Thermoplastic Starch Films Research Articles

Facile fabrication of thermoplastic starch/poly (lactic acid) multilayer films with superior gas and moisture barrier properties

Multilayer films comprised of thermoplastic starch (TPS) and poly (lactic acid) (PLA) were fabricated via a reactive extrusion, compression molding, and dip coating processes. Maleic anhydride (MA) modification of TPS was employed to improve the interfacial adhesion between TPS and PLA layers of the film. The level and effect of TPS modification were evaluated using Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (H NMR), titration, and thermogravimetric analysis (TGA). Nanoclays were incorporated in the TPS and maleated TPS (MTPS) matrices to further enhance the physico-mechanical properties of the multilayer films. The optimized multilayer film fabricated in this study, which was the nanoclays-filled maleated thermoplastic starch and PLA multilayer film (MTPS-3C/PLA) displayed good transparency and tensile properties, and excellent moisture and oxygen barrier properties. This multilayer film assembly provided 1300% improvement in moisture barrier compared to TPS films, and 3300% improvement in oxygen barrier properties as compared to PLA films adjusted for thickness. Moreover, these multilayer films are composed of compostable, food-grade, inexpensive, and bio-based ingredients and as such they are expected to be compostable with great cost structure and environmentally friendly.

Effect of the incorporation of lignin microparticles on the properties of the thermoplastic starch/pectin blend obtained by extrusion

The present study aimed to produce thermoplastic starch films with different concentrations of thermoplastic pectin and the addition of 4% lignin microparticles as a reinforcing and active agent. The pectin improved the modulus of elasticity, and decreased the elongation at break. In addition, it improved the UV light protection to 100% at 320 nm and 95.9% at 400 nm. The incorporation of lignin microparticles improved the thermal stability of the blends made with 25% and 50% thermoplastic pectin when compared to the pectin-free blends. The blend with 25% thermoplastic pectin led to an increase of 75.8% and 34% in elongation at break and deformation of the films, respectively. This blend also improved the UV light protection to 100% due to its dark brown color. Regarding the permeability properties, the films with 25% and 50% thermoplastic pectin showed lower oxygen permeability (48% and 65%) and an increase in the antioxidant activities from 2.7% to 71.08% and 4.1% to 79.28%, respectively. Thus, the polymer blend with 25% thermoplastic pectin with the incorporation of lignin microparticles proved to be a good alternative for use in foods sensitive to the effects of oxygen and UV light.

On the Use of OPEFB-Derived Microcrystalline Cellulose and Nano-Bentonite for Development of Thermoplastic Starch Hybrid Bio-Composites with Improved Performance

Thermoplastic starch (TPS) hybrid bio-composite films containing microcrystalline cellulose (C) and nano-bentonite (B) as hybrid fillers were studied to replace the conventional non-degradable plastic in packaging applications. Raw oil palm empty fruit bunch (OPEFB) was subjected to chemical treatment and acid hydrolysis to obtain C filler. B filler was ultra-sonicated for better dispersion in the TPS films to improve the filler–matrix interactions. The morphology and structure of fillers were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). TPS hybrid bio-composite films were produced by the casting method with different ratios of B and C fillers. The best ratio of B/C was determined through the data of the tensile test. FTIR analysis proved the molecular interactions between the TPS and the hybrid fillers due to the presence of polar groups in their structure. XRD analysis confirmed the intercalation of the TPS chains between the B inter-platelets as a result of well-developed interactions between the TPS and hybrid fillers. SEM images suggested that more plastic deformation occurred in the fractured surface of the TPS hybrid bio-composite film due to the higher degree of stretching after being subjected to tensile loading. Overall, the results indicate that incorporating the hybrid B/C fillers could tremendously improve the mechanical properties of the films. The best ratio of B/C in the TPS was found to be 4:1, in which the tensile strength (8.52MPa), Young’s modulus (42.0 MPa), elongation at break (116.4%) and tensile toughness of the film were increased by 92%, 146%, 156% and 338%, respectively. The significantly improved strength, modulus, flexibility and toughness of the film indicate the benefits of using the hybrid fillers, since these features are useful for the development of sustainable flexible packaging film.

Robust multiphase and multilayer starch/polymer (TPS/PBAT) film with simultaneous oxygen/moisture barrier properties

The demands for bioplastics that provide good barrier properties against moisture and oxygen while simultaneously displaying good physical properties without compromising their biodegradability is ever-increasing. In this work, a multiphase and multilayer film assembly composed of thermoplastic starch (TPS) and its maleated counterpart (MTPS) with poly(butylene adipate-co-terephthalate) (PBAT) was constructed as a suitable barrier film with excellent mechanical properties. The bioplastic film assemblies were fabricated through reactive extrusion, compression molding, and dip-coating process. The incorporation of PBAT co-blend with TPS in the core layer enhanced the multilayer film's interfacial bond. The MTPS/PBAT film assembly provided 86.8% and 74.3% improvement in moisture barrier and oxygen barrier as compared to the baseline TPS and PBAT films, respectively. Overall, the multiphase and multilayer film assembly displayed good mechanical properties in conjuncture with excellent barrier properties indicating their potential as a biodegradable and cost effective alternative to conventional plastics used in the packaging industry.

Effect of greenly synthetized silver nanoparticles on the properties of active starch films obtained by extrusion and compression molding

Replacing packaging plastics with biodegradable active materials is an emerging concern. In this context, thermoplastic starch (TPS) films and nanocomposites containing different concentrations of silver nanoparticles synthetized with starch and yerba mate (TPS-AgNP1: 0.006 wt.% and TPS-AgNP2: 0.015 wt.%) were developed by extrusion and compression molding. Spherical AgNP of 20−130 nm were obtained after the green synthesis and excellent adhesion between AgNP and the matrix was observed. Consequently, both composites exhibited higher stiffness and tensile strength values than TPS, indicating a reinforcing effect of AgNP. TPS-AgNP1 showed the highest strain at break and toughness values, and TPS-AgNP2 presented the lowest moisture content and ability to delay E. coli growth. Additionally, all materials disintegrated after 4 weeks of burial and resulted thermally stable up to 240 °C. This investigation provides a convenient and inexpensive way to develop starch-based nanocomposites with improved properties which appear to be promising as active packaging materials.

Exploring the effect of humidity on thermoplastic starch films using the quartz crystal microbalance

The quartz crystal microbalance (QCM) is used as a non-destructive and efficient characterization tool for thin thermoplastic starch (TPS) films. Thin TPS films (1-2 μm) were prepared with 30% (w/w starch) plasticizers using either glycerol or an ionic liquid, 1-ethyl-3-methylimidiazolium acetate ([emim+][Ac−]), as the plasticizer. The differences in the mechanical properties and environmental effects on the plasticized TPS films were explored. The modulus of starch-glycerol films was higher than starch-[emim+][Ac−], consistent with literature data and bulk AFM measurements, likely due to superior plasticization by the ionic liquid. The starch-[emim+][Ac−] films were shown to have relative stable properties at low humidity that may be due to some antiplasticization effects at low water content despite absorbing more water than starch-glycerol films at higher humidity.

Production of thermoplastic starch and poly (butylene adipate-co-terephthalate) films assisted by solid-state shear pulverization

A novel processing technique involving Solid-State Shear Pulverization (SSSP) was used to produce thermoplastic starch (TPS) and Poly (Butylene Adipate-co-Terephthalate) (PBAT) films to improve processability and produce well-dispersed blends. Four different compositions (50−80 wt% TPS content) were processed using two different production routes. In one instance, the compositions were pre-treated by SSSP before melt extrusion (SSSPE). Secondly, starch was initially plasticized and thereafter blended with PBAT by melt extrusion (EXT) method. Flat films were produced using both routes and processability, visual and tactical aspects, mechanical and optical properties, crystallinity, and water absorption behavior were evaluated. High starch content films (70 and 80 wt%) prepared based on SSSP incorporation showed easier processability, and better visual aspect and mechanical integrity than EXT ones. However, EXT films with 50 and 60 wt% of starch presented higher elongation at break and lower water absorption due to finer dispersion of TPS and better starch plasticization.

Investigation of Functionalized Surface Charges of Thermoplastic Starch/Zinc Oxide Nanocomposite Films Using Polyaniline: The Potential of Improved Antibacterial Properties.

Improving the antibacterial activity of biodegradable materials is crucial for combatting widespread drug-resistant bacteria and plastic pollutants. In this work, we studied polyaniline (PANI)-functionalized zinc oxide nanoparticles (ZnO NPs) to improve surface charges. A PANI-functionalized ZnO NP surface was prepared using a simple impregnation technique. The PANI functionalization of ZnO successfully increased the positive surface charge of the ZnO NPs. In addition, PANI-functionalized ZnO improved mechanical properties and thermal stability. Besides those properties, the water permeability of the bionanocomposite films was decreased due to their increased hydrophobicity. PANI-functionalized ZnO NPs were applied to thermoplastic starch (TPS) films for physical properties and antibacterial studies using Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The PANI-functionalized ZnO bionanocomposite films exhibited excellent antibacterial activity for both E. coli (76%) and S. aureus (72%). This result suggests that PANI-functionalized ZnO NPs can improve the antibacterial activity of TPS-based bionanocomposite films.

Starch-based films enriched with nanocellulose-stabilized Pickering emulsions containing different essential oils for possible applications in food packaging

Consumers are increasingly demanding biodegradable food packaging with a minimal amount of synthetic preservatives and, at the same time, worried about potential contaminants, particularly during any pandemic event. Plant essential oils (EO) are natural compounds with remarkable antimicrobial properties. This study aimed to prepare thermoplastic starch films (TPS) containing nanocellulose-stabilized Pickering emulsions (PE) of different essential oils: ho wood (Cinnamomum camphora), cardamom, and cinnamon, and investigate the suitability of biopolymer films as packaging material. The films were prepared via casting method and were characterized concerning chemical interactions by FT-Raman and FTIR, mechanical, crystallinity, thermal, and water vapor permeability properties. PE Ho wood-starch films showed strong chemical interactions, which significantly improved the film's mechanical resistance. The films with cardamom and cinnamon showed low compatibility, with a decrease in tensile strength. All films showed less crystallinity than the pristine TPS, which can be attributed to the starch chain organization's changes. The films showed high thermal stability due to the strong molecular interactions among starch chains and PE, as confirmed by TGA and DSC analysis. The films' thermal stability is an indication that it can be safely applied in the food industry. Besides, the films showed a lower water vapor transmission rate, and the water may act as a carrier for PE, improving the release of the active compounds. This study reveals the differences between three essential oils incorporated into starch-based films. The ho wood films are the most promising PE to be applied as biodegradable active packaging.

Effects of nitrite incorporated active films on quality of pork

Nitrite (0.25–2%) incorporated thermoplastic starch (TPS) and linear low-density polyethylene (LLDPE) blend films were produced by the conventional blown-film extrusion process. Films were characterized and determined for efficacy as active packaging for pork steak. Scanning electron micrographs showed enhanced starch granule disruption due to melting. Increased nitrite contents enhanced the starch network and improved mechanical properties. Water vapor and barrier properties of blend films were improved by nitrite incorporation, with increased compatibility between TPS and LLDPE networks. Films containing 0.5% nitrite effectively improved redness and corresponded to 0.06 ppm residual nitrite and 75 ppm nitrosomyoglobin in packaged pork. Nitrite addition modified protein secondary conformation involving CO stretching bonds via H-bonding, while films with 1% and 2% nitrite significantly inhibited growth of lactic acid bacteria, yeast and mold, and retained softer texture during storage. Nitrite incorporated films were demonstrated as efficient active packaging to improve the quality of red meat products.

Physico-chemical and mechanical thermo-rheological characterization of three varieties of triticale starches

Nowadays, starch is an excellent biodegradable option instead of synthetic polymers, to avoid contamination. In this work, triticale starch from three varieties (Faraón, Peteroa and Aguacero) was isolated and the physico-chemical and thermo-rheological properties were evaluated. Also, mechanical properties of thermoplastic films using this starch were assessed. From the physico-chemical analysis it was found that the moisture, protein and lipids contents were slightly different among starches. Amylose value was similar. Thermo-rheological behavior measured by Mixolab® revealed that initial water uptake was higher for Faraón variety due to the grain morphology observed by Scanning Electron Microscopy (SEM). Values for gelatinization temperature obtained were 82.2 °C for Faraón starch, followed by Peteroa (72.0 °C) and finally Aguacero (65.6 °C). From the mechanical properties, Faraón thermoplastic starch (TPS) films showed the highest value of Young’s modulus (1.90 ± 1.09 MPa) for the composition 50/25/25 (starch/glycerol/water). The highest elongation at break (64.77 ± 14.14 %) was obtained for Peteroa composition 50/35/15 (starch/glycerol/water). Then, triticale mainly used to feed animals more than for human consumption, could be good alternative for preparing biodegradable films with potential applications in agriculture and food packaging.

Physico-chemical and mechanical thermo-rheological characterization of three varieties of triticale starches

Nowadays, starch is an excellent biodegradable option instead of synthetic polymers, to avoid contamination. In this work, triticale starch from three varieties (Faraón, Peteroa and Aguacero) was isolated and the physico-chemical and thermo-rheological properties were evaluated. Also, mechanical properties of thermoplastic films using this starch were assessed. From the physico-chemical analysis it was found that the moisture, protein and lipids contents were slightly different among starches. Amylose value was similar. Thermo-rheological behavior measured by Mixolab® revealed that initial water uptake was higher for Faraón variety due to the grain morphology observed by Scanning Electron Microscopy (SEM). Values for gelatinization temperature obtained were 82.2 °C for Faraón starch, followed by Peteroa (72.0 °C) and finally Aguacero (65.6 °C). From the mechanical properties, Faraón thermoplastic starch (TPS) films showed the highest value of Young’s modulus (1.90 ± 1.09 MPa) for the composition 50/25/25 (starch/glycerol/water). The highest elongation at break (64.77 ± 14.14 %) was obtained for Peteroa composition 50/35/15 (starch/glycerol/water). Then, triticale mainly used to feed animals more than for human consumption, could be good alternative for preparing biodegradable films with potential applications in agriculture and food packaging.

Active meat packaging from thermoplastic cassava starch containing sappan and cinnamon herbal extracts via LLDPE blown-film extrusion

• Active packaging from conventional blown extrusion of herb compounding TPS/LLDPE. • Films with sappan and cinnamon gave antimicrobial and preserved redness of beef. • Cinnamon gave higher compatible nano- and micro-structures between starch and LLDPE. Compounding of starch and herbal extracts containing antimicrobial functions possibly produces active packaging to preserve food quality. Active meat packaging was developed from thermoplastic starch (TPS) containing herbal extracts namely sappan or cinnamon powders via LLDPE blown-film extrusion. Higher TPS and herbal contents caused dispersion of clumps within film matrices, giving decreased mechanical properties (60–80 % for tensile strength and 30–90 % for elongation at break) due to non-homogeneous microstructures. Surface topography indicated increased roughness by 2.0–4.0 times with addition of TPS and herbal extracts and revealed nanovoids in films containing high sappan contents. Infrared spectra indicated hydrogen bonding between starch and herbal extracts which limited disruptions of starch granules during extrusion. Increased TPS raised water vapor permeability (WVP) but decreased oxygen permeability (OP) due to increased hydrophilicity of the film matrices. Cinnamon gave higher WVP (1.7–2.0 times) than sappan but similar OP. Increased herbal contents at 2 times increased OP by 1.8–2.9 times due to the formation of microvoids. Furthermore, films were used as minced beef packaging (direct contact) and determined for meat appearance and microbial counts. Films containing ≥ 8.6 % sappan and ≥ 6.7 % cinnamon showed preserved redness of packaged minced beef due to phenolic interaction. Moreover, films containing ≥ 3.3 % herbal extracts (sappan and cinnamon) gave lower total microbial counts in packaged meat due to antimicrobial capacity of sappan and cinnamon extracts, prolonging the shelf-life of minced beef. TPS films containing sappan and cinnamon extracts effectively preserved redness and delayed microbial growth, producing active packaging.

Effect of the Temperature and of the Drawing Conditions on the Fracture Behaviour of Thermoplastic Starch Films for Packaging Applications

In this work the effects of testing temperature and drawing orientation on the fracture behaviour of biobased and biodegradable thermoplastic starch based films, currently applied in the food packaging field, were investigated. At this aim, the Essential Work of Fracture (EWF) approach was applied on samples tested at 0 °C, 25 °C and 50 °C both in machine (MD) and in cross (CD) directions. The specific essential work of fracture (we) values strongly decreased with the testing temperature, and we values of CD samples were systematically higher than those of the corresponding MD samples. Considering that photograms of the CD samples taken during the EWF tests highlighted that the yielding zone became progressively opaque as an effect of the strain induced crystallization, it was hypothesized that in CD specimens part of the tensile energy applied during the straining process was utilized for the orientation of the macromolecules along the strain direction, rather than for the propagation of the crack in the ligament zone. Tensile tests under quasi-static conditions on dumbbell specimens highlighted that, regardless to the drawing direction, the stiffness and the resistance at yield and at break decreased with the temperature, while the strain at break was considerably enhanced. Moreover, because of the strong anisotropy induced by the molecular orientation in the drawing direction, MD tested samples had higher elastic modulus, yield resistance, and stress at break compared to CD samples.

Flexible thermoplastic starch films functionalized with copper particles for packaging of food products

Biodegradable films based on thermoplastic corn starch (TPS) and copper particles with antimicrobial capacity were developed. Copper nanoparticles (Cu) and silica coated copper microparticles (Si-Cu) in the range of 0.25 to 5% were used. Composite films were obtained by melt-mixing and subsequent thermo-compression. Particles distribution within TPS matrix and the presence of some pores and cracks, induced by Si-Cu particles, was evaluated by SEM. The presence of both fillers gave composite films a brown pigmentation and decreased their transparency; these effects were more pronounced at higher particles concentrations. Regarding mechanical properties, copper particles at 1 and 5% acted as reinforcing agents increasing the maximum tensile strength but their presence lead to a decrease in elongation at break, affecting films ductility. Composites inhibited the growth of Gram+ and Gram- bacteria, demonstrating their antimicrobial capacity. Copper effectively migrated to a simulant of aqueous foods and naked particles concentration in the simulant medium resulted higher than the minimum inhibitory concentration for bacteria. The characteristics and properties of developed composite films make them an interesting material for food primary packaging, mainly for meat fresh products.

Synergic antimicrobial properties of Carvacrol essential oil and montmorillonite in biodegradable starch films

This work evaluated the synergic effect of carvacrol essential oil (EO) and montmorillonite (MMT) (named hybrid compound), incorporated in thermoplastic starch (TPS) films in different contents (4.5, 9, and 15 wt%). TPS films were characterized by FTIR, FT-Raman, DSC, XRD, and antimicrobial assay. FTIR and FT-Raman indicated new hydrogen bonds between hybrid and starch, altering the thermal properties and requiring more energy to destroy the TPS-hybrid bonds. XRD analysis showed slight crystallinity changes, and TPS-15 hybrid showed an amorphous structure that allows the diffusion of EO thought the films. TPS-hybrid films showed antimicrobial behavior against E. coli due to the synergistic effect of MMT and EO, which resulted in strong antimicrobial effects due to the destabilization and partial destruction of the bacteria cell membrane. The hybrid probably changed the E. coli cell permeability, respiration, and electron transport. TPS-15 hybrid sample presented the lowest crystallinity, facilitating the film's oil diffusion, maximizing the bacterium inhibitory effect, and acting as a biocidal agent. The results demonstrated that a hybrid compound is a good option for starch antimicrobial films for fresh food, such as fruits and vegetables.

Fabrication of starch blend films with different matrices and their mechanical properties

The objective of the study was to determine the effects of molecular sizes of amylose (AM) and starch granules on the mechanical properties of thermoplastic starch (TPS) blend films. Leached amylose solution from cassava (CS_ AM) and mung bean (MB_AM), and two forms of amylopectin (AP) (granular; g and non-granular; ng) of waxy cassava (WxCS) starch were used. Four types of film matrices were fabricated and all TPS blend films contained same amount of AM and glycerol. Results displayed that molecular weight profiles of starch films and presence of granule remnants significantly controlled the film matrix formation, types of crystal formation, and percent of relative crystallinity (%RC) (p < 0.05). Tensile property of TPS films was controlled by %RC and presence of granule remnants. Percent elongation at break (%Eb) of TPS films increased when the films had a large range of molecular weight distribution (from 5.5 × 107 g/mol to 0.4 × 105 g/mol) and contained a high weight fraction (~58%) of starch molecules with Mw~0.4 × 105 g/mol.

Preparation, reinforcement and properties of thermoplastic starch film by film blowing

Starch is considered as the most promising material of biodegradable polymer films. However, up to date, the preparation of starch film by film blowing technique is still a challenge. Herein, cassava starch, glycerol and nano-silica (nano-SiO2) were used to prepare thermoplastic starch (TPS) films by film blowing technique. The effects of glycerol and nano-SiO2 on the mechanical properties, thermal properties and structure of TPS films were investigated. The results showed that the elongation at break of the TPS film with 40 parts of glycerol per 100 parts of dried starch (40 phs glycerol) was up to 108%. After the addition of 1 part of nano-SiO2 per 100 parts of dried starch (1 phs nano-SiO2), the tensile strength significantly increased by about 95%, while the elongation at break did not decrease. The thermal stability of starch increased with the increase of glycerol and nano-SiO2, while its melting transition temperature did not change significantly. The crystalline structure of starch changed after processing, and the crystallinity of starch decreased with increasing glycerol and nano-SiO2.

Nanoarchitectonics Composites of Thermoplastic Starch and Montmorillonite Modified with Low Molecular Weight Polylactic Acid.

Nano montmorillonite (MMT) was modified by low molecular weight polylactic acid (PLA), then, the PLA modified MMT and raw MMT were added into thermoplastic starch (TPS) to prepare biodegradable nanocomposite films, respectively. For both nanocomposite films with raw MMT and modified MMT, the Tmax of degradation was enhanced and the mechanical properties were improved. The composite films containing 4 wt.% MMT displayed tensile strength of 5.06 MPa, approximately 1.4 times of that for the pure TPS films. The tensile strength of composite films containing 4 wt.% modified MMT is 6.74 MPa approximately 2 times of those for pure starch films. On the other hand, the composite film containing 4 wt.% modified MMT displayed elongation at break as high as 34.25%, which is 1.3 times of that of the pure starch film, while the composite films containing raw MMT had reduced elongation at break. This study showed that the MMT modified with PLA could significantly enhance the mechanical properties of TPS, and provides a new method to prepare fully biodegradable starch-based nanocomposites.

Nanocellulose Reinforced Thermoplastic Starch (TPS), Polylactic Acid (PLA), and Polybutylene Succinate (PBS) for Food Packaging Applications.

Synthetic plastics are severely detrimental to the environment because non-biodegradable plastics do not degrade for hundreds of years. Nowadays, these plastics are very commonly used for food packaging. To overcome this problem, food packaging materials should be substituted with “green” or environmentally friendly materials, normally in the form of natural fiber reinforced biopolymer composites. Thermoplastic starch (TPS), polylactic acid (PLA) and polybutylene succinate (PBS) were chosen for the substitution, because of their availability, biodegradability, and good food contact properties. Plasticizer (glycerol) was used to modify the starch, such as TPS under a heating condition, which improved its processability. TPS films are sensitive to moisture and their mechanical properties are generally not suitable for food packaging if used alone, while PLA and PBS have a low oxygen barrier but good mechanical properties and processability. In general, TPS, PLA, and PBS need to be modified for food packaging requirements. Natural fibers are often incorporated as reinforcements into TPS, PLA, and PBS to overcome their weaknesses. Natural fibers are normally used in the form of fibers, fillers, celluloses, and nanocelluloses, but the focus of this paper is on nanocellulose. Nanocellulose reinforced polymer composites demonstrate an improvement in mechanical, barrier, and thermal properties. The addition of compatibilizer as a coupling agent promotes a fine dispersion of nanocelluloses in polymer. Additionally, nanocellulose and TPS are also mixed with PLA and PBS because they are costly, despite having commendable properties. Starch and natural fibers are utilized as fillers because they are abundant, cheap and biodegradable.