Abstract: An apparatus for making aromatic heterocyclic polymeric fibers having enhanced compressive strength is disclosed. Individual polymeric fibers, while being made according to otherwise conventional methods, are full twisted as they are drawn from a spinnerette hole so that their internal fibrils and microfibrils become entangled. The twisting is performed before coagulation of the fibers. The entangled fibrils and microfibrils are believed to provide mutual support to adjacent fibrils/microfibrils to resist buckling under compression.

Abstract: A method and apparatus for making aromatic heterocyclic polymeric fibers having enhanced compressive strength are disclosed. Individual polymeric fibers, while being made according to otherwise conventional methods, are full twisted as they are drawn from a spinnerette hole so that their internal fibrils and microfibrils become entangled. The twisting is performed before coagulation of the fibers. The entangled fibrils and microfibrils are believed to provide mutual support to adjacent fibrils/microfibrils to resist buckling under compression.

Abstract: Provided is a molecular composite comprising a rigid-rod aromatic heterocyclic polymer, a flexible, coil-like thermoplastic polymer and a thermosetting polymer.Also provided is a method for fabricating a molecular composite film or fiber which comprises the steps of forming a biphasic, stir opalescent solution of a rigid-rod aromatic heterocyclic polymer, a thermoplastic polymer, a thermosetting polymer and a solvent which is common to the three polymers, adding solvent to the solution until the solution becomes isotropic and stir opalescence has ceased to determine the critical concentration of polymers in the solvent, adding additional solvent to the solution so that the polymer concentration is below the critical concentration, extruding the solution into a non-solvent for the polymers to form the desired film or fiber, drying the film or fiber and hot drawing the film or fiber at a temperature above the Tg of the thermoplastic, but below the polymerization temperature (Tpoly) of the thermosetting resin.

Abstract: A process for fabricating rod-like aromatic heterocyclic polymer-reinforced composite materials into shaped articles which comprises the steps of:(a) dissolving a rigid-rod aromatic heterocyclic polymer and a flexible, coil-like thermoplastic polymer in a common solvent at a concentration less than the critical concentration point of the solution;(b) extruding the solution resulting from step (a) into a liquid bath for removing the solvent;(c) placing the extrudate from step (b), in the liquid-wet state, into a mold, and consolidating the extrudate in the mold to provide a molded article;(d) drying the molded article resulting from step (c); and(e) compression molding the article to provide a fully consolidated, solid article.

Abstract: Provided is a molecular composite comprising a rigid-rod aromatic heterocyclic polymer, a flexible, coil-like thermoplastic polymer and a thermosetting polymer.Also provided is a method for fabricating a molecular composite film or fiber which comprises the steps of forming a biphasic, stir opalescent solution of a rigid-rod aromatic heterocyclic polymer, a thermoplastic polymer, a thermosetting polymer and a solvent which is common to the three polymers, adding solvent to the solution until the solution becomes isotropic and stir opalescence has ceased to determine the critical concentration of polymers in the solvent, adding additional solvent to the solution so that the polymer concentration is below the critical concentration, extruding the solution into a non-solvent for the polymers to form the desired film or fiber, drying the film or fiber and hot drawing the film or fiber at a temperature above the Tg of the thermoplastic, but below the polymerization temperature (Tpoly) of the thermosetting resin.

Abstract: Polymeric molecular composites at the molecular level that are analogous to chopped fiber composite comprising reinforcing rigid rod heterocyclic polymer dispersed in a thermoplastic polymer matrix are disclosed. A process for the preparation thereof and laminates comprised of plies of these composites are also disclosed.

Abstract: Shaped articles are prepared from rigid rod heterocyclic liquid crystalline polymers. The articles are prepared by polymerizing the polymer in a reaction medium whereby a solution of the polymer is formed and by forming the articles directly from the polymer solution.

Abstract: A novel method is taught for preparing polymeric alloys composed of a mixture of an aromatic heterocyclic rod-like reinforcing polymer and an aromatic heterocyclic coil-like amorphous mixture with vastly improved mechanical properties.

Abstract: Para-ordered aromatic heterocyclic polymers characterized by having p-benzbisoxazole, p-benzbisthiozole or p-benzbisimidazole units and containing diphenoxybenzene structures. The diphenoxybenzene structures function as "swivels" in the polymer chains, imparting flexibility thereto and making it possible to cast strong films from solutions of the polymers.

Abstract: Rod-like aromatic heterocyclic polymers are used as reinforcement in coil-like heterocyclic polymer matrices to provide composites at the molecular level that are analogous to chopped fiber composites.

Abstract: Films and coatings are prepared from a dispersion of microscopic sheets of para ordered aromatic heterocyclic polymers by collecting the sheets from the dispersion either by filtration on a porous surface or by drawing a metal surface through the dispersion, and allowing the dispersion medium to evaporate. Upon drying the microscopic sheets coalesce to form the films or coatings. This procedure makes possible the fabrication of high quality, thermally stable films and coatings without the use of high temperature cures or other severe conditions.

Abstract: An improved process is provided for the precipitation of a polymer from a solution to form a particulate polymeric material exhibiting an unusually high surface area, i.e. having a surface area of at least 125 square meters per gram. A non-solvent for the polymer initially is added to the polymer solution until the solution is rendered turbid, a specified additional quantity of the non-solvent is added to the solution, and the resulting turbid solution is added to a major quantity of the non-solvent under conditions found capable of yielding the desired particulate polymeric material. High surface area particles of a BBB type polymeric material are formed in a preferred embodiment of the process. The resulting particles are rendered more readily compactable to form three-dimensional shaped articles, etc. because of their increased surface energy resulting from the large surface area.

Abstract: Normally intractable high temperature resistant polymers which lack plastic flow characteristics, such as polymers of the BBB type [i.e., poly(bisbenzimidazobenzophenanthroline) and related nitrogenous polymers], are rendered capable of undergoing facile molding to form three-dimensional shaped articles. A minor proportion of a cross-linkable additive polymer exhibiting a recognizable glass transition temperature below its decomposition temperature (e.g., a polybenzimidazole) or precursors capable of forming the same is incorporated in substantially uniform physical admixture with the normally intractable polymer, the admixture shaped to form a three-dimensional article, and the resulting article is heated until the additive polymer is cross-linked and the thermal stability of the article is enhanced.