Surface Properties of Thermoplastic Starch Materials Reinforced with Natural Fillers

Gutiérrez, Tomy J.; Ollier, Romina P.; Álvarez, Vera A.

doi:10.1007/978-3-319-66417-0_5

Cited by 30 publications

(15 citation statements)

References 93 publications

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“…Materials degradation is defined as a detrimental change in their appearance, mechanical, physical properties, and chemical structure [26]. Appearance of TPS specimens before and after UV exposure at different assayed times is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Oxidative Degradation of Thermoplastic Starch Induced by UV Radiation

Quispe¹,

López²,

Villar³

2019

Journal of Renewable Materials

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Among biopolymers, thermoplastic starch (TPS) is a good candidate to obtain biomaterials because of its natural origin, biodegradable character, and processability. Exposure to ultraviolet (UV) radiation causes significant degradation of starch-based materials, inducing photooxidative reactions which result in breaking of polymer chains, production of free radical, and reduction of molar mass. These changes produce a deterioration of TPS mechanical properties, leading to useless materials after an unpredictable time. In this work, changes induced on TPS by UV radiation, analyzing structural properties and mechanical behavior, are studied. TPS was obtained through thermo-mechanical processing of native corn starch in the presence of water (45 % w/w) and glycerol (30 % w/w) as plasticizers. Films were obtained by thermocompression and, before testing, specimens were conditioned to reduce material fragility. Photodegradation process was performed by exposing TPS to 264 h UV radiation in a weathering test chamber. Specimen's weight loss was determined gravimetrically. Chemical changes were studied by Fourier Transform Infrared Spectroscopy (FTIR) and morphological modifications were analyzed by Scanning Electron Microscopy (SEM). Reduction of weight average molar mass was measured by Static Light Scattering (SLS). Changes in mechanical properties were studied from tensile tests. After 96 h exposure, TPS specimens presented a weight reduction of 4-6%, mainly attributed to plasticizers lost by evaporation. SEM observations showed that UV radiation induced morphological changes on TPS, evidenced by an increment of specimens cracking. By FTIR, it was detected the presence of an additional band located at 1726 cm -1 in samples submitted to UV radiation, attributed to the formation of -C=O groups. Weight average molar mass of native starch was in the order of 107 g mol -1 . TPS exposure to UV radiation decreased significantly its molar mass, confirming molecular degradation of the biopolymer. When TPS was exposed during 48 h, it was detected a considerable decrease in elongation at break values (~ 85%), indicating that TPS flexibility was reduced. On the other hand, after 48 h exposure, TPS elastic modulus was 55 times higher than those of the unexposed specimens, evidencing an increase in material rigidity. TPS maximum tensile strength was also increased by UV light, with an increment of ~ 400% after 48 h exposure. Results revealed that starch-based materials can be degraded by exposure to UV radiation, modifying their microstructure and mechanical performance.

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Section: Resultsmentioning

confidence: 99%

Oxidative Degradation of Thermoplastic Starch Induced by UV Radiation

Quispe¹,

López²,

Villar³

2019

Journal of Renewable Materials

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“…For example, surface energy, and the g d s and g P s components of surface energy should be determined, since the surface energy may be enough to achieve the collapse of the water drop on the surface of the material, even when this surface is hydrophobic (Guti errez, Ollier, & Alvarez, 2018). This could explain the lower water contact angle value in the TPS þ BE films compared to the TPS film.…”

Section: Contact Anglementioning

confidence: 99%

Bionanocomposite films developed from corn starch and natural and modified nano-clays with or without added blueberry extract

2018

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Edible and bionanocomposite films were developed by extrusion followed by thermo molding. Corn starch (Zea mays), glycerol, and several nano-clays were used as the carbohydrate polymer, plasticizer and nano-fillers, respectively. Pure blueberry (Vaccinium corymbosum) extract (BE, 100% anthocyanin), as well as natural and modified montmorillonites (Mnt) with or without BE nano-packaged within their layers were incorporated into the thermoplastic starch (TPS) matrix. Previous studies by our research group have shown that BE, and BE nano-packaged within natural and modified Mnt, are pH-sensitive. With this in mind, we set out to develop edible and intelligent (pH-sensitive) bionanocomposite films with improved properties. Unfortunately however, none of the films formulated were pH-sensitive. All the films showed X-ray diffractograms typical of semicrystalline, albeit largely amorphous, materials coinciding with the morphological observations made under scanning electron microscopy. The results confirmed that total starch gelatinization occurred under the selected extrusion conditions. Films prepared from corn starch containing BE showed a plasticizing effect, giving materials with lower thermal resistance and surface moisture values, which were also more opaque, denser, and rougher. All the nanofillers tested were completely exfoliated within the TPS matrix, except for the natural Mnt that was partly exfoliated and partly intercalated in the matrix. In general, materials containing nano-fillers with a greater degree of interlayer spacing (more exfoliated) showed higher thermal resistance and Young's modulus, but lower strain at break values.

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“…The most important finding of this study was a substantial decrease in the wettability of alginate films that makes these films more applicable for packaging purposes. Among the treatments applied in this study, the deposition of a thin layer of LSO increased the contact angle to near 90°, which means very low wetting by contacting the films with water will be occurred 49 …”

Section: Resultsmentioning

confidence: 93%

“…The contact angle increases with an increase in surface hydrophobicity. The contact angles greater than 65° define a hydrophobic surface 49 . (There are reports that are proposed the value 90° as the cutoff between hydrophobicity and hydrophilicity 50 …”

Section: Resultsmentioning

confidence: 99%

“…Smaller contact angles indicate that the affinity of the surface toward water is higher, and water will spread over a large area on the surface, while greater contact angles (that obtained in this study by oil coating) mean that the wetting properties of the surface are unfavourable, and the affinity of the film surface to water is less. Therefore, water will minimize its contact with the surface and form a compact liquid droplet 49,51 …”

Section: Resultsmentioning

confidence: 99%

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Improving the water barrier properties of alginate packaging films by submicron coating with drying linseed oil

2021

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Alginates with excellent film‐forming ability have a promising potential as a safe and biodegradable food packaging material, but as a hydrophilic biopolymer, its general weakness against water has limited its applications. To surpass this weakness, in this study, coating of calcium alginate films with linseed or sunflower oils in micrometric (about 4.55 μm) and submicrometric (about 0.45 μm) thickness was performed, and the characteristics of the films were evaluated. All of the films were homogeneous, transparent and almost colourless. Micro‐coated films presented improved ultraviolet absorbing spectra. The scanning electron microscopy (SEM) images proved the formation of homogeneous and continuous submicron‐coated oil layers for both types of the oils, while some inhomogeneity and defects were observed in the micro‐coated films. Oxidative polymerization of linseed oil was confirmed by Fourier transform infrared (FTIR) spectral analyses. The mechanical strength of the films micro‐coated with linseed oil increased. Submicron coating improved water vapour barrier properties (from 2.20 to 2.92 g/mm/m2/day/kPa) as well as water vapour absorption of the alginate film compared to other films. This result was confirmed by thermogravimetric analyses. The increase in surface hydrophobicity of the films by coating resulted in a significant increase in contact angle (from 46.3° to 89.9° in maximum) and reduction of wettability. The film submicron coated with linseed oil showed the best performance with the least water vapour permeability, water vapour absorption and wettability.

show abstract

Surface Properties of Thermoplastic Starch Materials Reinforced with Natural Fillers

Cited by 30 publications

References 93 publications

Oxidative Degradation of Thermoplastic Starch Induced by UV Radiation

Oxidative Degradation of Thermoplastic Starch Induced by UV Radiation

Bionanocomposite films developed from corn starch and natural and modified nano-clays with or without added blueberry extract

Improving the water barrier properties of alginate packaging films by submicron coating with drying linseed oil

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