Study On Processing Performance Of Thermoplastic Starch-based Biomaterials Blend

Starch is a natural low-cost natural polymer,with a high degree of crystallinity(20 % to 45 %),strong hydrogen bond between starch molecules,limiting the movement of the molecular chain,so the starch does not possess the properties of thermoplastic processing.By adding some small molecule of plasticizer,under the action of heating and mixing outside the physical factors can be prepared thermoplastic starch material.However,thermoplastic starch has insufficient barrier properties and mechanical properties,limiting its use as a material.In this experiment,the thermoplastic starch was prepared by using potato starch as raw material,glycerol(glycerol),carbonamide(urea)as plasticizer,gelatin as binder and carrageenan as reinforcing agent.The structure and influencing factors of the thermoplastic starch and its blends were analyzed by scanning electron microscopy and rotary rheometer.The effects of different plasticizer groups on the plasticizing properties,mechanical properties,rheological properties,thermodynamic properties,microstructure and thermal stability of thermoplastic starch were studied.The thermoplastic starch prepared by thermoplastic colloid was modified by hydrophilic colloid,and the effect of gelatin and carrageenan on the properties of thermoplastic starch.The results show that the natural starch passes through the interaction of temperature and shear force with small molecular plasticizer,which makes the grain structure disappear and finally plasticized into the homogeneous structure of plastic.The plasticizing effect of the plasticizer on the starch depends on the molecular structure of the plasticizer,the active group of the plasticizer and the size of the molecular weight.With the increase of the amount of plasticizer,the effect of thermoplasticization of starch was enhanced.The tensile strength of thermoplastic starch decreased after plasticizing,the elongation at break increased and the crystal structure was destroyed.Glycerol components and urea components have different water absorption process and balance of water absorption,showing the phenomenon of swelling of water,and urea component of the water absorption process is always absorbed and dissolved.Comprehensive properties Consider the use of 20 wt% glycerol plasticized starch to prepare thermoplastic starch,the tensile strength of the material is 8.2 MPa and the elongation at break is 25.6%.Gelatin and TPS blends favor improved toughness,while also increasing the balance torque of the mixer during plasticizing.The mechanical properties of the blends are related to the gelatin content.In general,the compatibility of the blends is optimized.The addition of gelatin will increase the water absorption and water absorption of TPS,and the water absorption will reach 627.1%.With the increase in the amount of carrageenan,the carrageenan molecules can form more hydrogen bonds with the starch,with the result that the tensile strength of the material is improved and the elongation at break is gradually reduced.Gelatin and carrageenan between the segments can be formed by the local electrostatic interaction with each other to form a certain network structure.When the blends were blended at 80:20:10 mass fraction,the tensile strength reached 26.62 MPa and the elongation at break was 73.47%.The combination of the two can improve the mechanical properties,thermal stability and processability of the thermoplastic starch.