Studies On A Hydrophobic Starch Thermoplastic Modified Using Polyurethane Microparticles

In this thesis, polyurethane prepolymers (PUPs) were synthesized from various hydrophobic soft segments, and reactively mixed with native starch for preparing modified TPS in a solid state mixer, then study the effects of polyurethane structure, processing temperature and polyurethane content on the structure and properties of modified starch.First, study the effects of polyurethane structure on the structure and properties of modified starch. The experimental results showed that the ratio of PUP used for preparing modified starch was98.6±0.4%, suggesting a high efficiency of the solid-state for starch modified. Compared with the un-modified starch, the toughness and hydrophobic property of modified starch was improved. Morphology analysis suggested that the modified starch exhibited miscibility between PU particle and starch matrix, leading to the slight improvement of breaking elongation.Second, study the effects of different processing temperature on the structure and properties of modified starch. The experimental results showed that the ratio of PUP used for preparing modified starch was high at different processing temperature between30℃and90℃. The elongation at break of starch modified at90℃was11.1±2.1%, which was2.5times to the elongation at break of starch modified between30℃and60℃. And the hydrophobic property of modified starch was improved.Final, study the effects of polyurethane content on the structure and properties of modified starch. The experimental results showed that the toughness and hydrophobic property of modified starch was improved by the increase of polyurethane content in modified starch.The toughness and hydrophobic property of thermoplastic starch modified with water plasticizer and polyurethane by solid state reactions under intensive mixing conditions was improved. And the efficiency of prepare the thermoplastic starch was high. The toughness of thermoplastic starch processed at gelatinization temperature was high compared with the starch processed under the gelatinization temperature. The solid state method for preparing hydrophobic starch may be suitable for preparing other hydrophobic natural polymers such as protein, chitosan, cellulose and so on.