Starch-glycerol-water blends

The time-dependent properties of TPS are a combined result of starch retrogradation, water content fluctuation, and plasticizer (e.g., glycerol) diffusion. These factors are difficult to be controlled during the storage and service life of TPS. As a result, TPS is rarely used alone but is often blended with hydrophobic thermoplastic polymers to form starch-containing polymer blends so that the mechanical performance, moisture resistance, and dimensional stability of TPS can be improved. 

To coimter the loss of water dining the process and a significant degradation of the material, to prevent, e.g., the formation of cellular stractures output from an extruder, and to obtain a material with controlled properties, we use a non-volatile plasticizer such as glycerol or other polyols (sorbitol, xylitol, fructose, polyethylene glycol, etc.) [AVE 04a, XIE 12]. Blends of these different polyols are also used [CHI 10b]. Other, notably nitrogenous plasticizers (urea, ammonium derivatives, amines, etc.) can also be used. Plasticized starches are thus created. They are... 

Follain N., Joly C., Dole R, Roge B., Mathlouthi M., Quaternary starch based blends Influence of a fourth component addition to the starch/water/glycerol system, Carbohydr. Polym., 63, 2006,400-407. 

Due to the brittleness of starch materials, plasticizers are commonly used. A frequently utilized low weight hydroxyl compoxmd is glycerol. Another effective plasticizer is water, although not the best because it evaporates easily. Still, starch-based materials readily absorb water and this may result in significant changes in the mechanical properties. Different routes have been explored in order to improve the mechanical properties and water resistance of starch materials. These are chemical modifications to the starch molecule, blends with polymers such as polycaprolactone [61], or reinforcement with different types of cellulose-based fillers, such as ramie crystaUites [62], and timicin whiskers [63], or montmorillonite clay particles [64]. 

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