A simplified time-lag technique was developed to measure the average diffusion coefficient for solvent extraction during coagulation in wet spinning. The accumulated amount of solvent diffused from the uncoagulated fiber while dry-jet wet spinning into a finite spin bath was measured as a function of time. From this experiment a time-lag θ in the solvent built-up can he measured easily. From this, the average diffusion coefficient D can be determined from D = R2/8θ, where R is the filament radius.
Some experimental results using the time-lag technique in a polymer/sulfuric acid/water system were obtained and compared with results using a conventional measuring method.
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