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Properties And Uses Of Cellulose Derivatives
Jan 24, 2018

By replacing the reagent selection and process design, the product can be dissolved in water, dilute alkali solution or organic solvent, or have thermoplastic properties for the manufacture of chemical fibers, films, substrates, plastics, insulating materials, coatings, pastes , Polymeric dispersants, food additives and daily chemical products. The nature of the cellulose derivative depends on the nature of the substituent, the extent to which the three hydroxyl groups on the glucosyl group are substituted, DS, and the distribution of the substituent along the macromolecular chain. Due to the randomness of the reaction, except for products that are uniformly substituted when all three hydroxyl groups are substituted (DS = 3), in all other cases (homogeneous or heterogeneous), the following three substitution positions are obtained (DS is 1, C, C or C position is replaced, the structural formula see cellulose); ② disubstituted (DS is 2, C, C, C, C Or C, C position is replaced); ③ full substitution (DS is 3). Therefore, the properties of the same cellulose derivative with the same substitution value may also be very different. For example, cellulose diacetate esterified directly to DS 2 is insoluble in acetone, but cellulose diacetate saponified with fully esterified cellulose triacetate is completely soluble in acetone. This heterogeneity of substitution is related to the basic rules of cellulose ester and etherification.

Basic rules of esterification and etherification of cellulose In cellulose molecules, the positions of three hydroxyl groups in different glucosyl groups are different, and the effects of adjacent substituents and space obstructions are also different. The relative degree of acidity and dissociation of the three hydroxyl groups is: C> C> C In an etherification reaction in a basic medium, the C hydroxyl group first reacts, then the C hydroxyl group, and finally the C primary hydroxyl group. When carrying on the esterification reaction in the acid medium, the reaction of each hydroxyl group is opposite to the order of the etherification reaction. With the larger substitution reagents, the space obstruction has an important effect on the space obstruction less C hydroxyl than C, C hydroxyl reaction easily.

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