Study On Preparation And Performance Of Monosaccharide Plasticized Starch-Based Degradable Material

In this thesis,thermoplastic starch(TPS)was prepared by using hexanose D-fructose and hexalose glucose as plasticizer and corn starch as raw material.The plasticizing effects of the two monosaccharides were compared by FTIR and XRD.The monosaccharides with the best plasticizing effect and the mass ratio of monosaccharides to starch were blended with PBAT to prepare TPS/PBAT composites to improve the properties of thermoplastic starch.Modified nano-silica was selected as filler to enhance the mechanical strength of TPS/PBAT composites.Through the study of rheological properties,water resistance and cross-section morphology,the effect of nanometer silica content on the properties of TPS and TPS/PBAT was discussed.There are differences in the mechanism of starch plasticized by D-fructose and glucose.FTIR shows that the wavenumber of starch-OH plasticized by D-fructose is 3366cm^-1,which shifts more to low frequency than glucose plasticizer-OH.Both monosaccharide plasticizers weaken the crystallization properties of starch,but both produce VH type crystals in the system,and when the monosaccharide content is higher(more than 40%),the crystallization properties of starch are improved.The glass transition temperature of 40%D-fructose and 40%glucose plasticized starch is 70?and 63?respectively,the contact angle is 50.1°and 59.4°,the initial decomposition temperature is 202?and 172?respectively,and the balance torque is 15.3N·m and 17.5N·m,respectively.TPS and PBAT are combined with each other through hydrogen bond association,and the stretching vibration peaks of carbonyl group and hydroxyl group show a tendency to shift to a lower wave number.TPS does not change the crystalline type of PBAT but will change its crystallinity.Because the polarities of the two are quite different,and TPS is a hydrophilic polymer and PBAT is a hydrophobic polymer,the compatibility of the two phases is not good.With the increase of TPS content,the crystallinity of PBAT decreased from 16.3 to 9.07,and the melting point decreased from 131.36°C to 124.24°C.The crystallization temperature of the TPS/PBAT blend shifted to high temperature.The tensile strength,elongation at break,and elastic modulus of the TPS/PBAT composite are 12.3MPa,166%,and 216Mpa,respectively,and the melt index is 10.4g/10min.The infrared test shows that the methylene characteristic absorption peak of KH550appears at 2924cm^-1and 1751cm^-1of the infrared spectrum of modified nano-silica,and SEM shows that the modified treatment weakens the agglomeration of nano-silica and has good dispersibility,indicating that the effect of KH550-modified nano-silica is better.The modified nano-silica shortened the plasticizing time of TPS from 55s to 47s.The melting temperature of TPS/modified nano-silica increased from 128.9?to 140.7?,and the water absorption of TPS/PBAT/modified nano-silica decreased from 4.3%to 1.4%.The modified and unmodified nano-silica with the same content of 3%were blended with TPS,the equilibrium torque was 19.8N·m and 26.3N·m,and the melting temperature was 146.4?and 129.5?,respectively.With the increase of nano-silica content,the tensile strength of TPS/PBAT/nano-silica composites increased from 13.9Mpa to 25.6Mpa,and the elongation at break decreased from 134%to 101%,and the effect of modified nano-silica on the mechanical properties of the materials was more obvious.SEM shows that the addition of modified nano-silica can improve the interfacial adhesion between TPS and PBAT and improve their compatibility.