Preparation And Characterization Of Cellulose Aerogel And Its Composites

Cellulose aerogel had the characteristics of large surface area,light texture,interpenetrating porous network and good biodegradability.It had broad application prospect in food,medicine and health,energy,biotechnology and environmental protection.In order to explore and broaden the application of cellulose aerogel matrix composites in heat storage and medical dressing,the preparation,characterization and properties of cellulose aerogel and cellulose aerogel matrix composites were studied,aiming at the construction of cellulose aerogel based hot compress pack.The purpose of this study was to obtain an aerogel-based composite phase change heat storage material with heat storage function by melting impregnation and to assemble a medical dressing which could be used for hot compress using hydroxyapatite/cellulose aerogels with good biocompatibility as substrate.In order to obtain the limited carrier of organic solid-liquid phase-change composites,a series of modified cellulose aerogels（MCA）were constructed by acylation reaction and hydrophobic-ene click reaction with microcrystalline cellulose as raw material.The morphology,structure,chemical stability and oil absorption properties of MCA were studied.The results showed that the prepared series of MCA were all three-dimensional network structure and showed good chemical stability and hydrophobicity.When the molar ratio of cellulose hydroxyl group to acrylyl chloride was 1:1,MCA showed excellent oil absorption performance and its maximum adsorption capacity was 14.8 g·g^-1.Good oil absorption performance gave MCA a potential as a phase change material limited carrier.Using stearic acid（SA）as the phase change material and modified cellulose aerogel as the carrier,MCA/SA-1 and MCA/SA-2 composite phase change materials were prepared by solution impregnation method and melting impregnation method respectively.The effects of preparation methods on the heat storage performance of the composite phase change materials were discussed.The morphology,structure and thermophysical properties of the composite phase change materials were analyzed.The results showed that when the loading rate of SA was 66%and 80%,respectively,MCA/SA-1 and MCA/SA-2 showed good shape stability without obvious leakage after continuous heating at 80℃for 1 h.In the composite phase change material,there is only physical interaction between the carrier and the phase change material,showing excellent SA encapsulation performance.Compared with that of pure SA,the thermal conductivity of MCA/SA-2(0.2227 W·（m·K）^-1)was reduced by 25.34%.The latent heat of melting and solidification phase transition of MCA/SA-2 were 179.75 J·g^-1 and178.70 J·g^-1,respectively.MCA carrier provided a large specific surface area,so that SA formed nanoclusters on its surface.The high density of nanoclusters made the latent heat of phase transition of composite PCM higher than the theoretical enthalpy value.The cyclic test results showed that the thermophysical properties of MCA/SA-2 had little fluctuation and good cyclic stability.High enthalpy value and good cycle stability made MCA/SA-2 had great potential in the field of hot compress.When the cellulose composite phase change material was directly applied to hot compress,it would cause some discomfort to human body.In order to relieve the discomfort caused by this,reduce the risk of leakage damage of composite phase change materials and restrain overheating,the excipients with good biocompatibility could be used as the substrate.Three kinds of hydroxyapatite（HA）/cellulose composites were prepared by biomimetic mineralization method,in situ compound method and solution blending method using cellulose aerogel as substrate.The results showed that HA and cellulose in the three kinds of composites were combined by physical interaction and had good chemical stability.The thermal conductivity test results showed that the thermal conductivity of the composite was lower than that of pure cellulose aerogel,and the thermal conductivity of the composite prepared by biomimetic mineralization method was the lowest(0.0357 W·（m·K）^-1),which had good temperature control ability.The cell viability experiments showed that all the three kinds of composites had good biocompatibility,but the biomimetic mineralized composite had better performance than the other two composite materials and had great potential in biological applications.To sum up,the biomimetic mineralized composite had the best performance among the three kinds of composite materials.It was selected to combine with MCA/SA-2 to construct cellulose-based hot compress functional material.The results showed that the constructed hot compress material could apply hot compress to the human body for 360 s,and the hot compress temperature would not burn the skin,which had great potential for application in the field of medical dressing.