Thermoplastic Starch Samples Research Articles

Influence of Choline Chloride/Urea and Glycerol Plasticizers on the Mechanical Properties of Thermoplastic Starch Plastics.

Bio-based plastics made of food-safe compostable materials, such as thermoplastic starch (TPS), can be designed into films that have potential to replace many non-biodegradable single-use plastic (SUP) items. TPS film characteristics, such as elongation at break and tensile strength, are largely affected by the choice of the plasticizers used in formulation. Our work identifies the mechanical properties and the chemical structural differences between TPS films made with two different plasticizer mixtures that have not yet been compared alongside one another: deep eutectic solvent choline chloride/urea (1:2) (CC:U) and glycerol with an acetic acid catalyst (AA:G). Potato-based TPS samples were formed by mixing each plasticizer with a consistent amount of potato starch and distilled water with heat. After gelation formation, the viscous TPS mixture was centrifuged to degas and extruded. Films were dried at controlled room temperature. Characterization included the tensile testing of coupons according to ASTM (American Society of Testing and Materials) standard D638, attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), melting point (MP), and scanning electron microscopy (SEM). The AA:G films displayed significantly higher tensile strength (M = 2.04 ± 1.24 MPa) than the CC:U films (M = 0.18 ± 0.08 MPa); however, the CC:U films had higher elongation at break (M = 47.2 ± 3.6%) than the AA:G films (M = 31.1 ± 12.6%). This can be explained by the difference in functional groups, composition, and the degree of crystallinity evidenced by the FTIR, XRD, MP, and SEM results. Our findings suggest that potato-based TPS films with an AA:G plasticizer mixture hold promise for SUP applications that require more strength, while CC:U films may be more suited for wraps and bags that require flexibility. These innovations can aid to mitigate the environmental impact of harmful plastic waste.

Effect of oxidation on physicochemical characteristics of thermoplastic canna starch

AbstractThe effects of oxidation on physicochemical characteristics of thermoplastic canna starch were investigated. Thermoplastic starch (TPS) of native canna starch (CS) and oxidized canna starch (OCS) were prepared with different contents of sodium hypochlorite (1%, 3%, and 5% w/w) and 30 wt% of glycerol as plasticizer. Native starch‐based TPS (NTPS) and oxidized starch‐based TPS (OTPS) samples were tested for physicochemical, morphological, thermal, and mechanical properties. In OCS, the content of carboxyl and carbonyl groups increased with the increase in the content of oxidant, and this contributed to the improvement in CS plasticization efficiency. SEM images indicated that the morphology of OTPS samples was smoother than that of NTPS. The stronger interaction between OCS and plasticizer in OTPS was indicated by FTIR spectra. XRD confirmed that the crystallite type of starch was changed and their decrease in crystallinity is attributed to effects of both oxidation and plasticization. The carbonyl and carboxyl content had a large impact on Tg and ΔHg of OTPS. The higher content of these groups in OCS leads to the lower Tg and the lower ΔHg, which could make the plasticization easier. Due to the better plasticization in OTPS, their mechanical properties and thermal stability were enhanced.

Effect of different proportions of glycerol and D-mannitol as plasticizer on the properties of extruded corn starch.

In this study, thermoplastic starch (TPS) was prepared by melt extrusion process, in which glycerol and/or D-mannitol were used as plasticizers, and the effect of different glycerol/D-mannitol ratios (4:0, 3:1, 2:2, 1:3, and 0:4) on the physicochemical properties of the extruded starch samples was investigated. The short-range molecular order, crystallization, gelatinization, thermal stability, and thermal properties of the TPS samples were analyzed through attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), rapid visco analysis (RVA), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The results showed that the crystallinity and short-range molecular order of the TPS samples increased with increasing glycerol content. Conversely, the water absorption index (WAI) and water solubility index (WSI) of the TPS samples decreased with increasing glycerol content. In addition, the TPS samples with higher glycerol content exhibited higher gel and thermal stabilities. This study provides a theoretical basis for starch extrusion and plasticization in the preparation of TPS-based materials with specific properties.

Upcycling waste tempura flake-derived starch powder as an environment-friendly polymer matrix filler for thermoplastic starch compounds

Waste tempura flakes collected from local restaurants were upcycled to be utilized as a polymer filler material. The oil fraction in collected waste tempura flakes were extracted two times via centrifugal solid-liquid separation and organic solvent extraction. Then, oil-extracted residual starch was freeze-milled to produce fine powders. Waste tempura flake-derived starch powder was substituted with 1%, 3%, and 5% (wt%) of virgin starch powder to produce thermoplastic starch. Composition, X-ray diffraction, and Fourier transform infrared analyses showed that the mixture was successfully thermally plasticized. Substitution of waste tempura flake-derived starch decreased tensile strength while increasing elongation at break of some samples. Produced thermoplastic starch samples again were compounded with polylactic acid (PLA) and poly-butylene adipate-co-terephthalate (PBAT) following a mixing ratio of 3:5:2. The analyses indicated that thermoplastic starch, PLA, and PBAT were successfully compounded. The compound containing 1 wt% substituted thermoplastic starch showed the minimal mechanical strength decrease. This study revealed the possibility of upcycling waste fried food into a valuable bioplastic material. Waste tempura flakes can be utilized as both bio-jet fuel and bioplastic filler material.

Thermoplastic starch/bentonite clay nanocomposite reinforced with vitamin B2: Physicochemical characteristics and release behavior

This study presents the development and characterization of a nanocomposite material, consisting of thermoplastic starch (TPS) reinforced with bentonite clay (BC) and encapsulated with vitamin B2 (VB). The research is motivated by the potential of TPS as a renewable and biodegradable substitute for petroleum-based materials in the biopolymer industry. The effects of VB on the physicochemical properties of TPS/BC films, including mechanical and thermal properties, water uptake, and weight loss in water, were investigated. In addition, the surface morphology and chemical composition of the TPS samples were analyzed using high-resolution SEM microscopy and EDS, providing insight into the structure-property relationship of the nanocomposites. The results showed that the addition of VB significantly increased the tensile strength and Young's modulus of TPS/BC films, with the highest values observed for nanocomposites containing 5 php of VB and 3 php of BC. Furthermore, the release of VB was controlled by the BC content, with higher BC content leading to lower VB release. These findings demonstrate the potential of TPS/BC/VB nanocomposites as environmentally friendly materials with improved mechanical properties and controlled release of VB, which can have significant applications in the biopolymer industry.

Preparation of thermoplastic starch with comprehensive performance plasticized by citric acid

AbstractTo prepared thermoplastic starch (TPS) with good thermal plasticization processibility and resistance to retrogradation is important in this field. Herein, TPS plasticized with different plasticizers were successfully produced using a twin‐screw‐extruder. Effects of glycerol, xylitol, and citric acid on the retrogradation properties of TPS were studied by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). It showed that citric acid can improve the thermal plasticization processibility of TPS through three mechanisms, that is, chemical reaction between citric acid and starch, chain fragmentation of starch molecule due to the acidolysis of citric acid, and decrease of interaction between starch molecular chains. Since citric acid can be chemically fixed in the starch, excellent retrogradation resistance was achieved. After the accelerated retrogradation at 60°C/80RH for 48 h, the retrogradation and crystallinity of CA4TPS are 0.8% and 4.26%, respectively, which were lower than TPS without citric acid. In this work, a series of TPS samples with citric acid content from 0 to 8 wt% were prepared, and the DSC and XRD results showed that the TPS with 4 wt% citric acid yielded the least amount of retrogradation. The results of this investigation lay a solid foundation for the preparation and application of TPS with excellent performance.

Improving mechanical and water sorption properties of thermoplastic starch by incorporating chitosan filler

To develop an adequate matrix polymer for agricultural or packaging applications, thermoplastic starch (TPS)/chitosan composites were prepared in a wide composition range either by injection moulding or in an internal mixer followed by compression moulding. Chitosan behaves as filler forming dispersed structure in TPS samples prepared by thermomechanical methods without any additional acid. In the TPS composites chitosan has a considerable reinforcing effect. Regardless of the production methods, the Young's modulus and tensile strength increase significantly. Furthermore, addition of chitosan has a considerable effect on the water sorption of TPS-based composites. Chitosan slightly decreases the maximum water uptake of composites and reduces significantly the water sorption rate especially in the samples prepared by injection moulding. Besides, chitosan can greatly reduce the shrinkage of injection moulded TPS composites and delay the appearance of mould on the surface even at high humidity.

Effect of Different Fillers on the Biodegradation Rate of Thermoplastic Starch in Water and Soil Environments

This work investigates the effect of filler type on the rate of biodegradation of thermoplastic starch-based films in water and soil environments. The authors applied the casting method to create films of thermoplastic starch, based on waste paper, filled with clays or organic fillers. Since such materials made from cellulose tend to absorb water, we hydrophobized the surfaces of the filled thermoplastic starch samples. The structures of the blends were characterized by infrared spectroscopy, while atomic-force microscopy was applied to observe change in surface topography and the distribution of the filler. We also studied moisture resistance of the blends. Biodegradation tests revealed that surface topography, distribution of the filler and starch-to-filler interactions were non-critical to the rate and degree of biodegradation of the blends. The biodegradation rate of the blends was strongly affected by the environmental conditions (relative humidity 54%, 100%, respectively; temperature 25 °C, 37 °C, respectively). Under anaerobic conditions, it was the mixtures that biodegraded to the greatest extent, whereas the hydrophobized mixtures did so the least.

Rheological, Thermal, Superficial, and Morphological Properties of Thermoplastic Achira Starch Modified with Lactic Acid and Oleic Acid.

The modification of achira starch a thermoplastic biopolymer is shown. Glycerol and sorbitol, common plasticizers, were used in the molten state with organic acids such as oleic acid and lactic acid obtaining thermodynamically more stable products. The proportion of starch:plasticizer was 70:30, and the acid agent was added in portions from 3%, 6%, and 9% by weight. These mixtures were obtained in a torque rheometer for 10 min at 130 °C. The lactic acid managed to efficiently promote the gelatinization process by increasing the available polar sites towards the surface of the material; as a result, there were lower values in the contact angle, these results were corroborated with the analysis performed by differential scanning calorimetry and X-ray diffraction. The results derived from oscillatory rheological analysis had a viscous behavior in the thermoplastic starch samples and with the presence of acids; this behavior favors the transitions from viscous to elastic. The mixture of sorbitol or glycerol with lactic acid promoted lower values of the loss module, the storage module, and the complex viscosity, which means lower residual energy in the transition of the viscous state to the elastic state; this allows the compounds to be scaled to conventional polymer transformation processes.

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.

Solid-state 1H and 13C NMR of corn starch plasticized with glycerol and urea

1H and 13C NMR spectroscopy was used for the study of corn starch plasticized with urea and/or glycerol. The information on the interactions between plasticizers and starch macromolecules as well as the arrangement of starch macromolecules depending on the storage time (from 1 day to 52 weeks), were obtained from the broad-line and magic-angle spinning 1H NMR spectra measured at 22 °C and within the range from 30 to 140 °C and the cross-polarization magic-angle spinning (CP MAS) 13C NMR spectra measured at 30 °C. The 1H chemical shifts for the groups of the plasticizer molecules enabled characterization of the interactions between urea and glycerol molecules in starch plasticized with a mixture of urea and glycerol. With increasing temperature, the signal related to water molecules gradually vanished due to water evaporation, and resolved 1H peaks associated with starch macromolecules were detected above 100 °C. The free water amount in the thermoplastic starch samples was also estimated using MAS 1H NMR spectra. Formation of double helices due to sample ageing was observed through the CP MAS 13C NMR spectra.

Effect of Storage Time on the Structure and Mechanical Properties of Starch/Bentonite Nanocomposites

Thermoplastic starch (TPS), plasticized with glycerol and water, and its nanocomposites containing up to 7.5 parts per hundred resin (phr) pristine bentonite (BT) are prepared by melt compounding. Effects of the BT reinforcement and storage time on the morphology, water content, and mechanical properties of the related TPS nanocomposites are investigated on compression molded specimens. Morphology change is followed by wide‐angle X‐ray scattering (WAXS) measurements. The presence of BT increases the rate of transformation from A‐ to V‐type crystalline form. It is also found that BT particles hinders the recrystallization (retrogradation) of TPS. BT becomes intercalated in TPS, which is supported by the water used as additional plasticizer for the compounding of maize starch. According to gravimetric measurements, TPS samples lose part of their water content during retrogradation/aging. Both the incorporation of BT and the time of aging result in increased strength and stiffness, however at the cost of elongation at break. This is associated with enhanced strength and stiffness, which is ascribed to a change (from more to less hydrated) in the interphase. According to scanning electron and atomic force microscopy analysis, the reinforcing BT particles are homogenously dispersed on nano and micron scale within the TPS matrix.

Biodegradable extruded thermoplastic maize starch for outdoor applications

In the recent years, great progress was achieved in the development of biodegradable products based on agricultural raw materials. Among them, one of the most promising and diffused biomaterials is represented by starch. For this reason, different approaches have already been explored to use starch as a natural source for the production of biodegradable thermoplastic polymers. However, there is still a lack of a controlled, easy and cheap procedure to process maize native starch in order to obtain a highly performing thermoplastic polymer. The purpose of this paper is the development of a simple and reproducible method able to produce a thermoplastic starch that can be easily transformed into extruded objects, suitable for several potential applications. To reach this aim, a proper plasticizer was added to a commercial maize starch at different concentrations corresponding to mass fraction from 50 to 70% (in the following text %). The effect of the different amounts of the plasticizer on the processability of the starch powder was assessed by varying the parameters during the extrusion process. The interaction of the structure of starch with the plasticizer, firstly, and the final thermal and physical–mechanical properties of the extruded thermoplastic starch samples, secondly, were analysed by using several techniques: differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, UV transmittance, moisture absorption, colorimetric and mechanical tests. The samples containing 50% of plasticizer, in possess of the best physical and thermal performances, were further characterized in terms of durability, in order to predict their lifetime in outdoor conditions, by using artificial ageing tests, such as moisture absorption and QUV accelerated weathering tests.

Gelatinization and retrogradation phenomena in starch/montmorillonite nanocomposites plasticized with different glycerol/water ratios

This study aims to gain insights into the intermolecular interactions present in thermoplastic starch (TPS)/montmorillonite (MMT) nanocomposites prepared using water and/or glycerol as plasticizers. Specifically, the impact of using different glycerol/water proportions on the nature of gelatinization and retrogradation processes is studied. Nanocomposites were characterized by rheometry, scanning electron microscopy (SEM) and X-rays diffraction (XRD). It is shown that clay tactoids preferentially interact with glycerol molecules rather than starch macromolecules. Consequently, the effects of MMT incorporation strongly depend on the glycerol/water ratio; when a ratio of 0.5 is used minor variations were observed on the starch gelatinization process—although stronger clays–starch interactions were evident—whereas at higher ratios the addition of clays significantly increased the gelatinization temperature, up to values over 100°C. In the gelatinization process of starch in TPS samples having only glycerol as a plasticizer, the leaching of amylose and the melting of amylopectin crystalline domains seem to occur simultaneously. This different gelatinization mechanism produces a TPS having a substantially different morphology, which exhibited reduced retrogradation characteristics.

A response surface study on microstructure and mechanical properties of poly(lactic acid)/thermoplastic starch/nanoclay nanocomposites

Poly(lactic acid) was modified with thermoplastic starch and nanoclay in order to reduce its brittleness and enhance its mechanical properties, respectively. First, two mixing protocols were used to compound poly(lactic acid), 36 wt% sorbitol-plasticized starch, and nanoclay as screening runs. Afterwards, nine experimentally designed – using response surface method – samples were produced via the best protocol with different thermoplastic starch and nanoclay contents. Blend morphology and mechanical properties of poly(lactic acid), poly(lactic acid)/thermoplastic starch samples, and poly(lactic acid)/ thermoplastic starch/nanoclay nanocomposites were investigated via X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy, as well as tensile and impact testings. Incorporation of sorbitol as plasticizer resulted in well-dispersed thermoplastic starch in poly(lactic acid) matrix even in the absence of any compatabilizer, as witnessed by field emission scanning electron microscopy, and consequently increased the melt strength of the nanocomposites. X-ray diffraction patterns and transmission electron microscopy micrographs showed intercalated microstructure for the prepared nanocomposites. In the end, response surface methodology was applied to study the mechanical behavior of the nanocomposites in terms of thermoplastic starch and nanoclay contents.

The effects of cross-linked starch on the properties of thermoplastic starch

In order to improve the poor tensile properties and high water absorption of thermoplastic starch (TPS), cross-linked starch was added into the TPS matrix. The cross-linked starch contents ranged from 0wt% to 20wt%. The TPS/cross-linked starch composites were analyzed for the morphology of their fractured surfaces, the thermal decomposition temperatures, ability to absorb water and mechanical properties. The results showed that the incorporation of cross-linked starch into the TPS matrix caused considerable improvement to tensile strength. The maximum tensile strength was obtained with addition of 20wt% cross-linked starch. Moreover, water absorption of the TPS samples was clearly reduced by the inclusion of cross-linked starch. The thermal degradation temperatures of the composites were also higher than those of the TPS matrix.

TPS/PCL Composite Reinforced with Treated Sisal Fibers: Property, Biodegradation and Water-Absorption

Sisal fibers bleached with sodium-hydroxide followed by hydrogen peroxide treatment were incorporated in a thermoplastic starch/e-polycaprolactone (TPS/PCL) blend via extrusion processing. These samples with smooth and homogenous surfaces were examined for their property, biodegradability and water absorption. Scanning electron microscopy revealed that the fibers were well dispersed in the matrix. In addition, it was found that the fibers and matrices interacted strongly. Blends with 20 % (dry weight-basis) fiber content showed some fiber agglomeration. Whereas blends with 10 % fibers showed increased crystallinity and lower water absorption capacity. The CO2 evolution study showed that the thermoplastic starch samples without any additives had the highest rate and extent of degradation whereas the neat PCL samples had the lowest degradation rate. Addition of fiber to the TPS/PCL blend exhibited the degradation rates and extents that were somewhere in between the pure TPS and neat PCL. This work demonstrates that TPS/PCL composites reinforced with bleached sisal has superior structural characteristics and water resistance and thus, can be used as polymeric engineering composites for different applications.

Influence of Aging Time on the Structural Changes of Cassava Thermoplastic Starch

ABSTRACTIn this work the change in the structural properties of cassava (manihot sculenta Crantz) thermoplastic starch (TPS) under controlled environment (humidity and temperature) was studied. Fourier Transform Infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results showed an evident increasing in the amorphous phase of the TPS regarding the native starch. There was a relative decrease of the band at 1047 cm-1 associated to crystalline structure of starch compared to the amorphous peak at 1022 cm-1. The X-ray diffraction patterns confirmed the increment of the amorphous phase in the TPS samples. Likewise the X-ray diffraction patterns shows evidence of residual type C crystallinity and the formation of a new crystalline phase type VH due to the orientation induced in plasticization process. In first stage of conditioning the tensile yield stress drops from 7.5 drops to 0.5 MPa and the break strain increases 1000%. At the same time it seems that the crystallinity of the samples increases as was evidenced by the gradually increasing of the FTIR band at 1047 cm-1. In a second stage, the yield stress increases, the break strain drops and the crystallinity continue growing steadily. These findings suggest that coexist two phenomena simultaneously in the samples. A phenomenon of re-crystallization (retrogradation) that tends to make the material more stiff and a process of plasticization that tends to softening it. It seems that the latter mechanism predominates in the first stage, at short times, and the former in the second stage, at older times.

Application of extrusion-cooking for processing of thermoplastic starch (TPS)

Thermoplastic starch (TPS) as fully biodegradable biopolymer appeared to be one of the most useful and promising materials for packaging purpose. To obtain TPS thermal and mechanical processing should disrupt semi-crystalline starch granules. As the melting temperature of pure starch is substantially higher than its decomposition temperature, there is a necessity to use plasticizers, e.g. a glycerol.Various blends of potato starch mixed with glycerol were extrusion-cooked to obtain different range of TPS pellets, then processed using film blowing and injection molding techniques. Starch modification under high temperature, glass transition temperature, visco-elastic properties of TPS samples (DMTA), the storage modulus E′ and loss modulus E″ were evaluated for several frequencies. The mechanical properties, the texture and the structure of the obtained materials were measured using standard methods.

Thermoplastic starch plasticized by an ionic liquid

Thermoplastic starch (TPS) plasticized by 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was obtained by melt processing. The resulting electrically conductive TPS samples were less hygroscopic than glycerol plasticized TPS samples. Despite this lower water uptake, [BMIM]Cl seems to be intrinsically a more efficient plasticizer of starch. [BMIM]Cl plasticized TPS samples show a much higher elongation at break in the rubbery state than the glycerol plasticized TPS samples. Their unusually low rubbery Young's modulus for thermoplastic starch (0.5 MPa) suggests a strong reduction of hydrogen bonds between the starch chains due to the presence of the ionic liquid. A detailed IR spectroscopy analysis supports this interpretation.