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Title: Synthesis, characterization and antibacterial activity ofbiodegradable Starch/PVA composite films reinforced withcellulosic fibre
Author: Vinod Kumar Gupta Bhanu Priya Deepak PathaniaAmar Singh Singh
PII: S0144-8617(14)00276-8DOI: http://dx.doi.org/doi:10.1016/j.carbpol.2014.03.044Reference: CARP 8706
To appear in:
Received date: 14-2-2014Revised date: 4-3-2014Accepted date: 7-3-2014
Please cite this article as: Gupta, V. K., Priya, B., Pathania, D., & Singh, A.S.,Synthesis, characterization and antibacterial activity of biodegradable Starch/PVAcomposite films reinforced with cellulosic fibre, Carbohydrate Polymers (2014),http://dx.doi.org/10.1016/j.carbpol.2014.03.044
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Synthesis, characterization and antibacterial activity of biodegradable Starch/ PVA 1
composite films reinforced with cellulosic fibre 2
Vinod Kumar Gupta1*, Bhanu Priya2, Deepak Pathania2, Amar Singh Singh3 3
1Department of Chemistry, Indian Institute of Technology Rookree, Roorkee- 247667, India 4
2 Department of Chemistry, Shoolini University, Solan -173212, Himachal Pradesh, India 5
3 Department of Applied Chemistry, National Institute of Technology Hamirpur, 177005, 6
Himachal Pradesh, India 7
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*Corresponding author: E-mail: [email protected] ; [email protected] 18
Fax: 00911332273560; Tel: 00911332285801, 19
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Abstract 26
Cellulosic fibres reinforced composite blend films of Starch/poly(vinyl alcohol) (PVA) were 27
prepared by using citric acid as plasticizer and glutaraldehyde as the cross-linker. The 28
mechanical properties of cellulosic fibres reinforced composite blend were compared with 29
starch/PVA crossed lined blend films. The increase in the tensile strength, elongation 30
percentage, degree of swelling and biodegradability of blend films was evaluated as 31
compared to starch/PVA cross linked blend films. The value of different evaluated 32
parameters such as citric acid, glutaraldehyde and reinforced fibre to Starch/PVA (5:5) were 33
found to be 25wt.%, 0.100 wt.% and 20wt.%, respectively. The blend films were 34
characterized using Fourier transform-infrared spectrophotometry (FTIR), scanning electron 35
microscopy (SEM) and thermogravimetric analysis (TGA/DTA/DTG). Scanning electron 36
microscopy illustrated a good adhesion between Starch/PVA blend and fibres. The blend 37
films were also explored for antimicrobial activities against pathogenic bacteria like 38
Staphylococcus aureus and Escherichia coli. The results confirmed that the blended films 39
may be used as exceptional material for food packaging. 40
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Keywords: Starch/PVA blend film; Mechanical properties; Degree of swelling; Thermal 42
analysis; Antibacterial activity 43
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1. Introduction 51
In the latest years, industries have been working to decrease the dependence on petroleum 52
based fuels and products due to the increase in environmental consciousness. This leads to 53
investigate the environmentally friendly sustainable materials to replace the existing ones. 54
The tremendous increase in production and use of plastics in our life resulted in generation of 55
huge plastic wastes. Due to disposal problems, as well as strong regulations and criteria for 56
cleaner and safer environment, have directed great part of the scientific research toward eco-57
composite materials (Bledzki & Gassan, 1999). In order to solve the problems generated by 58
plastic waste, many efforts have been made to obtain the environmental friendly materials. 59
Many researchers are working on the substitution of the petro-based plastics by 60
biodegradable materials with similar properties and low in cost. Several studies have been 61
reported the use of biodegradable starches from different sources to prepare films and 62
coatings with different properties (Bertuzzi, Armada & Gottifredi, 2007; Larotonda, Matsui, 63
Sobral & Laurindo, 2005; Mali, Grossmann, Garcia, Martino & Zaritzky, 2005; Mali, 64
Sakanaka, Yamashita, & Grossmann, 2005). Starch is the most important polysaccharide 65
polymer used to develop biodegradable films, as it has potential to form a continuous matrix. 66
Starch exhibits some disadvantages such as a strong hydrophilic character and poor 67
mechanical properties as compared to conventional synthetic polymers, which make it 68
inadequate for some packaging purposes (Alves, Costa, Hilliou, Larotonda, Goncalves & 69
Sereno, 2006; John & Thomas, 2008).Poly(vinyl alcohol) is an important synthetic 70
biodegradable polymer having excellent gas barrier properties, high strength, tear and 71
flexibility. However, it has poor dimensional stability due to high moisture absorption. 72
Moreover, it has relatively high price compared to other commercial polymers. Therefore, 73
blended with renewable and abundant agro-resource based such as polysaccharides, 74
particularly starch can be utilized to reduce the manufacturing cost. Blending with starch 75
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resulted in improved moisture resistance and accelerated degradation (Russo, O'Sullivan, 76
Rounsefell, Halley, Truss & Clarke, 2009; Han, Chen & Hu, 2009). However, the properties 77
of the blends deteriorated as starch content in the blend formulation increased, owing to poor 78
compatibility between the two components and phase separation during blend preparation. 79
Many techniques have been reported to improve the compatibility between PVA and starch 80
such as addition of suitable plasticizers, cross-linking agents, fillers and compatibilizers 81
(Siddaramaiah & Somashekar, 2004; Sreedhar, Sairam, Chattopadhyay, Rathnam & Mohan, 82
2005; Sin, Rahman, Rahmat & Samad, 2010; Yoon, Chough & Park, 2006; Krumova, Lopez, 83
Benavente, Mijangus & Perena, 2000; Jia, Cheng, Zhang & Zhang, 2007; Dean & Petinakis, 84
2008; Peng, Kaishuen, Wei & Lui, 2005; Zhu, Zhang, Lai & Zhang, 2007; Nath, Gupta, Yu, 85
Blackburn & White, 2010; Sanghavi, Sitaula, Griep, Karna, Ali & Swami, 2013; Sanghavi, 86
Mobin, Mathur, Lahiri, & Srivastava, 2013; Sanghavi & Srivastava, 2013). However, some 87
of these cross-linking agents always display toxicity and thus their potential applications as 88
biomaterials have been limited. To overcome these disadvantages, certain nontoxic functional 89
additives and simple modification techniques are required to improve the mechanical 90
properties and water resistibility of the St/PVA films. Citric acid (CA) with one hydroxyl and 91
three carboxyl groups exists widely in citrus fruits as main organic acid. Due to its multi-92
carboxylic structure, interaction could take place between the carboxyl groups of CA and the 93
hydroxyl groups on the starch. It resulted in improved water resistibility (Borredon, Bikiaris, 94
Prinos & Panayiotou, 1997), prevent recrystallization and retrogradation and enhance the 95
mechanical properties (Yoon, Chough, & Park, 2006; Shi, Zhang, Liu, Han, Zhang & Chen, 96
2007; Raddy & Yang 2010; Park, Choughy, Yun & Yoon, 2005; Imam Cinelli, Gordon & 97
Chiejjini, 2005; Shi et al 2008; Park, Choughy, Yun & Yoon, 2005; Yoon, Chough & Park 98
2006). CA is nontoxic metabolic product of the body (Krebs or citric acid cycle) and has been 99
approved by FDA for using in food formulations (Ghanbarzadeh, Almasi & Entezami, 2011). 100
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It has been reported that sorbitol, glycerol, urea are used as the plasicizer blend films but 101
citric acid showed improved properties (Imam, Cinelli, Gordon & Chiellini 2005; Park, 102
Chough, Yun & Yoon 2005). Several studies has been reported on the development of 103
composite blends of starch with polyethylene of low and high density (LDPE, HDPE), starch 104
and poly(vinyl alcohol) (PVA), poly(3-hydroxybutyrate co-3-hydroxyvalerate) (PHBV) and 105
poly(lactic acid) (PLA), poly (butylene succinate) (PBS) with cellulosic fibres such as 106
banana, pineapple leaf, sisal, jute, ramie and bamboo fibres (Avella, Martuscelli & Raimo, 107
2000; Averous & Boquillon, 2004; Cao, Shibata & Fukumoto, 2006; Carvalho, Curvelo & 108
Agnelli, 2001; Chen, Qiu, Xi, Hong, Sun & Chen, 2006; Choi, Lim, Choi, Mohanty, DrzaL & 109
Misra, 2004; Cunha, Liu, Feng, Yi & Bernardo, 2001; Fang & Fowler, 2003; Godbole, Gote, 110
Latkar & Chakrabarti, 2003; Misra, Misra, Tripathy, Nayak & Mohanty, 2002; Zobel, 1988; 111
Luo & Netravali, 1999; Kunanopparat, Menut, Morel & Guilbert, 2008; Digabel, Boquillon, 112
Dole, Monties & Averous, 2004; Rodriguez, Ramsay & Favis, 2003; Ma, Yu & Kennedy, 113
2005; Guimaraes, Wypych, Saul & Ramos, 2010; Lee & Wang, 2006; Pinto, Carbajal, 114
Satyanarayana, Fernando & Ramos, 2009; Tripathi, Mehrotra & Dutta, 2009; Sanghavi & 115
Srivastava, 2010; Gadhari, Sanghavi & Srivastava, 2011; Sanghavi, Kalambate, Karna & 116
Srivastava, 2014). Globally, efforts have been made to develop bioplastics from renewable 117
polymers for use as mulch film, materials for green-house construction, packaging, and aids 118
for transporting and transplanting plants/seedlings and antimicrobial properties which 119
improve the food safety and shelf-life. Antimicrobial packaging has one of the most 120
promising active packaging systems. Antimicrobial packaging has been used for the 121
inhibition of certain bacteria in foods, but barriers to their commercial implementation 122
continue to exist (Tripathi, Mehrotra & Dutta, 2009). 123
This paper describes the preparation of cellulosic Grewia optiva fibre reinforced 124
composite cast films from blends of corn starch and PVA. Citric acid and glutaraldehyde 125
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have been used as plasticizer and crosslinker, respectively. The effect of citric acid and 126
gluteraldehyde on mechanical properties and degree of swelling were also attempted. Further, 127
the composite blend films were characterized with Fourier transform infrared 128
spectrophotometer (FTIR), Scanning electron microscopy (SEM) and Thermogravimertic 129
analysis (TGA). The antibacterial activity of St/PVA crosslinked blend films and composite 130
blend films were explored on food pathogenic bacteria such as Escherichia coli and 131
Staphylococcus aureus. 132
2. Experimental 133
2.1 Materials and methods 134
Starch (corn starch) (St), Gluteraldehyde (GLU) and polyvinyl alcohol (PVA) were 135
obtained from CDH India and used without any further purification. Citric acid (CA) was 136
obtained from Aldrich Company India. PVA was 99% hydrolyzed with average molecular 137
weight of 99,000-10,00,000. The weighing of the samples has been done on Libror AEG-220 138
(Shimadzu, Japan) electronic balance. Bacterial strain, S. aureus ATCC 43300 and E. coli 139
MTCC 739 were used by Bio Tech. Research Laboratory Shoolini University, Solan, 140
Himachal Pradesh, India. Antibiotic discs (Amoxicillin 25µg/disc) and Nutrient agar were 141
obtained from Himedia Laboratories Limited. 142
2.2 Preparation of St/PVA blend films 143
St/PVA blend films were prepared by casting method. In this method, 5 g of PVA was 144
dissolved in hot water (90°C). The gelatinized starch was mixed to form homogeneously gel 145
solution. The mixture was continuous stirring for 5 min on a mechanical stirrer (1500 rpm) at 146
room temperature. CA (5-30%) and GLU (0.05-0.250%) were added to above mixture with 147
continuous stirring. The total amount of polymeric mixture was 100 g. The mixing 148
compositions of different additives were shown in Table 1. The reaction parameters such as 149
mixing time, CA and GLU concentration were optimized. Bubbles formed during the 150
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preparation of blend films were removed by using an aspirator. The suspension so formed 151
was poured onto teflon plate to prepare blend film. The blend films were dried at room 152
temperature for 72 h. 153
2.3 Reinforcing material 154
In this study Grewia optiva fibres collected from local resources were used as 155
reinforcing material. The fibres were washed with mild detergent to remove the impurities 156
involved during extraction of fibres. The fibres were dried at hot air oven maintained at 80°C 157
for 12 h. After drying the fibres were converted into fine particle using ball mill (FRITCH 158
Pulbersette-5) of dimension 15-20µm. 159
2.4 Synthesis of lignocellulosic fibre reinforced St/PVA blend films 160
Grewia optiva fibres of dimension 15-20µm were mixed thoroughly with St/PVA 161
blend using a mechanical stirrer, at different loadings (5-30% in terms of weight). This 162
mixture was poured into teflon plate and allowed to dry at room temperature. The mixing 163
composition of raw Grewia optiva fibre was shown in Table 1. 164
2.5 Mechanical properties of St/PVA blend films and fibre reinforced St/PVA blend films 165
Tensile strength (TS) and elongation percentage (%E) of St/PVA blend films and 166
fibre reinforced St/PVA blend films were performed on a computerized Universal Testing 167
Machine (Hounsfield H25KS). The tensile test was conducted in accordance with the ASTM 168
D 638 method. The specimen average thickness was about 1mm and operated at a cross-head 169
speed of 20mm/min at 30°C. 170
2.6 Degree of swelling (DS) of St/PVA blend films 171
In this, dried St/PVA blend films were immersed in distilled water at room 172
temperature (35°C) and kept for 24 h, moisture on the surface of the film was removed, and 173
the weight of the films was measured. The degree of swelling (DS) of St/PVA blend films 174
were calculated as (Ghanbarzadeh, Almasi & Entezami, 2011): 175
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176
Where, Wi is the initial weight of St/PVA blend films and Wf is the final weight of St/PVA 177
blend films. 178
2.7 Fourier transforms infrared (FTIR) spectroscopy 179
FTIR spectra of St/PVA blend films were recorded on a Perkin Elmer 180
spectrophotometer using KBr pellets. The spectrum was recorded in the range from 4000 to 181
400 cm-1 with a resolution of 2 cm-1. 182
2.8 Scanning electron microscopy (SEM) 183
The scanning electron microscopic analysis of different samples was performed on a 184
Leo Electron Microscopy Machine (No. 435-25-20). 185
2.9 Thermogravimetric analysis 186
Thermogravimetric analysis of starch/PVA blend film was performed using EXSTAR 187
TG/DTA 6300 at a heating rate of 10 °C/min under nitrogen atmosphere. 188
2.10 Antibacterial activity 189
Antibacterial activities of Starch/PVA blend films were measured against Gram 190
negative (E. coli) and positive bacteria (S. aureus) with disc diffusion method (Vimala et al., 191
2007). 192
2.11 Biodegradability in Soil 193
In this method, samples of Starch/PVA films, 20×20×1mm small pieces were 194
weighted and placed for 120 days into the agricultural soil in a pot. The pot was covered with 195
a plastic net and exposed to atmospheric conditions for 120 days. Variations in film 196
morphology, the time of films disintegrated and weight loss were recorded. To determine the 197
weight loss the specimen of each sample was quickly washed with cold water and dried in an 198
oven at 70°C to constant weight. The weights of the sample, before and after washing were 199
recorded (Imam, Cinelli, Gordon & Chiejjini, 2005). 200
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3. Results and discussion 201
3.1 Optimization of different parameters on mechanical properties 202
3.1.1 Effect of mixing time 203
Fig. 1a shows Tensile strength (TS) and elongation (%E) of St/PVA blend film 204
without additives for 40 min at 90°C. At the mixing time of 10 min, TS and %E were found 205
to be 16.4 MPa and 68.74% respectively. Further, increase in time resulted in change in 206
colour and decrease in TS and %E of blend films. 207
3.1.2 Effect of citric acid (CA) 208
Effect of CA on TS and %E of St/PVA blend film was shown in Fig. 1 b. The CA as 209
the crosslinker and the plasticizer in the St/PVA blend films. With the initial increase in CA 210
value from 5-30 wt.%, value of TS and %E increases. It has been evident that with increase in 211
CA wt.%, the decrease in TS (17.11-11.35 MPa) and increase of the %E (70.65-198.59%) 212
was observed. The residual CA in the blends acted as the plasticizer, which reduced the 213
interactions among the macromolecules. The decrease in the interactions may be due to the 214
presence of hydroxyl group and carboxyl groups present on CA, which form hydrogen bonds 215
between St/PVA and additive molecules (Yoon, Chough & Park 2006; Ghanbarzadeh, 216
Almasi & Entezami, 2011). It has been extensively used to improve the flexibility due to its 217
diplex function (Avella, Martuscelli & Raimo, 2000). 218
3.1.3 Effect of glutaraldehyde as crosslinking agent 219
Fig. 1c shows the effect of GLU (0.05-0.250%) on TS and %E of St/PVA/CA blend 220
film. The effect of crossslinking of GLU on St/PVA films has been reported (Yoon, Chough 221
& Park, 2006). It has been found that TS (43.4 MPa) increases and %E (204.23%) decreases 222
with the increased in wt.% of GLU from 0.05-0.150%. The blend film so formed was referred 223
as St/PVA crosslinked blend film with remarkable TS and %E. 224
3.1.4 Effect of fibre loading on St/PVA crosslinked blend films 225
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TS and %E of Grewia optiva fibre loading onto St/PVA crosslinked blend films was 226
shown in Fig. 1d. Fibres were added to crosslinked blend from 5-30 wt.%. The result 227
indicated that TS increased on reinforcement with cellulosic fibres. It has been observed that 228
at 20% loading, TS and %E were found to be 38.53 MPa and 182.1%, respectively. The film 229
so formed was referred as fibre reinforced St/PVA composite blend film. 230
3.2 Degree of swelling 231
The swelling behaviour of St/PVA, St/PVA/CA, St/PVA/CA/GLU and fibre 232
reinforced St/PVA composite blend films were shown in Table 2. It was observed that degree 233
of swelling decreased with increase in time. The addition of CA and GLU in St/PVA blend 234
films decreased the DS value which confirmed the superior reactivity of CA and GLU 235
(Krumova, Lopez, Benavente, Mijangus & Perena, 2000). The slight increase in DS value 236
was recorded in fibre reinforced St/PVA composite blend films, which may be due to the 237
greater affinity of water for OH groups present in the fibre reinforced St/PVA blend films. 238
3.3 FTIR analysis 239
FTIR spectra of raw Grewia optiva fibre, St/PVA crosslinked blend films and fibre 240
reinforced St/PVA composite blend films were shown in Fig. 2 a-c. FTIR spectra of raw 241
Grewia optiva fibre (Fig. 2a) showed a broad peak at 3431.39 cm-1 due to bonded OH groups. 242
The absorption peak at 2922.31, 1431.01, and 1021.93 cm-1 were due to -CH2, C–C, and C–243
O stretching, respectively(Singha & Rana, 2012; Singha, Rana & Guleria, 2012). Fig. 2b 244
showed the IR spectra of St/PVA crosslinked blend films. The peak at 3434 cm-1 was 245
assigned to the stretching vibration of the hydroxyl groups. Broad peak at 1717 cm-1 may be 246
due to the C=O stretching vibration and it was probably caused by the ester bond and 247
carboxyl C=O groups in CA (Shi et al., 2008). The peak at 2858.10 cm-1 and 2925 cm-1 248
corresponds to C-H stretching of aldehydic group of gluteraldehyde cross linked to blend 249
(Tudorachi, Cascaval, Rusu & Pruteanu, 2000). The change in peak intensity at 3434 cm-1 in 250
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Fig. 2c confirmed the number of the hydroxyl groups rises due the interaction of fibre with 251
St/PVA crosslinked blend. 252
3.3 Surface morphology 253
Scanning electron micrographs of corn starch, PVA, St/PVA crosslinked blend film 254
and fibre reinforced St/PVA composite blend film were shown in Fig. 3 a-e. The corn starch 255
(Fig. 3a) showed polyhedra or polygon shape granules. Fig. 3b confirmed the smooth surface 256
of PVA film. The St/PVA crosslinked blend film (Fig. 3c) was found to be smooth without 257
any cracks and pores. The SEM images of Grewia optiva fibre confirmed the rough surface 258
(Fig. 3d). Morphological investigations of fibre reinforced St/PVA composite blend film (Fig. 259
3e) clearly indicate the proper mixing of fibre particles with the St/PVA crosslinked blend. 260
3.4 Biodegradability in Soil 261
The crosslinked and fibres reinforced St/PVA composite blend films were exposed to 262
soil for 120 days under prevailing environmental conditions. After 120 days of exposure in 263
soil, films eventually diminished in size and appeared hard and fragile. Film deterioration 264
was also accompanied by loss in their total weight after soil exposure (Table 2). The weight 265
loss may be due to adhering of soil and debris partial to the film surface (Imam, Cinelli, 266
Gordon & Chiejjini, 2005). The decay of 34.54% and 45.65% weight loss were recorded for 267
St/PVA crosslinked film and fibres reinforced St/PVA composite blend films, respectively. 268
Thus, crosslinking results in slow rate of film deterioration in soil. 269
3.5 TGA analysis 270
Thermogravimetric analysis of Grewia optiva fibre, St/PVA crosslinked blend films 271
and fibres reinforced St/PVA composite blend films were studied as a function of percentage 272
weight loss with temperature and shown in Fig. 4 a-c and Table 3. In case of fibre, 273
depolymerization, dehydration and glucosan formation took place between the temperature 274
range of 26.0ºC to 190.0ºC followed by the cleavage of C-H, C-C and C-O bonds (Maiti, 275
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Kaith, Jindal & Jana, 2011; Thakur, Singha & Thakur, 2013). The initial decomposition 276
temperature (IDT) and final decomposition temperature (FDT) were found to be 241.18ºC 277
(8.04% weight loss) and 356.38ºC (77.11% weight loss). On the other hand, in case of 278
St/PVA crosskinked blend films, two stage decomposition was observed. The IDT and FDT 279
have been found to be 156.06ºC (7.29% weight loss) and 490.29ºC (79.03% weight loss), 280
respectively. The degradation temperatures for fibres reinforced St/PVA composite blend 281
films fall between the degradation temperatures for the blend films and the fibres. It has been 282
observed that for fibres reinforced composite blend films, IDT and FDT was 210.40ºC 283
(13.85% weight loss) and 450.99ºC (82.26 % weight loss), respectively. It indicated that the 284
presence of cellulose fibres affect the degradation process. TGA studies were further 285
supported by DTA curve as shown in Fig. 4 a-c. Two peaks were observed in the DTA curve 286
of Grewia optiva fibre and St/PVA crosslinked blend films. Fibre reinforced St/PVA 287
composite blend films shows three DTA peaks. The TGA and DTA curves revealed that the 288
Grewia optiva fibre, St/PVA blend films and fibres reinforced St/PVA composite blend films 289
decompose in different stages in the temperature range of 199-500ºC, 150-600ºC and 190-290
600ºC, respectively. The magnitude and location of peaks found in the derivative 291
thermogravimetric (DTG) curve also provide similar information (Tudorachi, Cascaval, Rusu 292
& Pruteanu, 2000; Jiang, Qiao & Sun, 2006). 293
3.6 Antibacterial activity 294
St/PVA crosslinked blend film and fibres reinforced St/PVA composite blend film 295
were screened for their antibacterial activity against Gram-positive (S. aureus) and Gram 296
negative (E.coli) bacteria as shown in Fig. 5 a-b. Antibiotic amoxicillin (25µg/disc) was used 297
as a standard (+ control). The inhibitory effect was measured based on clear zone surrounding 298
circular film disc. Measurement of clear zone diameter included diameter of film disc, 299
therefore, the values were always higher than the diameter of film disc whenever clearing 300
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zone was present. If there is no clear zone surrounding, it suggests that there is no inhibitory 301
zone, and furthermore, the diameter was valued as zero. Films showed fair antibacterial 302
activity against Gram-positive (S. aureus) and Gram negative (E.coli) bacteria. Inhibitory 303
zone against S. aureus and E. coli was measured to be 1.5 and 1.2 cm, 1.7 and 1.5 cm for 304
St/PVA crosslinked blend film and fibre reinforced St/PVA composite blend films, 305
respectively (Tripathi, Mehrotra & Dutta 2009; Arora, Lala, Sharma &Aneja, 2011; 306
Abdelgawada, Hudsona & Rojas, 2014). 307
Conclusion 308
St/PVA blend films were prepared by a casting method using citric acid as the plasticizer and 309
glutaraldehyde as crosslinker. Addition of GLU increases the tensile strength and degree of 310
swelling of St/PVA blend films. The mechanical properties of fibre reinforced St/PVA 311
composite blend films were found to be higher than those of the St/PVA crosslinked blend 312
films with 20% of Grewia optiva fibre loading. These properties can make Grewia optiva 313
fibres a potential material for the synthesis of a new class of bio-composites. The composite 314
films were characterized using Fourier transform-infrared spectrophotometry (FTIR), 315
scanning electron microscopy (SEM) and thermogravimetric analysis (TGA/DTA/DTG). 316
TGA analysis confirmed the good thermal properties of blend films. The antibacterial 317
experiment indicated that St/PVA blends had good activity against the Gram-negative (E. 318
coli) and Gram- positive (S. aureus) bacteria. Thermal and antibacterial study reveals that the 319
synthesized blend films might be used as potential materials in food packaging. 320
Acknowledgements 321
The authors are thankful to Shoolini University of Biotechnology and Management Sciences, 322
Solan and Director, National Institute of Technology Hamirpur (H.P.) for providing 323
necessary laboratory facilities to complete this work. 324
325
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519
Figure captions 520
Fig. 1. Tensile Strength (TS) and % Elngation (%E) of (a) St/PVA (b) St/PVA/CA (c) 521
St/PVA/CA/GLU (d) St/PVA/CA/GLU/Grewia optiva fiber. 522
Fig. 2. FT-IR of (a) raw Grewia optiva fibre, (b) St/PVA crosslinked blend film and (c) fibres 523
reinforced St/PVA composite blend film. 524
Fig. 3. SEM images of (a) Starch, (b) PVA film, (c) St/PVA crosslinked blend film, (d) raw 525
Grewia optiva fibre and (e) fibres reinforced St/PVA composite blend film. 526
Fig. 4. TGA/DTA of (a) raw Grewia optiva fibre, (b) St/PVA crosslinked blend films and (c) 527
fibres reinforced St/PVA composite blend film. 528
Fig. 5. Inhibitory effect of St/PVA crosslinked blend film and fibres reinforced St/PVA 529
composite blend film against (a) S. aureus and (b) E. coli. 530
531
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Table caption 531
Table 1 532 Composition of St/PVA blend films and fibres reinforced St/PVA composite blend films. 533 534 Table 2 535 Degrees of swelling of St/PVA blend films and Weight loss in St/PVA crosslinked blend film 536 and fibre reinforced St/PVA composite blend film exposed to soil for 120 days. 537 538 Table 3 539 Thermogravimetric analysis of Grewia optiva fibre, St/PVA crosslinked blend film and fibres 540 reinforced St/PVA composite blend film. 541 542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
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Table 1 561 Composition of St/PVA blend films and fibres reinforced St/PVA composite blend films. 562
Sample Starch (%)
PVA (%)
CA (wt.%)
GLU (wt.%)
Fibre loading (wt.%)
St/PVA 5 5 - - -
St/PVA/CA 5 5 5 - -
St/PVA/CA 5 5 10 - -
St/PVA/CA 5 5 15 - -
St/PVA/CA 5 5 20 - -
St/PVA/CA 5 5 25 - -
St/PVA/CA 5 5 30 - -
St/PVA/CA/GLU 5 5 25 0.050 -
St/PVA/CA/GLU 5 5 25 0.100 -
St/PVA/CA/GLU 5 5 25 0.150 -
St/PVA/CA/GLU 5 5 25 0.250 -
St/PVA/CA/GLU 5 5 25 0.300 -
St/PVA/CA/GLU/fibre 5 5 25 0.100 5
St/PVA/CA/GLU/fibre 5 5 25 0.100 10
St/PVA/CA/GLU/fibre 5 5 25 0.100 15
St/PVA/CA/GLU/fibre 5 5 25 0.100 20
St/PVA/CA/GLU/fibre 5 5 25 0.100 25
St/PVA/CA/GLU/fibre 5 5 25 0.100 30
563
564
565
566
567
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Table 2 568 Degree of swelling of St/PVA blend films and Weight loss in St/PVA crosslinked blend film 569 and fibre reinforced St/PVA composite blend film exposed to soil for 120 days. 570
571
572 573 Table 3 574 Thermogravimetric analysis of Grewia optiva fibre, St/PVA crosslinked blend film and fibres 575 reinforced St/PVA composite blend film. 576
Sample
IDT (˚C)
FDT (˚C)
DT (˚C) at 20%wt.
loss
DT(˚C)at 40%wt.
loss
DT(˚C)at 60%wt.
loss
Residual left (%)at 800˚C
Grewia optiva Fibre
241.18 356.38 287.74 326.35 348.77 18.93
St/PVA/CA/ GLU
156.6 490.23 224.93 296.00 371.64 -
fibres reinforced St/PVA composite blend film
210.43 450.43 240.74 310.17 367.66 9.82
577
578
Sample Degree of Swelling (DS)
% wt. loss
St/PVA 2.8 -
St/PVA/CA 1.72 -
St/PVA/CA/GLU 0.53 35.54
Fibre reinforced St/PVA blend film 0.74 45.65
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Highlights 578
• Starch/PVA blend films were prepared using citric acid (CA) and glutarldehyde 579
(GLU) as plasticizer and crosslinker, respectively. 580
• Blend film shows increased tensile strength and degree of swelling. 581
• The mechanical properties of Grewia optiva fibre reinforced composite blend films 582
have been found to be higher than those of the Starch/PVA cross-linked blend films. 583
• TGA showed the good thermal properties of blend films. 584
585
586
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0 5 10 15 20 25 30 35 40 45
12
13
14
15
16
17
Tensile Strength
% Elongation
Mixing time(min)
Te
nsile
Str
en
gth
(MP
a)
% E
longa
tion
50
60
70
80
90
100
110
120
130
a
5 10 15 20 25 30
11
12
13
14
15
16
17
18
Tensile Strength
% Elongation
Citric acid content(wt.%)
Te
nsile
Str
en
gth
(MP
a)
b
60
80
100
120
140
160
180
200
% E
lon
ga
tion
0.05 0.10 0.15 0.20 0.25
5
10
15
20
25
30
35
40
45
50
Tensile Strength
% Elongation
Glutardehyde content(wt.%)
Te
nsile
Str
en
gth
(MP
a)
c
80
100
120
140
160
180
200
220
% E
lon
ga
tion
5 10 15 20 25 30
30
32
34
36
38
40
42
44 Tensile Strength
% Elongation
Fiber reonforcement(wt.%)
Te
nsile
Str
en
gth
(MP
a)
d
100
110
120
130
140
150
160
170
180
190
200
% E
lon
ga
tion
Fig. 1. Tensile Strength (TS) and % Elngation (%E) of (a) St/PVA (b) St/PVA/CA (c)
St/PVA/CA/GLU (d) St/PVA/CA/GLU/Grewia optiva fiber.
4000 3500 3000 2500 2000 1500 1000 500
Wavelength cm-1
a
b
c
%T
Fig. 2. FT-IR of (a) raw Grewia optiva fibre, (b) St/PVA crosslinked blend film and (c) fibres
reinforced St/PVA composite blend film.
Figure(s)
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Fig. 3. SEM images of (a) Starch, (b) PVA film, (c) St/PVA crosslinked blend film, (d) raw
Grewia optiva fibre and (e) fibres reinforced St/PVA composite blend film.
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(a)
(b)
(c)
Fig. 4. TGA/DTA of (a) raw Grewia optiva fibre, (b) St/PVA crosslinked blend films and (c)
fibres reinforced St/PVA composite blend film.
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Fig. 5. Inhibitory effect of St/PVA crosslinked blend film and fibres reinforced St/PVA
composite blend film against (a) S. aureus and (b) E. coli.
