Study Of Effective Thermal Conductivity Of Plant Fiber Materials With Network Structure Based On Fractal Theory

With excessive CO2 emissions,the climate becomes more and more warming and the bad weather appears constantly, reducing carbon emissions have become the focus of global concern, however, the development of biomass material will provide an important approach to solve the problem of energy crisis and building energy efficiency. Based on the liquid foam theory, preparing a new light porous materials with the fiber for the skeleton——network structure plant fiber materials, which owns the excellent properties of small density and great insulation and well sound absorption, therefore, it will have broad application prospects in many areas, such as packaging, insulation, environmental protection and so on. The thermal conductivity of network structure plant fiber materials is studied in this thesis using several experimental and theoretical methods, moreover, the influence of inorganic materials to the thermal conductivity is discussed.First, inculding raw material type(mao bamboo pulp,ci bamboo pulp,green bamboo pulp), slurry concentration(4%,4.6%,5%), the amount of foaming agent (30ml,50ml,70ml), foaming time(4min,6min,8min), the amount of adhesives(20ml,30ml,50ml), the influence to the thermal conductivity under different preparative process conditions is investigated. Under the technology conditions of orthogonal experiment table L18(37),using the raw material after beating and dehydrating, the different properties test samples are made after foaming, molding and drying, whose thermal conductivity and mechanical properties are detected, and the writer obtain a optimum process scheme with the raw material type of chemical wood pulp10%,fir fluff pulp20%,ci bamboo pulp70%, slurry concentration 4.6%, the amount of foaming agent 50ml, foaming time 6min, the amount of adhesives 30ml. Meanwhile, the variance analysis results of the orthogonal experiment show that the raw material type and slurry concentration are very significant, and the amount of foaming agent and foaming time are outstanding, and the amount of adhesives is not significant for the influence to the thermal conductivity. On the base of the optimum process scheme, a single factor experiment to each technology condition is made and the results show tha the thermal conductivity of network structure plant fiber materials with different raw material type changes as: mao bamboo pulp > ci bamboo pulp > green bamboo pulp > chemical wood pulp > fir fluff pulp, and with the slurry concentration, the amount of foaming agent and foaming time increase, the thermal conductivity of the network structure plant fiber materials decreases and then increases, and when the slurry concentration reachs 4.6%, the amount of foaming agent is 50ml and the foaming time gets 6min, it achieves the minimum. Secondly, in order to research the microstructure of network structure plant fiber materials, this passage has introduced a fractal theory whose research object is just the irregular geometric shape. On the basis of the porous materials obtain by experiments shape, the writer makes use of the graphic analytic technology aided by computer, and calculates the fractal dimension of its section to establish a material structure model, a simplified heat-conduction model, and figures out its coefficient of thermal conduction(?)The result shows that the calculated value from this method is inconformity with the actual data, which proves the fractal model fairly reasonable. Further, the influence factors of the thermal conductivity of network structure plant fiber materials are analyzed quantitatively and the results show that the thermal conductivity relates to pore ratio, fractal dimension, the thermal conductivities of gas and solid. With the pore ratio and fractal dimension increase, and the thermal conductivities of gas and solid decrease, the thermal conductivity of materials increases.Finally, the effect of inorganic materials to the properties of network structure plant fiber materials has been discussed preliminarily, and inorganic materials strengthen the material and improve its flame retardant properties, and the effect of silica, sodium silicate and boric acid is good. In order to study the influences of various kinds of acid and alkaline inorganic materials, nine inorganic materials selected, in this paper, whose influences to the thermal properties have studied emphatically, and compares the thermal conductivity with different amounts of various inorganic, and the results show that the thermal conductivity of network structure plant fiber materials after adding inorganic materials changes a little, and only increases slightly, which proves the fractal model of network structure plant fiber materials effectively. The change trend of each material with adding different inorganic materials and amount is disaffinity specially, in a word, the change rules and influence factors of network structure plant fiber materials from experimental analysis should card mutually the analysis conclusion from fractal model of network structure plant fiber materials.