Study On The Structure And Properties Of Cellulosic Porous Materials

Due to its abundant reserves,good mechanical and chemical performance,biocompatibility and renewability,cellulose is one of the best natural polymer sources for the preparation of materials with good environment friendliness and biocompatibility.Synthesizing porous materials using cellulose as raw material is of great value for research and application.Dimethylacetamide(DMAC)was utilized for the activation to microcrystal cellulose(MCC)for the cellulose dissolving in LiCl/DMAc at room temperature.And the mechanism of thermal activation of DMAc was studied.The transparent hydrogel with large absorption for UV light was prepared through sol-gel method.Then the hydrogel was prepared to cellulose porous material with controlled pore structure by supercritical CO2 drying and freeze drying.The composite for thermal storage was prepared from the cellulose porous material encapsulating the PEG mixed with graphene powder(particle size d<23?m).With the characterization of the porous material and thermal storage use composite,the mechanism of factors influencing on the pore structure of cellulose porous material and the pore structure influencing on the stability,heat storage performance and thermal conductivity of composite are all discussed,by the method of X ray diffraction(XRD),Fourier transform infrared spectroscopy(FTIR),scanning electron microscope(SEM)and differential Scanning Calorimetry(DSC).The research result shows that:At 150?,DMAc can cause the lattice deformation of MCC,by which the accessibility for DMAc/LiCl to dissolve MCC at room temperature was highly improved,leading to the dissolving of MCC inside LiCl/DMAc at room temperature.For the cellulose condensed on the ice crystal boundary when the temperature was decreased,before the freeze-drying to prepare cellulose porous material,The final pore structure of porous material has been fixed by pre-freeze condition,on which the growth process,final size,distribution of ice crystal are depended.The leakage of PEG inside the phase change composite for the thermal storage is influenced by the pore size of cellulose.The as-prepared material has good stability due to the proper pore size and structure of the cellulose.The conduction heat resistance increases and the thermal conductive property decreases with the increasing intensity of cellulose sheets.During the process of phase change,the latent heat of phase change is lower than the amount of latent heat of crystallization of PEG,which is probably influenced by the hydrogen bond formed between PEG and cellulose.The research work improved the theory for the preparation of cellulose porous material.And a kind of method to control the properties and structure of cellulose porous structure is promoted,which expand the application of cellulose porous material.