低温溶解纤维素的NaOH/添加剂水溶液溶剂体系因其价廉环保、溶解快速的特点引起了广泛的关注,但因为溶解能力的限制使其难于工业化.因此本文以较高聚合度(DP>740)的商业竹溶解浆为实验原料,通过正交偏光显微镜观察了其在7%NaOH/12%尿素、9.5%NaOH/4.5%硫脲和8%NaOH/8%尿素/6.5%硫脲等NaOH/添加剂水溶液溶剂体系中低温溶解的行为.通过生成的透明纤维素溶液的粘度测试、溶解率的测定,UV-Vis光谱分析、动态光散射(DLS)测试和未溶残渣的XRD分析比较了3种NaOH/添加剂水溶液溶剂体系对高聚合度竹溶解浆的溶解能力.实验结果表明,8%NaOH/8%尿素/6.5%硫脲水溶液对竹溶解浆表现出最佳的溶解能力,约达到60%的浆纤维溶解.即不同于纯纤维素和其它低聚合度的化学木浆,纤维刚硬的高聚合度竹溶解浆在低温需要较高浓度的碱液和复配强氢键破坏能力的添加剂的溶剂体系才能获得较好的溶解效果.
NaOH/additives aqueous solution solvent being able to dissolve cellulose at low temperature widely attracted the focus of many researchers because of its low cost, environmental protection and rapid dissolution.However, this solvent is difficult to be applied in industry due to its limited solubility.Therefore, commercial bamboo dissolving pulp with high degree of polymerization(DP) was selected as experimental materials in this paper, and its dissolution behavior in 7%NaOH/12% urea aqueous solution,9.5%NaOH/4.5% thiourea aqueous solution and 8%NaOH/8% urea /6.5% thiourea aqueous solution at low temperature was investigated by polar microscopy.In addition, the dissolving capacity of three NaOH/ additives aqueous solution systems was compared by viscosity measurement of transparent cellulose solution, determination of dissolving proportion, UV-Vis spectrum analysis, dynamic light scattering (DLS) test and XRD analysis of insoluble residues.The results showed that 8%NaOH/8%urea/6.5%thiourea solvent system displayed a strong capacity of dissolving cellulose, about 60% dissolving proportion, namely, different from pure cellulose and other lower DP chemical wood pulps, better dissolution of high DP bamboo dissolving pulp with rigid fibers in NaOH/ additives solvent system at low temperature need higher concentration of alkali solution and several additives capable of breaking hydrogen bond.
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