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Factors affecting viscose ripening
Author(s) -
Easterwood Marie,
Mueller W. A.
Publication year - 1960
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1960.070041003
Subject(s) - viscose , sulfate , sulfite , dilution , chemistry , pulp (tooth) , dissolving pulp , dissolution , salt (chemistry) , cellulose , mineralogy , materials science , polymer chemistry , organic chemistry , thermodynamics , dentistry , medicine , physics
Ripening of spinnable viscoses has shown dexanthation rates to be constant for sulfate pulps; however, sulfite pulps appeared to ripen slightly faster than the sulfate pulps. The rate of dexanthation was unaffected by changes in alkalinity over relatively narrow ranges, and slightly affected by sulfur and cellulose content. Dilution of the viscose increased the dexanthation rate. A molar activation energy of 23 kcal. was calculated from a study of temperature effects on dexanthation of a high alpha sulfate pine pulp. Changes in salt index with respect to degree of substitution for all viscoses xanthated and dissolved at 25°C. followed the same linear function. For viscoses prepared at lower xanthation and/or dissolving temperatures, the ripening curves exhibited an initial rise suggesting two simultaneous changes: dexanthation and a randomizing of substitution. Split xanthation (the final xanthation step under essentially homogeneous conditions) yielded viscose having random substitution and exceptionally high salt index. As this solution ripened the salt index decreased linearly with respect to degree of substitution and eventually followed the same function as normally xanthated viscose, indicating that the final internal structures of the two solutions are similar.