Biodegradable Thermoplastic Starch Research Articles

Effect of thermoplastic starch/poly(lactic acid) weight fraction on phase morphology and performance of biodegradable blends and their jute fiber composites.

The present work investigates the phase morphology and properties of biodegradable thermoplastic starch (TPS)-poly(lactic acid) (PLA) blends and their jute fiber (JF) biocomposites. The TPS/PLA blends and TPS/PLA/JF composites were fabricated using a twin-screw extruder and then injection molded into the test specimens, varying the TPS/PLA weight fractions (80/20, 60/40, 40/60, and 20/80) while keeping the JF content constant (10 wt%). At 80 wt% TPS, the TPS/PLA blend showed a co-continuous structure, whereas the remaining blends (20, 40, and 60 wt% TPS) exhibited a TPS droplets-PLA matrix structure. The TPS/PLA/JF composites displayed a PLA droplets-TPS matrix structure at 80 wt% TPS, a co-continuous structure at 60 wt% TPS, and a TPS droplets-PLA matrix structure at 20 and 40 wt% TPS. Increasing the proportion of PLA increased the melt flow ability, tensile strength, Young's modulus, storage modulus, thermal stability, and water contact angle of the blends and composites. The addition of jute fibers altered the phase morphology of the blends, enhanced their strength and stiffness, increased PLA nucleation, and improved the TPS-PLA phase compatibility. The blends and composites herein exhibit great potential in developing environmentally friendly injection-molded products, such as stationery, toys, gardening supplies, etc.

Mechanical Properties of Thermoplastic Cassava Starch/Coconut Fibre Composites: Effect of Fibre Size

This research aims to study the thermal and mechanical properties of biodegradable thermoplastic cassava starch (TPCS) reinforced with various sizes of coconut husk fibre (CHF). The range of fibre sizes used was 125, 200, and 300 μm. These CHFs were integrated into a thermoplastic cassava starch matrix to make bio-composites. After integrating all components, the bio-composites were hot-pressed at 155°C for 60 minutes to produce thermoplastic sheets. Tensile and flexural tests were carried out to examine the mechanical characteristics of TPCS/CHF composites. The samples were also characterised using Thermogravimetric Analysis (TGA), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM). The findings demonstrated that a smaller 125 μm CHF improved the mechanical properties higher than other fibre sizes. Fibre with 300 μm showed more voids, which led to lower material strength. TGA results showed that 300 μm fibres enhanced the crystallinity and thermal stability of the material. FTIR and TGA showed that CHF incorporation increased intermolecular interactions and thermal stability. Overall, a smaller fibre size of 125 μm showed a better reinforcement effect than the larger fibre sizes, which enhanced the materials’ tensile and flexural properties. This study demonstrated that modified TPCS/CHF has shown enhanced functionality than neat TPCS.

Mechanical properties and water resistance improvement of thermoplastic modified starch, carboxymethyl cellulose, and zinc oxide nanometal particles by reactive blending

Novel biodegradable thermoplastic starch (TPS) with high mechanical properties and water resistance was developed using reactive blending technique. Effect of zinc oxide (ZnO) addition to TPS properties and reaction was investigated. Thermoplastic modified starch (TPMS) was prepared by melt-mixing modified starch with glycerol 70/30%wt/wt. Carboxy methyl cellulose (CMC) 5%wt was incorporated with modified starch, glycerol, and zinc oxide (ZnO) 0–5 %wt. Fourier-transform infrared (FTIR) spectroscopy analysis confirmed the formation of the carboxyl anion (OZn) between the –COO− of CMC and the free Zn+ ion of ZnO. The tensile strength of the TPMS/CMC/ZnO blend increased 7 time with ZnO 5 % (14 MPa) addition compared to TPMS (2 MPa). The color (∆E) of TPMS/CMC/ZnO differed notably at high ZnO concentrations (1–5 %wt). The TPMS/CMC blend displayed a smooth fracture surface due to the miscibility of the materials. Small particles of ZnO dispersed finely in the TPMS matrix and increased the interfacial tension and water contact angle of the blends. The miscibility of TPS with CMC and the occurrence of ionic interactions of –COO− of CMC and –OH of starch with the Zn+ ion as physical crosslinking were indicated to improve the mechanical properties and water resistance of the blends.

Use of Raw Peach Gum as a Sustainable Additive for the Development of Water-Sensitive and Biodegradable Thermoplastic Starch Films.

In this study, formulations of thermoplastic starch (TPS) with 5, 10, and 15 parts per hundred resin (phr) of raw peach gum (PG) were prepared by melt extrusion followed by injection molding to obtain standard specimens for characterization. In addition, biodegradable films were developed by compression molding. It was determined that TPS with 5 phr and 10 phr of PG presented similar mechanical behavior to pure TPS after the processing. However, results indicated that adding PG in 10 phr slowed down the starch's retrogradation, delaying the TPS structure's stiffening. Moreover, the TPS-PG formulations presented improved solubility, which increased by 24% with 10 and 15 phr of PG compared to that shown for TPS. Additionally, PG enhanced the compostability of TPS, causing the sample to disintegrate in a shorter period. In conclusion, it was determined that raw PG added in 10 phr could be added as a sustainable additive to modify the biodegradation and water sensitivity of TPS without affecting its mechanical behavior after processing and delaying the retrogradation of the TPS structure, increasing its shelf life.

The role of natural hybrid nanobentonite/nanocellulose in enhancing the water resistance properties of the biodegradable thermoplastic starch

Abstract This study focuses on investigating the effect of hybrid nanofillers on the hydration characteristics and soil biodegradability of the thermoplastic corn starch (TPCS) hybrid nanofiller biocomposite (TPCS-HB) films. The data were benchmarked with that of the pure TPCS and TPCS single nanofiller biocomposite (TPCS-SB) as control films. The water absorption properties of TPCS, TPCS-SB, and TPCS-HB films were analyzed and fitted with the standard Guggenheim–Anderson–de Boer equation to study the water activity of the films. Besides, the water permeability test, water vapor permeability, and soil biodegradability of the films were also studied and correlated with the films’ surface morphology. The results indicated that the TPCS-HB films possess excellent hydration resistance and comparable biodegradable rate with the TPCS-SB films. The optimal water resistance properties were achieved when the optimal ratio of nanobentonite/nanocellulose (4:1) was incorporated into the TPCS matrix. The outcomes of this study provide an innovative idea and new insights that, by using natural and hybrid nanofillers, the hydrophobicity of the TPCS films could be enhanced. TPCS-HB films show great potential to be developed into a fully green biodegradable TPCS biocomposite film, especially for single-use plastic applications.

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.

Antimicrobial and improved performance of biodegradable thermoplastic starch by using natural rosin to replace part of glycerol

To improve the mechanical and water resistance of biodegradable thermoplastic starch (TPS) and endow the material with antibacterial properties, a novel strategy was proposed to use low-cost and renewable rosin to replace some glycerol in traditional TPS with invariable glycerol content. The mechanical properties, fractured cross-section images, crystallization behavior, dynamic mechanical analysis (DMA), water wettability, moisture absorption and antimicrobial activity were systematically evaluated. The tensile and bend strength increased from 1.42 to 4.61 MPa and 0.40–8.33 MPa for pure and rosin-modified 80R-TPS, respectively, indicating an improvement of approximately 3.25 and 20 times; the loss peak at high temperature (Tα) increased from 33.34 to 55.62 °C; the surface contact angle increased from 30.8° to 68.0°; and the equilibrium moisture absorption gain after 970 h decreased from 9.253% to 6.249%. These results proved that the mechanical properties and water resistance of rosin modified TPS produced via extrusion and injection molding were obviously enhanced, accompanied by obvious antimicrobial activity, which has potential application at the commercial scale in food packaging materials and biomedical and agricultural fields.

Characterization and Properties of Biodegradable Thermoplastic Arrowroot Starch Crosslinked by Glutaraldehyde Processed by Compression Molding Technique

Although starch is available and biodegradable, hydrophilicity and mechanical properties are still main disadvantages for many applications. In this study, arrowroot starch, a perennial herb found in tropical climates and extracted from the tubers of the arrowroot plant was used. The arrowroot starch was chemically modified by crosslinking with different amounts of glutaraldehyde in order to overcome the starch disadvantages. The crosslinked starch was then prepared as thermoplastic starch by plasticizing with glycerol, compounding in an internal mixer and finally shaping in a compression molding machine. An increase of gel fraction and decrease of swelling as well as the moisture uptake of different thermoplastic crosslinked arrowroot starch samples were observed, all of which indicated a crosslinking reaction of glutaraldehyde with the starch molecules. The thermal degradation temperature of thermoplastic crosslinked arrowroot starch, determined from thermogravimetric analysis technique, increased when compared with thermoplastic arrowroot starch. The extensibility of the thermoplastic crosslinked arrowroot starch also improved via glutaraldehyde crosslinking. Higher content of glutaraldehyde also caused lower swelling and moisture uptake including higher gel fraction and extensibility. Moreover, crystallinity, morphology and biodegradability were also examined.

Films Based on Thermoplastic Starch Blended with Pine Resin Derivatives for Food Packaging.

Completely biobased and biodegradable thermoplastic starch (TPS) based materials with a tunable performance were prepared for food packaging applications. Five blends were prepared by blending TPS with 10 wt%. of different pine resins derivatives: gum rosin (GR), disproportionated gum rosin (RD), maleic anhydride-modified gum rosin (CM), pentaerythritol ester of gum rosin (LF), and glycerol ester of gum rosin (UG). The materials were characterized in terms of thermo-mechanical behavior, surface wettability, color performance, water absorption, X-ray diffraction pattern, and disintegration under composting conditions. It was determined that pine resin derivatives increase the hydrophobicity of TPS and also increase the elastic component of TPS which stiffen the TPS structure. The water uptake study revealed that GR and LF were able to decrease the water absorption of TPS, while the rest of the resins kept the water uptake ability. X-ray diffraction analyses revealed that GR, CM, and RD restrain the aging of TPS after 24 months of aging. Finally, all TPS-resin blends were disintegrated under composting conditions during the thermophilic incubation period (90 days). Because of the TPS-resin blend’s performance, the prepared materials are suitable for biodegradable rigid food packaging applications.

The effect of different mineral fillers on starch/rice husk composite properties

The objective of this research was to study the feasibility of producing biodegradable thermoplastic starch rice-husk composites. The effect of different types of mineral fillers on the various properties of thermoplastic starch composites filled with rice-husk flour, an agricultural waste residue, was studied. The mineral fillers aluminum trihydrate (ATH), magnesium dihydroxide (MDH), nanoparticulate MDH, and nanoclay were studied. It was found that the addition of the mineral fillers and especially nanofillers improved the dimensional stability and the mechanical properties of the composites, while decreasing their biodegradability. The thermogravimetric analysis (TGA) showed that substituting mineral fillers for some part of the lignocellulosic component increased the extents of weight-loss in the first and second steps, but decreased the weight-loss in the last step. This substitution also led to a slight decrease in the thermal decomposition temperatures at the curve peaks.

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.

Fabrication and properties of thermoplastic starch/montmorillonite composite using dialdehyde starch as a crosslinker

AbstractThe poor mechanical properties and high water solubility of biodegradable thermoplastic starch (TPS) represent the main disadvantages of TPS in many applications. In this work, TPS film was prepared from a water solution of corn starch modified by 5 wt% dialdehyde starch (DAS) as crosslinking agent and 3 wt% montmorillonite (MMT) as reinforcing additive. Interactions occurring in the TPS films were investigated by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, XRD, DSC, dynamic mechanical thermal analysis (DMTA) and TGA. The results obtained fom FTIR spectroscopy and DSC suggest the formation of hydrogen bond interactions between the hydroxyl group of starch, DAS, the MMT layers and glycerol. DMTA indicated that the relaxation of films with DAS and MMT appears in a higher and broader temperature range due to the starch backbone stiffness; the extreme increase in the storage modulus confirmed the suggested interactions. The determination of the weight loss of the films in water indicated a significant increase of the water resistance of TPS due to incorporation of DAS and MMT. Changes in mechanical properties of the films containing DAS and clay were determined, showing a substantial increase in tensile strength from 2.7 to 6.7 MPa, while Young's modulus increased by 15 times for TPS modified with 5% DAS and 3% MMT. Therefore, the outcomes of this study confirmed that DAS is a suitable biomacromolecule crosslinker for starch and can significantly enhance TPS and TPS/MMT properties. © 2019 Society of Chemical Industry

Thermoplastic Starch Composites Filled With Isometric and Elongated TiO2-Based Nanoparticles

Biodegradable thermoplastic starch (TPS) composites with isometric titanium dioxide nanoparticles (TiO2; diameter  100 nm) and elongated titanate nanotubes (TiNT; diameter  20 nm and aspect ratio >50) were prepared from wheat and tapioca starch. The preparation was based on our recently developed two-step procedure consisting of the solution casting (SC) followed by the melt mixing (MM), which had been shown to yield highly homogeneous TPS in our previous study. In this work we demonstrated that the type of the TPS matrix and the type of the filler had significant impact on the morphology and the properties of the final composites. Multiple microscopic techniques (LM, SEM and TEM) evidenced that the TPS/TiO2 composites exhibited a very homogeneous dispersion of the filler, while the TPS/TiNT composites contained micrometer-size agglomerates of TiNT. Moreover, all composites with the wheat starch matrix (TPS(w)) showed a higher filler agglomeration than the corresponding composites with the tapioca starch matrix (TPS(t)). Rheological experiments showed that the TiO2 and TiNT fillers had quite small impact on the viscosity of the TPS(w) matrix, probably due to slightly higher agglomeration, poorer dispersion and weaker matrix-particle interactions. On the other hand, the TPS(t) matrix was influenced by both fillers significantly: the TiO2 nanoparticles with almost ideal dispersion formed a physical network in the TPS(t) matrix, which significantly increased the viscosity of the composite, whereas the TiNT nanotubes seemed to destruct the TPS(t) matrix partially, resulting in decreased viscosity of the composite. DMTA results confirmed the rheological measurements: Storage moduli (G') showed that TPS(t) and its composites with TiO2 were stiffer than the corresponding TPS(w) samples, while the TPS(t)/TiNT composites were less stiff than TPS(w)/TiNT. Also loss moduli (G) confirmed the difference between tapioca starch and wheat starch composites, which differed by their glass transition temperatures (Tg of TPS(w) < Tg of TPS(t)). The rheological and DMTA results were supplemented and supported by IR, XRD and TGA measurements.

Extraction of Starch from Marine Microalgae, Chlorella salina: Efficiency and Recovery

The issues of plastic waste arise owing to the global increase in plastic demand, which has surpassed the plastic recycling rate. Microalgae have become a sustainable feedstock to produce biodegradable thermoplastic starch because of their high yield, high photosynthetic efficiency, ease of cultivation and eco-friendliness. This research was conducted to determine the efficiency of different methods for starch extraction and recovery. Starch was extracted through ultrasonication, bead-beating and physicochemical methods and then separated, dried and analysed with a Megazyme total starch analysis kit. Of these tested methods, the physicochemical method (90 °C, 30 min) was the most efficient method for starch extraction, where the starch increment was 323.05% ± 32.03% relative to the control. However, the bead-beating method was the most efficient method when starch recovery was conducted on Chlorella salina cells, exhibiting the highest increment (96.60% ± 2.73%). Therefore, the physicochemical and bead-beating methods were the viable methods for enhancing the efficiency of starch extraction and recovery, respectively.

Biodegradability of blends based on aliphatic polyester and thermoplastic starch

In this work, biodegradable aliphatic polyester blends of polycaprolactone and polylactide were melted and blended with a natural and biodegradable thermoplastic starch (TPS). The TPS employed in this study was obtained by plasticization of isolated wheat starch using glycerol as plasticizer. Morphology as well as thermal properties of the blends was investigated, and water vapor permeability as a barrier property was also monitored. The biodegradability of the biodegradable blends was performed by a composting process on laboratory scale. The composting process was conducted in an adiabatic closed reactor for 21 days and during the composting process, the temperature, pH value, % moisture and volatile matter and evolved CO2 were monitored. Biodegradation of the blends was determined by weight loss, as well as monitoring of morphological surface change. The thermophilic phase prevailed in the composting process, indicating intensive biodegradation of substrate as well as biodegradation of investigated ternary blends. Since microorganisms use starch as a carbon source, addition of TPS causes considerable acceleration of biodegradation of ternary blends due to higher water vapor permeability as a result of the hydrophilic nature of starch. The thermoplastic starch was first degraded within the blend, which was facilitated access to the microorganisms of other ingredients in the blend, encouraging the biodegradation of other components.

Effect of PVA and PDE on selected structural characteristics of extrusion-cooked starch foams

Abstract The aim of this work was to determine selected physical properties of biodegradable thermoplastic starch (TPS) filling foams manufactured by extrusion-cooking technique from different combinations of potato starch and two additives: poly(vinyl alcohol) PVA and Plastronfoam PDE. Foams were processed with seven starch/additives combinations at two different extruder-cooker’s screw rotational speeds. The densities of starch foams depended significantly on the additive type and content. The linear relationship between the Young modulus and the ultimate compression force and apparent density was found. The foams processed with the addition of PVA had low density, porosity and lower values of the Young modulus than the foams prepared with PDE.

Environmental impact of biodegradable food packaging when considering food waste

From a waste management perspective, high-barrier, multi-layer, biodegradable food packaging could be a useful replacement for current multi-layered packaging that is non-recyclable and non-degradable. Whilst there is still technical research required, it is envisioned that a biodegradable thermoplastic starch (TPS) and polyhydroxyalkanoate (PHA) layered material could be a promising target. However, there is currently limited research identifying what environmental trade-offs are associated with using such a material – meaning there is no guidance regarding what design characteristics are important to consider during development of such packaging. The aim of this study was to quantify the greenhouse gas (GHG) trade-offs associated with using the proposed biodegradable packaging and identify the important design considerations. To our knowledge this is the first study to discuss the implications of including food wastage when assessing biodegradable food packaging materials. It also considers the impacts of landfill methane capture efficiency, which is an important aspect as biodegradable packaging may release methane when disposed of in a landfill whereas non-biodegradable packaging is inert. However, a key result is that when food waste is included in the system boundaries, it contributes over 50% of the GHG emissions associated with the system, regardless of whether the package is biodegradable or not. This shows that even for biodegradable packaging, reducing food waste is a key design consideration. In fact, the negative environmental impacts associated with disposal of a PHA-TPS packaging in landfill with low gas capture rates can actually be offset if the package reduces food wastage (beef) by approximately 6%. The overarching result is that a PHA-TPS food packaging only delivers positive GHG outcomes if it reduces food wastage or increases the viability of biological food waste processing.

Production of Cassava Starch Bioplastic Film Reinforced with Poly-Lactic Acid (PLA)

Biodegradable thermoplastic starch from cassava starch was produced in this study. The thermoplastic starch (TPS) produced was reinforced with Polylactic Acid (PLA) so as to improve their physical properties. The TPS was produced using a casting method of polymer preparation and later subject to a compression moulding to form a 2 mm film. Glycerol was used as the plasticizer with content varying from 10 to 30% along with the varying amount of water (40 - 60%) and acetic acid (0 – 10%) content. The results show that glycerol has a significant effect on the tensile strength of the material while the effect of water was more significant in the elongation and water absorption properties of the TPS. An optimum value of tensile strength (11 MPa), percentage elongation at break (12%) and percentage water absorption (32%) was derived at 28, 60, and 2% of glycerol, water and acetic acid respectively. Addition of Poly-Lactic Acid (PLA) to the TPS at 10, 20, 30, 40 and 50% results in a significant positive improvement on the tensile strength (11 MPa to 38 MPa) and reduction in the percentage water absorption (30% to 10%) of the TPS with no significant improvement on the percentage elongation of the material. The TPS/PLA composite with higher tensile strength and lower water absorption can be utilized in some applications to replace the non-biodegradable synthetic plastic so as to reduce the unsustainable waste generation from the use of synthetic plastic.

Biodegradable thermoplastic starch of peach palm (Bactris gasipaes kunth) fruit: Production and characterisation

ABSTRACTThe objective of this study was to produce and characterise biodegradable thermoplastic starch (TPS) derived from the fruit of pejibaye palm (Bactris gasipaes Kunth) plasticised with glycerol and sorbitol. The plasticised starch yielded a strength (σ) of 1.3 ± 0.2 MPa, deformation (ε) of 9.4 ± 1.6%, and Young’s modulus (E) of 191 ± 72.0 MPa. The thermal analysis showed a 61.14% mass loss over the temperature range 290–388°C and an endothermic peak at 130°C. X-ray diffractograms of the TPS revealed peaks corresponding to crystallites of type Vh at 19.4° and type V at 22.6°. Morphological studies, by scanning electron microscopy, showed the plasticised starch had a homogeneous surface, without phase separation and without cracks, with few granules not gelatinised. The analysis of its biodegradation by soil burial tests showed a total mass loss of 84.4 ± 4.4%, after 18 weeks. Biodegradable TPS was successfully obtained from the pejibaye palm fruit, presenting resistant to traction and to the thermal degradation.

Effect of nanocellulose as a filler on biodegradable thermoplastic starch films from tuber, cereal and legume

Starches from different vegetal sources (tuber, cereal and legume) were plasticized with an invariant glycerol content and reinforced with cellulose nanocrystals by solution casting method. The influence of both, starch nature and filler amount, in the crystallinity and the extension of plasticization have been analyzed by X-ray diffraction. Thermoplastic starches (TPS) morphologies were obtained by scanning electron microscopy. Mechanical properties and thermal stability were analyzed by dynamomechanical and thermogravimetric analysis. Water absorption evolution was studied as well.A major extension in plasticization (high amylopectin starches) led to matrices with large starch-rich domains, a good thermal stability and resistance to water absorption but low stiffness. The incorporation of cellulose nanoparticles favoured plasticization and increased the rigidity in TPS films, as well as the thermal stability and moisture resistance. The aim of this work was to obtain bio-based thermoplastic starch films for replacing petroleum-derived ones in packaging industry, especially for short-life applications.