Preparation And Application Of Starch-based Functional Degradable Materials

Starch is a biomass polysaccharide polymer with abundant reserves,low price,and biodegradable,which has the characteristics of easy processing and molding,and surface chemical change.Taking starch as raw material and preparing functional degradation material for modification and modification have important development prospects in developing functional materials,improving the ecological environment,and improving the economic benefits of crops.Starch can be converted into liquid polyhydroxy compounds by biomass liquefaction technology and can be used as industrial raw materials for polymer processing aids.Through modification,the starch structure has a specific chemical functional group,giving starch new properties,broaden the functional application of starch material.Tannin acid is a polyphenol substance widely found in plants,which has a good chelating effect on heavy metal ions and can be used to cross-link starch to obtain adsorbent material.Tea polyphenol is a large number of natural compounds found in tea,is widely used in the natural antioxidant substances,tea polyphenols and starch cross-linking can make starch has good antibacterial antioxidant properties,in the field of functional food packaging materials has good application prospects.Using starch as a templating agent and reducing agent,and introduction of silver nitrate,silver nitrate in the starch structure can be reduced to nano-silver particles,composite polyethylene alcohol and then prepared with high strength,can be used as a stress sensor flexible conductive gel.The main contents and results of this paper are as follows:（1）Bio-polyether polyols are prepared by biomass liquefaction technology using ordinary corn starch as raw material.The mixture of polyethylene glycol 400 and glycerine（7:3,w/w）was used as a liquefaction solvent,and the solid acid derived from coffee grounds was used as a catalyst（1:10,w/w,solid acid/starch）to liquefy for 1.5 h at 160℃at atmospheric pressure.The liquefaction rate was more than 99%.Among them,coffee grounds derived solid acid were prepared via two steps:hydrothermal carbonization at 180℃for 12 h to prepare biochar,and then in 70℃H₂SO₄ sulfonated 10 h.PVA films with different ratios are plasticized with starch liquefied products（SLP）.The SLP/PVA blend film with a ratio of 0.4 has good mechanical properties（stretch strength 38.07 MPa,break elongation rate 1199%）,good transparency,and excellent flexibility.The results show that the SLP blend PVA film has broad application prospects in the development of biodegradable packaging materials.（2）Based on the good processing and molding characteristics of high amylose starch（HAS）,cross-linked TA by glutaraldehyde,and mixed with PVA,the method of solution spinning is constructed to obtain high amylose starch/polyethylene alcohol（TA@HAS/PVA）fiber,and its U（VI）adsorption properties are studied.Adsorbents that absorb U（VI）from aqueous solutions should have several key characteristics,such as sufficient mechanical strength to withstand the impact of stirring,anti-biofouling activity to prevent microorganisms from sticking to the active point.It is studied that the stretch strength of TA@HAS/PVA fiber is 11.31 MPa,the stretching stress is 159.56%shows good mechanical performance,and has good anti-biofouling activity,adsorption capacity,and reusability.The TA@HAS/PVA fiber can be used as an ideal material for industrial extraction of U（VI）.（3）The HAS and tea polyphenols were cross-linked to prepare antibacterial and antioxidant food packaging film,and the microwave-assist method was used to improve the efficiency of cross-linking reaction.The temperature,time of microwave reaction,and tea polyphenol addition were optimized.The results of the study showed that tea polyphenols added20wt%（tea polyphenol/HAS）,at 50℃,microwave reaction 5 min was the best microwave-assisted tea polyphenol cross-linked HAS condition,and the cross-linking rate was as high as96.31%.After tea polyphenols and HAS cross-linked the glycerol was added as a plasticizer,and the tea polyphenols@HAS film was prepared by casting technique and drying into a film.The mechanical properties,physical structure,antibacterial and antioxidant properties of the film were characterized.The results show that the tea polyphenol cross-linked HAS film has good mechanical properties,antibacterial and antioxidant properties,and UV-blocking properties.As a food packaging tea polyphenols@HAS film can extend the shelf life of cherry and salmon.（4）With DMSO/H₂O as a solvent system,HAS as both template agent and reducer,and the in situ reductions of Ag NO₃ at 125℃affords Ag nanoparticles（Ag-NPs）,The solution system was cooled and added PVA,heated to dissolve the mixture,frozen gel to obtain Ag-NPs@HAS/PVA conductive gel.The gel has good solvent retention,mechanical properties,conductivity properties,and stress sensing performance.The results show that Ag-NPs@HAS/PVA conductive gel has the application potential as a flexible sensing material.