Blends of polybenzimidazoles and aromatic polyamides, aromatic

Abstract

A novel miscible blend of component polymers comprised of from about 5 weight percent to about 95 weight percent of a polybenzimidazole and from about 95 weight percent to about 5 weight percent of an aromatic polyamide, aromatic polyamide-hydrazide or aromatic polyamide containing heterocyclic linkages. Miscibility of the component polymers of the blend is indicated by infrared, X-Ray and Differential Scanning Calorimetry analyses and scanning electron photomicrographs. In a film or molded article of a blend mostly comprised of a polybenzimidazole, it is preferred that the aromatic polyamide, aromatic polyamide-hydrazide or aromatic polyamide containing heterocyclic linkages be present in the blend in an amount sufficient to result in a blend with improved tensile properties compared to the polybenzimidazole and that is more thermally processable than the polybenzimidazole. In a blend mostly comprised of an aromatic polyamide, aromatic polyamide-hydrazide or aromatic polyamide containing heterocyclic linkages, it is preferred that the polybenzimidazole be present in the blend in an amount sufficient to result in a blend with increased thermal stability and nonflammability compared to the aromatic polyamide, aromatic polyamide-hydrazide or aromatic polyamide containing heterocyclic linkages. The blends, particularly in the form of films or molded articles, may be post-treated with heat or sulfonating agent in order to minimize their shrinkage when subsequently subjected to heat and in order to increase their resistance to solvents and acids.