Thermoplastic Starch Films Research Articles

Properties of Starch‐Based Nanocomposites with Starch‐Coated ZnONP Obtained by Flat‐Die Extrusion

AbstractFast‐growing environmental concern has made nanotechnology surge as an enhancer of eco‐friendly materials. In this research, biodegradable and active nanocomposites are developed from thermoplastic starch films with the incorporation of different concentrations of zinc oxide nanoparticles eco‐friendly synthesized with starch (ZnONP) (0, 0.5, 1, 2, and 5 wt.%) by flat‐die extrusion. ZnONP at 2 and 5 wt.% enhances Young's modulus (E), strain at break (εb), and tensile toughness (T), and decreases the water solubility (WS) and moisture content (MC), also inhibiting the growth of Escherichia coli. Additionally, with 5 wt.% of nanofiller, a hydrophobic material with UV‐A and UV‐B shielding is also achieved. Furthermore, all films are fully biodegraded in vegetal compost at around 4 weeks. The results show that ZnONP can be a very promising alternative as a reinforcing and active agent for preparing new starch‐based nanocomposites for the food packaging and coating industry.

Co-Plasticization of Starch with Glycerol and Isosorbide: Effect on Retrogradation in Thermo-Plastic Cassava Starch Films.

Thermoplastic starch (TPS) has emerged as an essential alternative to produce environmentally friendly packaging; however, retrogradation is a disadvantage that affects its shelf life. This study analyzed the co-plasticizing effect of isosorbide on the mechanical, thermal, physicochemical, and microstructural properties and the retrogradation of films obtained by blown film extrusion from thermoplasticized starch with mixtures of glycerol and isosorbide in different ratios (3:0, 2:1, 1:2, and 0:3, respectively). The results showed that the higher concentration of isosorbide significantly increased the tensile strength; however, it reduced the elongation. Retrogradation modeled using the Avrami equation showed that the presence of isosorbide reduced the retrogradation rate (k) and modified the recrystallization mechanism (n). The relative crystallinity in the plasticized TPS films was reduced to 89%, and the adsorption significantly decreased. Isosorbide was very important in reducing the retrogradation of TPS. The best performance was obtained with the 2:1 ratio of glycerol/isosorbide due to the synergistic effect between the plasticizers. The results would allow tuning the properties of TPS films by combining glycerol/isosorbide in different ratios, which enables the design of materials tailored to potential application requirements.

Toughening mechanism of thermoplastic starch nano-biocomposite with the hybrid of nanocellulose/nanobentonite

High flexibility and toughness are key criteria for an effective bioplastic packaging film. However, in most studies, the flexibility of thermoplastic starch (TPS) films is always neglected when targeting their tensile strength improvement. Low film flexibility has limited the development of TPS films in replacing the petrochemical-based plastic packaging films. In this communication, we report a method to produce thermoplastic corn starch (TPCS) films with excellent mechanical strength, high flexibility and high toughness through the hybridization of two natural nanofillers: nanobentonite and nanocellulose. The synergistic effect of the hybrid nanofillers can be observed through the arrangement of alternating nacre structures where the nanobentonite silicate layers are responsible for mechanical strength, while the nanocellulose promotes free volume in the TPCS matrix and triggers high film elongation at break. Structural, morphological, and thermomechanical analysis were conducted, and the detailed strengthening mechanism of the TPCS hybrid nano-biocomposite films was revealed.

Horse chestnut thermoplastic starch nanocomposite films reinforced with nanocellulose

Abstract The starch-based materials such as thermoplastic starch film are a promising alternative to non-renewable petroleum-based plastics. The development of an alternative conventional plastic from bio-based materials has gained great interest following its biodegradable, non-hazardous and renewable advantages. Following that, horse chestnut is an exciting source of starch for producing thermoplastic starch film. Nonetheless, the thermoplastic starch film is weak in strength and easily affected by water due to its highly hydrophilic property, thus limiting its practicability. In this regard, the additions of nanocellulose into thermoplastic starch have shown drastic improvement in its mechanical properties and water permeability of the film. This chapter discusses the potential of nanocellulose reinforced plasticized starch from horse chestnut as a replacement for petroleum-based plastic in packaging applications.

Rice thermoplastic starch nanocomposite films reinforced with nanocellulose

Abstract Rice starch is a raw material with proven potential in obtaining biodegradable polymers. Plasticization improves the flexibility characteristics of starch-based films, although they still tend to have low tensile strength and high hydrophilicity. The addition of nanocellulosic materials is an alternative to improve these characteristics. In this chapter, the effects of adding different sources and concentrations of nanocellulose (NC) on the properties of thermoplastic rice starch films (TRSF) are addressed. One can highlight as main effects the increase of tensile strength and transparency of the films, the reduction of water vapor permeability and water solubility. The type of NC used, the way it is obtained, as well as its interaction with starch molecules are factors that influence the effects. Further studies involving the interaction of TRSF and NC should be conducted in order to overcome the lack of information.

Evolution of the free volume during water desorption in thermoplastic starch/citric acid films: In situ positron annihilation studies

The effect of citric acid (CA) concentration and water content on the free hole volume of thermoplastic cassava starch films (TPS) was studied. To this aim, continuous in situ positron annihilation lifetime spectroscopy measurements were performed at fixed moisture content and during water desorption. The results show that the increase in CA concentration leads to wider free hole volume distributions with lower mean values. During water desorption, the mean values and width of such distributions systematically decrease with the exposure time, and the evolution of the hole volumes was well-described using the Kohlrausch-Williams-Watts function. The water vapour permeability was significantly higher in films incorporating 5 % (w/w) of CA, in line with the more open network of this material that was revealed in the hole volumes distribution. The Young's modulus of all the developed films increased significantly after partial water desorption, which was attributed to the plasticizer loss reflected in a decrease in the mean hole volume value (between 4 % and 13 %). This work evidences that the control and report of the relative humidity are essential when testing TPS-based films, as their nanostructures are strongly dependent on external conditions.

Characterization of Thermoplastic Starch Plasticized with Ternary Urea-Polyols Deep Eutectic Solvent with Two Selected Fillers: Microcrystalline Cellulose and Montmorillonite

The aim of the study was to prepare and characterize composite materials based on thermoplastic starch (TPS)/deep eutectic solvent (DES). Potato starch was plasticized with ternary DES: urea:glycerol:sorbitol and modified with the selected fillers: microcrystalline cellulose and sodium montmorillonite. Films were prepared via twin-screw extrusion and thermocompression of the extrudates. Then, the physicochemical properties of the TPS films were examined. The ternary DES effectively plasticized the polysaccharide leading to a highly amorphous structure of the TPS (confirmed via mechanical tests, DMTA and XRD analyses). An investigation of the behavior in water (swelling and dissolution degree) and water vapor transmission rate of the films was determined. The introduction of the two types of fillers resulted in higher tensile strength and better barrier properties of the composite TPS films. However, montmorillonite addition exhibited a higher impact than microcrystalline cellulose. Moreover, a cone calorimetry analysis of the TPS materials revealed that they showed better fire-retardant properties than TPS plasticized with a conventional plasticizer (glycerol).

Effects of different sources of cellulose on mechanical and barrier properties of thermoplastic sweet potato starch films

Sweet potato starch and different celluloses were mixed by thermoplastic extrusion and then thermoplastic starch/cellulose composite films were prepared using a casting method. The effect of different celluloses on the mechanical and barrier properties of thermoplastic sweet potato starch films were studied and compared. The results indicated that among thermoplastic starch/cellulose composite films, the hydrogen bond interaction between starch and sugarcane cellulose was more obvious and the crystallization melting temperature difference was smaller, indicating better compatibility between sugarcane cellulose and sweet potato starch. Thermoplastic starch/sugarcane cellulose film had the largest FTIR ratio values of 1047 cm−1/1022 cm−1, resulting in the highest tensile strength (3.75 MPa), largest contact angle (68.44°), or stronger surface hydrophobicity. Thermoplastic starch/cornstalk cellulose film had the highest thermal degradation temperature (325 °C). Thermoplastic starch/wheat or bamboo cellulose film had lower UV transmittance (about 36%), indicating stronger UV Resistance. Thermoplastic starch/rice bran cellulose film had the largest elongation at break value (49.03%). Thermoplastic starch/bamboo or cornstalk cellulose films had lower water vapor permeability, whereas thermoplastic starch/rice bran cellulose had higher water vapor permeability. The outcoming would provide a new theoretical basis for choosing an optimal cellulose compatible with thermoplastic sweet potato starch to enhance mechanical properties, water resistance and barrier property of thermoplastic starch films.

Controlling the properties of thermoplastic starch films with hydrogen bonding plasticizers

Four deep eutectic solvents were used to produce plasticized thermoplastic starch films by a solution casting method. The mechanical properties of thin films, the stability of these properties over time, and the effects of humidity were investigated with the quartz crystal microbalance. The crystallinity, glass transition temperature, modulus and elongation at break for thicker films was measured using a combination of x-ray diffraction, differential scanning calorimetry and tensile testing. The films had very low glass transition temperatures (-50 ∘C or lower), with mechanical properties determined by the crystallinity of the films. The crystallinity did not change significantly over a period of one week, giving materials with a stable mechanical response. Deep eutectic solvents containing ammonium acetate, glycerol, and urea produced films with a crystalline structure that was much more stable at high humidity values than films plasticized only with glycerol or a traditional ionic liquid. These effects are attributed to the complex hydrogen bonding interactions between the different components of the deep eutectic solvents, and between these components and the starch polymer.

Influence of Urea Content in Deep Eutectic Solvents on Thermoplastic Starch Films’ Properties

The goal of the study was to prepare deep eutectic solvents (DESs) with different urea (U) contents and apply them as potato-starch plasticizers to investigate the influence of various DES compositions on the physicochemical properties of thermoplastic starch (TPS) obtained via thermocompression. As hydrogen bond acceptors, quaternary ammonium compounds, choline chloride (CC) and betaine (B-anhydrous and monohydrate) were used. The molar ratios of CC or B to U were 1:2, 1:3, 1:4 and 1:5. Before starch processing, the DESs were thermally characterized (DSC, TGA). The increase in U content in the eutectics led to higher phase-transition temperatures and lower thermal stability. The influence of the DESs on thermocompressed TPS mechanical (tensile test) and thermal–mechanical (DMTA) properties, morphology (XRD and FTIR), sorption/dissolution behavior and surface contact angle was investigated. The mechanical tests revealed that the increase in U led to higher elongation at break and a highly amorphous structure. The FTIR results indicated that the starch underwent some carbamation derivatization with the presence of B. The DESs with high U content plasticized starch effectively; therefore, preliminary extrusion tests for starch were performed with selected CC and B-based DES with the molar ratio of 1:5.

Enhancing the Thermo-Mechanical Properties of Thermoplastic Starch Films Using Rice Straw Fibers as Reinforcement

Enhancing the Thermo-Mechanical Properties of Thermoplastic Starch Films Using Rice Straw Fibers as Reinforcement

The relationship between molecular structure and film-forming properties of thermoplastic starches from different botanical sources

To illustrate the correlations between molecular structures and the film-forming properties of thermoplastic starch from various botanical sources, starches from cereal, tuber and legume were modified by thermoplastic extrusion and the corresponding thermoplastic starch films were prepared including thermoplastic corn starch (TCS), thermoplastic rice starch (TRS), thermoplastic sweet potato starch (TSPS), thermoplastic cassava starch (TCAS) and thermoplastic pea starch (TPES) films. TPES film displayed a higher tensile strength (6.28 MPa) and stronger water resistance, such as lower water solubility (15.70 %), water absorption (42.35 %), and water vapor permeability (0.285 g·mm·h−1·m−2·kPa−1) due to higher contents of amylose and B1 chains. TCAS showed a smoother and more amorphous film due to higher amylopectin content, resulting higher elongation at break and larger opacity. TCS film was the most transparent due to a compacter network and more ordered crystallinity structure, which was suit for the packaging of fresh vegetables and aquatic products, whereas TCAS film was the opaquest, which protected package foods from light such as meat products, etc. The outcome would provide an innovative theory to regulate accurately the functional properties of thermoplastic starch films for different food needs.

Effects of Quercetin and Organically Modified Montmorillonite on the Properties of Poly(butylene adipate-co-terephthalate)/Thermoplastic Starch Active Packaging Films.

The poly(butylene adipate-co-terephthalate) (PBAT)/thermoplastic starch (TPS) film stands out owing to its acceptable price, low impact on the environment, and excellent mechanical properties. The main objective of this study was to improve the antioxidant properties of the PBAT/TPS film by incorporation of quercetin (Q) through the extrusion blow process. Another specific objective was to incorporate the organically modified montmorillonite (OMMT) to prolong the release of Q and improve the poor barrier properties of the PBAT/TPS/Q film. The films were analyzed in terms of their morphology, mechanical properties, gas and water barrier properties, and antioxidant and anti-UV properties. Optimization of the OMMT content resulted in a fiber-like, co-continuous morphology of the PBAT/TPS/Q film. The incorporation of quercetin enhanced the antioxidant and anti-UV properties of the PBAT/TPS film, while OMMT improved the mechanical properties, ultraviolet barriers, and gas and water barrier properties. The results show that the films incorporating Q and OMMT provided the oxygen and water barrier by up to 94 and 54%, respectively. Also, the amount of polymer required for 50% 2,2-diphenyl-1-picrylhydrazyl (DPPH) inhibition is as low as 0.03 g, and the UV transmission rate was reduced by about 50%. Moreover, PBAT/TPS/Q/OMMT films successfully delayed the decay of the banana and blueberry due to their excellent antioxidant properties and suitable water vapor permeability.

Reduced Aging of Thermoplastic Starch Films with Green Hybrid Filler

Thermoplastic starch film (TPSF) and hybrid thermoplastic starch film (HTPSF) were stored for 3 months to study the effect of aging on the mechanical properties and crystalline structure of the starch biopolymer. The alteration of the mechanical properties and crystalline structure of the films were analyzed through tensile test and differential scanning calorimetry (DSC) analysis. The incorporation of the hybrid filler (microcrystalline cellulose + nanobentonite) in the HTPSF has effectively prevented retrogradation happen in the starch structure. In contrary, the TPSF showed high degree of retrogradation resulted in significant decrement in elongation at break which was not observed in the HTPSF after 3 months of aging test.

Characterization of the Structural and Physical Properties of the Thermoplastic Starch Film with Kaolinite and Beeswax Addition

Characterization of the Structural and Physical Properties of the Thermoplastic Starch Film with Kaolinite and Beeswax Addition

Thermoplastic Starch Composites Reinforced with Functionalized POSS: Fabrication, Characterization, and Evolution of Mechanical, Thermal and Biological Activities.

Rapid advancements in materials that offer the appropriate mechanical strength, barrier, and antimicrobial activity for food packaging are still confronted with significant challenges. In this study, a modest, environmentally friendly method was used to synthesize functionalized octakis(3-chloropropyl)octasilsesquioxane [fn-POSS] nanofiller. Composite films compared to the neat thermoplastic starch (TS) film, show improved thermal and mechanical properties. Tensile strength results improved from 7.8 MPa to 28.1 MPa (TS + 5.0 wt.% fn-POSS) with fn-POSS loading (neat TS). The barrier characteristics of TS/fn-POSS composites were increased by fn-POSS by offering penetrant molecules with a twisting pathway. Also, the rates of O2 and H2O transmission were decreased by 50.0 cc/m2/day and 48.1 g/m2/day in TS/fn-POSS composites. Based on an examination of its antimicrobial activity, the fn-POSS blended TS (TSP-5.0) film exhibits a favorable zone of inhibition against the bacterial pathogenic Staphylococcus aureus and Escherichia coli. The TS/fn-POSS (TSP-5.0) film lost 78.4% of its weight after 28 days in natural soil. New plastic materials used for packaging, especially food packaging, are typically not biodegradable, so the TS composite with 5.0 wt.% fn-POSS is therefore of definite interest. The incorporation of fn-POSS with TS composites can improve their characteristics, boost the use of nanoparticles in food packaging, and promote studies on biodegradable composites.

Production of Thermoplastic Starch-Aloe vera Gel Film with High Tensile Strength and Improved Water Solubility.

Biodegradable film packaging made from thermoplastic starch (TPS) has low mechanical performance and high water solubility, which is incomparable with synthetic films. In this work, Aloe vera (AV) gel and plasticized soluble potato starch were utilised to improve the mechanical stability and water solubility of TPS. Dried starch was mixed with glycerol and different AV gel concentrations (0% to 50%). The TPS + 50% AV gel (30 g TPS + 15 g AV gel) showed the best improvement compared to TPS alone. When compared to similar TPS films with AV gel added, this film is stronger and dissolves better in water. Mechanical qualities improved the tensile strength and Young’s modulus of the TPS film, with 1.03 MPa to 9.14 MPa and 51.92 MPa to 769.00 MPa, respectively. This was supported by the improvement of TPS water solubility from 57.44% to 46.6% and also by the increase in decomposition temperature of the TPS. This promises better heat resistance. The crystallinity percentage increase to 24.26% suggested that the formation of hydrogen bonding between TPS and AV gel enhanced crosslinking in the polymeric structure. By adding AV gel, the TPS polymeric structure is improved and can be used as a biodegradable food-packaging film.

Biodegradable Films from Spray Dried Starch Inclusion Complexes with Bioactive Compounds—The Effect of Glycerol and pH

AbstractIn the present study, thermoplastic films are prepared using spray dried starch‐bioactive compound systems powders with different concentrations of glycerol (20% or 40%). The starch‐based films are produced by casting after dissolution under neutral (pH 7) or alkaline conditions (pH 12). Results reveal that elevated glycerol contents lead to increased moisture and hygroscopicity which is related to the availability of more ─OH groups. ANOVA shows that the glycerol concentration, the pH value, and the interactions of bioactive compounds with glycerol, bioactive compounds with pH, and glycerol with pH, influence significantly the mechanical properties of the thermoplastic starch films. Young's modulus of elasticity increases alongside with glycerol content, indicating improved flexibility of the films. Stress decreases with higher glycerol contents and lower pH while strain on the contrary, increases as the glycerol and pH increase in the films. Significant differences are also observed in water adsorption and water vapor transmission rate values. As expected, water adsorption increases with increasing relative humidity (RH) with the glycerol content positively affecting the water uptake by the films. Microscopic examination indicates the homogeneous distribution of the bioactive compounds in the matrix of the films.

Effect of Psyllium Husk Addition on the Structural and Physical Properties of Biodegradable Thermoplastic Starch Film.

The research subject was the analysis of the microstructure, barrier properties, and mechanical resistance of the psyllium husk (PH)-modified thermoplastic starch films. The tensile tests under various static loading conditions were not performed by researchers for this type of material before and are essential for a more precise assessment of the material’s behavior under the conditions of its subsequent use. The film samples were manufactured by the casting method. PH addition improved starch gelatinization and caused a decrease in failure strain by 86% and an increase in failure stress by 48% compared to pure films. Fourier transform infrared spectroscopy results showed the formation of additional hydrogen bonds between polysaccharides in starch and PH. An increase in the number of hydrophilic groups in the modified films resulted in a faster contact angle decrease (27.4% compared to 12.8% for pure ones within the first 5 s); however, it increased the energy of water binding and surface complexity. The modified films showed the opacity at 600 nm, 43% higher than in the pure starch film, and lower transmittance, suggesting effectively improving barrier properties to UV light, a potent lipid-oxidizing agent in food systems.

Effective Aging Inhibition of the Thermoplastic Corn Starch Films through the Use of Green Hybrid Filler

Recently, hybrid fillers have been widely used to improve the properties of biopolymers. The synergistic effects of the hybrid fillers can have a positive impact on biopolymers, including thermoplastic corn starch film (TPCS). In this communication, we highlight the effectiveness of hybrid fillers in inhibiting the aging process of TPCS. The TPCS, thermoplastic corn starch composite films (TPCS-C), and hybrid thermoplastic corn starch composite film (TPCS-HC) were stored for 3 months to study the effect of hybrid filler on the starch retrogradation. TPCS-C and TPCS-HC were prepared by casting method with 5 wt% of fillers: nanocellulose (NC) and bentonite (BT). The alteration of the mechanical properties, aging behavior, and crystalline structure of the films were analyzed through the tensile test, Fourier transform infrared (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and water absorption analysis. The obtained data were correlated to each other to analyze the retrogradation of the TPCS, which is the main factor that contributes to the aging process of the biopolymer. Results signify that incorporating the hybrid filler (NC + BT) in the TPCS/4BT1NC films has effectively prevented retrogradation of the starch molecules after being stored for 3 months. On the contrary, the virgin TPCS film showed the highest degree of retrogradation resulting in a significant decrement in the film’s flexibility. These findings proved the capability of the green hybrid filler in inhibiting the aging of the TPCS.