Glass transition temperature of thermoplastic starches

International Agrophysics (Impact Factor: 1.12). 01/2005; 19(3).
Source: DOAJ


Thermoplastic starch was produced by mixing potato starch and glycerol in a single screw extruder. The glass transition temperatures of the materials obtained were measured by differential scanning calorimetry (DSC). Both the influence of extruder parameters and material parameters, such as moisture and glycerol content and amyloses/amylopectine ratio were investigated. Repeated extrusion cycles affect the glass transition temperature only to a very small extent.

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    • "Moreover, a decrease in the Tg has been associated with the greater mobility of the starch chains, caused by the greater interaction between the hydroxyl groups of the starch chains and the molecules of the plasticizer (glycerol) (Mali, Grossmann, García, Martino, & Zaritzky, 2006). Additionally, lower enthalpy values (DH) associated to the glass transition have been related to the weakening of the inter and intramolecular interactions between starchestarch chains (García et al., 2000a, b; Mali et al., 2002; Mitrus, 2005; Pelissari et al., 2013). According to Bair (1981), García et al. (2000b), and Bertuzzi, Vidaurre, Armada, and Gottifredi (2007), this leads to a decrease in growth of the crystal phase in these semi-crystalline biomaterials, since this impedes the alignment and recrystallization of starch molecules. "
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    ABSTRACT: Different studies have been performed on edible films. However, the surface properties and the relationship with their properties has not been analyzed. Edible films were obtained from native and modified plantain flour, with and without the incorporation of beet flour. Moisture content, stability in acidic or alkaline solutions, thermogravimetric analysis (TGA), X-ray diffraction pattern (XRD), differential scanning calorimetry (DSC), attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM) and color parameters were determined. The systems evaluated with the incorporation of beet flour showed a plasticizer effect, which led to the obtaining of more transparent, smoother and wet films. This also was related with higher transmittance and slightest thermodynamic stability. Similarly, the modified plantain flour by cross-linking with sodium trimetaphosphate, allowed to obtain films transparent, smoother, more plastic and degradable. Considering the results, it was concluded that the minor interaction between the starch-starch chains, allowed to obtain films with lower development of the crystalline phase, which favored the obtaining of films transparent, smoother, more plastic and degradable.
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    ABSTRACT: Environmental problems with conventional packaging materials developed the need of searching for new alternatives. Thermoplastic starch polymer (TPS) has been found to be a good source of raw materials for new packaging materials. In the paper changes of microstructure of TPS produced from different type of starch with glycerol content have been discussed. In general it can be stated that an increase of glycerol content in the mixture improves material structure quality.
    Preview · Article · Jan 2006 · International Agrophysics

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