The Studies On The Processing, Microstructures And Properties Of Thermoplastic Starch

The native starch was transformed to thermoplastic starch (TPS) by the torque rheometer, single screw extruder and plasticizers. The morphology of native starch, TPS and its blends were analyzed through scanning electron microscope (SEM) and differential scanning calorimeter (DSC) to investigate the plasticized mechanics of the native starch. The effects of the necessary conditions, plastication factors such as plasticizing process, granule structure of starch, polyvinyl alcohol (PVA) and the contents and kinds of plasticizer on the plastication characteristic, mechanical properties and hygroscopic property of TPS were studied through the torque rheometer experiment, mechanical and hygroscopic properties test. The effectiveness of the Peleg's model, used in hygroscopic property test, was demonstrated. The biodegradation process of TPS was characterized by soil burial test and the home-made biodegradation device established according to the GB standard. The rate of biodegradation was quantitatively determined by titrating CO₂ generated during biodegradation process of TPS to study the biodegradation ability of TPS, polylactic acid (PLA)/TPS blends. The following conclusions can be drawn from the paper:1. The granular structure of native starch would be disrupted by the combination of temperature, shear stress and plasticizers, and be transformed into uniform structure as single component thermoplastic at last. The plastication of glycerol would be reinforced and accelerated by raising processing temperature, elongating processing time and intensifying shear field.2. The plastication of the plasticizers was determined by their molecular structure. The plastication of formamide was better than that of glycol and glycerol because the maximum and equilibrium torque and equilibrium time of the formamide-plasticized TPS were smaller than that of glycol-plasticized and glycerol-plasticized TPS. The tensile strength of formamide-plasticized and glycol-plasticized TPS was decreased and the fracture elongation of them was increased with the increasing contents of plasticizers whose plastication is more clearly.3. The crystalline and void ratio in granule, the microstructure, mechanical properties and...