Developing acrylated epoxidized soybean oil coating for improving moisture sensitivity and permeability of starch-based film

Accepted Manuscript Developing acrylated epoxidized soybean oil coating for improving moisture sensitivity and permeability of starch-based film

Xiaoyan Ge, Long Yu, Zengshe Liu, Hongsheng Liu, Ying Chen, Ling Chen PII: DOI: Reference:

S0141-8130(18)35478-3 https://doi.org/10.1016/j.ijbiomac.2018.11.239 BIOMAC 11116

To appear in:

International Journal of Biological Macromolecules

Received date: Revised date: Accepted date:

13 October 2018 13 November 2018 26 November 2018

Please cite this article as: Xiaoyan Ge, Long Yu, Zengshe Liu, Hongsheng Liu, Ying Chen, Ling Chen , Developing acrylated epoxidized soybean oil coating for improving moisture sensitivity and permeability of starch-based film. Biomac (2018), https://doi.org/10.1016/ j.ijbiomac.2018.11.239

This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT Developing acrylated epoxidized soybean oil coating for improving moisture sensitivity and permeability of starch-based film

1

CR

IP

T

Xiaoyan Ge1, Long Yu1,3*, Zengshe Liu2**§, Hongsheng Liu1,3, Ying Chen1, Ling Chen1

Centre for Polymers from Renewable Resources, SFSE, South China University of

US

Technology, Guangzhou 510640, China

National Center for Agricultural Utilization Research, ARS/USDA, Peoria, IL, USA

3

Sino-Singapore International Joint Research Institute, Knowledge City,

M

AN

2

ED

Guangzhou-510663, China

PT

Corresponding author: *Long Yu (E-mail: [email protected]; Tel: +86-2-87111971; Fax:

CE

+86-2-87111971); **Zengshe Liu (E-mail: [email protected]; Tel:

§

AC

+01-309-681-6104; Fax: + 01-309-681-6524).

Mention of trade names or commercial products in this publication is solely for the

purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture. USDA is an equal opportunity provider and employer.

1

ACCEPTED MANUSCRIPT ABSTRACT Acrylated epoxidized soybean oil (AESO)-based coatings were developed to reduce moisture sensitivity and permeability of starch-based materials. The coating was applied on starch based films by dipping the samples on AESO-based coating solutions, followed

IP

T

by crosslinking with ultraviolet (UV) light. Effect of AESO concentration, photoinitiator content and processing conditions on the performance of coated starch-based film was

CR

systematically investigated, in particular the effect of coating on moisture absorption,

US

permeability and mechanical properties. The modified surface was characterized by scanning electronic microscopy and Fourier transform infrared spectroscopy. The results

AN

showed that the moisture sensitivity of the starch-based sheets was reduced significantly

M

since the crosslinked AESO acted as a hydrophobic layer. Moisture permeability was decreased more than 10 times after AESO treatment. It was found that the crosslinking

PT

good water resistance.

ED

density acted as one of the key factors, so even a very thin layer of AESO could achieve

AC

resistance.

CE

Keywords: starch; coating; acrylated epoxidized soybean oil; UV crosslinking; moisture

2

ACCEPTED MANUSCRIPT 1.

INTRODUCTION Starch is one of the most promising materials used in the effort to replace

petroleum-based polymers. It offers a very attractive component of new biodegradable polymers due to their low material cost and ability to be processed with conventional

T

plastic processing equipment [1, 2]. Starch-based materials have also exhibited the

IP

advantages of biocompatibility and biodegradability in medicinal drug release, packaging

CR

and agricultural applications [3-7]. However, the hydrophilic nature of starch makes it

US

susceptible to moisture uptake, resulting in inadequate performance, in particular water vapor permeability and tensile strength[8, 9]. To improve the moisture resistance and

AN

mechanical properties of starch-based materials, various blending and compositing

M

techniques have been developed[10-12], such as mixing with lipids/oil[13-15], blending with protein/gelatin[16-20], reinforcing with mineral filler[21], cellulous fibers[22-24],

ED

polysaccharide-based particles[25-28] and self-reinforcing techniques[29].

PT

A blend containing starch cannot become hydrophobic until starch content is low enough to form a separate domain phase in a hydrophobic polymer matrix, in which case

CE

starch only acts as filler. On the other hand, adding any chemically extracted filler,

AC

including all kinds of nano-scale fillers, to improve the performance of starch-based materials, is potentially harmful to human health as they may contain harmful toxic residues that are not permitted for use in food packaging applications. The advantages of surface coating and crosslinking includes ease of processing, lower cost, flexibility to control thickness, maximizing natural properties of matrix, etc. Actually crosslinking is a common approach to improve the performance of starch for various applications. Starch and starch products have been crosslinked with various crosslinking agents, such as 3

ACCEPTED MANUSCRIPT phosphorus oxychloride, sodium trimetaphosphate, sodium tripolyphosphate, epichlorohydrin and 1,2,3,4-diepoxybutane, to improve the mechanical and moisture stability properties [30-35]. Citric acid is one of the most popular crosslinking agents for starch [30, 31] but needs to be mixed initially with a starch suspension before film casting.

T

Most of the crosslinking agents have to be added to a starch solution during film casting.

IP

However, this method is not suitable for industrial manufacture, in which film or sheet is

CR

mainly produced by extrusion casting. Surface coating and surface crosslinking are more suitable for post-treatment. Furthermore, the most efficient, low cost and convenient

US

technique of crosslinking is irradiation. Photosensitizers, for example various sodium

AN

salts, have been used and included into a starch sheet surface layer as an aqueous solution and then crosslinked under ultraviolet (UV) irradiation [36-38].

M

In this work, an acrylated epoxidized soybean oil (AESO)-based coating was

ED

developed to reduce the moisture sensitivity and improve the gas permeability of starch-based film. Similar to starch, soybean oil also comes from renewable resource.

PT

AESO has been used as an additive to inks and coatings [39] and as a major component

CE

for a number of natural resins. AESO has been developed for coating films with the trifunctional acrylate monomer and trimethylol propanetri methacrylate (TMPTMA) as a

AC

crosslinkable active diluents cured under UV radiation[40]. Liu and Tisserat[41] recently reported the distillers dried grains with soluble (DDGS)-flax composites coated with AESO and polymerized by UV light. The objective of this work is to develop AESO-based coatings used for reducing moisture sensitivity and permeability of starch-based materials. This work focused on the effect of AESO concentration, initiator content and processing conditions on the performance of coated starch-based films. The 4

ACCEPTED MANUSCRIPT treated films were characterized by moisture absorption, permeability, tensile testing, FTIR and SEM to establish the relationship between microstructures and performance.

2.

EXPERIMENTAL

Materials:

IP

2.1.1

T

2.1 Materials and Sample Preparation

CR

All the materials used in this work are commercially available. Starch (hydroxypropyl high-amylose cornstarch with amylose content 80%) was obtained from

US

Penford, Australia. Acrylated epoxidized soybean oil was obtained from Sigma-Aldrich

AN

(Milwaukee, WI, USA). UV initiatorIrgacure®819 was purchased from BASF Company

Film preparation:

ED

2.1.2

M

(Vandalia, IL, USA).

Starch films were extruded using Haake twin-screw extruder (Rheomex PTW

PT

24/40p, Ø30, screw diameter D=24 mm, and screw length L=28D) with a 150mm wide

CE

sheet die. There are eight temperature controlling zones along the barrel of the extruder, and each temperature is 40, 60, 90, 120, 120, 100, 95 respectively °C. A haul-off device

AC

was used for collecting the extruded films. The thickness of the extruded film is about 0.30 mm. The details of the film extrusion have been reported in a previous paper[42]. 2.1.3

Surface coating and crosslinking:

AESO and the initiator (Irgacure®819), were dissolved in ethyl acetate to prepare photosensitizer aqueous solutions with different concentrations. The starch films were initially conditioned at 57% relative humidity (RH) to reach water equilibrium and were 5

ACCEPTED MANUSCRIPT then cut into small pieces (5 cm ×5cm) and soaked in the photosensitizer aqueous solution for a short time. The films were then removed from the solution and were allowed to dry. The starch films containing photosensitizer on their surface layer were exposed to ultraviolet (UV) light at normal atmospheric conditions with a UV

T

mini-crosslinking machine (Scients03-II, Ningbo Xinzhi Biological Science and

IP

Technology Co. Ltd., Ningbo, China). The size of the exposure chamber is 34 cm wide,

CR

29.5 cm deep and 15 cm high. There are five parallel tube lamps (28 cm long, 10W each, emitting at 254 nm) on the top of the chamber. The samples were put at the chamber

US

bottom for irradiating to a desired dose by using the energy (J/cm2) setting system

AN

provided in the UV mini-crosslinking machine. This setting system uses radio meter to measure the irradiation dose continuously, and the irradiation stops automatically when

M

the energy dose at the chamber bottom has reached the set value. Our primary

ED

experimental results showed that the polymerization of the AESO monomer was finished after exposing to the ultraviolet (UV) light for 7min so the time was used in this work.

CE

PT

Table 1 lists solution concentration and treatment conditions.

Table 1 Sample codes and coating conditions AESO

Irgacure®819

Irradiation

Irradiation

codes

content

content

time(min)

distance(cm)

S

0

0

0

0

S-AESO5I6

0.05

0.06

7

15

S-AESO7I6

0.07

0.06

7

15

S-AESO10I6

0.10

0.06

7

15

AC

Sample

6

ACCEPTED MANUSCRIPT 0.14

0.06

7

15

S-AESO20I6

0.20

0.06

7

15

S-AESO30I6

0.30

0.06

7

15

S-AESO10I4

0.10

0.04

7

15

S-AESO10I7

0.10

0.07

7

15

2.2 Characterizations Fourier transform infrared spectroscopy:

US

2.2.1

CR

IP

T

S-AESO14I6

AN

A Tensor 37 (Bruker) spectrophotometer (Bruker Corporation, Billerica, MA) was used to obtain the Fourier Transform Infrared (FTIR) spectra of the samples. In order to

M

eliminate the effect of environmental moisture, samples (film) were measured using ATR

ED

mode with the ZnSe ATR Accessory. FTIR spectra were collected with 64 scans, and the

OPUS 6.5 software.

Water absorption:

CE

2.2.2

PT

spectral range and spectral resolution were 4000–600 cm-1and 4 cm1, respectively, by

AC

The water absorption of the films was evaluated by the measurement of weight percentage of the film after immersing in distilled water. The film specimens (5 cm×5 cm) were placed in a 500ml beaker containing 300ml distilled water under ambient temperature (25°C). The samples were then brought out at explicit intervals and the superfluous water on the surface was removed carefully with Whatman filter paper. Weight of the samples was measured by a weighing balance (with an accuracy of 0.01g) and the water absorption was expressed as follows: 7

ACCEPTED MANUSCRIPT Water absorption (%) = (Mt-Mo)/Mo×100

(1)

where Mo and Mt are weights of the initial specimen and the weight of specimen after soaking it for certain time, t, in water, respectively. Tensile testing:

T

2.2.3

IP

Tensile properties were evaluated in accordance with ASTM D882-12 standard test

CR

method (ASTM, 2012). Tensile bar shaped specimens of definite size were cut from the films along machine-direction. Apparatus used for tensile testing (Instron 5565) was run

US

at a cross-head speed of 10 mm min-1 at room temperature (25°C). All the specimens

AN

were conditioned at 57% RH for water equilibrium before testing, while the results given are average of seven specimens.

Scanning electron microscopy (SEM):

M

2.2.4

ED

SEM (ZEISS, Oberkochen, Germany) was used to investigate the surface and

PT

interface between the matrix and coating. All the samples were fixed on metal “stubs” using double-sided adhesive tape and sputter coated with gold using an Eikosputter coater

CE

(Matsubo Corporation, Japan) under vacuum. A lower voltage of 5kV was used in this

2.2.5

AC

part of the experimental work to avoid damaging the surfaces. Moisture permeability:

Water vapor permeability (WVP) was determined gravimetrically using water permeability tester (LanGuang, TSY-TIH, China) according to GB/T 1037 standard test method (Standardization Administration of China, 1988) with proper modification. The films were fixed on top of the sample holder and then placed in a constant humidity (90%) 8

ACCEPTED MANUSCRIPT chamber with controlled temperature (38°C). The exposure area for testing was 33 cm2 for each sample and the balance time was 3h, yielding three replicates for each sample.

RESULTS AND DISCUSSION

T

3.

IP

3.1 Surface and interface characterization:

CR

The surfaces of starch films before and after coating were investigated by FTIR

US

spectroscopy with ATR (see Fig 1). A pure AESO film was used as reference. The spectral differences are observably. There are unique peaks for AESO, such as at the

AN

1720 cm-1 shift in the ester carbonyl band of the AESO. Another significantly different absorption band is observed in the spectrum at 1635 cm-1, 1409 cm-1and 809 cm-1

M

indicating the presence of vinyl functionality (–CH=CH2) of the AESO monomer[43].

ED

With the decrease of AESO content of the film, the bands at 1635 cm-1 disappeared

PT

because of polymerization of the AESO monomer (see Scheme 1)[40]. Due to disappearance of double bonds, the conjugated system of the carbonyl and double bond

CE

was destroyed. As a result, the groups of carbonyl (C=O) atb1720 cm-1 were slightly

AESO.

AC

shifted towards the higher frequency, which also suggested complete polymerization of

9

ACCEPTED MANUSCRIPT

S-AESO5I6 S-AESO10I6 S-AESO20I6 S-AESO30I6

AESO

-1

T

1635cm

-1 -1

809cm

800

CR

2200 2000 1800 1600 1400 1200 1000

IP

1409cm

-1

1720cm

Wavenumbers(cm-1)

CE

PT

ED

M

AN

US

Fig 1. FTIR spectra of the surface of starch film coating with AESO.

AC

Scheme 1. Polymerization of acrylated epoxidized soybean oil.

Fig 2 shows the SEM images of the surface of starch film without (A) and with (B) AESO coating. It can be seen that the surface of starch-based film is reasonably smooth, while the morphology of the AESO coated surface appears clearly different. There are many irregular but homogeneous marks on the coated surface, which could be due to shrinking of the AESO film after crosslinking.

10

ACCEPTED MANUSCRIPT

CR

IP

T

Fig 2. SEM surface of starch film without (A) and with (B) AESO coating.

Fig 3 shows the cross-section of the surface of starch film without (A) and with (B)

US

AESO coating. The coated AESO layer can be clearly identified on the surface of the starch-based film. The coating is a continuous layer that provides good moisture barrier.

AN

Typically, the thickness of AESO coating was about 2μm when the 10% AESO solution

M

was used. Since the AESO film is a soft elastomeric material, the deformation of the film

CE

PT

ED

during cutting (sample preparation) can be seen clearly in Fig 3(B).

AC

Fig 3. Cross-section of the surface of starch film without (A) and with (B) AESO coating.

3.2 Moisture resistance: Figs 4 and 5 show the effect of AESO coating on the water absorption of the starch film immersed in distilled water. It can be seen that the water absorption rate was 11

ACCEPTED MANUSCRIPT decreased significantly after coating with AESO, which was expected since crosslinked AESO is hydrophobic and water resistant. Pure starch films lost their strength after immersing in distilled water for 30 min and were also swelled significantly. The effect of AESO concentration on the water absorption rate of starch based films

T

is showed in Fig 4. It was found that the water absorption rate decreased with increasing

IP

AESO concentration as expected due to a thicker layer of AESO formed on the starch

CR

films at higher concentration. Fig 5 is shows the effect of concentration of initiator on the water absorption rate of starch based films. Lower the water absorption rate was observed

US

at higher concentration of initiator. The initiator content controls the crosslinking density

AN

500 450 400 350 300 250 200 150 100 50 0

M

S S-AESO5I6 S-AESO7I6 S-AESO10I6

PT

ED

S-AESO14I6

0

CE

Water Absorption(%)

of AESO, which in turn controls the water permeability of starch-based films.

30

60

90

120

AC

Time(min)

Fig 4. Effect of AESO concentration on water absorption.

12

500 450 400 350 300 250 200 150 100 50 0

S S-AESO10I4 S-AESO10I6

0

30

60

90

IP

T

S-AESO10I7

120

Time(min)

AN

US

Fig 5. Effect of initiator content on water absorption.

CR

Water Absorption(%)

ACCEPTED MANUSCRIPT

M

3.3 Moisture permeability:

ED

The water vapor permeability (WVP) of the starch-based films coated with different concentration of AESO is presented in Fig 6. It can be seen that the highest value for

PT

WVP (531.81g/m2*24h) is of the control film specimen (without AESO coating).

CE

Significant improvement in moisture permeability was observed after coating the starch film with corsslinked AESO. Hydrophilic-hydrophobic ratio of the film constituents is

AC

generally seen as a factor strongly related to water vapor transmission[44]. It has been noticed that the moisture permeability of the films was decreased with increasing AESO concentration. WVP decreased markedly from 531.81 to 46.79 g/m2*24h with the increase in concentration of AESO from 0% to 30%. As the hydrophobic AESO concentration was increased, the hydrophobicity of the film increased, and water vapor penetration became more difficult. The results of water vapor permeability are in accordance with the water absorption rate (see Figs 4 and 5). 13

500 400 300 200

IP

A ES O 30 I 6

CR

S-

A ES O 20 I 6

S-

S-

O 5I 6 SA

ES

A ES O 10 I 6

T

100 S

Moisture Permeability (g/m2*24h)

ACCEPTED MANUSCRIPT

AN

US

Fig 6. Effect of AESO coating on moisture permeability.

M

3.4 Mechanical properties:

ED

Figs 7 show the effect of the AESO coating on the tensile properties of the starch-based film. There are no significant impact of AESO coating on the tensile

PT

properties of starch-based films since the coating is very thin and contributes a limited

CE

fraction to the mechanical properties of starch-based matrix. Furthermore, the AESO film is a soft elastomer so that it slightly decreased the modulus with increasing AESO

AC

concentration, while the higher density of crosslinking slightly increased slightly the modulus (Fig 7)[45]. It is expected that the AESO coating will improve the mechanical properties of the starch-based films under higher humidity conditions and will be studied in our future work.

14

100 90 80 70 60 50 40 30 20 10 0

Elongation(%) Modulus(MPa)

1400 1200 1000 800 600 400

Modulus(MPa)

200 0 S

S-AESO5I6

S-AESO7I6

S-AESO10I6

T

Elongation(%)

ACCEPTED MANUSCRIPT

IP

Elongation(%) Modulus(MPa)

1400

CR

100 90 80 70 60 50 40 30 20 10 0

1200

600 400 200 0 S

S-AESO10I4

S-AESO10I6

S-AESO10I7

M

I(%)

US

800

AN

1000

Modulus(MPa)

Elongation(%)

AESO(%)

ED

Fig 7. Effect of AESO concentration (top) and initiator content (bottom) on tensile

CONCLUSION

CE

4.

PT

properties.

AC

Coatings based on AESO reduced the moisture sensitivity and permeability of starch-based films. SEM observed a continuous layer of AESO coating on the surface of starch-based films and FTIR detected the crosslinking reactions. Improvement in moisture sensitivity and permeability of starch-based films was due to the crosslinked AESO that acted as a hydrophobic layer. It was found that the crosslinking density acted as one of the key factors in improving moisture permeability, so even a very thin layer of AESO could achieve good water resistance. Since the coating and initiator treatment are 15

ACCEPTED MANUSCRIPT simple and easy to process, this can be a promising technique to solve the well-known weaknesses of starch-based materials.

ACKNOWLEDGEMENTS

T

The authors from South China University of Technology, China, would like to

IP

acknowledge the research fund National Natural Science Foundation of China(31571789),

CR

National Key R&D Program of China (2018YFD0400700) and 111 Project (B17018).

US

REFERENCES

AN

[1] H. Liu, F. Xie, L. Yu, L. Chen, L. Li, Thermal processing of starch-based polymers, Prog. Polym. Sci. 34(12) (2009) 1348-1368.

M

[2] A.X. Bioresour TechnolBioresour TechnolSong, Y.H. Mao, K.C. Siu, J.Y. Wu,

ED

Bifidogenic effects of Cordyceps sinensis fungal exopolysaccharide and konjac glucomannan after ultrasound and acid degradation, Int. J. Biol. Macromol. 111 (2018)

PT

587-594.

CE

[3] M.M. Reddy, S. Vivekanandhan, M. Misra, S.K. Bhatia, A.K. Mohanty, Biobased plastics and bionanocomposites: Current status and future opportunities, Prog. Polym.

AC

Sci. 38(10-11) (2013) 1653-1689. [4] G. Chen, B. Liu, B. Zhang, Characterization of composite hydrocolloid film based on sodium cellulose sulfate and cassava starch, J. Food Eng. 125 (2014) 105-111. [5] L. Zhang, Y. Wang, H. Liu, L. Yu, X. Liu, L. Chen, N. Zhang, Developing hydroxypropyl methylcellulose/hydroxypropyl starch blends for use as capsule materials, Carbohydr. Polym. 98(1) (2013) 73-9. 16

ACCEPTED MANUSCRIPT [6] N. Zhang, H. Liu, L. Yu, X. Liu, L. Zhang, L. Chen, R. Shanks, Developing gelatin-starch blends for use as capsule materials, Carbohydr. Polym. 92(1) (2013) 455-61. [7] X.-y. Bao, A. Ali, D.-l. Qiao, H.-s. Liu, L. Chen, L. Yu, Application of Polymer

T

Materials in Developing Slow/Control Release Fertilizer, Acta Polymerica Sinica (9)

IP

(2015) 1010-1019.

CR

[8] R. Thakur, B. Saberi, P. Pristijono, J. Golding, C. Stathopoulos, C. Scarlett, M. Bowyer, Q. Vuong, Characterization of rice starch-iota-carrageenan biodegradable edible

US

film. Effect of stearic acid on the film properties, Int. J. Biol. Macromol. 93(Pt A) (2016)

AN

952-960.

[9] A.S. Singha, H. Kapoor, Effect of Silk Fibroin Reinforcement on the Properties of

M

Potato Starch-Polyvinyl Alcohol Blend Films, Int. J. Polym. Anal. Charact. 19(3) (2014)

ED

212-221.

[10] A. Nawab, F. Alam, M.A. Haq, Z. Lutfi, A. Hasnain, Mango kernel starch-gum

CE

(2017) 869-876.

PT

composite films: Physical, mechanical and barrier properties, Int. J. Biol. Macromol. 98

[11] C. Gao, L. Yu, H. Liu, L. Chen, Development of self-reinforced polymer

AC

composites, Prog. Polym. Sci. 37(6) (2012) 767-780. [12] L. Yu, K. Dean, L. Li, Polymer blends and composites from renewable resources, Prog. Polym. Sci. 31(6) (2006) 576-602. [13] T.A. Nascimento, V. Calado, C.W.P. Carvalho, Development and characterization of flexible film based on starch and passion fruit mesocarp flour with nanoparticles, Food Res. Int. 49(1) (2012) 588-595. 17

ACCEPTED MANUSCRIPT [14] W. Ma, C.-H. Tang, S.-W. Yin, X.-Q. Yang, Q. Wang, F. Liu, Z.-H. Wei, Characterization of gelatin-based edible films incorporated with olive oil, Food Res. Int. 49(1) (2012) 572-579. [15] J.H. Han, G.H. Seo, I.M. Park, G.N. Kim, D.S. Lee, Physical and Mechanical

T

Properties of Pea Starch Edible Films Containing Beeswax Emulsions, J. Food Sci. 71(6)

IP

(2006) E290-E296.

CR

[16] E.J. Hopkins, C. Chang, R.S.H. Lam, M.T. Nickerson, Effects of flaxseed oil concentration on the performance of a soy protein isolate-based emulsion-type film, Food

US

Res. Int. 67 (2015) 418-425.

AN

[17] K. Limpisophon, M. Tanaka, K. Osako, Characterisation of gelatin–fatty acid emulsion films based on blue shark (Prionace glauca) skin gelatin, Food Chem. 122(4)

M

(2010) 1095-1101.

ED

[18] M.B. Vásconez, S.K. Flores, C.A. Campos, J. Alvarado, L.N. Gerschenson, Antimicrobial activity and physical properties of chitosan–tapioca starch based edible

PT

films and coatings, Food Res. Int. 42(7) (2009) 762-769.

CE

[19] J. Osés, I. Fernández-Pan, M. Mendoza, J.I. Maté, Stability of the mechanical properties of edible films based on whey protein isolate during storage at different

AC

relative humidity, Food Hydrocoll. 23(1) (2009) 125-131. [20] T. Sivarooban, N.S. Hettiarachchy, M.G. Johnson, Physical and antimicrobial properties of grape seed extract, nisin, and EDTA incorporated soy protein edible films, Food Res. Int. 41(8) (2008) 781-785.

18

ACCEPTED MANUSCRIPT [21] H.-M. Wilhelm, M.-R. Sierakowski, G.P. Souza, F. Wypych, The influence of layered compounds on the properties of starch/layered compound composites, Polym. Int 52(6) (2003) 1035-1044. [22] X. Li, C. Qiu, N. Ji, C. Sun, L. Xiong, Q. Sun, Mechanical, barrier and

T

morphological properties of starch nanocrystals-reinforced pea starch films, Carbohydr.

IP

Polym. 121 (2015) 155-62.

CR

[23] F.X. Espinach, M. Delgado-Aguilar, J. Puig, F. Julian, S. Boufi, P. Mutje, Flexural properties of fully biodegradable alpha-grass fibers reinforced starch-based

US

thermoplastics, Composites, Part B 81 (2015) 98-106.

AN

[24] A. Jiménez, M.J. Fabra, P. Talens, A. Chiralt, Effect of lipid self-association on the microstructure and physical properties of hydroxypropyl-methylcellulose edible films

M

containing fatty acids, Carbohydr. Polym. 82(3) (2010) 585-593.

ED

[25] A. Ali, F. Xie, L. Yu, H. Liu, L. Meng, S. Khalid, L. Chen, Preparation and characterization of starch-based composite films reinfoced by polysaccharide-based

PT

crystals, Composites, Part B 133 (2018) 122-128.

CE

[26] A. Ali, L. Yu, H.S. Liu, S. Khalid, L.H. Meng, L. Chen, Preparation and characterization of starch-based composite films reinforced by corn and wheat hulls, J.

AC

Appl. Polym. Sci. 134(32) (2017) 9. [27] M. Li, D. Li, L.-j. Wang, B. Adhikari, Creep behavior of starch-based nanocomposite films with cellulose nanofibrils, Carbohydr. Polym. 117 (2015) 957-963. [28] J.S. Alves, K.C. dos Reis, E.G.T. Menezes, F.V. Pereira, J. Pereira, Effect of cellulose nanocrystals and gelatin in corn starch plasticized films, Carbohydr. Polym. 115 (2015) 215-222. 19

ACCEPTED MANUSCRIPT [29] C. Lan, L. Yu, P. Chen, L. Chen, W. Zou, G. Simon, X. Zhang, Design, Preparation and Characterization of Self-Reinforced Starch Films through Chemical Modification, Macromol. Mater. Eng. 295(11) (2010) 1025-1030. [30] E. Olsson, C. Menzel, C. Johansson, R. Andersson, K. Koch, L. Jarnstrom, The

IP

containing citric acid, Carbohydr. Polym. 98(2) (2013) 1505-13.

T

effect of pH on hydrolysis, cross-linking and barrier properties of starch barriers

CR

[31] N. Reddy, Y. Yang, Citric acid cross-linking of starch films, Food Chem. 118(3) (2010) 702-711.

US

[32] K. Das, D. Ray, N.R. Bandyopadhyay, A. Gupta, S. Sengupta, S. Sahoo, A.

AN

Mohanty, M. Misra, Preparation and Characterization of Cross-Linked Starch/Poly(vinyl alcohol) Green Films with Low Moisture Absorption, Ind. Eng. Chem. Res. 49(5) (2010)

M

2176-2185.

ED

[33] B. Sreedhar, D.K. Chattopadhyay, M.S.H. Karunakar, A.R.K. Sastry, Thermal and surface characterization of plasticized starch polyvinyl alcohol blends crosslinked with

PT

epichlorohydrin, J. Appl. Polym. Sci. 101(1) (2006) 25-34.

CE

[34] I. Simkovic, Cross-linking of starch with 1, 2, 3, 4-diepoxybutane or 1, 2, 7, 8-diepoxyoctane, Carbohydr. Polym. 55(3) (2004) 299-305.

AC

[35] J.B. Hirsch, J.L. Kokini, Understanding the mechanism of cross-linking agents (POCl3, STMP, and EPI) through swelling behavior and pasting properties of cross-linked waxy maize starches, Cereal Chem. 79(1) (2002) 102-107. [36] J. Zhou, J. Zhang, Y. Ma, J. Tong, Surface photo-crosslinking of corn starch sheets, Carbohydr. Polym. 74(3) (2008) 405-410.

20

ACCEPTED MANUSCRIPT [37] A.P. Kumar, R.P. Singh, Biocomposites of cellulose reinforced starch: improvement of properties by photo-induced crosslinking, Bioresour. Technol. 99(18) (2008) 8803-9. [38] M. Seker, M.A. Hanna, Sodium hydroxide and trimetaphosphate levels affect properties of starch extrudates, Ind. Crops Prod. 23(3) (2006) 249-255.

T

[39] G.W. Borden, O.W. Smith, D.J. Trecker, Acrylated epoxidized soybean oil urethane

IP

derivatives, Google Patents, 1977.

CR

[40] F. Habib, M. Bajpai, Synthesis and characterization of acrylated epoxidized soybean oil for UV cured coatings, (2011).

US

[41] Z. Liu, B.H. Tisserat, Coating applications to natural fiber composites to improve

AN

their physical, surface and water absorption characters, Ind. Crops Prod. 112 (2018) 196-199.

M

[42] M. Li, P. Liu, W. Zou, L. Yu, F. Xie, H. Pu, H. Liu, L. Chen, Extrusion processing

106(1) (2011) 95-101.

ED

and characterization of edible starch films with different amylose contents, J. Food Eng.

PT

[43] N. Auclair, A. Kaboorani, B. Riedl, V. Landry, Acrylated betulin as a comonomer

CE

for bio-based coatings. Part I: Characterization, photo-polymerization behavior and thermal stability, Ind. Crops Prod. 76 (2015) 530-537.

AC

[44] Z. Honarvar, M. Farhoodi, M.R. Khani, A. Mohammadi, B. Shokri, R. Ferdowsi, S. Shojaee-Aliabadi, Application of cold plasma to develop carboxymethyl cellulose-coated polypropylene films containing essential oil, Carbohydr. Polym. 176 (2017) 1-10. [45] P. Li, S. Ma, J. Dai, X. Liu, Y. Jiang, S. Wang, J. Wei, J. Chen, J. Zhu, ltaconic Acid as a Green Alternative to Acrylic Acid for Producing a Soybean Oil-Based Thermoset: Synthesis and Properties, ACS Sustainable Chem. Eng. 5(1) (2017) 1228-1236. 21

ACCEPTED MANUSCRIPT

Table and Figure Captions

IP

T

Table1 Sample code and coating conditions

CR

Fig 1.FTIR spectra of the surface of starch sheet coating with AESO.

US

Fig 2. SEM of the surface of starch sheet without (A) and with(B) AESO coating.

AN

Fig 3. Cross-section of the surface of starch sheet without (A) and with (B)AESO coating.

M

Fig 4. Effect of AESO concentration on water absorption.

ED

Fig 5. Effect of initiator content on water absorption.

PT

Fig 6. Effect of AESOcoating on moisture permeability.

CE

Fig 7. Effect of AESO concentration (top) initiator content (bottom) on tensile properties.

AC

Scheme 1. Polymerization of acrylated epoxidized soybean oil (AESO).

22

ACCEPTED MANUSCRIPT

Highlights

Acrylated epoxidized soybean oil-based coatings were developed.



AESO coatings reduce moisture sensitivity and permeability of starch films.



Crosslinking density acted as one of the key factors.

AC

CE

PT

ED

M

AN

US

CR

IP

T



23