Preparation And Properties Of Carboxylated Nanocellulose Silver-loaded Functional Composite Material

Cellulose,as one of the most abundant natural polymers on earth,is a renewable biomass resource with good biocompatibility,degradability,high strength and good stability.One of the most effective ways to utilize cellulose is to nanometer cellulose,which can be applied to biomedicine,energy environment and nanocomposites.However,the catalytic performance and antibacterial activity of nanocellulose are relatively weak,while silver nanoparticles(Ag NPs),as nanomaterials,are the most widely used antimicrobial agents,which can enhance the antibacterial and catalytic activities of nanocellulose.In this study,nanocellulose was used as the carrier and no chemical stabilizer was used to"green"and efficiently prepare silver nanoparticles and study their application properties.In this thesis,the following researches are carried out for the above purposes:(1)Carboxylated oxidized nanocellulose was prepared using TEMPO-Na Br-Na Cl O oxidation system with larch pulp board as raw material.Adjust the relative size of cellulose fibers by ultrasonic mechanical treatment,and prepare cellulose membrane(TOCN)by vacuum filtration.FTIR was used to study pulp cellulose and TOCN,after TEMPO is found to be oxidized,the C=O characteristic diffraction peak of-COOH appeared at 1732cm^-1.By ultrasonic treatment of cellulose membrane is still maintained a cellulose?type of crystal structure,and as the ultrasound time increases,the light transmittance of the cellulose film also increases to 90%,and the cellulose film becomes denser.(2)Using nanocellulose as substrate and nanocellulose as additive,nanocellulose/nanocellulose composite membrane was prepared by covalent bonding method.The results show that spherical silver nanoparticles with a diameter of 20-70 nm are uniformly dispersed on the surface of the nanocellulose fibers and have a face-centered cubic crystal structure.The silver nanoparticles/nanocellulose composites have high thermal stability;after 30 days,the nanosilver/nanocellulose composite still has good stability.Nanosilver and nanosilver/nanocellulose composites showed high catalytic activity in the reaction of MB and CR,and were easy to be extracted and separated.In view of its excellent catalytic and recycling performance,nanosilver/nanocellulose composites have a broad application prospect in the treatment of dye wastewater.(3)With polyvinyl alcohol as the substrate and nanosilver/nanocellulose as the additive,the nanosilver/nanocellulose/polyvinyl alcohol.The results showed that the silver ions in the silver nitrate solution were successfully reduced in situ to nanosilver particles and adsorbed in the nanocellulose framework.Silver nanoparticles are spherical,square or triangular in shape with diameters ranging from 5 to 20 nm.As the concentration of nanosilver increases,the tensile strength and elongation at break of composite films increased first and then decreased;the antibacterial properties of the composite film showed that the composite film could maintain the antibacterial rate above 80%and had good antibacterial durability;the results show that the storage and preservation effect of composite film is better than that of pure PVA film,which is a new idea to prepare polyvinyl alcohol composite film and apply it to food packaging.