Abstract: A method for forming a homogeneous, concentrated, prepolymer composition, and a method of using the concentrated prepolymer composition to uniformly coat fibers is described. The prepolymer mixture is formed by dissolving a dialkyl, trialkyl, or tetraalkylester of biphenyltetracarboxylic acid in a solvent comprising ethyl acetate and methanol in a molar ratio of from about 1:3 to about 1:60, to form an ester solution. Diamine and end cap compound are added to the ester solution to form a monomer mixture solution. The end cap compound is a divalent compound characterized by (i) at least one unsaturated moiety, (ii) capable of reacting with the diamine or the ester to form an end cap radical that precludes further reaction of the diamine with the ester, and (iii) capable of undergoing addition polymerization. A portion of the solvent is evaporated from the monomer solution to form the substantially homogeneous, concentrated, prepolymer composition.

Abstract: A method for forming a homogeneous, concentrated, prepolymer composition, and a method of using the concentrated prepolymer composition to uniformly coat fibers is described. The prepolymer mixture is formed by dissolving a dialkyl, trialkyl, or tetraalkylester of biphenyltetracarboxylic acid in a solvent comprising ethyl acetate and methanol in a molar ratio of from about 1:3 to about 1:60, to form an ester solution. Diamine and end cap compound are added to the ester solution to form a monomer mixture solution. The end cap compound is a divalent compound characterized by (i) at least one unsaturated moiety, (ii) capable of reacting with the diamine or the ester to form an end cap radical that precludes further reaction of the diamine with the ester, and (iii) capable of undergoing addition polymerization. A portion of the solvent is evaporated from the monomer solution to form the substantially homogeneous, concentrated, prepolymer composition.

Abstract: A method for forming a homogeneous, concentrated, prepolymer composition, and a method of using the concentrated prepolymer composition to uniformly coat fibers is described. The prepolymer mixture is formed by dissolving a dialkyl, trialkyl, or tetraalkylester of biphenyltetracarboxylic acid in a solvent comprising ethyl acetate and methanol in a molar ratio of from about 1:3 to about 1:60, to form an ester solution. Diamine and end cap compound are added to the ester solution to form a monomer mixture solution. The end cap compound is a divalent compound characterized by (i) at least one unsaturated moiety, (ii) capable of reacting with the diamine or the ester to form an end cap radical that precludes further reaction of the diamine with the ester, and (iii) capable of undergoing addition polymerization. A portion of the solvent is evaporated from the monomer solution to form the substantially homogeneous, concentrated, prepolymer composition.

Abstract: Polyimide resins useful at high temperatures are prepared from:(a) a dialkyl, trialkyl or tetraalkylester of biphenyltetracarboxylic acid;(b) phenylenediamine, preferably the phenylenediamine comprises a mixture of meta-and para-phenylenediamine; and(c) a divalent end cap compound that is capable of undergoing addition polymerization.

Abstract: Polyimides having a high thermal and oxidative stability are prepared by reacting a mixture of monomers comprising (a) a dialkyl, trialkyl, or tetraalkylester of an aromatic tetracarboxylic acid, (b) an aromatic diamine, and (c) an end cap compound. The ratio of (a), (b), and (c) is chosen so that upon heating the mixtures, low molecular weight prepolymers are formed, the prepolymers having only one end cap radical and being suitable for chain extension and crosslinking to form high molecular weight, thermally stable polyimides. Upon heating, the prepolymers form polyimide resins, which can have T.sub.g in excess of 600.degree. F. and superior physical properties.

Abstract: Polyimides having a high thermal and oxidative stability are prepared by reacting a mixture of monomers comprising (a) a dialkyl, trialkyl, or tetraalkylester of an aromatic tetracarboxylic acid, (b) an aromatic diamine, and (c) an end cap compound. The ratio of (a), (b), and (c) is chosen so that upon heating the mixtures, low molecular weight prepolymers are formed, the prepolymers having only one end cap radical and being suitable for chain extension and crosslinking to form high molecular weight, thermally stable polyimides. Upon heating, the prepolymers form polyimide resins, which can have T.sub.g in excess of 600.degree. F. and superior physical properties.

Abstract: Polyimides having a high thermal and oxidative stability are prepared by reacting a mixture of monomers comprising (a) a dialkyl, trialkyl, or teThis invention was made with Government support under F33615-88-C-5409 awarded by the Department of the Air force. The Government has certain rights in this invention.

Abstract: Polyimides having a high thermal and oxidative stability are prepared by reacting a mixture of monomers comprising (a) a dialkyl, trialkyl, or tetraalkylester of an aromatic tetracarboxylic acid, (b) an aromatic diamine, and (c) an end cap compound. The ratio of (a), (b), and (c) is chosen so that upon heating the mixtures, low molecular weight prepolymers are formed, the prepolymers having only one end cap radical and being suitable for chain extension and crosslinking to form high molecular weight, thermally stable polyimides. Upon heating, the prepolymers form polyimide resins, which can have T.sub.g in excess of 600.degree. F. and superior physical properties.

Abstract: A curing agent for a polyepoxide has the formula: ##STR1## wherein R.sub.1 is a divalent aryl radical such as phenylene and wherein R.sub.2 is a tetravalent aryl radical such as a tetravalent benzene radical. An epoxide is cured by admixture with the curing agent. The cured epoxy product retains the usual properties of cured epoxides and, in addition, has a high char residue after burning, on the order of 45% by weight. The high char residue is of value in preventing release to the atmosphere of carbon fibers from carbon fiber-epoxy resin composites in the event of burning of the composite.

Abstract: A composition for making polyimide resin-reinforced fibers or fabric. The composition is of the type disclosed in U.S. Pat. No. 3,745,149 and includes a polyfunctional ester, a polyfunctional amine, and an end-capping agent. The composition is impregnated into fibers or fabric and heated to form prepreg material. The tack retention characteristics of this prepreg material are improved by incorporating into the composition a liquid olefinic material compatible with the other ingredients of the composition. The prepreg material is heated at a higher temperature to effect formation of the polyimide resin and the monomeric additive is incorporated in the polyimide polymer structure.