J Polym EnvironDOI 10.1007/s10924-011-0357-6 ORIGINAL PAPERPreparation and Characterization of Gamma Irradiated SugarConta...
J Polym Environenvironmentally advantageous biodegradable alternatives             Materials and Methodsto conventional no...
J Polym EnvironCharacterization Methods                                       Electron Microscope (SEM) at an accelerating...
J Polym Environ                                                                           Fig. 3 Effect of gamma irradiati...
J Polym EnvironFig. 4 The FTIR spectrum offilm: a pure PVA, b starch/PVA/sugar blend (F3) film,c gamma- irradiated starch/PV...
J Polym EnvironFig. 5 Scanning electron microscopic images: a pure PVA film, b non-radiated starch/PVA/sugar blend (F3) film...
J Polym Environ                                                                Fig. 8 Comparison of DTG of pure PVA, starc...
J Polym Environ                                                                     loss of the starch/PVA/sugar blend film...
J Polym EnvironFig. 12 Photographs of thegamma-irradiated and non-irradiated starch/PVA/sugarblend (F3) films after 42 days...
J Polym Environ28. Gehring J (2000) Rad Phy Chem 57:361                       31. Rahman M, Brazel CS (2004) Prog Polym Sc...
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  1. 1. J Polym EnvironDOI 10.1007/s10924-011-0357-6 ORIGINAL PAPERPreparation and Characterization of Gamma Irradiated SugarContaining Starch/Poly (Vinyl Alcohol)-Based Blend FilmsFahmida Parvin • Mubarak A. Khan • A. H. M. Saadat •M. Anwar H. Khan • Jahid M. M. Islam •Mostak Ahmed • M. A. GafurÓ Springer Science+Business Media, LLC 2011Abstract 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 alsoamount of poly(vinyl alcohol) (PVA) constant, were pre- evaluated. In this study, sugar acted as a good plasticizingpared in the form of thin films by casting solutions. The agent in starch/PVA blend films, which was significantlyeffects 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 biodegradablemechanical properties showed improved tensile strength packaging materials.(TS) (9.61 MPa) and elongation at break (EB) (409%) ofthe starch-PVA-sugar blend film containing 10% sugar. Keywords Biodegradable materials Á Blend film ÁThe mechanical testing of the irradiated film (irradiated at Gamma irradiation Á Tensile properties Á Plasticizers200 Krad radiation dose) showed higher TS but lower EBthan that of the non-radiated film. FTIR spectroscopystudies supported the molecular interactions among starch, IntroductionPVA, and sugar in the blend films, that was improvedby irradiation. Thermal properties of the film were also Plastics are used as packaging materials due to theirimproved due to irradiation and confirmed by thermo- excellent thermo-mechanical properties and for economicalmechanical analysis (TMA), differential thermo-gravimet- reasons. But use of these materials has become seriousric 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-degradedInstitute of Radiation and Polymer Technology, Bangladesh polymers [3]. One of the possibilities to solve the problemsAtomic Energy Commission, Dhaka, Bangladeshe-mail: makhan.inst@gmail.com related to fossil resources and global environment is thor- ough recycling wasted polymeric materials. The recyclingF. Parvin Á A. H. M. Saadat of wasted plastics is limited, whether materials recycling orDepartment of Environmental Sciences, Jahangirnagar chemical recycling consumes a considerable amount ofUniversity, 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 orDepartment of Geography, University of California Berkeley, buried in landfills [4]. The use of biodegradable polymersBerkeley, CA 94720, USA for packaging offers an alternative and partial solution toM. A. Gafur the problem of accumulation of solid waste composed ofPP and PDC, BCSIR, Dhaka, Bangladesh synthetic inert polymers [5]. These materials provide 123
  2. 2. J Polym Environenvironmentally advantageous biodegradable alternatives Materials and Methodsto conventional non-biodegradable materials such aspolyethylene 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 Chemielacks the strength, water resistibility, processability, and Gmbh, Germany. Poly Vinyl Alcohol (Physical state: Whitethermal 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, whitepolymers [7, 8] and adding plasticizers have been investi- crystalline disaccharide, C12H22O11) was purchased fromgated enormously. Among the existing synthesized poly- local market (Fresh Company Ltd, Bangladesh). The watermers, Poly(vinyl alcohol) (PVA) possesses many useful used to prepare starch/PVA blend films was distilled afterproperties, such as excellent chemical resistance, good film deionization.forming capability, having emulsifying and adhesiveproperties, water solubility, high thermal stability, and an Preparation of Starch/PVA/Sugar Filmexcellent biocompatibility [5]. Due to its excellent opticaland physical properties, PVA is successfully used in a wide Films were prepared by the casting method. At first, starchrange of industrial fields [2, 9–13]. The strength, flexibility with PVA and sugar were blended in hot water at 150 °Cand water resistance of starch productions improved when for 1 h to form a homogeneous gel like solution. ThisPVA 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 infilms is the plasticizer. The addition of a plasticizing agent Table 1. The solutions were then poured up to a thicknessto edible films is required to overcome film brittleness, of 4 mm on the silicon paper covered glass plate. Watercaused by high intermolecular forces. Plasticizers reduce was evaporated from the moulds in an oven at 50 °C forthese forces and increase the mobility of polymer chains, 10 h. After cooling the dried films at room temperature forthereby improving flexibility, processability and extensi- 72 h, they were peeled from the silicon cloth and cut intobility of the film. On the other hand, plasticizers generally small pieces of length 70 mm and width 10 mm. Thedecrease gas, water vapor and solute permeability of the average thickness of the dried films was about 0.3 mm. Thefilm 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 theformed 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 Filmfew works have been performed on sugar, especiallysucrose, 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 andbi’ (physically blended 60% starch, 40% modified PVA and elongation at break) was chosen for irradiation by gammaplasticizers), have been produced in Japan [26]. Due to the rays (60Co gamma source, Inter Professional Investmentchemical reaction between PVA and starch molecules in PVA/ Ltd, UK). The film was irradiated with 350 krad/h dosestarch blend systems induced by irradiation, the tensile strength rate at different doses of 0, 25, 50, 100, 200, 500 krad andof PVA hydrogels was improved significantly. Radiation after 24 h, mechanical, thermal and water absorptiontechnology 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 byirradiation 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 ofbetween starch and PVA molecules under the action of ion- starch PVA sugarizing radiation. The aim of this study was to evaluate the effect F1 35 65 0of sugar (as a plasticizer) in starch/PVA based films. The F2 30 65 5effects of gamma radiation on the mechanical, thermal and F3 25 65 10water absorption properties of the prepared films were alsostudied in the study. F4 20 65 15123
  3. 3. J Polym EnvironCharacterization Methods Electron Microscope (SEM) at an accelerating voltage of 2 kV. The SEM specimens were sputter-coated with gold.Tensile Properties Testing Soil Burial TestTensile strength (TS) and elongation at break (EB) of thefilms (both irradiated and non-irradiated) were measured The degradation tendency of the films (both irradiated andwith universal Testing Machine (Hounsfield Series S, UK). non-irradiated) in the soil was studied. The films wereEach 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 content10 mm. Crosshead speed was 2 mm/min and gauge length of the soil was maintained at around 15–18%. In everywas 20 mm with load capacity of 500 N. ASTM D882 was week, samples were taken out from the soil. After cleaningfollowed for the tensile test and five replicates were tested carefully with water and drying at room temperature, theirfor 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 beforeThe 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 takena resolution of 8 cm-1 in the range of 650–4,000 cm-1. before and after soil burial treatment.Swelling Degree Results and DiscussionThe swelling degree of the irradiated and non-irradiatedfilms was monitored (up to 120 min) to find the profile of Effect of Sugar and Starch on Tensile Propertieswater uptake. Water uptake was determined using the of the Filmfollowing equation. As polymeric films may be subjected to various kinds ofWg ¼ ðWa À Wo Þ=Wo  100 stresses during being used, the study of the mechanicalwhere, Wg and Wa were the weights of the sample after and properties (tensile strength, elasticity, etc.) is of primarybefore soaking in water. importance for determining the performance of the mate- rials [5]. Figure 1 and 2 show the tensile strength andThermal 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 thecontrolled TG/DTA 6300 system controlled to an EXSTAR tensile properties of the films. The tensile strength (TS) and6000 STATION, Seiko Instrument Inc., Japan. The TG/ the elongation at break (EB) of the film increased initiallyDTA module used a horizontal system balance mechanism. with the increase of sugar content and decrease of starchAll the experiments were performed under nitrogen atmo- content and after reaching a maximum value, TS and EBsphere. Sample weights were 8–10 mg, and heating rate was values began to decrease. Previous study [30] suggested10 °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 filmsThermo-Mechanical Analysis (F3, 10% sugar and F2, 5% sugar) were found to be higher than that of the film (F1, without sugar). The increasedGlass transition temperatures were measured for all the sugar content in both F3 and F2 usually tends to reduce thematerials using thermo-mechanical analyzer (TMA) Lien- tensile strength of the film. But the strength of both of thesis 200 with an instrumental precision of ±3 °C. The films has increased in the study due to the decrease oftemperature 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 filmsMorphological Study (F3, 10% sugar and F4, 15% sugar) because of increasing of the sugar content. The increase of the sugar content inThe morphological studies of the (irradiated and non-irra- the film favors the plasticizing effect that increases thediated) blend films were done using a JEOL 6400 Scanning flexibility and elongation at break of a polymer [25, 31]. 123
  4. 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) filmFig. 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 theFig. 2 Effect of sugar and starch on the elongation at break of the tensile strength of the film decreased at low irradiationstarch/PVA/sugar blend film dose; then increased with an increase of the irradiation dose, but when the dose was further increased, the TSThe 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. Insugar) began to decrease with further increasing the sugar this study, the EB value of the irradiated film (e.g., 222% atcontent. An increase in the plasticizer concentration 25 krad) was found to be significantly lower than that ofresulted in decreasing the cohesive force of attraction the non-radiated film (409%). The higher radiation dosebetween 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 chainstrength and hardness of the polymer [31]. Since F3 com- scission of polymer that leads to the decrease of the EBposition exhibited the optimum performance for both ten- values [32].sile strength and elongation at break, this composition wasused for further investigation. FTIR Analysis of the FilmEffect of Gamma Irradiation on the MechanicalProperties 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 wason the mechanical properties of the starch/PVA/sugar attempted to characterize the incorporation of sugar and123
  5. 5. J Polym EnvironFig. 4 The FTIR spectrum offilm: a pure PVA, b starch/PVA/sugar blend (F3) film,c gamma- irradiated starch/PVA/sugar blend (F3) filmstarch into the PVA-based film without radiation and Scanning Electron Microscope Image analysisunder gamma radiation and then distinguish the IR bandsand vibrations shifts related to sugar and starch interac- The surface topography of pure PVA, non-radiated andtions 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 andwith inter- and intra-molecular hydrogen bonding in the homogeneous. The surface of starch/PVA/sugar blend filmblends. The cross-linking of these blends results in a (F3) appeared to be slightly rougher and more condenseddecrease in the intermolecular hydrogen bonds. The pure due to the incorporation of the starch and the sugar in filmPVA 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 fibrousC–H or C–H2 at 2,900 cm-1, bending vibration of C–H or like in the surface. The SEM observations seem to supportC–H2 (asymmetric) at 1,542 cm-1, bending vibration of the FTIR structural analysis and provide evidence for theCH or CH2 (symmetric) at 1,427 cm-1, stretching vibration enhanced properties by crosslinking obtained after gammaof 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 Filmsabsorption band at 3,380 cm-1 was broadened after starchand sugar addition, related to the increase of typical Thermomechanical Analysis of the Filmhydrogen bound O–H vibration of semi-crystalline starchand sugar indicating the formation of strong H-bond. The Thermomechanical analysis (TMA) was used to determineshifting of the bending vibration of C–H2 from 1427 cm-1 gel-melting temperature of the film. The comparison ofto 1334 cm-1 and the broadening of the peak also con- onset of melting, glass transition (Tg) and offset of meltingfirmed the formation of strong H-bond. In the FTIR spectra of the pure PVA, 35%starch/65%PVA, non-radiated andof 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 thefilm 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 hasH-bonded OH vibration. decreased. As starch acting as filler in PVA based film, it 123
  6. 6. J Polym EnvironFig. 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) filmFig. 6 The onset, glass pointand offset of meltingtemperature of pure PVA,starch/PVA, non-radiated andgamma-irradiated starch/PVA/sugar blend (F3) filmslowers the glass transition temperature of the blend film. gamma-irradiated film making a compact structure whichHowever, 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 Analysissugar blend film decreased significantly. When sugar wasincorporated into the thermally stable starch/PVA, the Figure 7 shows the Thermo Gravimetric Analysis (TGA) ofmelting 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 (formulationsperature of the host polymer [31]. After irradiation of the F3) film. Pure PVA curve showed a two-step decompositionfilm by gamma radiation, the onset, glass transition and pattern. The first step began at approximately 199 °C andoffset of melting temperatures of the starch/PVA/sugar the second one began at about 347 °C. The final temperatureblend film were regained (149, 166 and 177 °C, respec- of the decomposition was at 450 °C. The first step of weighttively) slightly. This may be due to crosslinking in the loss could be attributed to the loss of loosely bound water,123
  7. 7. J Polym Environ Fig. 8 Comparison of DTG of pure PVA, starch/PVA, non-radiatedFig. 7 Comparison of TG of pure PVA, starch/PVA, non-radiated and gamma-irradiated film starch/PVA/sugar blend (F3) filmsand gamma-irradiated starch/PVA/sugar blend (F3) films non-radiated and irradiated 25%starch/65%PVA/10%sugaraccompanied 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 predominantcomposed 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 filmThe first degradation occurred at approximately 209.1 °C. depicts two peaks at 370 °C and 437 °C, where the maximumThis 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) film314.5 °C and this was attributed to the thermal degradation showed several broad peaks because of the incorporation ofof 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 andblend 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 alsoPVA/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 gammaradiation 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 PVAPVA/sugar blend (F3) film showed a two-step decompo- shows two endothermic peaks at 140 and 222 °C indicatingsition 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 ofdue 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 and360 °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 appearedDifferential 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 crystallizablemetric (DTG) studies of pure PVA, 35%starch/65%PVA, component usually show a decrease in experimental 123
  8. 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 ofFig. 9 Comparison of DTA of pure PVA, starch/PVA, non-radiated time is 95% as shown in Fig. 10. This large difference inand 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-linkingmelting points with the addition of the amorphous com- between polysaccharide chain of starch and OH- groups ofponent, because the interaction of the two polymers PVA and sugar that creates a three-dimensional compactreduces the crystallite size. Significant changes of DTA structure. The compact irradiated film had a less chance forcurves of the blend films suggested the strong interactions the water molecule to be associated or absorbed within theamong starch, PVA and sugar molecules. The curve of the film.gamma-irradiated starch/PVA/sugar blend (F3) filmshowed a new exothermic peak appeared at 428 °C due to Soil Burial Testthe 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 filmAs starch and sugar is sensitive to water, it affects the in soil burial test is presented in Fig. 11 and the picture ofmechanical 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 blendrials is highly important. Figure 10 shows the % weight (formulations F3) film. At initial stage the biodegradationFig. 10 Comparison of water uptake between gamma-irradiated and Fig. 11 Comparison of weight loss between gamma-irradiated andnon-radiated starch/PVA/sugar blend (F3) films at different soaking non-radiated starch/PVA/sugar blend (F3) films at different soil burialtimes times123
  9. 9. J Polym EnvironFig. 12 Photographs of thegamma-irradiated and non-irradiated starch/PVA/sugarblend (F3) films after 42 daysof degradationrate was higher, as the interaction of microorganism on Acknowledgments We thank the staff of Institute of Radiation andstarch 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 fullydegraded, the PVA was further degraded, but the degra-dation rate of PVA was slower than that of the starch and Referencessugar molecule [29]. The degradability of the gamma-irradiated film was slightly lower than that of the non- 1. Khan RA, Salmieri S, Dussault D, Uride-Calderon J, Kamal MR,radiated film as because of cross-linking; the gamma-irra- Safrany A, Lacroix M (2010) J Agric Food Chem 58:7878diated film produces a compact structure, which degraded 2. Zhai ML, Yoshii F, Kume T (2003) Carb Polym 52:52311 3. Yun Y–H, Na Y–H, Yoon S–D (2006) J Polym Environ 14:71at a lower speed. 4. Parra DF, Tadini CC, Ponce P, Lugao AB (2004) Carb Polym 58:475 5. Tang H, Xiong H, Tang S, Zou P (2009) J Appl Polym Sci 113:34Conclusion 6. Bertuzzi MA, Armada M, Gottifredi JC (2007) J Food Eng 82:17 7. Griffin GJL (1980) Pure Appl Chem 52:399Development of biodegradable environmentally friendly 8. Siddaramaiah Raj B, Somashekar R (2004) J Appl Polym Scimaterials based essentially on natural polymers is a 91:630 9. Follain N, Joly C, Dole P, Bliard C (2005) Carb Polym 60:185continuing area of challenge for packaging technology. 10. Xiao CM, Yang ML (2006) Carb Polym 64:37Thus the main objective of this work was to prepare a 11. Zhai ML, Yoshii F, Kume T, Hashim K (2002) Carb Polymbiodegradable starch/PVA/sugar blend-based film and to 50:295develop the physical and chemical properties of the film by 12. Ibrahim MM, El-Zawawy WK, Nassar MA (2010) Carb Polym 79:694gamma irradiation. A PVA-based film containing 25% 13. Chang JH, Jang T, Ihn KJ, Lee W, Sur GS (2003) J Appl Polymstarch and 10% sugar performed enhanced tensile strength Sci 90:3208and elongation at break compared to the film containing 14. Cinelli P, Chiellini EJ, Lawton W, Imam SH (2006) Polym Deg35% starch and without sugar. Exposition of the starch/ Stab 91:1147 15. Tang X, Alavi S (2011) Carb Polym 85:7PVA/sugar films to gamma radiation revealed that at 200 16. Gontard N, Guilbert S, Cuq J–L (1993) J Food Sci 58:206krad the tensile strength of the film increased up to 25% 17. Sobral PJA, Menegalli FC, Hubinger MD, Roques MA (2001)compared to the non-radiated film. TGA analysis showed Food Hydrocolloids 15:423that gamma-irradiation improved the thermal stability of 18. Lawton JW, Fanta GF (1994) Carb Polym 23:275 19. Liu ZQ, Feng Y, Yi XS (1999) J Appl Polym Sci 74:2667starch/PVA/sugar blend-based film. DSC spectra also 20. Park H, Chough S, Yun Y, Yoon S (2005) J Polym Environsupported a better thermal stability of the gamma-irradiated 13:375films compared to the non-irradiated films. SEM analysis 21. Westhoff RP, Kwolek WF, Otey FH, Illinois P (1979) Starchof the film surface morphology provided further justifica- Starke 31:163 22. Tudorachi N, Cascaval CN, Rusu M, Pruteanu M (2000) Polymtion of the improved properties obtained by sugar incor- Testing 19:785poration in starch/PVA films and gamma irradiation of the 23. Zou GX, Jin PQ, Xin IZ (2008) J Elastomers Plast 40:303film. Moreover, SEM morphological results were in 24. Zhou XY, Cu YF, Jia DM, Xie D (2009) Polymer Plast Tech Engaccordance with the molecular interactions changes indi- 48:489 25. Parvin F, Rahman MA, Islam JMM, Khan MA, Saadat AHMcated by FTIR analysis. Biodegradability of the films was (2010) Adv Mat Res 123–125:351increased after starch and sugar addition and at 42 days of 26. Iwanami T, Uemura T (1993) Jap J Polym Sci Tech 50:767soil burial test, 35% of the sample was degraded. 27. Bhattacharya A (2000) Prog Polym Sci 25:371 123
  10. 10. J Polym Environ28. Gehring J (2000) Rad Phy Chem 57:361 31. Rahman M, Brazel CS (2004) Prog Polym Sci 19:122329. Tang S, Zou P, Xiong H, Tang H (2008) Carb Polym 72:521 32. Ghoshal S, Khan MA, Noor FG, Khan RA (2009) J Macromol Sci30. Khan MA, Bhattacharia SK, Kader MA, Bahari K (2006) Carb 46A:975 Polym 63:500 33. Song CL, Yoshii F, Kume T (2001) J Macromol Sci 38A:961123