Study On The Structure Of Citric Acid Crosslinked Cellulose Aerogels

Cellulose aerogels has low density and high porosity characteristic with traditional aerogels and combines excellent properties of material itself, such as the source of the cellulose is widespread, large reserves, no pollution, has good biodegradable properties and compatibility and so on, due to the above advantages make cellulose aerogels has great application value in insulation, adsorption materials, sustained release and composite template. And cellulose molecular chain contains a lot of hydroxyl groups for modification and functionalization of cellulose material design, as the world energy crisis makes cellulose aerogels become the key research direction of the researchers.In this paper, citric acid was used as a crosslinker to modify cellulose aerogels, and macrocrystalline cellulose was used for preparation of cellulose aerogels based on LiCl/DMAc solution system and through the processing of sol-gel, esterification crosslinking reaction and supercritical drying. Its structure and properties were characterized by variety of characterization methods such as SEM, DSC, FT-IR, XRD and some basic properties test. Analysing the effect of initial content of cellulose, selection of drying process and conditions, citric acid modification and crosslinking reaction conditions on the cellulose aerogels basic performance and the influence of network structure network structure, the above study indicate the following conclusions:Through the aerogel materials microstructure observation found that cellulose aerogels internal pore get smaller with the increase of the initial concentration of the cellulose, the pore distribution also become more closely. This is due to the increase of cellulose content increased the concentration of hydroxyl groups in cellulose network structure and improving the hydrogen bonding interaction and affect the network structure. At the same time, the moisture content and swelling property of cellulose gel reduced with the rise of cellulose concentration, through ultrasonic pretreatment of cellulose aerogel material has better internal porous structure and pore size distribution.By Fourier infrared spectrum analysis indicated that under the condition of relatively high temperature, modification effect of citric acid makes the hydroxy of cellulose molecules through esterification reaction to form the ester bond, the ester bond constitute the modified chemical crosslinking point, and at a lower temperature is difficult to obtain crosslinking point. At the same time, the higher the temperature of the crosslinking reaction or citric acid content of crosslinking agent, the greater the degree of esterification reaction, the more chemical crosslinking point, and the aerogel materials obtained with microscopic characteristic of chemical crosslinking network structure.Through the test of thermal stability and mechanical properties can be concluded that the chemical crosslinking point relative physical junction of the hydrogen bonds has better stability. By XRD diffraction pattern shows that modified cellulose aerogels also belongs to the amorphous structure, the modification effect of citric acid didn’t change the crystal type of cellulose, but to a certain extent, improved the microcosmic structure regularity of aerogel materials.Combined with the above characterization and researching of cellulose aerogels’ network structure change rule and the actual situation and the application of cellulose aerogels. Eventually get the materials design and optimization method of cellulose aerogels’network structure. Effectively improve the basic properties of the aerogel and the stability of its network structure, expended the application range of cellulose aerogels.