The flow behavior of four cellulose acetate–acetone solutions varying from 20.00% to 28.18% solids concentration was observed using flow visualization techniques at 24°C with an industrial‐type dry spinning sys...
The flow behavior of four cellulose acetate–acetone solutions varying from 20.00% to 28.18% solids concentration was observed using flow visualization techniques at 24°C with an industrial‐type dry spinning system. Fibrous particulate matter entertained in the solutions and crossed polars revealed the streamlines and the birefringence due to flow in glass spinnerets. The streamlines of the four solutions were radially convergent at all obtainable throughputs. The crossed polars revealed a cone of birefringence with the order of the interference colors decreasing upstream of the capillary inlet. The intensity and extent of birefringence varied somewhat with concentration and throughput. Except for kneeing, the emerging extrudates were undeformed. The kneeing was not a result of flow instability a t the capillary inlet but was due to another, undetermined instability. A separate study of the kneeing revealed both a concentration dependence and hysteresis. The birefringence of the emerging extrudates was a function of both concentration and throughput, and it yielded some information about the structure of the solutions.
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