Polyacrylonitrile composition admixed with low boiling acetonitrile fraction and high boiling compatible plasticizer

A polyacrylonitrile composition for melt extrusion consisting essentially of at least 50 weight percent of a high acrylonitrile polymer containing at least 85 percent polymerized units from acrylonitrile admixed with a plasticizing amount of a plasticizing system of about 40 to 70 weight percent low boiling acetonitrile fraction, said acetonitrile fraction consisting essentially of acetonitrile-water mixtures containing up to about 35 percent water and about 60 to 30 percent high boiling compatible plasticizer, said compatible plasticizer consisting essentially of a cyclic-organic ester containing from 3 to 5 carbon atoms and enabling continuous melt extrusion of coherent, undegraded shaped articles at a feed rate of at least 0.05 grams per minute per die orifice, said orifice having a transverse cross-sectional area of to about 0.005 square inch, at temperatures and pressures of about 75.degree. to 200.degree. C and 50 to 15,000 pounds per square inch guage, said shaped articles being characterized by an apparent melt viscosity of about 10.sup.4 to 10.sup.6 poise enabling a draw down of at least 105 to 500 percent during an uptake of at least 3 meters per minute.