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Title
Kinetics of cellulose regeneration from cellulose-NaOH/thiourea/urea/H2O system
Authors
Shuai Zhang Fa-Xue Li and Jian-Yong Yu
Received
April 19, 2010
Published
Volume 45 Issue 9-10 November-December
Keywords
NaOH/thiourea/urea, direct dissolution, coagulation rate, activation energy, coagulation
Abstract
The coagulation properties of cellulose-NaOH/thiourea/urea/HO solutions under various coagulation 2 conditions have been investigated, to determine the kinetics of this special coagulation process (known as including diffusion on the contact surfaces of the polymer solution with the precipitant and the chemical reaction between acid and alkali). The observation was made that, at the beginning of the coagulation process, thickness of the coagulated layer,?(t), is proportional to the square root of time, t , which agrees with Fick’s law. By building a coagulation model, the influence of precipitant composition and concentration, of coagulation time, bath temperature and cellulose concentration on the coagulation rate has been demonstrated. The process of cellulose shaping from NaOH/thiourea/urea/HO solutions can be 2 characterized by examining the thickness and surface morphology of the coagulated layer, which is a reliable and direct method for understanding and controlling the cellulose regeneration behavior. It was found out that the coagulation rate enhanced with the increase in coagulation temperature, and decreased with increasing cellulose concentration. The activation energy of coagulation was calculated to be of 10.808 KJ/mol. The kinetics of diffusion-controlled chemical reactions has been viewed as the mechanism of coagulation.
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