On the Plasticization Process of Potato Starch: Preparation and Characterization (original) (raw)
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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.
Morphology and Selected Properties of Modified Potato Thermoplastic Starch
Polymers
Potato thermoplastic starch (TPS) containing 1 wt.% of pure halloysite (HNT), glycerol-modified halloysite (G-HNT) or polyester plasticizer-modified halloysite (PP-HNT) was prepared by melt-extrusion. Halloysites were characterized by FTIR, SEM, TGA, and DSC. Interactions between TPS and halloysites were studied by FTIR, SEM, and DMTA. The Vicat softening temperature, tensile, and flexural properties were also determined. FTIR proved the interactions between halloysite and the organic compound as well as between starch, plasticizers and halloysites. Pure HNT had the best thermal stability, but PP-HNT showed better thermal stability than G-HNT. The addition of HNT and G-HNT improved the TPS’s thermal stability, as evidenced by significantly higher T5%. Modified TPS showed higher a Vicat softening point, suggesting better hot water resistance. Halloysite improved TPS stiffness due to higher storage modulus. However, TPS/PP-HNT had the lowest stiffness, and TPS/HNT the highest. Halloys...
Influence of plasticizer with different functional groups on thermoplastic starch
Journal of Applied Polymer Science, 2015
Retrogradation of amorphous thermoplastic starch (TPS) films obtained by compression molding of spray dried modified potato starch was investigated. The aim was to investigate the influence of plasticizers with similar molecular weight but different functionality, i.e., isoleucine, asparagine and malic acid, on the properties of plasticized powder and TPS films. Combinations of malic acid with glycerol, urea, and maltodextrin were also evaluated. Except for isoleucine formulated starch, all samples were obtained as amorphous powders and films. Malic acid was identified as a strong antiretrogradation agent as it inhibited recrystallization of starch over the full range of humidity levels. Malic acid was also found to inhibit the retrogradation of formulations containing urea, glycerol and maltodextrin. The converse of the strong inhibition implied strong moisture absorption and high strain at break values, and low tensile strengths. Malic acid was also identified as a potential crosslinking agent to control swelling of starchbased products.
Morphological and structural changes of starch during processing by melt blending
The morphological and structural changes of the granule architecture of normal starch during the melt blending in a batch mixer were investigated. Native potato, maize, and chestnut starch with different crystal structures were used as raw materials. Samples obtained at different times of melt blending were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and polarized light (PL) microscopy techniques. The variation of torque versus time depended on the starch type; the thermo-plasticization of potato starch (B-type) occurred in two steps, whereas that of maize (A-type) and chestnut (C-type) starches took place in one step. An enhancement of the thermo-plasticization after 15 min of starch processing was not observed by SEM and PL microscopy. However, the potato starch with longer amylopectin chains and higher phosphorus content presented a higher extent of destructurization when compared with the maize and chestnut starches. The XRD patterns of the plasticized starch samples showed residual and V-type induced crystallinity, corroborating the partial thermo-plasticization of starches. The extent of thermo-plasticization depended on the crystallinity type and phosphorus content of normal starch. : Additional supporting information may be found in the online version of this article at the publisher's web-site.
Industrial Crops and Products, 2011
Thermoplastic starch (TPS) was modified with ascorbic acid and citric acid by melt processing of native starch with glycerol as plasticizer in an intensive batch mixer at 160 • C. It was found that the molar mass decreases with acid content and processing time causing the reduction in melting temperature (T m ). As observed by the results of X-ray diffraction and DSC measurements, crystallinity was not changed by the reaction with organic acids. T m depression with falling molar mass was interpreted on the basis of the effect of concentration of end-chain units, which act as diluents. FTIR did not show any appreciable change in starch chemical compositions, leading to the conclusion that the main changes observed were produced by the variation in molar mass of the material. We demonstrated that it is possible to decrease melt viscosity without the need for more plasticizer thus avoiding side-effects such as an increase in water affinity or relevant changes in the dynamic mechanical properties.
Some effects of processing on the molecular structure and morphology of thermoplastic starch
Carbohydrate Polymers, 2008
Hydroxypropylated and oxidised potato starch (HONPS) was used together with glycerol and water to produce thermoplastic starch. The amount of glycerol was kept constant at 22 parts by weight per 100 parts of dry starch. The thermoplastic starch was converted into films/sheets using three different processing techniques; casting, compression moulding and film blowing. The last two methods represent typical thermoplastic conversion techniques requiring elevated processing temperatures. By means of size-exclusion chromatography, it was found that compression moulding and film blowing led to some degradation of high-molecular weight amylopectin as well as of highmolecular weight amylose-like molecules. The degradation was significantly less pronounced for the cast films. The morphology of the specimens was quite complex and phase separations on different levels were identified. In the cast films and, to a lesser extent, in the compression-moulded specimens, a fine network structure could be distinguished. Such a structure could however not be ascertained in the film-blown material and this is discussed in terms of the thermo-mechanical treatment of the starch materials.
Physical properties of starch plasticized by a mixture of plasticizers
European Polymer Journal, 2017
Highlights The effect of mixture of plasticizers glycerol and urea on properties of starch was investigated Urea plasticized starch has much higher tensile strength and Young's modulus. Urea is more efficient then glycerol ine destroying the hydrogen bonding in starch.
Deformation mechanisms of plasticized starch materials
Carbohydrate Polymers, 2014
The aim of this paper is to understand the influence of plasticizer and plasticizer amount on the mechanical and deformation behaviors of plasticized starch. Glycerol, sorbitol and mannitol have been used as plasticizers. After extrusion of the various samples, dynamic mechanical analyses and video-controlled tensile tests have been performed. It was found that the nature of plasticizer, its amount as well as the aging of the material has an impact on the involved deformation mechanism. The variations of volume deformation could be explained by an antiplasticization effect (low plasticizer amount), a phaseseparation phenomenon (excess of plasticizer) and/or by the retrogradation of starch.
Carbohydrate Polymers, 2007
The use of 2 wt% sugars as co-plasticizer in combination with glycerol was investigated for thermoplastic starch (TPS) from cassava. The results were compared to those for whole cassava root TPS, which naturally contains sugars in the same proportion. The main objective was to investigate the influence of natural sugars present in the cassava root on the properties of thermoplastic starch produced with cassava root. TPS produced with sugar and water without the addition of glycerol was also investigated. The materials were prepared by melt-processing cassava starch or ground and dried cassava root in a high-power batch mixer, Haake Rheomix 600, at 120°C. The samples were tested by X-ray diffraction (XRD), dynamic mechanical thermal analysis (DMTA), scanning electron microscopy (SEM) and water absorption experiments. The results showed that the addition of 2 wt% sugars (glucose, fructose and sucrose) to the starch-glycerol systems causes a reduction in the glass transition temperature (Tg) of the TPS accompanied by a reduction in the storage modulus determined by DMTA and inhibits the formation of V H -type crystal structures in the resulting TPS. The use of only sugar and water as plasticizers in the TPS causes a considerable reduction ($60%) in the subsequent water uptake.