The cover photo describes the scheme of the twin screw extruder for the preparation of thermoplastic starch (TPS). As discussed by M. Paula Guarás, this screw extrusion process is very advantageous for the preparation of TPS films with improved mechanical and water vapor absorption properties in any industrial processing line for plastic packaging products.
Effect of storage time, plasticizer formulation and extrusion parameters on the performance of thermoplastic starch films
M. Paula Guarás*, Vera A. Alvarez, Leandro N. Ludueña
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Investigaciones en Ciencia y Tecnología de Materiales (INTEMA), Grupo de Materiales Compuestos Termoplásticos (CoMP), Facultad de Ingeniería, Universidad Nacional de Mar del Plata, Av. Colón 10850 (B7606BVZ) Mar del Plata, Argentina
Adv. Mater. Lett., 2019, 10 (3), pp 206-214
Publication Date (Web): Dec 31, 2018
Copyright © 2018 VBRI Press
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A twin screw extrusion processing method was developed for the preparation of thermoplastic starch (TPS) for packaging applications. Different plasticizer combinations were used looking for the minimal temperature profile in the extruder in order to prevent the thermal degradation of TPS. The effect of storage time at 25 °C and 50% of relative humidity on the properties of TPS was studied. Plasticized TPS samples observed by scanning electron microscopy showed homogeneous fracture surfaces without unstructured starch granules. X-ray diffractometry tests showed retro gradation of all TPS formulations with progressive Vh-type crystal structure formation. Temperature for maximum thermal degradation rate of raw materials was shifted to higher values after preparing the TPS, suggesting not only physical but also chemical interactions between plasticizers and starch molecules. Mechanical properties were significantly improved replacing 10 wt. % of glycerol by water as plasticizer, which was attributed to the increased gelatinization degree and the reduction of thermal degradation.
Thermoplastic starch, processing condition, formulation, storage time.