Preparation And Property Of Down Fiber/Cellulose Nanofiber Composite Aerogel

In recent years,it is urgent to develop high value and available natural renewable resources with the increasingly prominent problem of environmental pollution and the continuous consumption of non-renewable resources.Cellulose-based aerogel has attracted wide attention due to its good biocompatibility,environmental friendliness,flexibility and degradability.However,its low mechanical strength,hydrophilic and highly flammable property seriously affect its practical application effect and safety.Therefore,strengthening hydrophobic and flame retardanting property of cellulose nanofiber aerogel materials is very important to expand the application field of this material.The main research contents and conclusions of this paper are as follows:Firstly,DF/CNF composite aerogel was prepared by directional freezing process with cellulose nanofiber(CNF)as natural raw material,down fiber(DF)as reinforcement,and1,2,3,4-butane tetracarboxylic acid(BTCA)as cross-linking agent.The results showed that the addition of DF significantly improved the compressive strength of the composite aerogel.After 100 cycles of compression at 60%compressive strain,DF-4/CNF-8 could maintain the longitudinal and transversal height recovery rates above 90%.Secondly,the presence of DF in the matrix promotes crystal nucleation,improved thermal stability and insulation performance.In addition,DF-4/CNF-8 has good adsorption capacity for methylene blue(MB),with a maximum adsorption capacity of 250.21 mg/g.The adsorption kinetics follow a pseudo-second-order kinetic model and are closely related to the Langmuir model(R~2=0.9999).Secondly,in order to improve the hydrophobic property of DF/CNF composite aerogel effectively,we used chemical vapor deposition to modify its surface,and optimized the process to prepare super hydrophobic and super oil absorbent composite aerogel.The hydrophobic,lipophilic and wet compression properties of MTMS/DF-4/CNF-8 with methyl trimethoxysilane(MTMS)as hydrophobic agent were studied.The results showd that the contact angle of MTMS/DF-4/CNF-8 after hydrophobic finishing is as high as 159.3°,and after durability tests,the contact angle can reach over 150°.The organic liquid adsorption experiment shows that the adsorption capacity of MTMS/DF-4/CNF-8 for various oil and organic solvent about 56.24 g/g～153.59 g/g.The cyclic adsorption experiment results show that MTMS/DF-4/CNF-8 has certain reusability.After 10 times of adsorption/desorption,the adsorption capacity of dichloromethane and sesame oil can reach 87.3%and 80.2%of the original adsorption capacity.Under the compression of 200 g weight,the height recovery rate of MTMS/DF-4/CNF-8 reached 91.2%after 10 oil suction compression cycles.Finally,in order to further improve the flame retardancy of DF/CNF composite aerogel,two flame retardants,montmorillonite(MMT)and sodium alginate(SA),were blended into the suspension of DF-4/CNF-8 to obtain flame retardant composite aerogel after freeze-drying.Explored the influence of the proportion of MMT in flame retardants on the microstructure,flame retardancy,insulation,and flexibility of DF-4/CNF-8,and further analyzed the residual carbon of DF-4/CNF-8 before and after flame retardant finishing to speculate its flame retardant mechanism.The results show that the MS-50/DF/CNF composite aerogel with 50%MMT can endow the base material with good flame retardancy while retaining good flexibility.The analysis of the morphology and structure of residual carbon shows that the flame retardant treated carbon residue is dense and has a lower I_D/I_G,mainly attributed to the synergistic effect of physical barrier of MMT,recombination of internal structure of SA under high temperature conditions,and gas phase barrier effect of micro nano pore structure inside the residual carbon.