Study On The Structure And Properties Of Inorganics Filled Modified Starch Produced By Biaxial Eccentric Rotor Extruder

Degradable thermoplastic starch(TPS)prepared from natural starch has become the focus of attention and is expected to replace traditional petroleum-based plastics.Filling modification with inorganic nanofillers can improve the comprehensive performance of TPS and expand its application fields.The manufacturing procedure has a great impact on the structure and performance of TPS nanocomposites.The traditional manufacturing method is dominated by shear flow.It is used to increase the processing speed to promote the uniform dispersion of nanofillers,but the strong shear flow brings by the high processing speed leads to starch degradation during processing easily.The polymer processing technology and equipment dominated by volume extensional rheology proposed by Professor Qu Jinping from the South China University of Technology have the characteristics of high heat and mass transfer efficiency and good mixing and dispersion effects,which is expected to improve the overall performance of TPS nanocomposites.In this paper,silica(SiO₂)and organic montmorillonite(OMMT)are selected as inorganic nanofillers,and TPS/Si O₂ and TPS/OMMT nanocomposites are prepared by a counter-rotating biaxial eccentric rotor extruder based on volumetric extensional flow.The team's previous research shows that the strength of the volume extensional rheology during processing is positively correlated with the processing speed.The strength of the volume extensional rheology is controlled by the processing speed.The effect of volume extensional rheology on the structure and performance of TPS/Si O₂ and TPS/OMMT nanocomposites has been studied.The test results show that the inorganic nanofillers cooperate with the volume extensional rheology promoting the melting and plasticization of starch,and improves the comprehensive performance of TPS.The tensile strength of TPS prepared at 60rpm is 3.49MPa,and the elongation at the break can be as high as 172.67%.Adding 8phr Si O₂ can increase the tensile strength to 4.89MPa while maintaining 129.83%elongation at the break;adding 8phr OMMT can increase the tensile strength to 5.51MPa,it has an elongation at the break of 74.17%at the same time;OMMT in TPS/OMMT nanocomposites mainly exists in an interlayer structure,and the interlayer spacing of OMMT increased from 2.57nm to 4.27nm,the interlayer spacing is significantly improved.The synergistic effect of inorganic nanofillers under the action of volumetric extensional rheology was further explored.Si O₂ and OMMT were mixed in a certain proportion as hybrid fillers,and TPS/Si O₂/OMMT nanocomposite was prepared using a counter-rotating biaxial eccentric rotor extruder at a processing speed of 60rpm,the effect of the hybridization ratio of Si O₂/OMMT hybrid filler on the structure and properties of the composite was studied.The experimental results show that when the ratio of Si O₂/OMMT hybrid filler is 1:4,OMMT can be peeled off and dispersed in the matrix.Compared with TPS/OMMT nanocomposites prepared at the same processing speed,the dispersion effect is greatly improved.The tensile strength is increased to 5.25MPa while maintaining 116.73%elongation at break.