Article

Effect of nanoclay incorporation method on mechanical and water vapor barrier properties of starch-based films

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Abstract

The objective of this study was to investigate the influence of nanoclay incorporation procedure on the mechanical and water vapor barrier properties of starch/nanoclay composite films. Cassava starch films were prepared with (nanocomposite) and without nanoclay (control) in two steps: firstly the production of extruded pellets and secondly thermo-pressing. The nanocomposite films were prepared via two different methods: in D samples the nanoclay was dispersed in glycerol and subsequently incorporated into the starch; and in ND samples all ingredients were added in a single step before the extrusion. All the composite-films were prepared with cassava starch using 0.25g of glycerol/g of starch and 0.03g of nanoclay/g of starch. Control samples showed VA-type crystallinity induced by the manufacturing process and the nanocomposites presented a semicrystalline and intercalated structure. The nanoclay improved the water vapor barrier properties of the starch film and this effect was more pronounced in D samples, where the water vapor permeability (Kw) was 60% lower than that of the control samples. The Kw reduction was associated with decreases in the effective diffusion coefficient (approximately 61%) and in the coefficient of solubility (approximately 22–32%). On the other hand, the incorporation of nanoclay increased the tensile strength and the rigidity of the films and this effect was more significant when the nanoclay was dispersed in glycerol. Thus, the incorporation of nanoclay into starch-based films is a promising way to manufacture films with better mechanical and water vapor barrier properties.

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... This study aimed to evaluate the effect of three different compatibilizers (maleic anhydride, citric acid, and 3-(trimethoxysilyl) propyl methacrylate) in starch-PLA biodegradable materials produced by extrusion and thermoplastic injection, on a pilot scale, with potential application in industrial production (Müller, et al., 2011;Olivato et al., 2012;Shirai et al., 2018) ...
... A), and operating at room temperature at 40kV. The RCI was estimated from the ratio between the area of the crystalline region and the sum of crystalline and amorphous regions, the total area (Equation 3) (Köksel et al., 1993;Müller et al., 2011). ...
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... Recent research has focused on clay nano-particles, a type of reinforcement material that, when added to TPS, improves the mechanical performance of the polymer, resulting in materials with greater tension resistance toughness [14][15][16][17][18]. As nanoclays can be found in the form of overlapping layers, this arrangement makes it difficult for water molecules to diffuse through the material, causing better resistance to moisture and other gases [5,18,19]. ...
... Table 4 presents the results of the tensile tests that were done to the sonicated samples and the control sample, for tensile strength (TS), percentage of elongation at break (ε), and Young's modulus (YM). As has been reported by other authors [4,5,14,19,29], the addition of nanoclay increased the TS and YM for all nanoclay concentrations compared to the values obtained by the SP sample, where the greatest increase is presented by SP1.0MMT-s (24% tensile strength and 50% Young's modulus). The clays' nanometric size and high surface area facilitate the formation of an effective interface for transferring tensile stresses. ...
Preprint
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... The Mt diffraction spectra present a well-defined peak at 7° (corresponding to a clay inter-layer), 19°, and 35° typical of this clay structure. The strong peak observed at 26° is indicative of the presence of SiO 2 [35] and the peak at 10° and those between 20 and 35° are due to the presence of kaolin and quartz [36]. In the diffractogram of P/BG hydrogel a broad peak at 2θ between 10 and 40° is related to the semicrystalline polymer complex which is usually found in many polysaccharide-based hydrogels [37,38]. ...
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... After that, they increased drastically. It seems that the formed hydrogen bonds between FT and starch matrix have restricted the movements of starch chains (Müller et al. 2011;Salarbashi et al. 2017). On the other hand, due to the low affinity between the nanoparticles and the matrix of the biopolymer, the aggregated FT facilitated the movement of starch chains like a ball bearing system (Goudarzi et al. 2017). ...
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... Dans les applications de retard de flamme, le choix initial s'est porté sur des composés halogénés. Mais la toxicité de leurs produits de combustion et la fumée l'accompagnant présentant un danger en soi, d'autres agents retardateurs de flamme ont été développés, ce sont par exemple les hydroxydes d'aluminium ou de magnésium.L'incorporation de charges inorganiques aux polymères est également apparue prometteuse en matière de propriétés barrières aux gaz et aux fluides[29][30][31]. L'amélioration de l'imperméabilité du composite est due à deux raisons : la première est une diminution de la concentration en polymère qui est la phase sensible aux gaz et aux fluides ; de plus, la présence des charges allonge le trajet des molécules externes pénétrant dans le système. ...
Thesis
Durant ces dernières décennies, de nombreuses actions de recherche au niveau international se sont intéressées aux biomatériaux présentant d'une part des caractéristiques équivalentes voire parfois supérieures à celle des produits d'origine fossile et d'autre part le caractère renouvelable des ressources est un atout environnemental. De plus, le problème des sédiments marins et fluviaux est un problème mondial. La gestion des sédiments de dragage constitue ainsi une préoccupation générale en raison des quantités produites et de leur nuisance potentielle. Dans ce travail, une étude expérimentale est menée sur la valorisation des sédiments marins à des pourcentages variant de 0% à 20% comme une charge minérale dans une matrice agrosourcée et d'apprécier leur influence sur les propriétés physicomécaniques, thermiques ainsi que sur la durabilité des composites élaborés HESM (hémoglobine/ sédiments Marins). Les résultats montrent que le module en compression, en flexion, en traction et la résistance à la compression ont été améliorés lors de l'ajout des sédiments marins, par contre la résistance à la traction et la résistance à la flexion ont été diminuées par rapport au matériau de référence. L'étude microstructurelle a permis de justifier l'effet de l'ajout des sédiments dans la matrice sur les propriétés mécaniques. Quant à la caractérisation thermique des biocomposites, les résultats montrent l'amélioration de la stabilité thermique des composites par rapport au polymère pur. Concernant la durabilité, l'ajout des sédiments marins n’a presque pas influencé les propriétés de durabilité et que le matériau chargé ou non ne doit pas être exposé aux intempéries sans protection. La modélisation par éléments finis du comportement mécanique en compression a donné des résultats satisfaisants permettant de valoriser ce nouveau biocomposite comme un revêtement de sol
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... This could be attributed to the formation of an immobilized pectin layer in the pectin/filler interphase, which consequently decreased the flexibility of films. This trend was also noted by other researchers for various systems: pectin/montmorillonite [31], alginate/montmorillonite [42], and starch/bentonite [43]. ...
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... By reducing free water, the intensity of enzymic and chemical destructive reactions of food products was reduced. Muller et al. [54] also reported reduced hydrophilic behavior of biopolymer films owing to the addition of nanoparticles. Ngo et al. [47] found that the moisture absorption of pectin-alginate control film is higher than that of a film containing ZnO-N. ...
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... Bioplastics developed with a high percentage of amylose (75%) and 20% glycerol resulted in materials with increased flexibility and reduced tensile strength, from the increase in the propylene oxide content (6-12%, w/w starch). The tensile strength was 18 propylene oxide) [82]. Effects on mechanical properties (reduction) were also observed in starch-based bioplastic with propylene oxide [93]. ...
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The present work shows the implementation of the response surface methodology, fed by an experimental central composite design (CCD) to find the conditions that allow maximizing the inhibition of the microorganism Staphylococcus aureus with nanoparticles of TiO2 silanized with 3-aminopropyltriethoxysilane (APTES) and doped with Ag. In addition, poly(lactic) acid composites were prepared with these Ag/TiO2 nanoparticles with the aim to confer their antimicrobial effect. The independent variables considered were pH, AgNO3/TiO2 ratio (% w/w), and TiO2 nanoparticles concentration (g/250 mL), and as the variable of response, the length of the diameter of the halo or zone of inhibition presented by the microorganism (mm). Statistical analysis found that maximization of S. aureus inhibition occurs at intermediate levels with a value of 10 for pH and 5 g of TiO2 solids, while for the concentration of AgNO3 high levels are required, greater than 10% w/w. Likewise, the statistical significance was determined using the Student's t test and the p value; it was found that the significant effect corresponds to the concentration of AgNO3, so a second experimental CCD design equiradial with two factors was considered, estimating AgNO3 concentration and TiO2 amount, the pH at constant 10 value. The second experimental design indicated that maximization in S. aureus inhibition occurs at an AgNO3 concentration between 20 and 25% w/w with high amounts of TiO2 solids (7–8 g), with a resulting zone of inhibition between 26 and 28 mm. The quadratic model obtained, which represents the relationship between the lengths of the zone of inhibition with the variables considered, shows an adjustment of experimental data with a coefficient of determination (R²) of 0.82. Graphic abstract
... However, nanomaterials are not easy to disperse, moreover with polar behavior, in apolar matrices. Good to moderate results have been obtained in nylons and starch using organically modified and unmodified nanoclays resulting in intercalated and exfoliated materials [14][15][16][17]. However, both matrices have a higher polarity than PLA, which facilitates their dispersion in the matrix. ...
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Packaging consumes around 40% of the total plastic production. One of the most important fields with high requirements is food packaging. Food packaging products have been commonly produced with petrol polymers, but due to environmental concerns, the market is being moved to biopolymers. Poly (lactic acid) (PLA) is the most promising biopolymer, as it is bio-based and biodegradable, and it is well established in the market. Nonetheless, its barrier properties need to be enhanced to be competitive with other polymers such as polyethylene terephthalate (PET). Nanoclays improve the barrier properties of polymeric materials if correct dispersion and exfoliation are obtained. Thus, it marks a milestone to obtain an appropriate dispersion. A predispersed methodology is proposed as a compounding process to improve the dispersion of these composites instead of common melt procedures. Afterwards, the effect of the polarity of the matrix was analyzing using polar and surface modified nanoclays with contents ranging from 2 to 8% w/w. The results showed the suitability of the predispersed and concentrated compound, technically named masterbatch, to obtain intercalated structures and the higher dispersion of polar nanoclays. Finally, the mechanical performance and sustainability of the prepared materials were simulated in a food tray, showing the best assessment of these materials and their lower fingerprint.
... Thermal, physical and chemical properties of the end products are strongly determined by the form and quantity of plasticizer used during TPS processing and used in flexible and durable packaging production market Kim, 2014a, 2014b;Mendes et al., 2016). In several instances, other ingredients or various structural enhancers, such as fibres, CMC, microcrystalline cellulose (MCC), nano-clays, carbon nanotubes (CNTs), have been applied to the polymer-starch matrix to alter the properties of TPS (Giron es et al., 2012;Ma et al., 2008;Müller et al., 2011). Different forms of this reinforced starch have already been applied in the packaging of fruits, vegetables, bread and meat products processed under normal conditions (Chauvet et al., 2017). ...
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Maintaining the safety and quality of food are major concerns while developing biomaterial based food packaging. It offers a longer shelf-life as well as protection and quality control to the food based on international standards. Nano-biotechnology contributes to a far extent to make advanced packaging by developing multifunctional biomaterials for potential applications providing smarter materials to consumers. Applications of nano- biocomposites may thus help to deliver enhanced barrier, mechanical strength, antimicrobial and antioxidant properties to novel food packaging materials. Starch derived bioplastics, polylactic acid and polyhydroxybutyrate are examples of active bioplastics currently in the food packaging sector. This review discusses the various types of biomaterials that could be used to improve future smarter food packaging, as well as biomaterials' potential applications as food stabilizers, pathogen control agents, sensors, and edible packaging materials. The regulatory concerns related to the use of biomaterials in food packaging and commercially available biomaterials in different fields are also discussed. Development of novel biomaterials for different food packaging applications can therefore guarantee active food packaging in future.
... This is attributed to nanoparticle agglomeration, as seen in the TEM micrographs (Fig. 2D) and SN crystallinity due to increasing concentration (15%) and the consequent difficulty of water molecule migration through the film. Müller et al.(2011), studied starch films and found that the addition of up to 5% SN lessens film water resistance, possibly due to SN aggregation. ...
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Studies have been made to explore the utilization of pea proteins in terms of edible film and coating materials. The reinforcement of biopolymer films with plant-based nanocrystals has been applied in order to improve their performance properties. The objective was to evaluate the effect of the incorporation of corn starch nanocrystals (SN) (0-15%) in pea protein isolate films. Thermal analysis showed that the addition of up to 5% starch nanocrystals increased thermal stability. A 22.3% decrease was observed in water vapor permeability with the addition of SN. Increasing the SN concentration altered the arrangement of the structure to interleaved, in the matrix, as seen in transmission micrographs. This study showed that the use of corn starch nanocrystals as reinforcement in pea protein films had an effect on the films. The incorporation of up to 10% SN is suggested in order to increase the performance properties of pea protein isolate films.
... As a result of the nanoclay addition, two new peaks at 2θ of 5.7° and 19.9° were observed. According to previous reports [23,45], these peaks correspond to the planes (001 and 002) of the silicate layer elements related to the presence of montmorillonite (bentonite). Another work mentioned that for bentonite nanoclay without purification as in this work, kaolin (K) at 2θ = 10° and quartz (Q) at 2θ = 28.2° ...
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... and the values ranged from 16.8 to 38.6 %. Few published works are also reported that relative crystallinity of starchbased polymers increased with increased content of normal and nanofractioned bentonite(Lendvai, Sajó, & Karger-Kocsis, 2018;Müller, Laurindo, & Yamashita, 2011) nano-SiO 2(Yao et al., 2011). ...
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Sufficient hydroxyl moiety, ease of accessibility, biodegradability and reaction compatibility with other molecules make starch a basic ingredient for polymeric synthesis and to prepare encapsulated controlled release fertilizers. This article aims to prepare biodegradable clay-polymeric (starch/PVA) blended encapsulating films (CPSBs) from starch/PVA and economically feasible clay-fractioned bentonite for CPSB-encapsulated diammonium phosphate (DAP) production. The XRD, TEM and FTIR spectroscopy recognized the compatibility of bentonite with starch/PVA blend; several micropores in CPSB surface was visible through SEM. Relative crystallinity index, density of CPSBs increased with increasing bentonite content (0-20 wt%); but, porosity, water absorption was decreased. Half-life of CPSB-10 was 37.4, 40.1 and 51.9 days with Aspergillus awamori, Trichoderma viride and uninoculated soil, respectively. Nitrogen (N) and phosphorus (P) release data from CPSB-encapsulated-DAP and uncoated DAP fitted well to Korsmeyer-Peppas model. Overall, greater bentonite content stabilizes the CPSB structure and CPSB-encapsulation reduced the N and P release from DAP.
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Organic montmorillonite/brominated butyl rubber nanocomposites are prepared by improved solution blending, i.e., preparation of organic clay suspension and suspension blending with brominated butyl rubber solution by adding polytetramethylene ether glycol as interface agent. Scanning electron microscopy and atomic force microscopy show that polytetramethylene ether glycol has good dispersing effect on organic clay. Transmission electron microscopy and X‐ray diffraction analysis demonstrates that both intercalated and exfoliated structures are obtained in organic montmorillonite/brominated butyl rubber nanocomposites. The mechanical performances and the gas barrier properties of the organic montmorillonite/brominated butyl rubber nanocomposites are improved greatly, which proves that the high‐performance clay/rubber nanocomposites are prepared in nonpolar solvent. The organic montmorillonite is nano‐dispersed in the brominated butyl rubber by the combination effect of solution compounding method and unique interface agent. The nanocomposites have excellent mechanical properties and gas barrier properties. In particular, the gas barrier properties are improved by more than 50%, which has great potential in the preparation of green tire inner layer.
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Poly (butylene adipate-co-terephthalate) (PBAT) is a fully biodegradable polymer with toughness and ductility. It is usually compounded with thermoplastic starch (TPS) to balance the cost for manufacturing biodegradable films such as disposable plastic bags. However, blending with TPS reduces valuable tensile strength, which limits the bearing capacity of PBAT film. In this study, microcrystalline cellulose (MCC) was employed as a reinforcement to strengthen the PBAT/TPS biodegradable film. The effect of MCC content on the mechanical, thermal, and morphological properties of the composite film were investigated. The optimal tensile strength and elongation at break reached 5.08 MPa and 230% when 4% MCC was added. The thermal stability and thermal resistance were improved with the addition of MCC; for example, Tmax increased by 1 °C and Tonset increased by 2–8 °C. Moreover, good compatibility among PBAT, TPS, and MCC can be achieved when the MCC content was below 6%. Consequently, the optimal MCC content was found to be 4%. These results could provide experimental data and method support for preparing high-performance PBAT hybrid films.
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The aim of present study was to develop and characterize the biodegradable sweet potato starch-based nanocomposite films reinforced with barley starch nanoparticles (SNP). Sweet potato starch-based films with varying concentrations of barley SNP (5–25% w/w) were manufactured by adopting solution casting method using glycerol as a plasticizer. The morphology, thickness, transparency, water solubility, water vapor transmission rate (WVTR), tensile strength, elongation at break and thermal stability properties of nanocomposite films were evaluated. The results showed that the incorporation of barley SNP led to a significant increase in tensile strength from 2.63 (control film) to 8.98 MPa (nanocomposite with 15% (w/w) SNP). Compared with the native starch film, the surface of the nanocomposite films became more rough and uneven with the increasing concentration of nanofillers. High concentration of SNP (upto 25%, w/w) significantly decreased the transparency and WVTR, and water solubility (upto 20%, w/w) of nanocomposite films. The WVTR decreased from 3294.53 to 349.06 g/m2/24 h. In addition, the thermal stability of nanocomposites got improved after incorporation of SNP into starch-film matrix.
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In the present study, soy protein isolate (SPI) multifunctional bioplastics were prepared by casting, with the addition of tannins extracted from Stryphnodendron adstringens and kraft lignin. The films were obtained through biopolymer composites and blends method, prepared at three pHs (8.5, 9.5 and 10.5) and characterized by thermochemical studies, Fourier-transform infrared spectroscopy, scanning electron microscopy, water vapor permeability (WVP), antioxidant activity, water contact angle, surface energy, wettability, and mechanical tests. The composites presented better results when compared to the blend and control films, respectively, in the polarity, hydrophobicity, WVP and especially in the antioxidant activity tests. Nevertheless, no significant difference between the samples was noticed in the thermochemical and spectroscopic studies. The results presented the potential of the composites to produce SPI biopolymers with tannins and kraft lignin, leading to the development of multifunctional materials as an alternative for sustainable packaging.
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Intended for food packaging, nanocomposites films based on poly (lactic acid) reinforced by polydopamine-wrapped carbon nanotubes (PLA/PDA-MWCNTs) or TiO2 modified PDA-MWCNTs (PLA/TiO2-PDA-MWCNTs) as nanofillers were elaborated via melt-blending and characterized by several techniques. The success of the synthesis of the modified MWCNTs was confirmed by transmission electron microscopy, Raman and Fourier transform infrared spectroscopies and thermogravimetric analysis. Properties such as slow crystallization rate, barrier, mechanical, antibacterial and antifungal properties, required for food packaging, have been investigated. As compared to a PLA pristine film, the PLA based modified MWCNTs at 3 wt% loading exhibited better properties, particularly the PLA/TiO2-PDA-MWCNTs nanocomposite film. Indeed, the crystallization rate increased about 10% for PLA/TiO2-PDA-MWCNTs and 7% for PLA/PDA-MWCNTs compared to the neat PLA. Besides, these improved results have positively impacted on the nanomechanical and barrier properties of PLA nanocomposites films. The Young modulus was increased by 161% for PLA/TiO2-PDA-MWCNTs and 113% for PLA/PDA-MWCNTs and the hardness was improved by 815% for PLA/TiO2-PDA-MWCNTs and 79% for PLA/PDA-MWCNTs, respectively, as compared to the pristine PLA. Furthermore, PLA based modified MWCNTs nanocomposite films displayed a strong antimicrobial and antifungal activity compared to pure PLA.
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Bio-based thermoplastic natural rubber (TPNR) has recently received much attention due to its sustainability. TPNR based on natural rubber (NR), poly(lactic acid) (PLA), thermoplastic starch (TPS), and nano-precipitated calcium carbonate (NPCC) was fabricated using a twin-screw extruder with two different mixing sequences: MI (NPCC was first compounded with PLA) and MII (NPCC was initially compounded with TPS), and then converted to a sheet through cast sheet extrusion. A constant weight ratio of NR:PLA:TPS at 30:40:30 and varying concentrations of NPCC at 0.5, 1, 3, and 5 wt% were employed. The effects of NPCC and mixing sequence on the properties of NR/PLA/TPS/NPCC nanocomposites were investigated. The NR and TPS phases were dispersed in the PLA matrix. The nanocomposites loaded with a small amount of NPCC (0.5 and 1 wt%) showed increased tensile strength and Young's modulus. NPCC enhanced melt flowability, slightly improved the water vapor barrier property of the NR/PLA/TPS blend and caused decreased Tg, Tcc, and Tm of PLA in the nanocomposites. The PLA phase of the MI nanocomposites contained a higher amount of NPCC, consequently having greater PLA chain scission and poorer tensile properties than that of the MII nanocomposites.
Chapter
This chapter reviews research about biodegradable bionanocomposite barrier films, which have the potential to replace petroleum-based barrier films that currently have a dominant role in the packaging and serving of food products. In addition to describing the state of research in this field, a series of pivotal questions are considered that may affect which materials and processes will emerge as the most successful options. Brittleness is a key issue that is considered in the light of published findings. Progress also has been achieved in the mechanistic modeling of bionanocomposite film performance. Bacterial cellulose stands out as a promising reinforcing material that has advantages for food contact, pharmaceutical, and medical applications. Finally, progress has been made in being able to form barrier films at relatively high speeds using procedures that can be scaled up and used industrially.KeywordsNanocellulosePoly(lactic acid)StarchWater vapor transmission (WVT)OxygenGreaseBacterial celluloseModeling
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Thermoplastic cassava starch (TPS)/sisal fiber (SF) composites were prepared by the melting method. The effect of SF on the retrogradation kinetics, morphology and size of spherulites, molecular interactions, short-range molecular structure, and crystal type of TPS was investigated. The results indicate that the retrogradation degree and rate of TPS increase with the addition of SF, and the spherulites become clearer and denser. The neat TPS sample forms an A-type crystal through double helix structure and a V-type crystal through single helix structure. After the addition of SF, the A-type crystal of the TPS/SF composite decreases and the V-type crystal increases. With the further increase of SF content, the TPS/SF composite mainly presents the V-type crystal. The TPS/SF composite has higher crystallinity, but smaller crystal size and interplanar spacing. The storage modulus, loss modulus, and glass transition temperature (T g ) of TPS get enhanced with the addition of SF.
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The study aimed to evaluate functional properties of rice starch‐based nanocomposite (NC) films. Silver nanoparticles (SNP) were synthesised using Saraca asoca leaf extract and found to be spherical with diameters ranging between (27‐45) nm. The SNP solution was added at three different levels: 50 mL, 100 mL and 150 mL to filmogenic solution (150 mL) and these films were designated as SNP‐50, SNP‐100 and SNP‐150, respectively. In addition to control film, two more films were made by adding AgNO3 solution (150 mL) and plant extract (150 mL) into filmogenic solutions. Addition of SNP improved tensile strength and decreased elongation at break of rice starch films. NC films showed enhanced UV‐Vis light barrier property due to increased colour intensity and opacity. SNP added films exhibited lower water solubility, water holding capacity and water vapour permeability. Scanning electron microscopy suggested that control film, SNP‐50 and SNP‐100 had the smoothest surfaces in comparison to all films. SNP incorporation delayed biodegradation of films. Silver nanoparticles in the form of colloid, filmogenic solution and even as discrete films showed excellent antibacterial activity against common food pathogens. The SNP concentration significantly correlated (R2 = 0.62‐0.96) to the functional properties of films. This article is protected by copyright. All rights reserved
Chapter
Lignin is one of the most abundant biodegradable and renewable natural biopolymers after cellulose. The main source of lignin comes from the by-product of the pulp and paper industries. Lignin has been added to various polymers to give blends, while in other cases, composites, depending on the involved interactions. The blending process of lignin with polymers is not easy, since the polarity of lignin molecules results in strong interactions. Moreover, lignin has a complex structure and it is difficult to characterize. Therefore, lignin is often modified in order to improve its miscibility with other polymers. Lignin can be introduced into bio-based polymers (polysaccharides, natural rubber, proteins, and polylactic acid), oil-based polymers (polyester, polyether, polyethylene, and polypropylene), and bio-based/oil-based polymers. The combination of the three materials (lignin, bio-based polymers, and oil-based polymers), such as in the case of polypropylene/polylactic acid/lignin (PP/PLA/lignin), is one of the most interesting cases of blends and composites. This chapter focuses on the effect of lignin on bio-based polymers and oil-based polymers, and special attention is given to the bio-based/oil-based polymer blends and composites.
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In this work, the chitosan/κ-carrageenan/acid-activated bentonite composite membranes were prepared through blending method and used to adsorb methylene blue dye. The prepared composite membranes were characterized with several spectroscopic and microscopic techniques. The results revealed the bentonite was homogeneously distributed in the membrane matrix, which means extensive porous structure was formed on the surface. The effects of initial concentration of methylene blue, adsorbent dosage, pH value, contact time, ionic strength, and temperature on methylene blue removal percentage the prepared membrane was investigated in detail. Adsorption kinetics and equilibrium adsorption isotherm fitted pseudo-second-order kinetic model and Freundlich isotherm model well, respectively. The thermodynamics analysis suggested that the adsorption process of methylene blue onto the chitosan/κ-carrageenan/acid-activated bentonite composite membrane was spontaneous and endothermic. The highest removal rate (98%) was achieved under the following conditions: adsorbent dose, 0.05 g; solution pH, 4; temperature, 50 °C; and time, 200 min. The maximum adsorption capacity for methylene blue was 16.27 mg/g at 50 °C. Moreover, the prepared composite membrane demonstrated the high reusability and adsorption rate (∼77%) without significant loss after sixth adsorption-desorption cycles. Considering of the above results, the prepared composite membrane can be a promising adsorbent candidate having low cost and high recyclability to remove methylene blue.
Chapter
Nowadays, natural fiber-based hybrid composites are receiving great global attention. They have wide application in various industries such as automotive, marine, aerospace, civil engineering, etc. The overall performance of natural fiber-based hybrid composites could be improved by nanomaterial reinforcement. Recently several studies have been reported about the use of nanoclay in improving the thermal and mechanical behavior of these hybrid composites. Hence, this chapter deals with the recent progress on the effect of nanoclay on thermal, flammability, melting, crystallization, and glass transition temperature of natural fiber-reinforced hybrid composites.
Chapter
Biopolymers are degradable materials obtained from renewable sources that have been studied as promissory alternatives to substitute partially or completely food packaging based on synthetic polymers. Several biopolymers such as carbohydrates, proteins, and lipids have been studied in the last years, aiming for food packaging applications. Before commercial application, it is necessary to understand the physicochemical properties of biopolymer-based materials such as gas barrier (H 2 O, O 2 , and CO 2 ), mechanical properties (elastic modulus, tensile strength, and elongation at break), thermal stability, and chemical properties related to the interaction with foods. Biopolymers are biodegradable materials and have low cost; however, films and coatings manufactured with these macromolecules have poor barrier and mechanical properties, limiting their food packaging applications. In the last years, several researchers have aimed to improve the physicochemical properties of biopolymer-based materials. In this sense, this chapter aimed to review the state of the art regarding the use of biopolymers as matrix to manufacture films and coatings with potential applications in the food sector.
Chapter
The number of studies on biomaterials and those added to nanocomposites to improve food packaging and enhance shelf life, sensory, and nutritional quality has increased in recent years. However, the important question is this: Could this material influence the biodegradation process? There are many articles about natural polymers and their blends, incorporation of nanocomposites, such as metallic oxide. The authors showed that biodegradability is not significantly affected by this new material; however, the changes improve mechanical, barrier, and sensory properties. In this chapter, the authors discuss how the incorporation of nanoparticles in natural polymers could influence biodegradability.
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In current investigation, various commercial nanoclays with different level of hydrophilicity i.e., hydrophilic bentonite (HB), cloisite 10A, and cloisite® 30B were incorporated to a hydrophilic semi-refined carrageenan (SRC) films to observe their presence in film matrix in regards with the final film’s properties. High shear mixing and sonication were applied to the film preparation to obtain high dispersion of nanoclays in the matrix. As expected, the hydrophilic clay showed better dispersion within the matrix as shown in Energy Dispersive X-Ray Spectroscopy (EDS) image. The more hydrophilic clay inclusion resulted in higher tensile strength, while the more hydrophobic resulted in higher stiffness of the films. The water vapour permeability was decreased in corresponded to the more hydrophobic clay incorporated, and the thermal properties of the films were overall enhanced by the nanoclays reinforcement. In general, nanoclays incorporation in SRC film improved the overall properties of the SRC film.
Thesis
The fight against plastic pollution implies the development of polymers as alternatives to synthetic polymers. Starch is a natural polymer that can easily be plastified by means of additives. Yet, thermoplastic starch-based materials are chiefly identified by feable, mechanical properties and a high sensitivity to water. This work aims at elaborating and identifying cassava starch-based plastic films. They are reinforced with kaolin and processed with heat or not in order to be used as packaging. The physico-chemical characterisation of the starch reveals that starch is acid (pH=4.7), fine (diameter:19µm) and content 21.2% of amylose. It displays a small quantity of water and minerals. The monostructural characterisations show that the starch of cassava is of type C and the granulous are displayed in conical, elliptical and angular shapes. The physicochemical characterisation of the kaolinitc clay highlights the presence of 75% of kaolinite, 11% of illite and 14% of quartz. The thermal processing of that kaolin at 700°C during one hour produces a metakaolin. The survey on plastic films developed with both kaolin and metakaolin testifies that metakaolin is a mineral filler which significantly improves the physico-chemical properties of plastic films. The metakaolin is then added to the different rates of masses (0; 5; 10; and 15 for 100g of starch) and to the mixture of starch and glycerol. The increase of the rate of metakaolin makes the plastic films become rigid by increasing the young's modulus and decreasing the lengthening of the breakage. The metakaolin induces some barriers effects at water intake and when emitting heat. All the plastic films are biodegradable items in the soil and on the soil surface. The rate 10% of metakaolin leads to a better compromise between both rigidity and deformation of the plastic films. Those plastic films may be used as packaging.
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This study was aimed at improving the gas barrier property of sugarcane based LLDPE using cellulose nanocrystals (CNCs). Specifically, this study evaluated the effect of CNC content on the crystallinity, tortuosity factor, carbon dioxide permeability (PCO2), and/or oxygen permeability (PO2) of bio-LLDPE sheets and films. All nanocomposites showed considerable improvement in gas barrier irrespective of the CNC content. The PCO2 coefficient of LLDPE sheets decreased by 36% by adding 10 wt% of CNCs into the sheet. Similarly, a significant decline in both PO2 (about 50%) and PCO2 (about 33%) coefficients of LLDPE films was obtained by adding 2.5 wt% of CNCs into the films. Nevertheless, no correlation was established between gas permeability and percent crystallinity of LLDPE sheet since the PCO2 coefficient decreased almost linearly with increasing CNC content whereas the percent crystallinity of LLDPE increased only up to 2.5% CNC content and remained constant thereafter. In contrast, the tortuosity factors calculated from the gas diffusion coefficients increased almost linearly with CNC contents and correlated well with the gas permeability improvement in bio-LLDPE-based nanocomposites. Consequently, the enhanced gas barrier in the nanocomposite was assigned to the tortuosity effect created by the impermeable CNCs rather than the changes in percent crystallinity.
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The present work shows the implementation of the Response Surface Methodology (RSM), fed by an experimental Central Composite Design (CCD) to find the conditions that allow maximizing the inhibition of the microorganism Staphylococcus aureus with nanoparticles of TiO 2 silanized with 3-Aminopropyltriethoxysilane (APTES) and doped with Ag. In addition, Poly(lactic) acid composites were prepared with these Ag/TiO 2 nanoparticles with the aim to confer their antimicrobial effect. The independent variables considered were pH, AgNO 3 /TiO 2 ratio (% w/w), and TiO 2 nanoparticles concentration (g/250 mL), and as the variable of response, the length of the diameter of the halo or zone of inhibition presented by the microorganism (mm). Statistical analysis found that maximization of S. aureus inhibition occurs at intermediate levels with a value of 10 for pH and 5 g of TiO 2 solids, while for the concentration of AgNO 3 high levels are required, greater than 10% w/w. Likewise, the statistical significance was determined using the Student's t-test and the p-value; it was found that the significant effect corresponds to the concentration of AgNO 3 , so a second experimental CCD design equirradial with two factors was considered, estimating AgNO 3 concentration and TiO 2 amount, the pH at constant 10 value. The second experimental design indicated that maximization in S. aureus inhibition occurs at an AgNO 3 concentration between 20-25% w/w with high amounts of TiO 2 solids (7-8 g), with a resulting zone of inhibition between 26-28 mm. The quadratic model obtained, which represents the relationship between the length of the zone of inhibition with the variables considered, shows an adjustment of experimental data with a coefficient of determination (R ² ) of 0.82.
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The increasing environmental pollution with petroleum‐based plastics has advanced research on biodegradable polymers. Thermoplastic starch (TPS) is one promising candidate due to wide availability from various renewable sources, low cost and biodegradability. However, TPS has significant shortcomings, as high water sensitivity and low mechanical properties. An approach to overcome these drawbacks is adding nanofillers as reinforcement of the starch matrix. Among the nanofillers, montmorillonite clays have the advantages of a wide availability, low cost, versatility and environmental friendliness. Bionanocomposites based on wheat starch plasticized with glycerol and reinforced with three types of montmorillonite nanoclays, one natural (Cloisite Na+) and two organomodified (Cloisite 30B and Cloisite 10A), were prepared by melt processing. The effect of nanoclay type and amount on processing properties, thermal stability, dynamic mechanical properties and water absorption was widely investigated. The properties strongly depended on the dispersion state of the nanoclay in the TPS matrix. The dispersion improved with the hydrophilicity of the nanoclay. Cloisite Na+, the most hydrophilic nanoclay, was the most effective in reinforcing TPS, improving the thermal stability and the dynamic mechanical properties, and showing a greater resistance to water absorption in normal humidity environments. Bionanocomposites of TPS andCloisite Na+ can be a good alternative for use in packaging applications.
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The starch-based polymer is an incredible substitute to petroleum-based plastics.It has an extraordinary possibility to form an edible, biodegradable film by blending in with various antimicrobial polymers, nanoparticles, and other antimicrobial blenders, for instance, essential oils from phenolic extracts. Characteristics, preparation methods , physicochemical properties, different modification methods for improvement of starch film properties are studid in this paper. This study surveys the sensibility of starch for food packaging.
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In this study, mixtures based on β-glucans and proteins are extracted from barley, in mild (MA) and high (HA) alkaline conditions, and employed with zinc oxide (ZnO) to prepare bioactive films for wound healing. Composition of extracts and properties of resulting films depend on pH extraction conditions. MA based samples show weak physical interactions among mixture components, whereas in HA films the extent of these interactions is larger. Consequently, their chemico-physical properties are significantly different, as demonstrated by FT-IR, thermal, mechanical and morphological analyses. ZnO with its bound water molecules acts as a slight plasticizer in MA, as shown by the lower Tg and the decrease of elastic modulus. In HA, this effect is evidenced up to ZnO 1%, and above this concentration an increase of strength at break is observed. Finally, MA and HA films show intrinsic antimicrobial properties, enhanced by ZnO, which make them exploitable as wound dressings.
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The purpose of this study was to evaluate the effect of nano-zinc oxide (ZnO-N) morphology on the functional and antimicrobial properties of tapioca starch films. For this reason, nanosphere (ZnO-ns), nanorod (ZnO-nr), and nanoparticle of ZnO (ZnO-np) at 0.5%, 1.0%, and 2.0% were added to the starch film. Then, physicochemical, mechanical, and barrier properties were evaluated. Also, UV–visible and Fourier transform infrared spectroscopy (FTIR) spectra and antibacterial activity of prepared nanocomposite films against Escherichia coli were examined. The results revealed that the ZnO-ns had the most effects on mechanical, physicochemical, and barrier properties. The highest values of the tensile strength (14.15 MPa) and Young's modulus (32.74 MPa) and the lowest values of elongation at break (10.40%) were obtained in the films containing 2% of ZnO nanosphere. In terms of UV transmission, ZnO-nr showed the most significant impact morphology. FTIR spectra indicated that interactions for all morphologies were physical interaction, and there are no chemical reactions between starch structure and nanoparticles. The antibacterial effect of the ZnO-ns was higher than that of other morphologies. In summary, ZnO-ns was the best morphology for using ZnO-N in starch-based nanocomposite films.
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Smart edible coating films can be used in food packaging. For this application, they must have good physical and mechanical properties. Herein, chitosan-beeswax based film is used to preserve Le Conte pears postharvest. The chitosan-beeswax films were characterized using XRD, FT-IR, and SEM analysis. Moreover, all films showed good self-healing aptitudes ranging from 86.7 to 96.3. The film treated with pollen grains showed an enhanced water contact angle compared with the chitosan film. The chitosan-beeswax/pollen grain film exhibited a two-fold lower WVTR value compared to the chitosan film, and showed the tendency to increase the stiffness of the film. The elongation% at break was reduced from 35.81 to 14.09. Fruit quality parameters were determined in cold storage for 105 days during shelf life after a simulated marketing period of 7 days. All coated fruits successfully showed decrease in weight loss, decay and rate of softening. Therefore, chitosan-beeswax/pollen grains can be considered safe and effective coating for the fruit preservation.
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The effects of nano-ZnO and nano-SiO2 nanoparticles on the properties of starch-based films prepared by extrusion blowing were investigated in this study. New hydrogen bonds between hydroxypropyl starch (HS) and nanoparticles during the extrusion process were formed as shown by Fourier transform infrared spectroscopy (FTIR). The diffraction patterns of nanocomposite films reinforced with nano-ZnO were similar to those of nano-ZnO, except that the peak intensity decreased, whereas, the addition of SiO2 nanoparticles decreased the intensity of the main characteristic peaks, regardless of the HS and nano-ZnO reinforced films. The thermal stability, tensile strength, moisture barrier property, and surface hydrophobicity of nanocomposite films were improved with the incorporation of nano-ZnO and nano-SiO2, the finding that could be attributed to a strong interplay between nano-ZnO, nano-SiO2, and the starch matrix during the extrusion film blowing process. Similarly, the nano-ZnO/nano-SiO2 composite-reinforced films showed smooth, flat, and uniform appearances by scanning electron microscopy (SEM) and atomic force microscope (AFM) tests. In sum, Nano-ZnO and nano-SiO2 nanoparticles can be used as composite reinforcing agents for preparation of starch-based films through extrusion blowing.
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Four different plastics were tested: potato starch based plastic (TPS-P)–BIOPLAST GF 106/02; corn starch based plastic (TPS-C)–BioComp BF 01HP; polylactic acid (polylactide) plastic (PLA)—BioComp BF 7210 and low density polyethylene, trade name Malen E FABS 23-D022; as a petrochemical reference sample. Using the blown film extrusion method and various screw rotational speeds, films were obtained and tested, as a result of which the following were determined: breaking stress, strain at break, static and dynamic friction coefficient of film in longitudinal and transverse direction, puncture resistance and strain at break, color, brightness and gloss of film, surface roughness, barrier properties and microstructure. The biodegradable plastics tested are characterized by comparable or even better mechanical strength than petrochemical polyethylene for the range of film blowing processing parameters used here. The effect of the screw rotational speed on the mechanical characteristics of the films obtained was also demonstrated. With the increase in the screw rotational speed, the decrease of barrier properties was also observed. No correlation between roughness and permeability of gases and water vapor was shown. It was indicated that biodegradable plastics might be competitive for conventional petrochemical materials used in film blowing niche applications where cost, recyclability, optical and water vapor barrier properties are not critical.
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Thermoplastic cassava starch (TPS) /nanosilica (nano-SiO2) composites were prepared by adding different surface properties of nanosilica. The effect of different surface properties of nano-SiO2 on the retrogradation kinetics, morphology, spherulites size, molecular interactions, short-range molecular structure and crystal type of TPS was investigated by differential scanning calorimetry (DSC), polarized light microscopy (PLM), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and 13C NMR. The results indicated that the retrogradation degree and rate of TPS containing hydrophobic nano-SiO2 were higher than that of hydrophilic nano-SiO2, and the spherulites were clearer. Hydrophobic nano-SiO2 could uniformly disperse in starch matrix. V-type crystal formed after adding hydrophilic nano-SiO2, and A + V types after adding hydrophobic nano-SiO2. The crystallinity of TPS adding hydrophobic nano-SiO2 was higher than that of hydrophilic nano-SiO2, but the crystal size and interplanar spacing were smaller. Hydrophobic nano-SiO2 could promote the formations of double helix structure and the ordered molecular structure.
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The objective of this study was to investigate the synergistic effect of nano titanium dioxide (TiO2-N) and Mentha piperita essential oil (MEO) on the equilibrum moisture sorption isotherm and microbial growth rate of Staphylococcus aureus of cassava starch film. For this purpose, cassava starch biocomposite film with the addition of 1, 3 and 5% TiO2-N and 1, 2 and 3% MEO, and glycerol as a plasticizer were obtained by the casting method. The equilibrium moisture absorption isotherm and antibacterial activity of prepared nanobiocomposite films against Staphylococcus aureus were examined. The obtained results demonstrated that by addition of nanoparticles and essential oil to the starch biocomposites, the equilibrium moisture absorption isotherm curve was shifted to lower moisture content. The microbial tests stated that the pure cassava starch film (control) showed no antibacterial activity against the Staphylococcus aureus and the antibacterial activity significantly increased with increasing concentration of both TiO2-N and MEO in the starch films (p<0.05). However, the antibacterial activity of TiO2-N nanoparticles was higher than MEO. Addition of TiO2-N and MEO increased lag phase and decreased log phase in microbial growth curve. Finally, according to the obtained results in this study, it can be concluded that incorporation of TiO2-N and MEO combination improved the antibacterial activity of cassava starch biocomposites against Staphylococcus aureus and these bionanocomposite films can be used for packaging and extending the shelf life of food products.
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Starch-based films have promising application on food packaging, because of their environmental appeal, low cost, flexibility and transparency. Nevertheless, their mechanical and moisture barrier properties should be improved. The aim of this work was to enhance these properties by reinforcing the films with cellulose fibers. Besides, the influences of both the solubility coefficient of water in the films (β) and the diffusion coefficient of water vapor through the films (Dw) on the films' water vapor permeability (Kw) were investigated. Films were prepared by the so-called casting technique, from film-forming suspensions of cassava starch, cellulose fibers (1.2mm long and 0.1mm of diameter), glycerol and water. The influence of fibers addition on Kw was determined at three relative humidity gradient ranges, ΔRH (2–33%, 33–64% and 64–90%). Films reinforced with cellulose fibers showed higher tensile strength and lower deformation capacity, and presented lower Kw than films without fibers. Kw showed strong dependency of β and Dw, presenting values up to 2–3 times greater at ΔRH=64–90% than at ΔRH=33–64%, depending on the film formulation. Therefore, adding cellulose fibers to starch-based films is a viable alternative to improve their mechanical and water barrier properties. Besides, this work showed the importance of determining film's water vapor permeability simulating the real environmental conditions the film will be used.
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Biodegradable thermoplastic starch (TPS)/clay hybrids were prepared by melt intercalation. Three organically modified montmorillonite (MMT) with different ammonium cations and one modified Na+ MMT (Cloisite Na+) were used. Cloisite Na+ showed the best dispersion in the TPS matrix. It was observed that the TPS/Cloisite Na+ hybrid showed an intercalation of TPS in the silicate layer due to the matching of the surface polarity and interaction of the Cloisite Na+ and TPS, which gives higher tensile strength and better barrier properties to water vapor as compared to the other TPS/organoclay hybrids as well as the pristine TPS. It was found that the dynamic mechanical properties of the TPS/clay hybrids were also affected by the polar interactions.
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The parameters of the `G.A.B.' equation are discussed from mathematical and physical point of view. Clear limits of those parameters are determined. The point of inflexion of the `G.A.B.' isotherm was also analysed with the conclusion that the `G.A.B.' isotherm behaves too rigidly to be able to describe complicated sorption cases. The different possibilities of some other isotherms for such a purpose were displayed.
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Wheat gluten/montmorillonite (WG/MMT) nanocomposite films were prepared by casting. Transmission electron microscopy observations showed that MMT nanoparticles were homogeneously distributed within the matrix but not completely exfoliated. Contact angles, water uptake and water vapour sorption measurements showed that the presence of MMT led to a significant reduction of the water sensitivity of WG-based materials. This effect was attributed to a different structuring of protein network in the presence of MMT. Significant changes in the permeability of films towards water vapour and aroma compounds were observed for MMT contents higher than 5wt%, while O2 and CO2 permeabilities remained unchanged. Finally, a slight improvement in tensile properties was obtained for filler contents higher than 2.5wt%.
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Starch/clay nanocomposites were prepared via solution casting method and the effects of starch source, clay cation, glycerol content, and mixing mode on clay intercalation and Young’s modulus of nanocomposites were investigated using a Taguchi experimental design approach. The clay intercalation was examined by X-ray diffraction (XRD) patterns. Nanocomposites prepared with montmorillonite (MMT) modified with citric acid demonstrated the highest Young’s modulus compared to pristine MMT and organoclay. A combined mechanical and ultrasonic mixing mode led to an extensive dispersion of silicate layers and thus the highest Young modulus in nanocomposites. The effect of clay content on tensile properties was also investigated. It was observed that the maximum stress strength would be attained for nanocomposite films with 6% (by weight) of clay loading. The chemical structure and morphology of the optimum sample was probed by FT-IR spectroscopy and transmission electron microscopy (TEM).
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Edible films were developed using different starch sources (corn starch and amylomaize). Starch suspensions were cold gelatinized with NaOH; either glycerol or sorbitol were used as plasticizer. Films were characterized by Differential Scanning Calorimetry (DSC), X-ray diffraction, Scanning Electron Microscopy (SEM) and gas (CO2 and O2) permeabilities. SEM observations showed that plasticizer addition was necessary for film integrity. The evaluation of film formation by DSC indicated that cold gelatinization was the main factor of thermal transitions. Film crystallinity was analyzed by DSC and X-ray diffraction during storage. For all tested formulations, film crystallinity increased while gas permeability decreased during storage. Films containing glycerol or sorbitol showed a lower crystalline/amorphous ratio by X-ray diffraction and DSC than unplasticized films. Amylomaize films with higher crystalline/amorphous ratio gave lower gas permeabilities than the corresponding corn starch films; films containing sorbitol showed lower permeability values than those containing glycerol.
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In this study, we investigated nanocomposites based on a plasticized natural biodegradable matrix. The polymer used was a natural potato starch, and the plasticizers were glycerol and a urea/ethanolamine mixture. A natural and an organically modified montmorillonite were studied. Two series of films containing 6 wt % nanoclays were prepared by a solution/cast process: the first series was based on neat starch, and the second one was based on 20 wt % plasticized starch. For all matrices, a mixture of intercalated and exfoliated structures was formed by the addition of pristine montmorillonite, whereas an aggregate structure was obtained with organoclay. The thermal stability was not significantly influenced by the addition of clays. Water sorption was examined as a function of the matrix and clay hydrophilicity. The significant reduction of oxygen permeability obtained with natural montmorillonite was related to the high dispersion state of this clay. For urea–ethanolamine composites, specific compatibilizer/clay interactions led to an improvement again in the barrier properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
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The effect of water content on the glass transition temperatures of cassava starch was determined by differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). Samples were transformed to the amorphous state by compression molding at high temperature (as demonstrated by wide angle X-ray diffraction, WAXS), and then the samples were moisture conditioned. Both DSC and DMTA showed that water anti-plasticized cassava starch at lower moisture contents, and plasticized it at higher water contents. Samples with higher moisture contents stored at room temperature, 45 °C and 80 °C underwent retrogradation as indicated by WAXS. Sorption isotherms of cassava starch showed that for aw values lower than around 0.85, the sorption capacity decreased with increasing temperature; while the opposite behavior was observed at aw > 0.85. This inversion point (aw = 0.85) was attributed to the fact that more active sites were exposed to the adsorption processes, due to the enhanced molecular mobility promoted in the amorphous regions by starch crystallization.
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Rice flour is a starchy material with low-cost, because it can be produced from rice that is broken during processing. The aim of this study was to develop biodegradable films based on rice starch and rice flour, and to characterize their physicochemical, microscopic and mechanical properties. Films from rice starch and rice flour were prepared by casting, with glycerol or sorbitol as plasticizer. SEM analysis of starch and flour films revealed compact structures. Rice flour films prepared in the present work have similar mechanical properties to those of starch based films. However, their water vapor permeabilities are two times higher than those of starch based films. Films with sorbitol were less permeable to water and more rigid, while films with glycerol are more plasticized and have poorer water vapor barrier properties. Therefore, preparing edible films from rice flour is a new alternative for using this raw material, which is sometimes much cheaper than commercial starches.
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Biodegradable nanocomposites have been successfully fabricated from the thermoplastic cornstarch (TPCS) and activated-montmorillonite (MMT) by melt-intercalation. TPCS was plasticized with novel plasticizers urea and formamide, and the activated-montmorillonites were obtained using citric acid as the activated solvent. Compared with urea and formamide-plasticized thermoplastic cornstarch (UFTPCS), the mechanical properties of nanocomposites were very good. The thermal analysis was investigated by Differential Scanning Calorimetry (DSC). The effect of water content on the mechanical properties of nanocomposites was studied. Dynamic Mechanical Thermal Analysis (DMTA) was also carried out. The structure and morphology of biodegradable nanocomposites were characterized by wide-angle X-ray diffraction (WAXD), scanning electron microscope (SEM) and transmission electron microscope (TEM). It was revealed that UFTPCS were intercalated into the layers of MMT successfully, and layers of MMT were fully exfoliated and so formed the exfoliated nanocomposites with MMT. This manufacturing process is simple and environmentally friendly.
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This review aims at highlighting on recent developments in preparation, characterization, properties, crystallization behaviors, melt rheology, processing, and future applications possibilities of biodegradable polymers and their layered silicate nanocomposites. These materials are attracting considerable interest in materials science research. Montmorillonite and hectorite are among the most commonly used smectite-type layered silicates for the preparation of nanocomposites. In their pristine form they are hydrophilic in nature, and this property makes them very difficult to disperse into biodegradable polymer matrices. The most common strategy to overcome this difficulty is to replace the interlayer clay cations with quarternized ammonium or phosphonium cations, preferably with long alkyl chains. A wide range of biodegradable polymer matrices is described in this review with a special emphasis on polylactide because of more eco-friendliness from its origin as contrast to the fully petroleum-based biodegradable polymers and control of carbon dioxide balance after their composting. Preparative techniques include (i) intercalation of polymers or prepolymers from solution, (ii) in situ intercalative polymerization method, and (iii) melt intercalation method. This new family of composite materials frequently exhibits remarkable improvements of mechanical and material properties when compared with virgin polymers or conventional micro- and macro-composites. Improvements can include a high storage modulus both in solid and molten states, increased tensile and flexural properties, a decrease in gas permeability and flammability, increased heat distortion temperature and thermal stability, increase in the biodegradation rate, and so forth.
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The Institute of Food Technologists has issued this Scientific Status Summary to update readers on the applications of nanotechnology in the food industry.
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As an attempt to develop environmentally friendly polymer hybrids, biodegradable thermoplastic starch (TPS)/clay nanocomposites were prepared through melt intercalation method. Natural montrorillonite (Na+ MMT; Cloisite Na+) and one organically modified MMT with methyl tallow bis-2-hydroxyethyl ammonium cations located in the silicate gallery (Cloisite 30B) were chosen in the nanocomposite preparation. TPS was prepared from natural potato starch by gelatinizing and plasticizing it with water and glycerol. The dispersion of the silicate layers in the TPS hybrids was characterized by using wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). It was observed that the TPS/Cloisite Na+ nanocomposites showed higher tensile strength and thermal stability, better barrier properties to water vapor than the TPS/Cloisite 30B nanocomposites as well as the pristine TPS, due to the formation of the intercalated nanostructure. The effect of clay contents on the tensile, dynamic mechanical, and thermal properties as well as the barrier properties of the nanocomposites were investigated.
Article
An organically modified clay (o-clay) and a pristine clay (p-clay) were used to prepare biodegradable thermoplastic starch (TPS)/clay nanocomposites by melt processing. The gelatinization behaviour of starch with glycerol/H2O was investigated and the gelatinized temperature (Tgel) was determined using a polarized optical microscopy (POM) equipped with a hot stage. The morphologies of gelatinized starch and extruded starch were revealed by scanning electron microscopy (SEM). Thermal stabilities of starch/clay nanocomposites were evaluated under N2 atmosphere using thermogravimetric analysis (TGA). Transparent films of starch/clay hybrids were fabricated by hot pressing. Intercalation of starch into clay galleries and crystalline structure of starch were investigated using X-ray diffraction (XRD). It was found that the increase in d-spacing of organically modified clay was due to starch molecular intercalation while the increase in d-spacing of pristine clay was mostly caused by glycerol intercalation because of the narrow valid d-spacing of pristine clay and special ring-like monomer of starch. The mechanism of starch intercalation in clay galleries was discussed.
Article
The effects of glycerol and sorbitol on the water sorption isotherms and water vapor permeability (Kw) of cassava starch films prepared by casting were investigated. Kw values were determined in three ranges of relative humidity, RH, (2–33%, 33–64% and 64–90%) and the GAB model was used to fit experimental water sorption isotherms. These data were used to determine the relative influence of the diffusion coefficient of water (Dw) and the average solubility coefficient () of water in the films on the Kw value. In all cases, an increase in Kw values were observed with increasing plasticizer concentration and RH. The Dw, and Kw values of films prepared with glycerol were greater than those of films prepared with sorbitol. For high RH, the values increased 6-fold for films with glycerol and 7-fold for films with sorbitol, while Dw values did not change significantly. These results indicate that Kw values are dependent on the solubility coefficient () of water in the film, which is not consistent with the proposal that an opening of polymer chains promoted by plasticizers leads to an increase in Dw and Kw.
Article
Montmorillonite (MMT), a kind of reinforced additive and glycerol-plasticized thermoplastic starch (GTPS) were used in the preparation of Montmorillonite-reinforced themorplastic starch composites (MTPSC) with the method of melt extrusion. Scanning electron microscope (SEM) revealed that MMT were uniformly dispersed in GTPS. Fourier Transform infrared (FT-IR) patterns showed that in the MTPSC the C–O groups of starch molecules shifted to the higher wavenumber, while the reactive hydroxyl groups of MMT shifted to the lower wavenumber. That was caused by the cooperation of the strong absorption that existed between MMT and starch molecules and hydrogen bonds that formed between the reactive hydroxyl groups of MMT and the hydroxyl groups of starch molecules. MMT was on the submicron filling transition state and acted as an obstructor. When MTPSC was stored for 14 days at RH (relative humidity)=39%, the tensile strength, Young's modulus and breaking energy of MTPSC were 27.34, 206.74 MPa and 1.723 N m, respectively. It was obvious that the mechanical properties of MTPSC were greatly improved. At the same time, the effect of water content on the mechanical properties was studied. X-ray diffraction revealed that MMT restrained the crystallization of GTPS effectively. Differential thermal analysis (DTA) and water absorption testing showed that the thermal stability and water-resistant properties of MTPSC were better than those of GTPS.
Article
Glycerol-plasticized starch/clay nanocomposites films were prepared from potato starch and three different loadings of montmorillonite aqueous suspensions by casting, to study the effect of the nanoclay in the properties of starch. The clay dispersion in the films was analyzed by X-ray diffraction (XRD). It was observed that the 001 diffraction peak of clay was shift to lower angles in the nanocomposites patterns providing strong evidence that the clay nanolayers formed an intercalated structure but not complete exfoliation. An improvement in the thermal resistance of starch with the addition of clay was also observed by means of thermogravimetric analysis (TGA). The water absorbed by the nanocomposites measured in an environment with a 75% of constant relative humidity was reduced by the addition of montmorillonite to the starch. The micro-tensile test was performed on the nanocomposite films showing significant improvement in the Young modulus up to 500% for the nanocomposite containing 5 wt% of clay.
Article
A series of gelatinized starch–clay nanocomposites which exhibit intercalated and exfoliated structures have been developed. Various nanoclay dispersions were prepared (either by standard mixing or through the use of ultrasonics) prior to their combination with a high amylose content starch using high-speed mixing and extrusion technology. Intercalated and exfoliated type structures were observed in the sheet extruded nanocomposites using X-ray diffraction and transmission electron microscopy (TEM). Due to the hydrophilic nature of the gelatinized starch nanocomposite a novel preparatory technique was developed to produce nano scale sections for TEM. A range of plasticiser levels were used in conjunction with different unmodified nanoclays (sodium montmorillonite (Na-MMT) and fluorohectorite (Na-FHT)) having different cationic exchange capacities. It was shown that an optimum level of both plasticiser and nanoclay existed to produce a gelatinized starch film with the highest levels of exfoliation, resulting in superior properties. The use of ultrasonics was only advantageous in terms of clay dispersions at medium clay concentrations in the Na-MMT nanocomposites and higher clay concentrations in the Na-FHT, most probably due to the difference in cationic exchange capacity; however when the level of clay, water and starch was optimised an exfoliated structure was produced via standard mixing which exhibited comparable improvements in mechanical properties to ultrasonically treated samples.
Article
A polycationic bentonite clay (PB) was organically modified with a quaternary organic salt and added to isotactic polypropylene (PP). The compounds were prepared by melt intercalation using a twin extruder then characterized by X-ray diffraction (XRD), thermogravimetry (TG) and scanning electron microscopy (SEM) for clarifying the composite nanostructure. Compression moulded films were exposed to a thermal oxidative environment at 110 °C in an attempt to evaluate the thermal stability of PP matrix after chemical modification of bentonite. The carbonyl index results, as obtained by infrared spectroscopy, showed that the modified clay had higher thermal stability in the solid state than the natural clay. This may be connected to a higher dispersion of clay particles, reducing oxygen diffusion through the sample. On the other hand, the degradation of the composites was more intense than the unfilled polymer and this may be due to the presence of acidic sites on the clay surface that act as a catalyst to the polymer oxidation, and/or due to salt decomposition, initiating the free radical degradation of PP.
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The mechanical properties (elastic modulus, EM; tensile strength, TS and % elongation, %E) of β-lactoglobulin (β-Lg) films plasticized with different plasticizers were determined. Six plasticizer types were studied over a range of concentrations. Propylene-glycol-plasticized β-Lg films were the most brittle, with mechanical properties independent of plasticizer content. Films with other plasticizers studied (glycerol, Gly; sorbitol, Sor; polyethylene glycol, PEG 200 and PEG 400 and sucrose, Suc) exhibited negative exponential dependence on plasticizer concentration for EM and TS, while they exhibited linear dependence on plasticizer concentration for %E. The EM and TS data for each plasticizer were fitted with an exponential model, while %E data were fitted with a linear model to quantify the plasticizer effect. The EM0, TS0 and %E0 of β-Lg films without plasticizer determined from the fitted equations were 1500, 37.28 MPa and 0, respectively. The kEM,kTS and kE values determined from the fitted EM, TS and %E data, respectively, reflect the efficiency of plasticizers. The kEM,kTS and kE values indicate that plasticizer efficiency generally decreased in the order Gly, PEG 200, PEG 400, Sor and Suc, on the bases of mole plasticizer-oxygen-atom/mole β-Lg and mass plasticizer/mass β-Lg. These results reflect the effect of plasticizer composition, size and shape. The kEM,kTS and kE value order was reversed when the basis was changed to mole plasticizer/mole β-Lg. The latter results clearly reflect the effect of plasticizer number of O atoms.
Article
PLA-based composite films with different types of nanoclays, such as Cloisite Na+, Cloisite 30B and Cloisite 20A, were prepared using a solvent casting method and their tensile, water vapor barrier and antimicrobial properties were tested. Tensile strength (TS), elongation at break (E), and water vapor permeability (WVP) of control PLA film were 50.45 ± 0.75 MPa, 3.0 ± 0.1%, and 1.8 × 10−11 g m/m2 s Pa, respectively. TS and E of nanocomposite films prepared with 5 g of clay/100 g of PLA decreased 10–20% and 11–17%, respectively, depending on the clays used. On the contrary, WVP of the nanocomposite films decreased 6–33% through nanoclay compounding. Among the clay types used, Cloisite 20A was the most effective in improving the water vapor barrier property while sacrificing tensile properties the least. The effect of clay concentration tested using Cloisite 20A showed a significant decrease in TS and WVP, with increases in clay content. Among the PLA/clay composite films tested, only PLA/Cloisite 30B composite film showed a bacteriostatic function against Listeria monocytogenes.
Article
In the quest for improved performance from polymers that offer biodegradation and therefore environmental acceptability, one approach is the addition of natural clays to produce nanocomposites. This study examines nanocomposites of glycerol-plasticized starch, with untreated montmorillonite and hectorite. Treated hectorite and kaolinite were added to produce conventional composites within the same clay volume fraction range for comparison. X-ray diffraction and transmission electron microscopy are used to confirm the type of composite. The ultrasonic pulse-echo technique was used to measure Young's and shear modulus. The nanocomposites presented greater increases in modulus for a given volume fraction of clay thus contributing to this new class of biodegradable and environmentally acceptable materials, although the results indicate that a plasticizer other than glycerol is preferable.
Article
The effects of incorporating various montmorillonite nanoclays into wheat, potato, corn, and waxy corn starch samples were examined by rheology and X-ray diffraction. The nanoclays included the hydrophilic Cloisite Na+ clay as well as the more hydrophobic Cloisite 30B, 10A, and 15A clays. Frequency sweep and creep results for wheat starch–nanoclay samples at room temperature indicated that the Cloisite Na+ samples formed more gel-like materials than the other nanoclay samples. X-ray diffraction results showed no intercalation of Cloisite Na+ clays at room temperature, suggesting that starch granules interacted only with the clay surface and not the interlayer. When the various wheat starch–nanoclay samples were heated to 95 °C, the Cloisite Na+ samples exhibited a large increase in modulus. In contrast, the more hydrophobic nanoclay samples had comparable modulus values to the neat starch sample. These results suggested that during gelatinization, the leached amylose interacted with the Cloisite Na+ interlayer, producing better reinforcement and higher modulus values. X-ray diffraction results supported this interpretation since the data showed greater intercalation of Cloisite Na+ clay in the gelatinized samples. The samples containing wheat and corn starch showed comparable elastic modulus values during gelatinization. However, the potato and waxy corn samples had modulus values that rapidly decreased at higher temperatures.