Reseach Of Starch-Based Sheet Used In Packaging

In this paper, starch gelatinization was made with two-screw extruder, then dried, crushed into pre-gelatinized starch. The mixture of pre-gelatinized starch, polyvinyl alcohol(PVA) and glycerol were extruded into thermoplastic starch, with two-screw extruder. The technological parameters during pressing sheet were analysed, and the sheet was made with the vacuum forming mold.The starch emulsion with55%and75%-water content were extruded into starch gelatinization with two-screw extruder, at temperature-I zone:110℃, II zone:120℃, the screw rate:44rpm, then dried, crushed into40mesh pre-gelatinized starch granule. The mixture of pre-gelatinized starch, PVA, glycerol was extruded again into thermoplastic starch, at temperature-I zone:120℃, II zone:110℃, the screw rate:44rpm.The figure of Polarizing microscope showed that the pre-gelatinized starch granule was made of crystal structure, as the same as the native starch, while the cures of X-ray diffraction showed that the water content of starch was higher before gelatinization, the crystal structure become worse.The cures of DSC showed that there are two melting endothermic peaks in the measurement of thermoplastic starch with the pre-gelatinized starch, as the same as the thermoplastic starch with the native starch, while the higher water content before gelatinization, the higher melting endothermic peak temperature.The thermoplastic starch was molded into the thermoplastic sheet. In this paper, the types and content of PVA addition, glycerol content, the temperature, the pressure, the time of pre-heating and heating were analysysed, with comparison with the thermoplastic starch with native starch. The type of PVA addition as granule are better than the solution of PVA with the water, the more PVA content, the better the tensile strength and the elongation; the tensile strength was reduced with the glycerol content increasing from25%to35%, while the elongation increasing; The mechanical properties were best at the temperature140℃, the pressure10MPa, the pre-heating time10min, the heating time5min.The thermoplastic starch was made into the the tray with self-made vacuum forming mold. The effect of glycerol content and low temperature treatment were analysed.