Preparation And Properties Of Peanut Shell Cellulose Nanofibrils And Their Composites

Because of the special crystal structure,great mechanical properties,low cost as well as biocompatibility and recycling,cellulose has attracted much attention on the study of biomass materials.However,the exploitation and utilization of cellulose is mainly focused on the application of wood in the traditional domains.A large number of non lignocelluloses are discarded as waste.Therefore,the utilization of biomass cellulose still should be improved.For the high value utilization of biomass cellulose,the present dessertatoin used crop waste materials as raw material and prepared cellulse nanofibers with defferent dimension from peanut shell by several fibrillated methods.On the basis of prepared cellulose nanofibers,we constructed several functional nanocomposites with different performance by different compound technique.Then the compound mechanism,strengthening and toughening mechanism as well as interfacial coherence of cellulose nanofibers with different materials were researched.The main research content can be summarized as follows:1.Hohocellulose and purified cellulose were respectively prepared after the removal of lignin and hemicellulose by chemical treatment.The raw peanut shell has porous morphology of the surface particles.The matrix components such as lignin and hemicelluloses are located in the outer waxy layer,so single fibers are difficult to be observed.After purification,the twisted rod-like structure of the peanut shell fibers about 10 ?m wide was observed and the individual microfibril bundles approximately 15 nm wide could be clearly seen from the fiber surfaces.Through three type of fibrillated mathods,grinding can fibrillated the cellulose fiber to the primary level of nano size which is between 100 nm and 200 nm.Followed by high pressure homogenization,the diameter of cellulose fiber can reach 50 nm.Finally,cellulose nanofibers with the diameter of about 15 nm were successfully prepared by ultrasonication.During the process of gradual fibrillation,the characteristic group of cellulose which remains the chemical composition and functional groups of purified cellulose was not aspected.While crystallinity and themal stability decreased slightly with the increase of mechanical processing.2.CNF suspension was slowly vacuum filtered using a polytetrafluoroethylene membrane to form three differet sheets.With the comparison of mechanical properties,optical properties and thermal stability of each other,the regular transmittance of the film with diameter of 15 nm was 66.7% at a 600 nm wavelength.Meanwhile,this kind of film also showed the highest tensile strength of 181 MPa and Young's modulus of 7.1 GPa as well as elongation at break of 7.3%.With these excellent performances,CNF can be widely used as base material of products such as flexcible displays,solar cells and electronic paper.Moreover,cellulose nanofibers were incorporated into PVA by impregnation method.We prepared the CNFs–reinforced PVA biocomposites with high fiber content up to 80 wt%.CNFs/PVA composites showed the original layered structure of CNFs film was well retained,while the PVA resin was just tightly attached on the surface of film,forming a characteristic sandwich structure.And even though the interface was magnified further,there was still no obvious delamination observed between PVA and cellulose nanofibers,revealing that the successful bonding formed during impregnation.Particularly the average values of modulus and tensile strength of the PVA increased from 0.6 GPa to 6.0 GPa and 31 MPa to 123 MPa,respectively.While the CTE of the composites is only 19.1 ppm/K and its regular transmittance is up to 84%.3.In order to improve the preparation efficiency and reduce the energy consumption,we prepared cellulose nanofibers with the diameter from 15 to 30 nm and the length about several micrometers just by grinding one time.Then CNF/MTM composites are prepared by the mothod of solution intercalation and the synergistic toughening effect is investigated.With the content of 50 wt% MTM,the composites are still highly flexible and foldable.The inorganic nanolayer,which embedded into the CNF matrix uniformly and orderly,played the role of orientation and layering.When the fiber content is high,the composite retained the inherent toughness of the CNF.The average values of modulus and tensile strength of 1M:3C film is up to 11.8 GPa and 191 MPa respectively,with the elongation of 6.23%,which indicated the excellent mechanical properties and toughness.In addition,with the existence of nanolayer,the degradation rate of the composite is obviously slowing down.This is also reflected in the combustion performance.The reason is that MTM nanolayer form a dense layer of fire which hindered the flame penetration.On the other hand,the nanolayer parallel to the film surface can form the pattern of detour mode.CNF/MTM composite is provided with excellent oxygen resistance owed to long path layer diffusion effect.The oxygen resistance coefficient of the composites is lower than 0.001 cm3·?m·mm-2·d-1·kPa-1 under the dry condition.4.The flexible energy storage material are prepard based on the intercalation structural composites.Two dimentional nanolayer supplied stable template for in-situ growth of aniline perpendicular to the film surface.Then two different polymerization statuses are formed.This kind of structure has a higher specific surface area which can provide more active sites for oxidation-reduction reaction of electrode materials.With the research on the structure and properties of the film,the specific capacitance of which is up to 421 F/g owed to CV curves.Constant current charge discharge curve is similar to the triangle,which indicated fast charge transfer behavior and redox dynamics.The Nyquist curves of the composite in 1 M H2SO4 electrolyte also showed the material has the ability of rapid redox reaction,but lower charge transfer rate will directly affect the charge distribution uniformity in the chain of PANI,which is caused by little active substrate.The charge transfer resistance of CNF/PANi and CNF/MTM/PANi films was 12.7 and 11.5 ?,respectively.After 1000 cycles of charge and discharge test,the capacitance retention of CNF/MTM/PANi film is only 58.9% which showed a fast reduction of capacitance.