Effect of starch types on properties of biodegradable polymer based on thermoplastic 1

starch process by injection molding technique 2

Yossathorn Tanetrungroj1* and Jutarat Prachayawarakorn1,2* 3

1 Department of Chemistry, Faculty of Science, King Mongkut’s Institute of Technology 4

Ladkrabang, Ladkrabang, Bangkok 10520, Thailand 5

2 Advanced Materials Research Unit, Faculty of Science, King Mongkut’s Institute of 6

Technology Ladkrabang, Ladkrabang, Bangkok 10520, Thailand 7

* Corresponding author 8

Email address: ksjutara@kmitl.ac.th Telephone number : +668-3298400 ext 6235 9

Abstract 10

Due to limitations of thermoplastic starch (TPS), effect of starch types on properties 11

of biodegradable polymer based on TPS was investigated. Different types of starch; 12

containing different contents of amylose and amylopectin, were used, i.e. cassava starch, 13

mungbean starch and arrowroot starch. The TPS polymers were compounded and shaped 14

using an internal mixer and an injection molding machine, respectively. It was found that the 15

amount of amylose and amylopectin contents on native starch influence the properties of the 16

TPS polymer. The high amylose starch of TPMS led to higher strength, hardness, degree of 17

crystallization than the high amylopectin starch of TPCS. In addition, function group analysis 18

by Fourier transforms infrared spectrophotometer (FTIR), water absorption and 19

biodegradation by soil burial test were also examined. 20

Keywords : Arrowroot starch, Biodegradable polymer, Injection molding, Mungbean starch, 21

Thermoplastic starch 22

1.Introduction 23

Due to environmental considerations, starch is now an attracting raw material in the 24

production of biodegradable materials because of its abundant, low price and availability. 25

Starch has a granular structure, which is built by two main carbohydrate polymers; the linear 26

amylose and the highly branched amylopectin. Both high molecular weight polymers are 27

formed by (1,4)-α-D-glucopiranosyl repeating units. Amylose is essentially linear; whereas, 28

amylopectin is highly branched with (1,6) glucosidic branching points occurring every 20–25 29

glucose units. The short chains of amylopectin are thought to be arranged as double helices, 30

in clusters of semicrystalline character (Leszczynski, 2004). Generally, starch sources have 31

been shown the influence the differences in amylose and amylopectin contents. 32

Starch can be processed under the action of both high temperature and shearing action 33

and this is called thermoplastic starch (TPS) (Stepto, 2000). TPS from various sources has 34

been studied, including corn and wheat starch (Naguleswaran et al., 2014) potato starch (Guo 35

et al., 2001) maize starch or wheat starch (Schirmer et al., 2013). Traditionally, the 36

difference in water content and the ratio of amylose to amylopectin of various native starches 37

have been attributed to the physical and barrier properties of thermoplastic starch (Zhou et 38

al., 2008). Many researchers have demonstrated on the influence of several starches on the 39

mechanical properties and biodegradability characteristics of biodegradable plastics produced 40

mainly by the extrusion, compression molding and casting techniques (Stepto, 2003; Rosa et 41

al., 2007; Soest et al., 1996; Altskar et al., 2008; Lopez et al., 2014). 42

In addition, there are many been investigations of the effects of starch type or 43

amylose/amylopectin ratio on the final properties of starch-based materials. It was reported 44

that a blend of TPS from wheat starch (0–22% w/w) with LDPE exhibited a decrease in the 45

Young’s modulus (Pierre et al., 1997). Moreover, high amylose maize starch and potato 46

starch were reported to produce strong films, probably due to amylose crystallization 47

(Durejaa et al., 2001; Soest et al., 1996; Cano et al., 2014). The starch films prepared from 48

the low amylose corn starches also showed low degree of crystallinity (García et al., 2000). 49

However, the effect of starch types on properties of biopolymers based on 50

thermoplastic starch prepared from arrowroot starch (TPAS), cassava starch (TPCS) and 51

mungbean starch (TPMS) and processed by an injection molding technique has not yet been 52

reported. Arrowroot is a powdery product made from the arrowroot plant, a starchy tropical 53

root. It is white and powdery just like cornstarch. Arrowroot starch also makes an excellent 54

substitute for talcum powder in cosmetics and it was once used in the several industries 55

(Jyothi and Sheriff, 2009). Mungbean has been used as raw material for producing starch 56

noodle. Mungbean starch is admired as the best of starch due to its high amylose content, 57

leading to strong gel strength. It is consumed mainly for its rich protein content (24%) but 58

carbohydrate (62–63%) is its major component (Ohwada et al., 2003). Besides, cassava 59

starch is one of the most staple foods in the developing world. It contains significant amounts 60

of rich in starch and poor amounts of other nutrients. It is an abundant, purity, clearness of its 61

paste and cheap agricultural source of starch and flour production. Moreover, it can be enable 62

to blend with other expensive synthesis polymers required to producing biodegradable 63

polymers. (Satyanarayana et al., 2009). 64

The objective of the present study was to evaluate the effect of starch types with 65

different amylose and amylopectin contents on properties of biodegradable polymer prepared 66

from the different types of selected thermoplastic starch, i.e. TPAS, TPCS, and TPMS and 67

processed by injection molding technique. The polymers were, then, characterized by 68

function group analysis by FTIR and crystallinity tested by X-ray diffraction; as well as, 69

morphology, water absorption, tensile properties and biodegradation properties. 70

71

2. Materials and Methods 72

2.1 Materials 73

Arrowroot starch was purchased from Chaopraya Phuchrai 1999 Co., Ltd. 74

(Kamphaengphet Thailand) and containing with 26.5 wt% amylose and 73.5 wt% 75

amylopectin. Mungbean starch was obtained from Sittihinan Co., Ltd. (Bangkok, Thailand), 76

contained approximately 37.9 wt% amylose and 62.1 wt% amylopectin. Cassava starch was 77

obtained from Thaitam (Chonburi, Thailand), composed approximately 16.4 wt% amylose 78

and 83.6 wt% amylopectin. The chemical compositions of arrowroot, mungbean and cassava 79

starches were shown in Table 1 (Erdman, 1986; Habibullah et al., 2003; Pushpadass et al., 80

2010). Glycerol (plasticizer) was purchased from Lab System Co., Ltd. (Bangkok, Thailand). 81

Low-density polyethylene (LDPE, DNDV-0405 R) with MFI of 32 g/10 min. was obtained 82

from Global Connections Public Co., Ltd. (Samuthprakarn, Thailand). Maleic anhydride-83

grafted-polyethylene (MAPE, MB100D) compatibilizer was obtained from Chemical 84

innovation Co., Ltd. (Bangkok, Thailand). 85

2.2 Sample preparation 86

Each kind of starch, i.e. arrowroot starch, cassava starch or mungbean starch was 87

pre-mixed with glycerol (plasticizer) in closed container at room temperature and kept 88

overnight. The weight ratio of starch and glycerol was maintained at 70:30. The TPS 89

polymers were firstly compounded with LDPE and MAPE compatibilizer. The weight ratio 90

of the TPCS and LDPE was kept at 80:20 and The MAPE content was maintained at 5% by 91

weight of the LDPE. The minor content of LDPE polymer was added in order to increase 92

flowability during injection process. Different TPS polymers were compounded using an 93

internal mixer (Lab-Tech Engineering, Bangkok, Thailand) at the temperature of 140°C at the 94

screw rotation speed of 40 rpm for 12 min in order to obtain a homogeneous sample and the 95

specimens were then shaped by the injection molding technique using injection pressure and 96

injection flow speed at 30 bar and 50 rpm, respectively. The injection temperature was varied 97

from 150-170°C (from feed zone to die end). 98

2.3. Fourier transforms infrared spectrophotometer, FTIR 99

FTIR spectrum of a sample was recorded on a Spectrum 2000 GX spectrometer 100

(Perkin Elmer, USA) using KBr disk technique with a resolution of 4 cm-1 in a spectral range 101

of 4000–600 cm-1 using 16 scans per sample. 102

2.4. X-ray diffraction (XRD) 103

X-ray diffraction measurements were carried out using a D8 Advance X-ray 104

diffractometer (Bruker, Madison, USA) with CuKα radiation (wavelength 0.1542 nm) 105

operating at 40 kV and 35 mA. The scattering angle (2θ) covered the range from 3o to 60o (θ 106

is the Bragg angle) with a step size of 0.02o and a sampling interval of 10 s. Percentage 107

crystallinity of a sample was determined by the following equation 108

Crystallinity (%) = Ac/(Ac + Aa) × 100 -----(1) 109

where Ac and Aa were the area of crystallinity region and the area of amorphous region of a 110

sample determined from a diffractogram, respectively. 111

2.5 Morphology 112

A JEOL-6400 scanning electron microscope (Tokyo, Japan) was employed to study 113

the morphology of a sample. Each tested sample was sputter-coated with a thin layer of gold 114

to prevent electrical charge during observation and a sample was immersed into liquid 115

nitrogen before being fractured. 116

2.6 Mechanical property 117

Mechanical tests were evaluated according to ASTM D-638 at the temperature of 118

23±1 oC and relative humidity of 60±5 %. The starch mixtures with different starch type as 119

prepared above were stored in a desiccator containing a saturated solution of ammonium 120

nitrate for 1 day to equilibrate the moisture content of 60±5 % before measurements. A 121

mechanical measurement of each dumbbell shaped specimen was carried out using a 122

Universal Testing Machine (Lloyd Instrument, LR 5K, West Sussex, UK) with a 100 N load; 123

and the crosshead speed was maintained at 40 mm/min. It should be noted that the 124

mechanical property results were obtained by averaging the measurement results of ten 125

independent specimens. Hardness test was conducted according to ASTM: D-2240 using 126

Shore A hardness durometer (Intro enterprise, Thailand). The hardness values were recorded 127

from ten different measurements for each samples. In addition, impact test was carried out 128

using a Izod Impact tester (Yazuda 199311, Japan) and was also measured ten independent 129

specimens according to ASTM: D-256. 130

2.7 Water absorption 131

Water absorption test was carried out according to ASTM: D-570. A samples was 132

dried at 105°C for 3 hour and then immersed in distilled water. The amount of water 133

absorbed by a sample was determined daily for 30 days. The percentage of water absorption 134

was calculated as followed: 135

Water absorption = (W2-W1)/W1 × 100 (2) 136

where W2 and W1 were the wet weight and the dried weight of a sample, respectively. 137

2.8 Biodegradable by soil burial test 138

A dumbbell sample was buried at approximately 10 cm under the soil surface. The 139

water content of the soil was maintained in the range of 30-40% and the test was carried out 140

for 0, 4, 8 and 12 weeks. After that, the tensile test of a soil-buried sample was conducted in 141

comparison with an original sample. 142

3. Results and Discussion 143

3.1 IR Spectroscopic Study 144

FT-IR is a powerful technique for identifying types of chemical bonds of polymers. 145

FTIR spectra of the different TPS polymers are shown in Figure 1. The broad band appeared 146

at 3500–3250 cm-1 was attributed to O–H stretching. The peak in the range of 1275–1070 147

cm-1 was characteristic of C–O–C stretching. The bands in the range of 1200–1000 cm-1 was 148

assigned for C–O–H stretching and 1646-1641 cm-1 was attributed to bounded water 149

presented in starch. These peak positions were due to the TPS component (Shi et al., 2007). 150

Other vibrational bands from LDPE component were found in the wavenumber range of 151

3000–2800 cm-1, assigned from C–H asymmetric stretching of –CH2–. The band in the range 152

of 1475–1450 cm-1 was characteristic of –CH2–deformation. Moreover, the wavenumber in 153

the range of 931-855 cm-1 were designed for C-H bending and the band at 718 cm-1 was 154

owing to CH2- rocking from of LDPE and MAPE component (Bower, 1996). 155

It was found from Figure 1 that all the TPS polymers showed the same IR peak 156

positions and no distinct new peak position could be observed since all different TPS 157

polymers consists of the same chemical structure of polysaccharides. 158

159

3.2 X-ray Diffraction 160

X-ray diffraction technique can be used to identify crystal structure and regular 161

molecular arrangement of starch. X-ray diffraction patterns of different TPS polymers are 162

shown in Figure 2. The peak at 2θ of 19.6 o corresponded to the Vh type pattern of starch due 163

to the amylose-lipid complex formation forming by the effective starch gelatinization (Hartel, 164

2001). Besides, the main peaks at 2θ of 21.4°, 23.7° and 36.0° represented the orthorhombic 165

crystal structure of LDPE component (Pereira et al., 1997). It should be noted that the 166

crystallinity of different TPS polymers mainly resulted from the LDPE component since the 167

LDPE component caused the major peak intensity in the diffractograms; eventhough, the 168

LDPE components was introduced into the TPS polymers in very small proportion. 169

Moreover, it was found that no significant difference in XRD patterns could be observed for 170

the different TPS polymers. This could be due to the similarity of the composition of the 171

different TPS polymers which was also consisted of starch and LDPE, leading to the similar 172

XRD peak patterns. 173

Nevertheless, the calculated percentage crystallinity values of different TPS polymers, 174

obtained from the diffractograms, were approximately 36.2%, 37.4% and 38.7% for the 175

TPCS, TPAS and TPMS polymers, respectively. It can be seen that the highest percentage 176

crystallinity value was found in the TPMS polymer and the percentage crystallinity value of 177

the TPAS polymer was higher than that of the TPCS polymer. The differences in crystallinity 178

values may also be attributed to different contents of amylose and amylopectin of native 179

starch sources as shown by the chemical compositions of different starches in Table 1. 180

From Table 1, it can be seen that the mungbean starch exhibited the highest amylose 181

content. The higher content of amylose led to the higher degree of crystallization. These can 182

be explained that the higher content of linear amylose molecules causes the effective 183

crystallization but amylopectin does not crystallize due to its very highly branched structure 184

and results in the formation of a less firm gel (Marie and Imada, 2004). 185

3.3 Morphology 186

Morphology of different TPS polymers was examined by SEM technique is presented 187

in Figure 3. The TPMS polymer (Figure 3(a)) showed the smoothest surface without phase 188

separation but the TPCS (Figure 3(b)) and TPAS polymers (Figure 3(c)) showed clearly 189

rough surfaces. This could be due to the highest amylose content and elasticity property of 190

the mungbean starch. Amylose content is the most important factor for the resulting of 191

rheological and morphology. The high amylose starch; i.e. mungbean starch, showed smooth 192

surface and better rheological property than the low amylose starches; i.e. cassava and 193

arrowroot starches, it might be due to a comparatively less branching chains and a less 194

compact arrangement of linear short chains. 195

It agrees with the findings by Tan et al. (2006) that the mungbean starch showed 196

smoother than sweet potato starch due to the higher amylose content of the mungbean starch. 197

198

3.4 Water absorption 199

Generally, TPS could absorb some amount of water from the environmental humidity. 200

The water absorption behavior of different TPS polymers is represented in Figure 4. 201

It can be seen that all TPS polymers showed the rapid increase of water absorption during the 202

1 days of testing. After that, the percentage water absorption tended to increase slowly and 203

reached its maximum. It should be noted that the TPMS polymer showed the rapidly increase 204

of water absorption during the 3 days of testing. After that, the TPMS polymer could not 205

absorb water because the TPMS specimen degraded and cracked during the water absorption 206

test. 207

It could be seen from Figure 4 that the lowest percentage of absorption was found in 208

the TPMS polymer. On the other hand, the highest percentage of water absorption was 209

present in the TPAS polymer. 210

From Table1, the mungbean starch showed the lowest amylopectin content, but the 211

cassava starch exhibited the highest amylopectin content. Unexpectedly, the TPCS polymer 212

did not show the highest of water absorption property. It could be explained by considering 213

the carbohydrate content in Table 1. The arrowroot starch consists of higher carbohydrate 214

content when compared with the cassava starch. More content of hydrophilic characteristics 215

of carbohydrate could lead to higher percentage of water absorption. Moreover, the lowest 216

water absorption of the TPMS polymer could be due to lowest carbohydrate content 217

(Table 1) and also the highest crystallization as confirmed by the XRD technique. 218

219

3.5 Mechanical Properties 220

The amount of amylose and amylopectin molecules of the various starch sources 221

(Table 1) also influences mechanical properties of TPS polymers. It can be observed from 222

Figure 5 that the highest stress at max load, Young’s modulus and hardness, the lowest strain 223

at max load and impact strength were found in the TPMS polymer, resulting from the highest 224

amylose content and lowest amylopectin content of the mungbean starch. 225

Additionally, the TPAS polymer presented higher stress at max load,Young’s modulus and 226

hardness, but lower strain at max load and impact strength than those of the TPCS polymer. 227

High amylose starch, generally, presents higher stiffness and hardness than high amylopectin 228

starch due to the comparatively less branching structures (Marie and Imada, 2004). The 229

results also confirms by the good phase morphology (Figure 3) and higher cystallinity (Figure 230

2). Similar observation was reported for high amylose rice film that was stiffer, less elastic 231

than those of low amylose rice film, prepared from casting method (Cano et al., 2014). 232

233

3.6 Biodegradable property 234

Biodegradable property of different TPS polymers, determined by soil buried tests 235

for 0, 4, 8 and 12 weeks is presented in Figure 6. It was found that the stress at maximum 236

load, Young’s modulus and strain at maximum load of all TPS polymers significantly 237

decreased after the biodegradation test. The results of water absorption properties (Figure 4) 238

also related to the biodegradable property. The TPS polymers could absorb water from the 239

soil TPS component, leading to the biodegradation of TPS polymer by the microorganisms 240

existed in soil. The most rapid degradation was found in the TPMS polymer since the 241

mungbean starch consists of high protein content (Table 1) that can be easily decomposed 242

(Diaz, 2008). 243

244

4. Conclusion 245

The influence of starch types on properties of biodegradable polymers based on TPS, 246

processed by injection molding technique, was examined. It was found that properties of 247

different TPS polymers depended on the amylose and amylopectin contents including 248

carbohydrate contents. The high amylose polymer of the TPMS polymer presented higher 249

degree of crystallization and mechanical properties than low amylose polymer of the TPCS 250

polymer. Besides, the high amylose polymer of the TPMS polymer presented the lowest 251

water absorption. The quickest biodegradation was also found in the TPMS polymer. 252

Moreover, the TPAS polymer presented higher degree of crystallinity and mechanical 253

properties including faster degradable property than those of the TPCS polymer. 254

255

Acknowledgements 256

The authors express their sincere appreciation to the KMITL Research Fund for 257

supporting the study financially. 258

References 259

Altskar, A., Andersson, R., Boldizar, A., Koch, K., Stading, M., Rigdahl, M. 260

and Thunwall, M. 2008. Some effects of processing on the molecular structure and 261

morphology of thermoplastic starch. Carbohydrate Polymers. 71, 591–597. 262

Bower, D.I. and Maddams, W.F. 1996. The Vibrational Spectroscopy of Polymers. 263

2nd ed, Cambridge University Press, Cambridge, U.K. 264

Cano, A., Jimenez, A., Chafer, M., Gonzalez, C. and Chiralt, A. 2014. Effect of 265

amylose:amylopectin ratio and rice bran addition on starch films properties. Carbohydrate 266

Polymers. 111, 543-555. 267

Diaz, E. 2008. Microbial Biodegradation: Genomics and Molecular Biology, Caister 268

Academic Press, ISBN 1-904455-17-4. 269

Dureja, H., Khatak, S., Khatak, M. and Kalra, M. 2011. Amylose Rich Starch as an 270

Aqueous Based Pharmaceutical Coating Material – Review. International Journal of 271

Pharmaceutical Sciences and Drug Research. 3(1), 8-12. 272

Erdman, M.D. 1986. Starch from arrowroot starch Grown at Tifton. Cereal chemistry 273

63, 277-279. 274

García, M.A., Martino, M.N. and Zaritzky, N.Z. 2000. Microstructural 275

characterization of plasticized starch-based films. Starch. 52, 118–24. 276

Guo, L., Liang, Q. and Du, X. 2001, Effects of molecular characteristics of tea 277

polysaccharide in green tea on glass transitions of potato amylose, amylopectin and their 278

mixtures. Food Hydrocolloids. 25, 486-494. 279

Habibullah, Mohammad, A. and Hamidullah, S. Proximate and mineral composition 280

of mungbean. Journal of Agriculture and Food chemistry. 2007. 23, 465-466. 281

Hartel, R.W. 2001. Crystallization in Foods. Aspen Publication, Marryland. 282

Jyothi, A.N. and Sheriff, J.T. 2009. Physical and Functional Properties of Arrowroot 283

Starch Extrudates. Journal of Food Science. 74, 97-104. 284

Leszczynski, W. 2004. Resistant starch –classification, structure, production, 285

Polish Journal of Food and Nutrition Sciences. 13, 37-50. 286

Lopez, O., Garcia, M.A., Villar, M.A., Gentili, A., Rodriguez, M.S. and 287

Albertengo, L. 2014. Thermo-compression of biodegradable thermoplastic corn starch films 288

containing chitin and chitosan. LWT - Food Science and Technology. 57, 106-115. 289

Naguleswaran, S., Vasanthan, T. and Hoover, R. 2014. Amylolysis of amylopectin 290

and amylose isolated from wheat, triticale, corn and barley starches. Food Hydrocolloids. 291

35, 686-693. 292

Marie, A. and Imada, F. 2004. Starch retrogradation. Biotechnology and Genetic 293

Engineering reviews. 21, 215-225. 294

Ohwada, N., Ishibashi, K., Hironaka, K. and Yamamoto, K. 2003. Physicochemical 295

properties of mung bean starch. Journal Apply Glycoscience. 50, 481–485. 296

Pereira, R.A., Mano, E.B., Dias, M.L. and Acordi, E.B. 1997. Comparative study on 297

the lamellar crystalstructure of high and low density polyethylenes. Polymer. 38, 707-714. 298

Pierre, N., Favis, B.D., Ramsay, B.A., Ramsay, J.A. and Verhoogt, H. 1997. 299

Processing and characterization of thermoplastic starch/polyethylene blends. Polymer. 38, 300

647– 655. 301

Pushpadass, H.A., Bhandari, P. and Hanna, M.A. 2010. Effects of LDPE and glycerol 302

contents and compounding on the microstructure and properties of starch composite films. 303

Carbohydrate Polymers. 82, 1082–1089. 304

Rosa, D.S., Guedes, C.G. and Carvalho, C.L. 2007. Processing and thermal, 305

mechanical and morphological characterization of post-consumer polyolefins/thermoplastic 306

starch blends, Journal of Materials Science. 42, 551-557. 307

Satyanarayana, K.G., Carbajal, A.G. and Wypych, F. 2009. Biodegradable composites 308

based on lignocellulosic fibers. An overview. Progress in Polymer Science. 34(9), 982–1021. 309

Schirmer, M., Hochstotter, A., Jekle, M., Arendt, E. and Becker, T. 2013. 310

Physicochemical and morphological characterization of different starches with variable 311

amylose/amylopectin ratio. Food Hydrocolloids. 32, 52-63. 312

Shi, R., Liu, Q., Ding, T., Han, Y., Zhang, L. and Tian, C.D. 2007. Ageing of soft 313

thermoplastic starch with high glycerol content. Journal of Applied Polymer Science. 103, 314

574–86. 315

Stepto, R.F.T. 2000. Thermoplastic starch. Macromolecular Symposia. 152, 73–82. 316

Stepto, R.F.T. 2003. The processing of starch as a thermoplastic. Macromolecular 317

Symposia. 201, 203-212. 318

Soest, J.J.G., Benes, K. and Wit, D. 1996. The influence of starch molecular mass on 319

the properties of extruded thermoplastic starch. Polymer. 37, 3543-3552. 320

Soest, J.J.G., Hulleman, S.H.D., Dewit, D. and Vliegenthart, J.F.G. 1996. Change in 321

the mechanical properties of thermoplastic potato starch in relation with changes in B-type 322

crystallinity. Carbohydrate Polymers. 29, 225-232. 323

Tan, H.Z., Gu, W.Y., Zhou, J.P., Wu, W.G. and Xie, Y.L. 2006. Comparative Study 324

on the Starch Noodle Structure of Sweet Potato and Mung Bean. Journal of Food Science. 325

71, 447-455. 326

Zhou, Y.B., Wang, D.F., Zhang, L. and Du, X.F. 2008. Effect of polysaccharides on 327

gelatinization and retrogradation of wheat starch. Food Hydrocolloids. 22, 505-512. 328

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Table captions 338

Table 1 Chemical compositions of different starches 339

340

Table 1 341

Chemical

composition (%)

Cassava starch Arrowroot

starch

Mungbean

starch

Moisture 0.5 8.6 9.3

Carbohydrate

Amylose

Amylopectin

85.0

16.4

83.6

94.4

19.9

75.4

82.3

37.9

62.1

Protein 0.3 4.2 23.3

Fat 1.1 0.2 1.9

Ash 0.2 2.4 3.0

Others 0.6 0.5 0.9

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Figure Captions 353

Figure 1 IR spectra of TPS polymers by different types of TPS (a), TPAS (b), TPCS and 354

(c) TPMS 355

Figure 2 X-ray diffraction patterns of different TPS polymers (a), TPAS (b), TPCS and 356

(c) TPMS 357

Figure 3 SEM micrographs of fracture surfaces of different TPS polymers (a), TPMS (b), 358

TPCS and (c) TPAS 359

Figure 4 Relationship between water absorption and immersion time of different TPS 360

polymers 361

Figure 5 Mechanical properties of different TPS polymers (a) Stress at maximum load and 362

Young’s modulus (b) Strain at maximum load and Hardness 363

Figure 6 Mechanical properties of the different TPS polymers after soil buried test for 0, 4 364

8 and 12 weeks 365

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Figure 1 373

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Figure 1 IR spectra of TPS polymers by different types of TPS (a), TPAS (b), TPCS and 375

(c) TPMS 376

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(a)

(b)

(c)

Figure 2 385

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Figure 2 X-ray diffraction patterns of different TPS polymers (a), TPAS (b), TPCS and 387

(c) TPMS 388

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(a)

(b)

(c)

19.6°

21.4°

23.7° 36.0°

Figure 3 396

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Figure 3 SEM micrographs of fracture surfaces of different TPS polymers (a), TPMS (b), 400

TPCS and (c) TPAS 401

Figure 4 402

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Figure 4 Relationship between water absorption and immersion time of different TPS 413

polymers 414

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Figure 5 428

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Figure 5 Mechanical properties of different TPS polymers (a) Stress at maximum load and 438

Young’s modulus (b) Strain at maximum load and Hardness 439

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Figure 6 453

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Figure 6 Mechanical properties of the different TPS polymers after soil buried test for 0, 4 476

8 and 12 weeks 477

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