Production of stabilized non-burning acrylic fibers and films

A process for the production of stabilized acrylic fibers and films which are capable of undergoing carbonization comprising:

• a. providing a solution consisting essentially of (1) an acrylic polymer selected from the group consisting of an acrylonitrile homopolymer and acrylonitrile copolymers containing at least about 85 mol percent of acrylonitrile units and up to about 15 mol percent of one or more monovinyl units copolymerized therewith wherein the pendant nitrile groups present in said acrylic polymer are uncyclized, (2) about 1 to 10 percent by weight based upon the weight of said acrylic polymer of a stabilization promoting agent selected from the group consisting of hydrochloric acid, phosphoric acid, nitric acid, methane sulfonic acid, an aromatic sulfonic acid, and a carboxylic acid having a pK.sub.A value below about 4.5, and (3) a solvent for said acrylic polymer and said stabilization promoting agent selected from the group consisting of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, butyrolactone, and N-methyl-2-pyrrolidinone, with said acrylic polymer being present in said solution in a concentration of about 10 to 25 percent by weight based upon the weight of said solvent, and with any heating utilized during the formation of said solution being insufficient to produce cyclization of said pendant nitrile groups of said acrylic polymer,
• b. extruding said solution through a shaped orifice via solution spinning to form an acrylic fibrous material or film wherein the pendant nitrile groups present in said acrylic polymer remain uncyclized and have incorporated therein about 0.1 to 10 percent based upon the weight of said acrylic polymer of said stabilization promoting agent which was initially present in said solution of step (a), and
• c. heating said acrylic fibrous material or film having about 0.1 to 10 percent based upon the weight of said acrylic polymer of said stabilization promoting agent which was initially present in said solution of step (a) incorporated therein in an oxygen-containing atmosphere at a temperature of about 200.degree. to 350.degree. C. until a thermally stabilized fibrous material or film is formed which is black in appearance, non-burning when subjected to an ordinary match flame and which is capable of undergoing carbonization.