Composite polymer solution of poly(M-phenylene isophthalamide) and copolymer made from 5(6)-amino-2-(P-aminophenyl)benzimidazole

A composite polymer solution suitable for extruding shaped articles, comprising a homogeneous mixture, in a solution comprising an amide solvent, of at least a first polymer and a second polymer;

• the first polymer having a structure derived from the reaction of one or more amine monomers and a plurality of acid monomers, wherein
• i) the one or more amine monomers being 100 mole percent 5(6)-amino-2-(p-aminophenyl) benzimidazole, or the combination of metaphenylene diamine and at least 60 mole percent 5(6)-amino-2-(p-aminophenyl)benzimidazole, based on the total amount of amine monomers;
• and
• ii) the plurality of acid monomers include those having a structure of
• Cl—CO—Ar1—CO—Cl and Cl—CO—Ar2—CO—Cl
• wherein Ar1 is an aromatic group having para-oriented linkages and Ar2 is an aromatic group having meta-oriented linkages, and wherein the plurality of acid monomers has at least 50 mole percent of the monomer containing aromatic group Ar2;
• and
• the second polymer having a structure derived from the reaction of metaphenylene diamine and isophthaloyl chloride;
• wherein the amide solvent is N-methyl pyrrolidone, dimethyl acetamide, or mixtures thereof;
• and
• wherein the mixture of first polymer and second polymer contains 25 to 80 weight percent of the first polymer, based on the total amount of first polymer and second polymer.