GPOM #551365, VOL 60, ISS 13

Preparation andCharacterization ofGelatin-Based PVA Film:Effect of GammaIrradiation

Mushfiqur Rahman, Kamol Dey, Fahmida Parvin,

Nusrat Sharmin, Ruhul A. Khan, Bapi Sarker,

Shamsun Nahar, Sushanta Ghoshal, M. A. Khan,

M. Masud Billah, Haydar U. Zaman, and A. M. S. Chowdhury

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Preparation and Characterization of Gelatin-Based PVA Film:Effect of Gamma IrradiationMushfiqur Rahman, Kamol Dey, Fahmida Parvin, NusratSharmin, Ruhul A. Khan, Bapi Sarker, Shamsun Nahar,Sushanta Ghoshal, M. A. Khan, M. Masud Billah, Haydar U.Zaman, and A. M. S. Chowdhury

Preparation andCharacterization ofGelatin-Based PVA Film:Effect of Gamma

5Irradiation

Mushfiqur Rahman,1,2 Kamol Dey,2 Fahmida Parvin,1

Nusrat Sharmin,2 Ruhul A. Khan,1 Bapi Sarker,2

Shamsun Nahar,2 Sushanta Ghoshal,2,3 M. A. Khan,1

M. Masud Billah,1 Haydar U. Zaman,1 and A. M. S. Chowdhury2

101Nuclear and Radiation Chemistry Division, Institute of Nuclear Science andTechnology, Bangladesh Atomic Energy Commission, Dhaka, Bangladesh2Department of Applied Chemistry and Chemical Engineering, Faculty ofEngineering and Technology, University of Dhaka, Dhaka, Bangladesh3Department of Technical Physics II, Faculty of Mathematics and Natural Science,

15Ilmenau University of Technology, Ilmenau, Germany

Gelatin-based polyvinyl alcohol (PVA) films were prepared (using a casting process)by mixing aqueous solutions of gelatin and PVA in different ratios. Monomer 1,4-butanediol diacrylate (BDDA) was dissolved in methanol. Films containing 95%gelatinþ 5% PVA were soaked in 3% BDDA monomer (w=w). These films were then

20irradiated under gamma radiation (60Co) at different doses (50–500krad) at a doserate of 350krad=h. The physico-mechanical and thermal properties of these filmswere evaluated. It was evident that 5% PVA-containing gelatin blend film exhibitedthe highest tensile strength (TS) value at 50 krad (51MPa), which was 46% higherthan that of non-irradiated blend films. It was also found that incorporation of PVA

25significantly reduced the TS value of the blend films compared to the raw film,whereas elongation at break (Eb) value was increased. A significant improvementof the blend films was also confirmed by thermo gravimetric analysis (TGA) and

Received &.Address correspondence to Dr. Ruhul A. Khan, Nuclear and Radiation ChemistryDivision, Institute of Nuclear Science and Technology, Bangladesh Atomic EnergyCommission, Dhaka 1000, Bangladesh. E-mail: dr.ruhul_khan@yahoo.com

Q5

International Journal of Polymeric Materials, 60:1–14, 2011

Copyright # Taylor & Francis Group, LLC

ISSN: 0091-4037 print=1563-535X online

DOI: 10.1080/00914037.2010.551365

3b2 Version Number : 7.51c/W (Jun 11 2001)File path : P:/Santype/Journals/TandF_Production/GPOM/v60n13/gpom551365/gpom551365.3dDate and Time : 14/09/11 and 14:06

thermo-mechanical analysis (TMA) when the acrylate group (from BDDA) wasintroduced into the film.

30Keywords bio-blend, cross-linking, gamma radiation, gelatin, polyvinyl alcohol

INTRODUCTION

Polymer blends played a pioneering role in the progress in scientific research

and commercial applications. Scientists and technologists applied huge effort

to the development of polymeric blended materials for various suitable appli-

35cations. Efforts are ongoing in these fields. Biodegradable polymers have

attracted a lot of attention as suitable biomaterials in environmental conser-

vation. Polymer blending is a technique to develop highly functional materials

in various industrial applications. Many researchers have investigated blends

using gelatin, chitosan, polyamide, polyether, cellulose, protein, etc., as the

40biological components [1–3].

The question of environmental concern caused by synthetic packaging has

favored, in a general way, an increase in research on biodegradable materials,

which are elaborated from renewable raw materials. Polysaccharides and pro-

teins are biopolymers capable of producing flexible films with biodegradable

45character. Gelatin was one of the first macromolecules employed in the pro-

duction of biomaterials. This biopolymer still attracts the attention of

researchers because it is produced abundantly, has a relatively low cost, and

possesses excellent functional and film-forming properties. For this reason,

gelatin has been studied in film technology both alone and in blends with other

50biopolymers [4]. Gelatin is a structural protein which is obtained by the partial

hydrolysis of collagen derived from skin, white connective tissue, and bones of

animals. Gelatin normally contains about 85%protein, 12–15% water, 1–4%

inorganic salts, and trace amounts of grease. The properties of gelatin depend

on the major protein constituent derived from the breakdown of collagen.

55Elemental percentages of gelatin are as follows: carbon 50.5%, hydrogen

6.8%, nitrogen 17%, and oxygen 25.2% [5]. In a general way, gelatin-based

films present good mechanical resistance, despite their reduced water vapor

barrier [4]. On the other hand, these films present high susceptibility to room

temperature and relative humidity conditions due to the hydrophilic nature of

60gelatin. A possible alternative to improve the mechanical properties of these

materials could be the addition of these biopolymers to synthetic monomers=

polymers. Bio-artificial polymeric materials have been prepared using PVA

as synthetic components and gelatin as biological components. PVA is a

hydrolysis product of poly-(vinyl acetate) (PVAc) and is a polar, water soluble,

65synthetic polymer. In addition, it is recognized as one of the few synthetic poly-

mers truly biodegradable under both aerobic and anaerobic conditions [6,7].

2 M. Rahman et al.

Grafting of gelatin by various polymers has been studied with the objec-

tive of improving or modifying the properties of gelatin and in order to develop

new materials combining the desirable properties of both natural and syn-

70thetic polymer. Many attempts, such as physical and chemical treatments,

have lead to changes in the surface structure and surface energy of the films.

Among them, physical treatments, such as ionizing or non-ionizing radiation,

can introduce better surface cross-linking between natural and synthetic poly-

mers, and reduce the hydrophilic nature of the film. Surface modification of

75the films can be carried out by the monomer treatment. The acrylate monomer

1,4-butanediol diacrylate (BDDA) induced cross-linking using their double

bonds [8–11].

The present study focused on the preparation of thin gelatin films and

their blends with PVA. The effect of PVA content on gelatin films was investi-

80gated by varying its percentages. The ultimate goal was to study the mechan-

ical and thermal properties of the gelatin and gelatin=PVA films followed by

the effect of PVA content and gamma irradiation on these films. The effect

of BDDA on a selected blend was also investigated.

EXPERIMENTAL

85MaterialsGelatin (185 Bloom; Type A, pharmaceutical grade) was collected from the

Opsonin Pharma Limited, Barishal, Bangladesh. The synthetic polymer PVA

(Molecular Weight: 72000) was purchased from Fluka Chemie AGCH-9470

Buchs. The monomer BDDA was purchased from E. Merck, Germany, and

90acetone from BDH Chemicals Limited, England. Methanol was purchased

from E. Merck, Germany.

MethodsPreparation of Films

Gelatin and PVA were dissolved separately in hot water with constant

95stirring to prepare the solutions. Then a calculated amount of PVA solution

(5, 10 and 15% w=w) was mixed with gelatin solution. Gelatin containing 5,

10, and 15% PVA solution was blended for preparing films. The compositions

are shown in Table 1. The solutions were blended in hot water for about 90 min-

utes to produce a homogeneous solution. The solutions were then cast onto the

100silicon paper-covered glass plate to form film. The solutions were maintained in

a thickness of 4mm on the glass plate. The films were dried at room tempera-

ture for 48 hours. The dried films were then peeled from the silicon cloth and

cut into small pieces of length 70mm and width 10mm. The thickness of the

Gelatin-Based PVA FilmQ1 3

dried films was about 300mm. The films were kept in a desiccator at room tem-

105perature and constant relative humidity of 65% prior to further treatment.

Treatment of Films

Gelatin and gelatin=PVA blend films were irradiated under gamma

radiation (60Co) with different doses such as 50, 100, 150, 250, and 500krad

at a dose rate of 350Krad=h. The films were then subjected to various

110characterizations.

Preparation of Soaking Formulation Using BDDA

One soaking solution was prepared with BDDA (3%) in methanol.

Treatment of Films with Soaking Formulation

Gelatin and gelatin=PVA blend films of the formulation G2 (95%

115Gelatinþ 5% PVA) were soaked in 3% BDDA at 3 minutes’ soaking time. After

soaking, these films were irradiated under gamma radiation (60Co) with differ-

ent doses such as 50, 100, 150, 250, and 500krad. The films were then

subjected to various characterizations.

Study of Properties120Mechanical Properties of the Films

Tensile strength (TS) and elongation at break (Eb) of the films were inves-

tigated by the Universal Testing Machine (INSTRON, model 1011, UK). The

load range was 500N with 10mm=min crosshead speed and 30mm gauge

length. The dimensions of the test specimen were 70mm� 10mm� 0.30mm.

125Thermal Analysis

Thermal properties of pure gelatin film, pure PVA film, and a blend G2

(95% gelatinþ 5% PVA) were determined by using the thermo-mechanical

Table 1: Composition of different blending formulation (%w=w)

Composition (% w/w)

Formulation Gelatin (%) PVA (%)

G1 100 00G2 95 05G3 90 10G4 85 15

4 M. Rahman et al.

analyzer (Linseis TMA, L-77, USA) and thermo-gravimetric analyzer (SEIKO

EXTAR TG=DTA 6300, USA).

130RESULTS AND DISCUSSION

Mechanical Properties of the Untreated andTreated FilmsPure gelatin film (G1) and three different blends (G2, G3, and G4) of

gelatin=PVA solutions were prepared. Each of the blends formed a homo-

135geneous solution, thus showing compatibility of the two components in the

solvent. It is important to note that the blend prepared from the 20% PVA

in gelatin showed opacity and phase separation. Consequently, mechanical

and thermal properties of the gelatin films containing 0% to 15% PVA were

investigated. Tensile strength (TS) is very important in selecting diverse appli-

140cations of the polymer. The results of TS values of the non-irradiated films for

G1, G2, G3, and G4 formulations are plotted in Figure 1. It is observed that

the TS values of the base polymer (gelatin) were significantly decreased when

PVA was grafted in gelatin. The TS values of non-irradiated and irradiated

films are plotted in Figure 2 against total gamma radiation dose. It is seen

145that due to exposure of radiation the TS values improved up to 50 krad dose

and then again decreased. In the case of pure gelatin, TS values also increased

with the increase of radiation doses and TS value attained a maximum of

57MPa at 50 krad and then decreased with increasing radiation doses.

Figure 1: Tensile strength (TS) of PVA-containing gelatin-based film.

Gelatin-Based PVA FilmQ1 5

Crosslinking and chain scission occurred when polymers were exposed to

150gamma irradiation [12]. Polysaccharides and other natural polymers gener-

ally degrade by breaking the glycosidic linkage under gamma radiation [12].

It is reported in the literature [12] that cellulose and chitosan molecules form

free radicals when irradiation is caused by a gamma source. Gelatin is a natu-

ral biopolymer that consists of protein molecules and can easily fragment due

155to gamma irradiation. The exposure of gamma irradiation produces the free

radicals due to the chain scission of the gelatin molecules. The generated

free radicals may crosslink each other and form more crosslinked sites with

the exposure of gamma irradiation; as a result, mechanical properties

might be increased. Higher gamma radiation might have caused degradation

160of the polymer and the film became hard and brittle while at lower doses

cross-linking might have dominated over chain seasoning.

From Figure 2, in the case of irradiated film, it is also evident that the TS

values of the film obtained from the G2 formulation reached a maximum value

of approximately 51MPa, for 50krad, and then decreased for further increas-

165ing of irradiation intensity as well as gelatin=PVA concentration. The G1, G3,

and G4 formulations also show the same trend as the G2 formulation. When

the gelatin=PVA film is subjected to the irradiation, the hydroxyl group from

PVA and gelatin radicals is initiated to form a cross linked network. So, TS

value increased with radiation, but higher radiation doses cause degradation

170due to the breaking of the polymer chains. At higher radiation doses TS value

decreases. TS values change with gamma irradiation dose at 50 krad for the

Figure 2: Tensile strength (TS) of gelatin-based PVA film against different gammairradiation dose (krad).

6 M. Rahman et al.

G1, G2, G3, and G4 formulations as tabulated in Table 2. It is clear that the TS

value of gamma treated film was higher than that of the untreated film. The

TS values of BDDA soaked and irradiated films of G2 formulation are plotted

175in Figure 3. It is found that the TS value of BDDA soaked and irradiated film

of G2 is increased up to some radiation dose and then decreases. The

maximum value of TS is found as 37MPa, for 50 krad, and then decreases

for further increasing of radiation doses. The effect of PVA concentration on

the TS values of the blend films is shown in Figure 4. It is clear that the

180maximum TS value of the untreated blend films is 35MPa for the 5% PVA con-

taining (G2) gelatin film. It is also seen that with the increasing of the PVA

concentration up to 15%, TS values of the films gradually decrease and then

TS values again increase when the PVA concentration is higher than 80%.

For 15% PVA-containing blend film, TS value is found as 11MPa, whereas it

185is 19MPa for 80% PVA-containing gelatin film.

Table 2: Tensile strength (MPa) changes with gamma irradiationdose at 50 krad

G1 G2 G3 G4

Non-irradiated 41.34 34.94 29.19 11.54Irradiated 56.65 51.67 32.11 28.45

Figure 3: Tensile strength (TS) of 3% BDDA soaked G2 blend film (95% gelatinþ 5% PVA)against different gamma irradiation dose (krad).

Gelatin-Based PVA Film 7

Elongation is an important mechanical property in the application of poly-

mers. The results of elongation at break (Eb) of the non-irradiated films for

G1, G2, G3, and G4 formulations are plotted in Figure 5. It is observed that

Eb value increases for blend films drastically due to incorporating PVA. This

Figure 4: Effect of PVA concentration on the tensile strength (TS) of blend film.

Figure 5: Elongation at break (Eb) of PVA-containing gelatin-based film.

8 M. Rahman et al.

190is due to the increasing concentration of highly flexible PVA into the blend

films. The highest Eb is found to be 5.6% for the film obtained from G4 formu-

lation (85% gelatinþ 15% PVA). The Eb values of irradiated films are plotted

(Figure 6) against gamma irradiation dose as a function of formulation. It is

found that Eb values decrease with the increase of irradiation dose for all for-

195mulations. In the case of blend films, the maximum Eb of 4.8% is observed for

the G2 formulation at 50 krad dose, followed by 3.8% and 4.2% for G3 and G4

formulation, respectively, at the same irradiation dose. Elongation at break

(Eb) changes with gamma irradiation dose at 50 krad are shown in Table 3.

It is clear that the Eb of gamma treated film is lower than that of untreated

200film. The effect of PVA concentration on the Eb of the blend films is shown

in Figure 7. It is clear that Eb value increases with the increasing of PVA con-

tent, which is expected. The Eb values of BDDA soaked and irradiated films of

G2 formulation are plotted in Figure 8. It is found that with increasingQ2 the

irradiation dose Eb values decrease.

Figure 6: Elongation at break (Eb) of gelatin-based PVA film against different gammairradiation dose (krad).

Table 3: Elongation at break (%) changes with gamma irradiation dose at50 krad

G1 G2 G3 G4

Non-irradiated 3.2 5.1 5.09 5.67Irradiated 3.16 4.79 3.83 4.23

Gelatin-Based PVA Film 9

205Polymer LoadingThe results of polymer loading (PL) values of the gamma irradiated films

are plotted in Figure 9 against gamma irradiation dose for the film obtained

Figure 7: Effect of PVA concentration on the elongation at break (Eb) of blend film.

Figure 8: Elongation at break (Eb) of 3% BDDA soaked G2 blend film (95% gelatinþ5%PVA) against different gamma irradiation dose (krad).

10 M. Rahman et al.

from G2 formulation at a 3-minute soaking time in 3% BDDA solution. The

acrylate monomer promoted a photo-induced cross-linking with gelatin=PVA

210using their double bonds. Soaking increases the penetration of monomer to

the film by swelling. As a result, more BDDA diffuses in the gelatin=PVA film.

The PL value increased with the increase in irradiation dose and attained the

maximum value of 4.6% at 100 krad and then the PL value decreased as the

irradiation dose increased. This might be caused by the radiation degradation

215at higher gamma radiation doses.

Thermo Gravimetric Analysis (TGA)TGA results of pure gelatin, pure PVA, and 5% PVA containing gelatin (G2

formulation) films are shown in Figures 10 and 11. The TGA curve of pure

gelatin shows two zones of weight loss. The first weight loss at approximately

22080–90�C is due to the loss of water; the second weight loss starts at about

260�C, showing that different extent thermal degradations of the gelatin are

taking place. PVA shows three steps of weight loss located at 90, 260, and

380�C. The former is attributed to moisture loss; weight loss at 260�C can

be related to thermal processes involving both melting of the PVA chains

225and onset of degradation. The third drop at 380�C is indicative of the occur-

rence of more extensive thermal degradation processes. TGA curve of

irradiated 5% PVA in gelatin film shows the greatest weight loss in the

Figure 9: Polymer loading (PL) of G2 blend film (95% gelatinþ 5% PVA) against differentgamma irradiation dose (krad).

Gelatin-Based PVA Film 11

temperature range of 280–290�C, which is believed due to the disintegration of

intermolecular and partial breaking of the molecular structure. The glass

230point obtained from TMA is plotted against % composition of PVA in gelatin

film in Figure 12. An almost linear trend in increasing glass point with

increasing amount of PVA incorporated with gelatin is observed. The glass

point of pure gelatin film is observed at 51.5�C, whereas it is 56.9�C for 5%

PVA-consisting gelatin film and 170.3�C for 95% PVA-containing gelatin film.

Figure 11: Derivatives TGA of pure gelatin, pure PVA, and treated G2 (95% gelatinþ5%PVA) blend films. (Figure is provided in color online.)

Figure 10: TGA of pure gelatin, pure PVA, and treated G2 blend films. (Figure is providedin color online.)

12 M. Rahman et al.

235The change in morphology due to incorporating PVA might have changed the

glass point. Thermal properties of the pure gelatin film G1 and blend film G2

(95% gelatinþ 5% PVA) are shown in Table 4. The blend films show better

thermal stability than pure gelatin film.

CONCLUSION

240The irradiated blend films exhibit higher thermal stability and mechanical

properties compared with the non-irradiated films. The results reported in

this study reveal that 5% PVA-containing gelatin blend film shows the highest

TS at 50 krad (51MPa), which is 46% higher than that of non-irradiated blend

film. It is also found that due to loading of PVA the TS values of the

245gelatin-based films are decreased significantly while Eb values are increased.

Figure 12: Change of glass point with PVA percentage.

Table 4: Thermal properties of the pure gelatin film G1 and blend film G2 (95%gelatinþ 5% PVA)

FormulationOnset of melting

point (�C)Melting

point (�C)Offset of melting

point (�C)

Pure Gelatin G1 46.3 51.5 54.1G2 (95%gelatinþ 5%PVA)

54.3 56.9 60.9

Gelatin-Based PVA Film 13

A significant improvement of the blend films is also found when the acrylate

group from BDDA is introduced into the film. The highest polymer loading

is achieved 4.7% at a radiation dose 100 krad for 5% PVA-containing gelatin

film. Therefore, it is found that using BDDA on gelatin-based PVA film, fol-

250lowed by gamma irradiation, decreases the Eb and improves the TS of the film.

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