Study On The Oxygen-alkali Cooking Of Wheat Straw And Its Thin-wall Cell Membran

In this thesis,wheat straws from Yunnan and Shandong were used as raw material for low-temperature alkali-oxygen(AO)pulping.Based on the analysis of the main factors affecting the results of AO pulping and the related experiments,the optimal pulping condition were determined.The properties of AO pulp prepared by the optimized process were compared with those from other pulping methods.For the parenchyma cells isolated and collected from low-temperature AO pulp,the morphology and structure of them and fiber cells as well were analyzed by SEM,XRD,FT-IR and BET.And then the parenchyma cells were used for preparation of the membrane to evaluate the related properties of the membranes,which laid an important foundation for further research and utilization of parenchyma cell menbrane.The results were summarized as follows:1.After optimizing AO pulping of Yunmai 42#and Lubei 1#,with the yield of screened pulp,kappa number,viscosity and other parameters as indicators,the low-temperature AO cooking conditions were alkali 26%,MgSO4 0.5%,cooking temperature 110℃,liquor ratio 6:1,time to maximum temperature 90 min,time at maximum temperature 360 min.The obtained pulp properties were screened pulp yield 45.9%,fines yield 16.8%,kappa number 8.6,viscosity 682mL/g,brightness 59.7%ISO.2.The Lubei 1#was cooked by low-temperature AO pulping,soda-AQ pulping and traditional AO pulping,individually.It was found that fines ratio in AO pulp was higher than that in soda-AQ pulp,and the chemical components of the pulps were similar except brightness and SiO2 content.However,the sheets handmade from the three pulps at process 45° SR showed that the strength characteristics of low-temperature AO pulp was the best.3.The parenchyma cells and fiber cells were characterized by SEM,XRD,FT-IR and BET,respectively.The results showed that the surface of the parenchyma cells was rough and fragile.It was also found that the chemical structure and crystalline structure in the two type of cells were basically similar with each other.Moreover,they all belonged to the mesoporous materials,and the specific surface area,average pore volume and pore diameter of the parenchyma cells were higher than those of the fiber cells.4.The parenchyma cell membranes with different basis weight were prepared and characterized.And the results showed that the tensile strength and elongation of the membranes increased with the increase of the basis weight,while the air permeance and transparency decreased.Meanwhile,the smooth,uniform membrane gradually became uneven.The chemical structure and crystalline structure of parenchyma cells has not changed by the membrane formation.It was noted through the TG that the membrane degradation started at 220℃,which means that the membrane had good thermal stability.In addition,the results of its degradation test in the soil showed that the membrane had good degradation properties.5.The membrane with the basis weight of 6g/m2 was prepared and analyzed after deflaking parenchyma cells.It turns out to be the case that the deflaking times had no effect on the transparency of the membrane,which had a positive effect on the tensile strength and elongation,and had a great influence on the smoothness and the air permeance.