Characterization of coated biodegradable trays by spectroscopic techniques

doi:10.1016/j.indcrop.2017.12.041

Industrial Crops and Products

Volume 112, February 2018, Pages 511-514

https://doi.org/10.1016/j.indcrop.2017.12.041 Get rights and content

Highlights

•
Biodegradable trays of starch/poly (lactic acid) (PLA) coated with beeswax (BW).
•
Trays characterized by Confocal Raman and Infrared spectroscopies.
•
Interaction by H-bonding between starch and PLA characterizing as immiscible blend.
•
Good adhesion of BW onto trays despite weak interaction between BW and PLA.
•
BW coating reduces trays hygroscopicity increasing the possibilities of use.

Abstract

Biodegradable trays of thermoplastic starch (TPS)/poly (lactic acid) (PLA) blends were produced by flat extrusion followed by thermopressing. The trays were coated by immersion in beeswax (BW) emulsion (1, 2, and 3 g BW/100 g ethyl alcohol + Tween 80 solution). The structural properties of the coated trays were characterized by Confocal Raman and Infrared spectroscopies to verify the coating-tray and TPS-PLA interactions. The characterization of the TPS/PLA biodegradable trays revealed that despite the low compatibility between starch (hydrophilic) and PLA (hydrophobic) there was interaction by hydrogen bonding between the starch and PLA carbonyl group, characterizing them as an immiscible blend. The BW showed weak interaction with PLA, but this interaction was sufficient to provide a good adhesion of the BW on the surface of the trays, reducing their hygroscopicity and enabling a commercial scale production of this biodegradable trays type.

Introduction

Starch-based trays are interesting due to their biodegradability and low cost, but they are highly hygroscopic and hydrophilic because of the thermoplastic starch (TPS) (Avérous et al., 2001; Huneault and Li, 2012). An alternative is to blend TPS with poly (lactic acid) (PLA) to produce less hygroscopic/hydrophilic materials and increased mechanical properties (Martin and Avérous, 2001; Ohkita and Lee, 2006; Shirai et al., 2013; Shirai et al., 2015; Soares et al., 2014; Teixeira et al., 2012; Wang et al., 2008; Xiong et al., 2013). Coating trays with food-grade waxes is also an option, such as beeswax (BW), which comprises a mixtures of esters (67 wt%), hydrocarbons (14 wt%), fatty acids (12 wt%), alcohols (1 wt%) and others (6 wt%) (Bonvehi and Bermejo, 2012; Polat et al., 2013; Tulloch, 1980) and has been studied by several researches (Cuq et al., 1995; Fabra et al., 2008; Martínez-Abad et al., 2014; Polat et al., 2013; Velickova et al., 2013).

The coating when applied on the trays surface can migrate, and to verify if the tray components are interacting among them and/or with the coating, the infrared spectroscopy techniques (IR) can be used, because they are able to identify and elucidate the structure of organic substances (Lopes and Fascio, 2004).

Another technique used to characterize materials is the Raman spectroscopy, a non-destructive, fast analysis technique that requires only small sample volumes and nearly no interference of water occurs (Edwards et al., 1996; Gelder et al., 2007; Kizil et al., 2002; Nawrocka and Lamorska, 2013; Vano-Herrera et al., 2015). Moreover, bands in Raman spectra are well resolved compared to similar spectroscopic techniques, such as infrared spectroscopy (Gelder et al., 2007).

In Raman technique with the aid of Confocal microscopy the Raman images of the trays are obtained, showing the distribution of starch, PLA and beeswax, and it is possible to identify the coating layer at the interface of the tray.

There are several techniques for the characterization of polymers, in this study the biodegradable trays were characterized in terms of their structural properties. The goal of this study was to characterize the components of biodegradable trays coated with beeswax and the interactions between them through Infrared and Confocal Raman spectroscopies.

Section snippets

Materials

The trays were produced with native cassava starch (17% wt amylose, 11% wt moisture) (Tereos Syral do Brasil, Brazil), poly (lactic acid) (PLA) (Ingeo 4043D, Nature Works LLC, Cargill, USA) and glycerol (Dinâmica, Brazil).

The coating emulsion were produced with beeswax (BW), courtesy of APOMEL (Associação dos produtores de mel de Ortigueira − PR, Brazil), ethyl alcohol P.A. (Exodo Científica, Brazil) and Tween 80 (CAAL, Brazil).

Trays production

Blends of 52.5g.100g⁻¹ starch, 17.5 g.100 g⁻¹ glycerol, and

Confocal Raman spectroscopy

Fig. 1 shows the Raman spectra of solid samples of the beeswax, PLA and starch. The spectra of the solid materials were used to check the nature of the material, based on the characteristic frequencies, and for the beeswax (Fig. 1a) the frequencies at 1463, 1441, 1419 and 1296 cm⁻¹ correspond to the CH₂ deformations and the band at 1173 cm⁻¹ is due to the C single bond C stretching (Edwards et al., 1996; Zimnicka and Hacura, 2006). The band of several esters of acetic acid, sulfonic acid, which are the main

Conclusion

The characterization of the TPS/PLA biodegradable trays revealed that despite the low compatibility between starch (hydrophilic) and PLA (hydrophobic) there was interaction by hydrogen bonding between the starch and PLA carbonyl group, characterizing them as an immiscible blend. The BW showed weak interaction with PLA, but this interaction was sufficient to provide a good adhesion of the BW on the surface of the trays, reducing their hygroscopicity and enabling a commercial scale production of

Acknowledgments

The authors thank CAPES, CNPq and Fundação Araucária for the financial support. We would like to express our appreciation to the Spectroscopy Laboratory (SPEC) at the PROPPG/UEL Multiuser Center.

References (32)

H.G.M. Edwards et al.
Fourier-transform Raman spectroscopic study of natural waxes and resins. I
Spectrochim. Acta A
(1996)
M.J. Fabra et al.
Tensile properties and water vapor permeability of sodium caseinate films containing oleic acid-beeswax mixtures
J. Food Eng.
(2008)
A. Martínez-Abad et al.
Antimicrobial beeswax coated polylactide films with silver control release capacity
Int. J. Food Microbiol.
(2014)
O. Martin et al.
Poly(lactic acid): plasticization and properties of biodegradable multiphase systems
Polymer
(2001)
W. Ning et al.
The influence of citric acid on the properties of thermoplastic starch/linear low-density polyethylene blends
Carbohyd. Polym.
(2007)
S. Polat et al.
The effects of the addition of corn husk fibre, kaolin and beeswax on cross-linked corn starch foam
J. Food Eng.
(2013)
M.A. Shirai et al.
Development of biodegradable flexible films of starch and poly(lactic acid) plasticized with adipate or citrate ester
Carbohyd. Polym.
(2013)
F.C. Soares et al.
Effect of cooling and coating on thermoplastic starch/poly(lactic acid) blend sheets
Polym. Test.
(2014)
E.M. Teixeira et al.
Properties of thermoplastic starch from cassava bagasse and cassava starch and their blends with poly (lactic acid)
Ind. Crop. Prod.
(2012)
E. Velickova et al.
Impact of chitosan-beeswax edible coatings on the quality of fresh strawberries (Fragaria ananassa cv Camarosa) under commercial storage conditions
LWT – Food Sci. Technol.
(2013)

A.E.S. Vercelheze et al.

Properties of baked foams based on cassava starch, sugarcane bagasse fibers and montmorillonite

Carbohyd. Polym.

(2012)

N. Wang et al.

Influence of formamide and water on the properties of thermoplastic starch/poly(lactic acid) blends

Carbohyd. Polym.

(2008)

Z. Xiong et al.

The properties of poly(lactic acid)/starch blends with a functionalized plant oil: tung oil anhydride

Carbohyd. Polym.

(2013)

R.A. Auras et al.

Poly(lactic Acid): Synthesis, Structures, Properties, Processing, and Applications

(2010)

L. Avérous et al.

Starch-based biodegradable materials suitable for thermoforming packaging

Starch-Stärke

(2001)

L.C.A. Barbosa

Espectroscopia no infravermelho na caracterização de compostos orgânicos

(2007)

Cited by (3)

Feasibility of Agaricus bisporus waste biomass to develop biodegradable food packaging materials
2023, Food Hydrocolloids
This work aimed to valorise Agaricus bisporus biomass residues to produce bio-based and biodegradable films. To this end, two of the most widely consumed varieties, Agaricus bisporus brunnescens (Abb) and Agaricus bisporus hortensis (Abh), were compositionally characterised and then, films were formed by extrusion and compression-moulding. Proteins and β-glucans were the major components in both varieties. Abb showed a higher protein content, whereas the amount of polysaccharides and lipids was higher in Abh. Thermally-processed Abh-films showed better mechanical and barrier performance than their counterparts prepared with Abb, mainly ascribed to the higher carbohydrate and lipid content. Thus, Abh was selected to optimize the processing conditions in terms of energy consumption (from 100 to 130 °C) and barrier properties. As a result, 110 °C was selected as the optimum processing temperature for Abh-films since the mechanical properties in terms of strength were not significantly modified and barrier properties were significantly improved. The resulting film was coated with a beeswax layer to reduce its hydrophilic nature. The coated films showed similar mechanical properties than their counterparts prepared without the beeswax coating but displayed significantly better water vapour barrier performance. Furthermore, both films were easily disintegrated under composting conditions according to ISO 20200.
Challenges and new opportunities on barrier performance of biodegradable polymers for sustainable packaging
2021, Progress in Polymer Science
Citation Excerpt :
In comparison, melt blending of 1 wt% beeswax with PLA only decreased the WVP of PLA to 43 with a 58% reduction as studied by Lim et al. [277]. Reis’ further study on beeswax coated biodegradable trays by spectroscopic techniques showed that adhesion of the beeswax on the surface of the trays is good enough despite the weak interaction between beeswax and PLA [362]. In addition to the provided water barrier, the wax coating can also be used to control the release of nanoparticles from polymer matrix, to meet the stringent regulations of particle immigration in food packaging [63].
Biodegradable polymers have emerged as a subject of enormous scientific and industrial interest due to their environmentally friendly compostability. For the benefit of the market economy and reoccurring environmental hazards, biodegradable materials should play a more critical role in packaging materials, which currently accounts for 60% of plastic products. However, various challenges remain for biodegradable polymers towards practical packaging applications. Particularly pertaining to the poor gas/moisture barrier issues which greatly limit the food packaging application of current biodegradable polymers. The chain architecture tailoring, crystallinity, melt blending/multi-layer co-extrusion, nanotechnology and surface coating have been considered as effective strategies for overcoming the poor gas/moisture barrier facing biodegradable polymers, which have been extensively researched for decades. In this review, we provide an in-depth study on the oxygen/water vapor barrier of representative biodegradable polymers in mainstream research with an emphasis on theoretical models and experimental modifications to improve their barrier properties. The influence of various strategies on the barrier improvement, and the pros/cons of each method are summarized. The limitations of current methods are discussed, and potential methods to overcome these limitations are presented. Finally, we conclude this review by listing current challenges associated with the barrier properties, processing and scalability of biodegradable polymers in the food packaging market, and future perspectives for these biodegradable polymers in sustainable composites field.
Study of the miscibility of poly (Lactic acid) / poly (butylene adipate-co-terephthalate) blends prepared by solvent-casting method
2021, Revista Materia

View full text

Characterization of coated biodegradable trays by spectroscopic techniques

Highlights

Abstract

Introduction

Section snippets

Materials

Trays production

Confocal Raman spectroscopy

Conclusion

Acknowledgments

Spectrochim. Acta A

J. Food Eng.

Int. J. Food Microbiol.

Polymer

Carbohyd. Polym.

J. Food Eng.

Carbohyd. Polym.

Polym. Test.

Ind. Crop. Prod.

LWT – Food Sci. Technol.

Carbohyd. Polym.

Carbohyd. Polym.

Carbohyd. Polym.

Poly(lactic Acid): Synthesis, Structures, Properties, Processing, and Applications

Starch-based biodegradable materials suitable for thermoforming packaging

Starch-Stärke

Espectroscopia no infravermelho na caracterização de compostos orgânicos