A study of spinnability in the wet‐spinning of acrylic fibers

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AbstractAn extensive study of spinnability is presented for the formation of acrylic fibers by wet‐spinning. The system consisted of an acrylonitrile–vinyl acetate copolymer with dimethylacetamide as the solvent and water in most instances as the nonsolvent. The term spinnability is used here to denote the type of filament breakage that occurs in the spin bath near the spinnerette face as the withdrawal speed V1 is increased to some critical value. This maximum speed V1, m depends on essentially every spinning variable. Data are presented for a wide range of spinnerette hole diameters, flow rates per hole, coagulation rates, temperatures, and polymer concentration in the spinning solution. The freely extruded velocity of the filaments, Vf, is also given over the same range of variables. The free velocity is much less than the average velocity because of the Barus effect. Some similarities are noted in the response of V1, m and Vf to certain variables. In fact, V1, m seems to be determined by Vf. Through this observation the influence of the Barus effect on spinnability is easily seen. Spinnability is discussed also in terms of coagulation rates. It is concluded that both rheological and coagulation phenomena are important in the breakage mechanism. These observations are probably applicable in part to other wet‐spinning systems.