolecular forces. Plasticizers reduce

these forces and increase the mobility of polymer chains,

thereby improving flexibility, processability and extensi-

bility of the film. On the other hand, plasticizers generally

decrease gas, water vapor and solute permeability of the

film and can decrease elasticity and cohesion [4, 16, 17]. In

recent years large number of researches have been per-

formed on the plasticization of starch/PVA blends using

glycerol [18, 19], sorbital [20, 21], urea [22], citric acid

[20, 23], as well as complex plasticizers [24]. However,

few works have been performed on sugar, especially

sucrose, which acts as a plasticizer [25].

Commercially, biodegradable starch/PVA plastics, ‘Mater-

bi’ (physically blended 60% starch, 40% modified PVA and

plasticizers), have been produced in Japan [26]. Due to the

chemical reaction between PVA and starch molecules in PVA/

starch blend systems induced by irradiation, the tensile strength

of PVA hydrogels was improved significantly. Radiation

technology has already been successfully used to improve the

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/

PVA based plastic sheets by inducing chemical reaction

between starch and PVA molecules under the action of ion-

izing radiation. The aim of this study was to evaluate the effect

of sugar (as a plasticizer) in starch/PVA based films. The

effects of gamma radiation on the mechanical, thermal and

water absorption properties of the prepared films were also

studied in the study.

Materials and Methods

Materials

Starch (pH 6–7, sensitivity: complying, sulfated ash: maxi-

mum 0.5%) was supplied from Sigma–Aldrich Chemie

Gmbh, Germany. Poly Vinyl Alcohol (Physical state: White

flake, Density: 1.19–1.31 g/cm3, Specific Gravity: 1.19–1.31)

was obtained from Merck, Germany. Sugar (Sucrose, white

crystalline disaccharide, C12H22O11) was purchased from

local market (Fresh Company Ltd, Bangladesh). The water

used to prepare starch/PVA blend films was distilled after

deionization.

Preparation of Starch/PVA/Sugar Film

Films were prepared by the casting method. At first, starch

with PVA and sugar were blended in hot water at 150 �C

for 1 h to form a homogeneous gel like solution. This

solution was used to prepare several formulations with

varying starch and sugar concentration keeping PVA con-

centration constant. The mixing composition is shown in

Table 1. The solutions were then poured up to a thickness

of 4 mm on the silicon paper covered glass plate. Water

was evaporated from the moulds in an oven at 50 �C for

10 h. After cooling the dried films at room temperature for

72 h, they were peeled from the silicon cloth and cut into

small pieces of length 70 mm and width 10 mm. The

average thickness of the dried films was about 0.3 mm. The

films were stored 24–48 h in a dessiccator at room tem-

perature (30 �C) and at RH 65% prior to performing the

measurements.

Gamma Irradiation of the Film

After making films from different formulations, the film

having best mechanical property (e.g., tensile strength and

elongation at break) was chosen for irradiation by gamma

rays (60Co gamma source, Inter Professional Investment

Ltd, UK). The film was irradiated with 350 krad/h dose

rate at different doses of 0, 25, 50, 100, 200, 500 krad and

after 24 h, mechanical, thermal and water absorption

properties of the films were studied.

Table 1 Composition of starch/PVA/sugar blends (%, w/w)

Formulation Percentage of

starch

Percentage of

PVA

Percentage of

sugar

F1 35 65 0

F2 30 65 5

F3 25 65 10

F4 20 65 15

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Characterization Methods

Tensile Properties Testing

Tensile strength (TS) and elongation at break (EB) of the

films (both irradiated and non-irradiated) were measured

with universal Testing Machine (Hounsfield Series S, UK).

Each piece of the film had a length of 20 mm and width of

10 mm. Crosshead speed was 2 mm/min and gauge length

was 20 mm with load capacity of 500 N. ASTM D882 was

followed for the tensile test and five replicates were tested

for each sample to assess the precision of the method. All

the tests were carried out at 20 �C and 50% RH.

Fourier Transformed Infrared Spectroscope (FTIR)

The IR spectra of the films were measured by FTIR Spec-

trophotometer (Perkin Elmer, UK). The FTIR spectrum was

taken in a transmittance mode. The spectra were obtained at

a resolution of 8 cm-1 in the range of 650–4,000 cm-1.

Swelling Degree

The swelling degree of the irradiated and non-irradiated

films was monitored (up to 120 min) to find the profile of

water uptake. Water uptake was determined using the

following equation.

Wg ¼ Wa � Woð Þ=Wo � 100

where, Wg and Wa were the weights of the sample after and

before soaking in water.

Thermal Analysis

The thermal test of the films was performed using computer

controlled TG/DTA 6300 system controlled to an EXSTAR

6000 STATION, Seiko Instrument Inc., Japan. The TG/

DTA module used a horizontal system balance mechanism.

All the experiments were performed under nitrogen atmo-

sphere. Sample weights were 8–10 mg, and heating rate was

10 �C/min within the temperature range of 50–600 �C.

Thermo-Mechanical Analysis

Glass transition temperatures were measured for all the

materials using thermo-mechanical analyzer (TMA) Lien-

sis 200 with an instrumental precision of ±3 �C. The

temperature range was 60–220 �C.

Morphological Study

The morphological studies of the (irradiated and non-irra-

diated) blend films were done using a JEOL 6400 Scanning

Electron Microscope (SEM) at an accelerating voltage of

2 kV. The SEM specimens were sputter-coated with gold.

Soil Burial Test

The degradation tendency of the films (both irradiated and

non-irradiated) in the soil was studied. The films were

buried in soil for (1, 2, 3, 4, 5, 6) weeks. Moisture content

of the soil was maintained at around 15–18%. In every

week, samples were taken out from the soil. After cleaning

carefully with water and drying at room temperature, their

weight changes were measured [29]. Weight changes (%)

were determined using the following equation:

Wg ¼ Wa � Woð Þ=Wa � 100;

where, Wa and Wo were the weights of the sample before

and after soil burial treatment.

The changes in physical appearance were also deter-

mined by comparing the photographs of the films taken

before and after soil burial treatment.

Results and Discussion

Effect of Sugar and Starch on Tensile Properties

of the Film

As polymeric films may be subjected to various kinds of

stresses during being used, the study of the mechanical

properties (tensile strength, elasticity, etc.) is of primary

importance for determining the performance of the mate-

rials [5]. Figure 1 and 2 show the tensile strength and

elongation at break of the starch/PVA/sugar blend film as a

function of both starch and sugar contents, respectively.

Starch and sugar content show the contrary effects on the

tensile properties of the films. The tensile strength (TS) and

the elongation at break (EB) of the film increased initially

with the increase of sugar content and decrease of starch

content and after reaching a maximum value, TS and EB

values began to decrease. Previous study [30] suggested

that TS of the film decreased with increasing starch content

of the polymeric film. In this study, the TS of the films

(F3, 10% sugar and F2, 5% sugar) were found to be higher

than that of the film (F1, without sugar). The increased

sugar content in both F3 and F2 usually tends to reduce the

tensile strength of the film. But the strength of both of the

films has increased in the study due to the decrease of

starch content. The EB of the films (F2, 5% sugar and F1,

without sugar) was found to be lower than that of the films

(F3, 10% sugar and F4, 15% sugar) because of increasing

of the sugar content. The increase of the sugar content in

the film favors the plasticizing effect that increases the

flexibility and elongation at break of a polymer [25, 31].

J Polym Environ

123

The maximum EB was found at a value of 409% for the

film (F3, 10% sugar). The TS and EB of the film (F4, 15%

sugar) began to decrease with further increasing the sugar

content. An increase in the plasticizer concentration

resulted in decreasing the cohesive force of attraction

between PVA and plasticizer or starch and plasticizer. The

plasticizers are expected to reduce the modulus, tensile

strength and hardness of the polymer [31]. Since F3 com-

position exhibited the optimum performance for both ten-

sile strength and elongation at break, this composition was

used for further investigation.

Effect of Gamma Irradiation on the Mechanical

Properties of the Film

The effects of gamma irradiation of 350 krad/h dose rate

on the mechanical properties of the starch/PVA/sugar

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

tensile strength of the film decreased at low irradiation

dose; then increased with an increase of the irradiation

dose, but when the dose was further increased, the TS

decreased with increasing irradiation dose.

Percent elongation indicates the flexibility of the film. In

this study, the EB value of the irradiated film (e.g., 222% at

25 krad) was found to be significantly lower than that of

the non-radiated film (409%). The higher radiation dose

(500 krad) also showed the lowest EB (130%). High-

energy radiation (usually gamma radiation) causes chain

scission of polymer that leads to the decrease of the EB

values [32].

FTIR Analysis of the Film

Figure 4 represents the comparison of FTIR spectra of

pure PVA, non-radiated starch/PVA/sugar film and irra-

diated starch/PVA/sugar film. In this analysis, it was

attempted to characterize the incorporation of sugar and

Fig. 1 Effect of sugar and starch on the tensile strength of the starch/

PVA/sugar blend film

Fig. 2 Effect of sugar and starch on the elongation at break of the

starch/PVA/sugar blend film

Fig. 3 Effect of gamma irradiation on the tensile strength and

elongation at break of the starch/PVA/sugar blend (F3) film

J Polym Environ

123

starch into the PVA-based film without radiation and

under gamma radiation and then distinguish the IR bands

and vibrations shifts related to sugar and starch interac-

tions with PVA and molecular interaction due to gamma

irradiation.

Starch and PVA molecules are in general associated

with inter- and intra-molecular hydrogen bonding in the

blends. The cross-linking of these blends results in a

decrease in the intermolecular hydrogen bonds. The pure

PVA spectrum are mainly assignable to the hydrogen

bound O–H vibration at 3400 cm-1, stretching vibration of

C–H or C–H2 at 2,900 cm-1, bending vibration of C–H or

C–H2 (asymmetric) at 1,542 cm-1, bending vibration of

CH or CH2 (symmetric) at 1,427 cm-1, stretching vibration

of C–O at 1,047 cm-1 and bending vibration of C–H (out

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

absorption band at 3,380 cm-1 was broadened after starch

and sugar addition, related to the increase of typical

hydrogen bound O–H vibration of semi-crystalline starch

and sugar indicating the formation of strong H-bond. The

shifting of the bending vibration of C–H2 from 1427 cm-1

to 1334 cm-1 and the broadening of the peak also con-

firmed the formation of strong H-bond. In the FTIR spectra

of gamma-irradiated starch/PVA/sugar blend film, the

absorption bands for most of the functional groups were

disappeared or weakened because the cross-linking of the

film resulted in a decrease of the intermolecular hydrogen

bonds. Only the peak at 3,622 cm-1 was broadened for the

gamma-irradiated film because of the increasing number of

H-bonded OH vibration.

Scanning Electron Microscope Image analysis

The surface topography of pure PVA, non-radiated and

gamma–irradiated starch/PVA/sugar blend (for formula-

tions F3) films were studied with SEM (See Fig. 5). The

surface of pure PVA film was found quite smooth and

homogeneous. The surface of starch/PVA/sugar blend film

(F3) appeared to be slightly rougher and more condensed

due to the incorporation of the starch and the sugar in film

formulation. The surface of gamma-irradiated starch/PVA/

sugar blend film (F3) appeared to have stripes or fibrous

like in the surface. The SEM observations seem to support

the FTIR structural analysis and provide evidence for the

enhanced properties by crosslinking obtained after gamma

irradiation on the starch/PVA/sugar blend film.

Thermal Analysis of the Films

Thermomechanical Analysis of the Film

Thermomechanical analysis (TMA) was used to determine

gel-melting temperature of the film. The comparison of

onset of melting, glass transition (Tg) and offset of melting

of the pure PVA, 35%starch/65%PVA, non-radiated and

irradiated 25%starch/65%PVA/10%sugar blend (formula-

tions F3) film are shown in Fig. 6. The onset of melting,

glass transition, and offset of melting temperatures of the

pure PVA film were found to be 198, 200 and 205 �C,

respectively. After blending starch with PVA the onset,

glass transition and offset of melting temperature has

decreased. As starch acting as filler in PVA based film, it

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

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123

lowers the glass transition temperature of the blend film.

However, the incorporation of sugar into starch/PVA, the

onset, glass transition and offset of melting temperatures

(130, 137 and 143 �C, respectively) of the starch/PVA/

sugar blend film decreased significantly. When sugar was

incorporated into the thermally stable starch/PVA, the

melting temperature of the blend film was decreased, as

sugar work effectively to lower the glass transition tem-

perature of the host polymer [31]. After irradiation of the

film by gamma radiation, the onset, glass transition and

offset of melting temperatures of the starch/PVA/sugar

blend film were regained (149, 166 and 177 �C, respec-

tively) slightly. This may be due to crosslinking in the

gamma-irradiated film making a compact structure which

increased the thermal stability of the film.

Thermo Gravimetric Analysis

Figure 7 shows the Thermo Gravimetric Analysis (TGA) of

pure PVA, 35%starch/65%PVA, non-radiated and irradi-

ated 25%starch/65%PVA/10%sugar blend (formulations

F3) film. Pure PVA curve showed a two-step decomposition

pattern. The first step began at approximately 199 �C and

the second one began at about 347 �C. The final temperature

of the decomposition was at 450 �C. The first step of weight

loss could be attributed to the loss of loosely bound water,

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

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accompanied by the formation of volatile disintegrated

products. The second step was mainly caused by the thermal

decomposition of the molecules and the products were

composed of small molecular carbon and hydrocarbon.

Starch/PVA film shows two major degradation stages.

The first degradation occurred at approximately 209.1 �C.

This first degradation process could be attributed to the loss

of water. The second degradation was started at about

314.5 �C and this was attributed to the thermal degradation

of semi-crystalline starch. Nearly 50% degradation of the

film occurred at approximately 369.0 �C. The starch/PVA

blend film lost its 90.5% weight at 423.5 �C.

The TGA curve of non-radiated and irradiated starch/

PVA/sugar blend (F3) films show higher rate of thermal

degradation compared to pure PVA and starch/PVA film.

As sugar is sensitive to thermal degradation, the incorpo-

ration of sugar into starch/PVA film intensifies its thermal

degradation. However, irradiation of the film by gamma

radiation slightly decreases the rate of thermal degradation.

This may be due to the crosslinking of the film, which

increases the resistant to thermal degradation. The starch/

PVA/sugar blend (F3) film showed a two-step decompo-

sition pattern as shown in Fig. 7. The first weight loss was

at approximately 197 �C due to the loss of water. The

second weight loss was started at approximately 296 �C

due to the thermal degradation of starch/PVA/sugar blend

(F3) and 50% degradation took place at approximately

360 �C. At 420 �C, the starch/PVA/sugar blend (F3) films

lost its 90% weight.

Differential Thermo Gravimetric Analysis

Figure 8 shows the comparative Differential Thermo Gravi-

metric (DTG) studies of pure PVA, 35%starch/65%PVA,

non-radiated and irradiated 25%starch/65%PVA/10%sugar

blend (formulations F3) film. Differential curves also indi-

cated similar effects of thermal stability (Fig. 7) of the films.

The DTG curve of pure PVA film depicted one predominant

peak at 378 �C in where the maximum degradation rate was

2.17 mg/min. The DTG curve of the starch/PVA based film

depicts two peaks at 370 �C and 437 �C, where the maximum

degradation rate was 0.621 mg/min. The DTG curve of non-

radiated starch/PVA/sugar blend (formulations F3) film

showed several broad peaks because of the incorporation of

starch and sugar into the PVA film and the maximum deg-

radation rate was found to be better than that of PVA and

starch/PVA film (0.79 mg/min at 363 �C). The DTG curve of

gamma-irradiated starch/PVA/sugar blend (F3) films also

showed several broad peaks in where the maximum degra-

dation rate was found to be 1.18 mg/min at 355 �C.

Differential Thermal Analysis (DTA)

Figure 9 shows the DTA curves of pure PVA, 35%starch/

65%PVA, non-radiated and irradiated 25%starch/65%PVA/

10%sugar blend (formulations F3) film. The pure PVA

shows two endothermic peaks at 140 and 222 �C indicating

the melting point of pure PVA and the loss of moisture,

respectively. Another endothermic peak at 361 �C indi-

cated the decomposition of the PVA chain. The curve of

the starch/PVA blend film depict two endothermic peaks at

138 �C and at 333 �C, indicating the melting point and

decomposition point of the starch/PVA containing film.

The curve of the non-irradiated starch/PVA/sugar blend

(F3) film showed a new endothermic broad peak appeared

in the temperature range of 120–330 �C due to the lower

melting temperature of the starch-PVA-sugar molecules.

Homogeneous polymer mixtures with a crystallizable

component usually show a decrease in experimental

Fig. 7 Comparison of TG of pure PVA, starch/PVA, non-radiated

and gamma-irradiated starch/PVA/sugar blend (F3) films

Fig. 8 Comparison of DTG of pure PVA, starch/PVA, non-radiated

and gamma-irradiated film starch/PVA/sugar blend (F3) films

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123

melting points with the addition of the amorphous com-

ponent, because the interaction of the two polymers

reduces the crystallite size. Significant changes of DTA

curves of the blend films suggested the strong interactions

among starch, PVA and sugar molecules. The curve of the

gamma-irradiated starch/PVA/sugar blend (F3) film

showed a new exothermic peak appeared at 428 �C due to

the crosslinking of starch, PVA and sugar molecules.

Water Absorption Test

As starch and sugar is sensitive to water, it affects the

mechanical properties of thermoplastic starch materials;

hence, any improvement in reducing water sensitivity and

enhancing water resistance of thermoplastic starch mate-

rials is highly important. Figure 10 shows the % weight

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

time is 95% as shown in Fig. 10. This large difference in

the degree of swelling between irradiated and non-radiated

could be due to the increased degree of cross-linking

between polysaccharide chain of starch and OH- groups of

PVA and sugar that creates a three-dimensional compact

structure. The compact irradiated film had a less chance for

the water molecule to be associated or absorbed within the

film.

Soil Burial Test

Non-radiated and irradiated starch/PVA/sugar blend (for-

mulations F3) films were buried into the soil for comparative

degradation study of the film. The weight change of the film

in soil burial test is presented in Fig. 11 and the picture of

the degraded films (42 days) is shown in Fig. 12. The non-

radiated film exhibit slightly higher weight change com-

pared to the gamma–irradiated starch/PVA/sugar blend

(formulations F3) film. At initial stage the biodegradation

Fig. 9 Comparison of DTA of pure PVA, starch/PVA, non-radiated

and gamma-irradiated film starch/PVA/sugar blend (F3) films

Fig. 10 Comparison of water uptake between gamma-irradiated and

non-radiated starch/PVA/sugar blend (F3) films at different soaking

times

Fig. 11 Comparison of weight loss between gamma-irradiated and

non-radiated starch/PVA/sugar blend (F3) films at different soil burial

times

J Polym Environ

123

rate was higher, as the interaction of microorganism on

starch and sugar molecule increased, the degradation was

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

sugar molecule [29]. The degradability of the gamma-

irradiated film was slightly lower than that of the non-

radiated film as because of cross-linking; the gamma-irra-

diated film produces a compact structure, which degraded

at a lower speed.

Conclusion

Development of biodegradable environmentally friendly

materials based essentially on natural polymers is a

continuing area of challenge for packaging technology.

Thus the main objective of this work was to prepare a

biodegradable starch/PVA/sugar blend-based film and to

develop the physical and chemical properties of the film by

gamma irradiation. A PVA-based film containing 25%

starch and 10% sugar performed enhanced tensile strength

and elongation at break compared to the film containing

35% starch and without sugar. Exposition of the starch/

PVA/sugar films to gamma radiation revealed that at 200

krad the tensile strength of the film increased up to 25%

compared to the non-radiated film. TGA analysis showed

that gamma-irradiation improved the thermal stability of

starch/PVA/sugar blend-based film. DSC spectra also

supported a better thermal stability of the gamma-irradiated

films compared to the non-irradiated films. SEM analysis

of the film surface morphology provided further justifica-

tion of the improved properties obtained by sugar incor-

poration in starch/PVA films and gamma irradiation of the

film. Moreover, SEM morphological results were in

accordance with the molecular interactions changes indi-

cated by FTIR analysis. Biodegradability of the films was

increased after starch and sugar addition and at 42 days of

soil burial test, 35% of the sample was degraded.

Acknowledgments We thank the staff of Institute of Radiation and

Polymer Technology, Bangladesh Atomic Energy Commission for

technical support and advice throughout the work.

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