| With the depletion of traditional resources such as oil and coal,environmental pollution has become increasingly serious.green,renewable and degradable materials have become the focus of attention.Due to its wide range of sources,environmental protection,renewable and high strength,nanocellulose can be used as a reinforcing modifier to compound with chitosan(CS)and polyvinyl alcohol(PVA)to improve their mechanical properties and other properties.As a co-dispersant,it interacts with graphene nanosheets,polypyrrole,etc.,and is used in functional materials such as flexible supercapacitors.The main contents are as follows:(1)In order to modify the tensile strength,water resistance,heat resistance and brittleness of the chitosan film,nanocellulose and chitosan are compounded by mechanical mixing and solution casting to prepare biodegradable composite film.The effects of different preparation methods and nanocellulose content on the properties of the composite membrane were investigated.The results show that the nanocellulose crystals(CNC)are dispersed first,and then the CS is dissolved,and the prepared composite membrane has a better effect.When the CNC content is 3%,the dispersion is the best,the tensile strength of the composite film reaches43.02 MPa,and the elongation at break reaches 41.64%.Compared with the chitosan film,the tensile strength and elongation at break increased by 13.1%and 56.48%,respectively,and the water resistance and heat resistance of the chitosan film were also improved.(2)In order to solve the problem of insufficient mechanical properties,liquid absorption properties and heat resistance of polyvinyl alcohol(PVA)foams,cross-linking,chemical+mechanical foaming technology is used to composite nanocellulose with polyvinyl alcohol.A PVA/CNC foam was prepared.The effect of CNC content on the properties of PVA/CNC foam was investigated.The results show that the foam has a very high porosity,the average pore diameter is between 200-300μm,and numerous macropores and pores are connected to each other,which is an open-cell structure with extremely low apparent density,all less than 0.1g/cm~3.They belong to high foaming foam.When the amount of the CNC/PVA foam added was2%,the compressive strength,compressive modulus,and compression specific strength were907.19 KPa,1295.98 KPa,and 12835.87 N·m/kg,respectively.Compared with the foamed PVA without CNC added,the performance was improved by 49.92%.When the amount of the CNC/PVA foam added was 2%,the compressive strength,compressive modulus,and compression specific strength were 9.04 KPa,12.91 KPa,and 1127.90 N·m/kg,respectively.Compared with the foamed PVA without CNC added,the compressive strength is increased by69.61%,and it can be recycled.The liquid absorption performance and heat resistance of the foamed PVA are improved to different extents.(3)In order to solve the problem that the conductive film prepared by polypyrrole(PPy)and graphene nanosheet(GNS)is too brittle and the specific capacitance is too low,it cannot be used on a flexible supercapacitor.Polypyrrole,GNS@PPy,etc.are stably dispersed in water by using nanocellulose fibers(CNF),and are formed into aerogel electrodes by freeze drying,tableting and the like.The electrochemical properties of different aerogel electrodes were investigated.The results show that the prepared aerogel electrode has good flexibility.After the aerogel is extruded,it still shows the layered structure,forming a good three-dimensional conductive network,which is beneficial to the adsorption and diffusion of ions in the electrolyte on its surface.The electrochemical performance of the GNS@PPy/conductive carbon black(CB)/CNF aerogel electrode is as high as 331.68 F/g at a current density of 0.5 A/g.Compared to the PPy/CNF aerogel electrode(45.38 F/g),it was 6.3 times higher.The AC impedance is0.88Ω.It is cyclically charged and discharged 3000 times at a current density of 5 A/g,and still has a specific capacitance retention ratio of 70%. |
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