| People shows great interest for lignocellulosic biomass due to restricted availability petrochemical resources. Wood as the main source of lignocellulosic biomass, since the complex chemical composition of its cell wall and the compact structure between components, so that the refining of wood components and the development of lignocellulosic biomass based materials were greatly hindered. Dissolution and separation of traditional solvents for wood exists series problems such as environmental pollution and large energy consumption. Nowadays with the enhancement of environmental consciousness, people turn to ionic liquids as solvents, ionic liquids as a new green solvent can effectively dissolve wood, and will play an important role in the sustainable development future. Ionic liquid is used for preparation of cellulose and lignocellulosic composite material, not only can reduce the dependence on petrochemical resources, but also can increase the use of wood fibers.The wood of Eucalyptus citriodora was researched in this study. The air-dried eucalyptus wood without barks were ground in a jar using steel ball under liquid nitrogen condition. Then wood powder was processed through different pretreatment, wood fibre after processing was dissolved in ionic liquids, lignocellulosic films were prepared using water vapor as coagulation bath. Finally, performance characterization and structure of lignocellulosic films were respectively tested by SEM, XRD, TG, DSC, UV-Vis and mechanical testing machine. Effects of pretreatment methods of 1,4-dioxane extraction, drying methods and high intensity ultrasonic and pretreatment methods of their various combinations on performance characterization of lignocellulosic film of eucalyptus were explored. In addition, effects of various 1,4-dioxane concentration and various ultrasonic time on performance characterization and structure of lignocellulosic film of eucalyptus were also explored. The main conclusions are as follows:Study on effects of pretreatment methods of various combinations on performance characterization of lignocellulosic film of eucalyptus:Dissolution time of raw material of unused 1,4-dioxane extraction was extremely long, viscosity of obtained suspension liquid was extremely low, what’s more, a certain mechanical strength of regeneration film not prepared after precipitation and solidification. Compared with the structure of before and after the solution of lignocellulose, crystalline structure of raw material was cellulose I, it of regeneration film was cellulose Ⅱ, moreover, the degree of crystallization of regeneration films was extremely low so that thermal stability of them was extremely low, and regeneration films and wood fiber had exothermic peak and endothermic peak during raising temperature, respectively. Compared with pretreatment methods of various combinations, the dissolution time of freeze-dried raw materials was effectively decreased, relative crystallinity of raw material was effectively reduced through ultrasonic method so that initial temperature of mainly thermal decomposition of the Wun was obviously higher than that of raw materials of ultrasonic pretreatment. The degree of crystallization and tensile stress of Fd90 were obviously higher than Ffn and Fun. In addition, ultraviolet of UVC and UVB wavelengths were not passed by three kinds of regeneration films, and transmission rate of ultraviolet of UVA wavelengths was extremely low. Compared with regeneration film of microcrystalline cellulose, the ability of absorbed ultraviolet light of lignocellulosic film was better, while the visible and near-infrared light transmittance of lignocellulosic film were lower.Study on effects of various 1,4-dioxane extraction concentration on performance characterization of lignocellulosic film of eucalyptus:With increasing of 1,4-dioxane extraction concentration, relative crystallinity of raw material was increased at the beginning and then tended to be stable, mainly started decomposition temperature, peak temperature of main decomposition and completely dissolved time of raw material were decreased. Lignin content, peak temperature of main decomposition and decomposition temperature range of regeneration film were Fd80> Fd85> Fd90. The degree of crystallization, tensile stress and elongation at break of Fd90 were significantly higher than Fdss and Fdso. In addition, with increasing of 1,4-dioxane extraction concentration, the ultraviolet-visible light transmittance of lignocellulosic film was increased.Study on effects of pretreatment methods in various ultrasonic time on performance characterization of lignocellulosic film of eucalyptus:With increasing of ultrasonic time, completely dissolved time of raw material was decreased, tensile stress of lignocellulosic film was increased at the beginning and then was decreased, the elongation at break of lignocellulosic film was slowly decreased at the beginning and then was quickly decreased to a minimum at ultrasonic 1 h. Mainly started decomposition temperature of Wuo.s was higher than the other three kinds of raw materials, and the degree of crystallization of Fu1 was higher than the other three kinds lignocellulosic films. In addition, comparing four kinds of regeneration film, ultraviolet and visible light transmittance had no obvious regularity. |
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