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《无机化学与普通化学杂志》2002,628(12):2557-2557
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Wilhelm Fresenius und Ferdinand Springer 《Fresenius' Journal of Analytical Chemistry》1956,152(1-3):1-2
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A review is given on comparative investigations onto the structure of regenerated cellulose fibers of the regular viscose type (modal) and of solvent spun fibers of the lyocell type, namely the NMMO fiber spun from a solution of cellulose in N–methylmorpholine N–oxide and water. It was found that in the lyocell fiber the mechanical properties in the wet state detoriate less. This is explained by an increased length of the crystallites, less clustering of the crystalline regions, and a shorter and better oriented amorphous portion. These structural features could be caused by a different spinning mechanism due to a preordered spinning solution in which the stiff complexed cellulose molecules are oriented lengthwise in the spinning direction. This will greatly facilitate their orientation during fiber formation in the elongtional deformation velocity field of the draw down zone. 相似文献
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Phosphorus-Carbon-Halogen Compounds. 16. On the Reaction of Alkyldiphenylphosphanes with Tetrachloromethane and a Convenient Preparation of (α-Chloroalkyl)diorganylphosphanes The reaction of alkyldiphenylphosphanes with carbon tetrachloride in aprotic solvents gives (dichloromethyl)alkyldiphenylphosphonium chloride and (α-chloroalkyl)diphenylphosphanes. Their formation is attributed to the dehydrochlorination of the intermediate dichloroalkyl diphenylphosphoranes by the ylid (dichloromethylene)alkyldiphenylphosphorane, also formed intermediately. In protic solvents the ylids abstract protons while the dichlorophosphoranes remain unchanged. Dehydrochlorination of alkylsubstituted dichlorophosphoranes by means of tertiary amines turned out to be a convenient synthesis of (α-chloroalkyl)diphenylphosphanes. 相似文献
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