Research And Preparation Of Nano-cellulose Based On NaOH/urea/thiourea System

Cellulose is the most abundant renewable polymer on earth and can be used to produce a variety of useful products through regeneration or derivatization.The preparation of nano-cellulose is one of the effective methods of using cellulose.Nano-cellulose has many excellent properties such as nano-scale effect,biodegradability,biocompatibility,high hydrophilicity,high transparency,high strength and stable chemical properties.It is one of the nano-materials with wide application prospects.It can be used in biomedical fields,chemical research,nano-composites,energy and environment.However,the conventional nano-cellulose preparation method has the problems of high energy consumption,low yield,failure to destroy the crystallized region and the problem of poor dispersion,which seriously hinders the application of the nano-cellulose.In this paper,preparation of nano-cellulose,improvement of nano-cellulose dispersibility and preparation of nanocellulose-based magnetic functional film were studied.Using waste paper as raw material,NaOH/urea/thiourea system was selected as the solvent,and distilled water was used as the coagulation bath.After the cellulose was regenerated,ultrasonication was performed to obtain nano-cellulose.The yield of nano-cellulose prepared by this method is 74.65%.The prepared nano-cellulose is a spherical nano-cellulose,and the average size of the nano-cellulose is measured using zeta electro-displacement to be 50 nm,having a cellulose II-type crystal structure,a low crystallinity.Nano-cellulose has a good thermal properties.The initial decomposition temperature and the highest decomposition rate of the prepared nanocellulose were262°C and 353°C,respectively.And it has potential applications in transistors and batteries with high thermal stability.Sulfuric acid was used as a modifier to improve the stability and dispersibility of the nano-cellulose suspension prepared by the above method.XRD results showed that the acid-treated nano-cellulose still maintained the crystalline structure of cellulose II and the crystallinity index increased slightly?28.6-35.73%?.Thermo gravimetric analysis showed that the acid-treated nano-cellulose still had good thermal stability.The acid-treated nano-cellulose has charged sulfate and sulfonate groups on the surface and releases more C-OH groups.The?-potential value was the lowest?-39.2 mV?at the 6 hour reaction time.SEM results showed that the size of nano-cellulose did not change significantly.Higher?-potentials and relatively small cellulose particles play an important role in improving the stability and dispersibility of the nano-cellulose particles.In the application of nano-cellulose,nano-cellulose based magnetic functional film was prepared with nano-cellulose as the substrate and Fe3O4 nano-particles as functional phases.Due to the electrostatic attraction between nano-cellulose and Fe₃O₄nano-particles and the electrostatic repulsive force generated by charged groups on the surface of nano-cellulose,Fe₃O₄ nano-particles can be stably dispersed in the nano-Fe₃O₄/nanocellulose suspension and uniformly dispersed in magnetic film.The magnetic film has good super paramagnetism,and the saturation magnetization can reach 11.14emug^-1 with the increase of the amount of nano-Fe₃O₄?2.5%to 10%?.The mechanical properties test results show that the addition of Fe₃O₄ nano-particles results in a decrease in the interaction force between the nano-cellulose,making the mechanical properties of the magnetic film worse.