The effect of glycerol/sugar/water and sugar/water mixtures on the plasticization of thermoplastic cassava starch (original) (raw)
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Macromolecular Symposia, 2005
Thermoplastic starches (TPS) based on cassava starch have been produced by extrusion at 120 8C, using glycerol as plasticizer. Three forms of cassava starch were employed, viz: cassava root (CR), cassava bagasse (CB) and purified cassava starch (PCS). The main differences between these are the presence of sugars and a few fibres in CR and high fibre concentration in CB. Conditions of processing and characteristics such as amylose and fibre content, crystallinity, water absorption and mechanical behaviour in the tension x deformation test were evaluated. The results demonstrated that the PCS and CR had amylose contents consistent with literature values (14-18%) and that CB is a material constituted mainly by amylopectin. It was found that fibres in high proportions (as in the bagasse) can confer reinforcement properties and are thus able to generate natural composites of TPS with cellulose fibre. The sugars naturally found in the root reduce the elongation of the TPS under tension. The PCS and CR TPS were stable with respect to indices of crystallinity after processing; and during a period of 90 d in a relative humidity of 53%, while the CB TPS tended to vary its crystallinity, probably because its amylose chain had low degree of polymerization.
Influence of Aging Time on the Structural Changes of Cassava Thermoplastic Starch
MRS Proceedings, 2012
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 sam...
Molekul, 2016
The use of cassava starch for excipient in the manufacturing of the tablet has some problems, especially on physical-mechanical properties. The purpose of this study was to determine the effect of the differentness of temperature and pH in the process of modification on the physical-mechanical properties of modified cassava starch. Modifications were performed by suspending cassava starch into a solution of 3 % (w/v) PVP K30. The effect of the difference of temperature was observed at temperatures of 25; 45 and 65 0C, while the effect of the difference of pH was observed at pH of 4.0; 7.0 and 12.0. The results showed that the temperature and pH did not affect the physical-mechanical properties of the modified cassava starch. Modification of cassava starch at pH and temperature of 7.0 and 45 0C was produced modified cassava starch with the most excellent solubility, while the best swelling power were formed by the modification process at pH and temperature of 7.0 and 25 0C. Overall, ...
Carbohydrate polymers, 2017
The aim of this study was to determine and compare the melting (Tm), glass transition (Tg) and mechanical relaxation (Tα) temperatures of a new waxy cassava starch. Thermal transitions measurements were obtained by Differential Scanning Calorimetry (DSC) and Dynamical Mechanical Thermal Analysis (DMTA). The experimental data showed a high correlation between water volume fraction and melting temperature (Tm) indicating that the Flory-Huggins theory can be used to describe the thermal behavior of this starch. The Tm of waxy cassava starch-water mixes were lower than a waxy corn starch-water reference system, but differences were not statistically significant. The mechanical relaxation temperatures taken at tan δ peaks were found 29-38°C larger than Tg. The Tα and Tg measured for waxy cassava starch exhibited similar properties to the ones of waxy corn starch, implying that waxy cassava starch can be used in food and materials industry.
Jurnal Sains Materi Indonesia, 2019
This study aimed to investigate the effects of different starch-glycerol concentration ratio on mechanical and thermal properties of cassava starch bioplastics. Bioplastics were prepared by mixing starch with glycerol at different starch-glycerol w/w ratio (2.5:1, 2.75:1, 3:1 and 3.5:1). Mechanical properties was evaluated by measuring tensile strength and elongation at break where thermal properties was assessed by thermogravimetric analysis to determine the glass transition temperature (Tg), melting temperature (Tm) and melting enthalpy (ΔHm) of bioplastics. Microstructure and chemical interactions in bioplastics were evaluated by SEM and FTIR. The surface hydrophobicity was determined by measuring the water contact angle. The increase of starch-glycerol concentration in bioplastics formed rough surface where the interaction of glycerol and starch molecules mainly occurred through hydrogen bonds. It also formed stronger and more rigid structure with the increase in tensile strengt...
Packaging Technology and Science, 2008
The aim of this work was to investigate the effect of glycerol contents on physical properties of cassava starch films. The films were prepared from film-forming solutions (FFS) with 2g cassava starch/100g water and 0, 15, 30 and 45g glycerol/100g starch, and were analysed to determine its mechanical properties by tensile tests, the glass-transition temperature (Tg) by differential scanning calorimetry (DSC) and the crystallinity by X-ray diffraction (XRD). The infrared spectra of the films were also recorded. The resistance values of the films decreased, while those of the elasticity increased with an increase in glycerol concentration due to the plasticizer effect of glycerol, which was also observed in DSC curves. The Tg of the films prepared decreased with the glycerol content. However, for samples with 30 and 45g glycerol/100g starch, two Tg curves were observed, probably due to a phase separation phenomenon. According to the XRD diffractograms, the films with 0 and 15gglycerol/100g starch presented an amorphous character, but some tendency to show crystalline peaks were observed for films with 30 and 45g glycerol/100g starch. The results obtained with Fourier transform infrared (FTIR) corroborated these observations. Copyright © 2007 John Wiley & Sons, Ltd.
Carbohydrate Polymers, 2015
Starch was combined with plasticizers such as glycerol, sorbitol, glycerol/sorbitol and urea/ethanolamine blends by means of high shear extrusion process to prepare thermoplastic starch (TPS). Effect of storage time and plasticizers on the structural stability of melt processed TPS was investigated. Morphological observation, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy reveal that melt extrusion process is efficient in transforming granular starch into a plasticized starch for all plasticizer compositions. XRD analysis highlights major changes in the microstructure of plasticized starch, and dependence of crystalline type and degree of crystallinity mainly on the plasticizer composition and storage time. Dynamical mechanical analysis (DMA) yields a decrease of the peak intensity of loss factor with aging time. The effect of ageing on tensile strength also appears to be highly dependent on the plasticizer composition. Thus, through different plasticizer combinations and ageing, starch-based materials with significant differences in tensile properties can be obtained, which may be tuned to meet the requirements of a wide range of applications.
Industrial Crops and Products, 2012
Cassava bagasse is an inexpensive and broadly available waste byproduct from cassava starch production. It contains roughly 50% cassava starch along with mostly fiber and could be a valuable feedstock for various bioproducts. Cassava bagasse and cassava starch were used in this study to make fiber-reinforced thermoplastic starch (TPS B and TPS I , respectively). In addition, blends of poly (lactic acid) and TPS I (20%) and TPS B (5, 10, 15, 20%) were prepared as a means of producing low cost composite materials with good performance. The TPS and PLA blends were prepared by extrusion and their morphological, mechanical, spectral, and thermal properties were evaluated. The results showed the feasibility of obtaining thermoplastic starches from cassava bagasse. The presence of fiber in the bagasse acted as reinforcement in the TPS matrix and increased the maximum tensile strength (0.60 MPa) and the tensile modulus (41.6 MPa) compared to cassava starch TPS (0.40 and 2.04 MPa, respectively). As expected, blending TPS with PLA reduced the tensile strength (55.4 MPa) and modulus (2.4 GPa) of neat PLA. At higher TPS B content (20%) the maximum strength (19.9 MPa) and tensile modulus (1.7 GPa) were reduced about 64% and 32%, respectively, compared to the PLA matrix. In comparison, the tensile strength (16.7) and modulus (1.2 GPa) of PLA blends made with TPS I were reduced 70% and 51% respectively. The fiber from the cassava bagasse was considered a filler since no increase in tensile strength of PLA/TPS blends was observed. The TPS I (33.1%) had higher elongation to break compared to both TPS B (4.9%) and PLA (2.6%). The elongation to break increased from 2.6% to 14.5% by blending TPS I with PLA. In contrast, elongation to break decreased slightly by blending TPS B with PLA. Thermal analysis indicated there was some low level of interaction between PLA and TPS. In PLA/TPS B blends, the TPS B increased the crystallinity of the PLA component compared to neat PLA. The fiber component of TPS B appeared to have a nucleating effect favoring PLA crystallization.
Carbohydrate Polymers, 2019
In this work, the effects of the multiphase transitions of starch, the screw configuration, and the conditions of reactive extrusion (REX) on the in situ thermoplasticization/succination of cassava starch were studied. Spectroscopic analyses indicated successful esterification during the REX with the appearance of characteristic bands of carbonyl ester groups. After the REX, the starch developed Band V-type structures, with the OSA starches showing an additional peak at 7.1°. As the degree of substitution increased, a greater number of partially gelatinized granules were embedded in the starch matrix; an additional degradation temperature of 364.5°C and a lower weight loss at the degradation temperature of the starch were observed. The incorporation of OS groups via REX imparts better thermal stability. The processing conditions helped prepare a thermoplastic-succinate starch in a single step through an environmentally friendly process.