[St. Clair Anne K.(Poquoson,VA), Stoakley Diane M.(Poquoson,VA), St. Clair Terry L.(Poquoson,VA), Singh Jag J.(Yorktown,VA)] A product and the process for preparing the same to improve the moisture resistance properties of epoxidized TGMDA and DGEBA resin systems by chemically incorporating chromium (III) ions therein without impairing the mechanical strength properties of the resins.

[St. Clair Anne K.(Poquoson,VA), St. Clair Terry L.(Poquoson,VA), Pratt J. Richard(Poquoson,VA)] A high-temperature stable, optically transparent, low dielectric aromatic polyimide is prepared by chemically combining equimolar quantities of an aromatic dianhydride reactant and an aromatic diamine reactant, which are selected so that one reactant contains at least one Si(CH.sub.3).sub.2 group in its molecular structure, and the other reactant contains at least one --CH.sub.3 group in its molecular structure. The reactants are chemically combined in a solvent medium to form a solution of a high molecular weight polyamic acid, which is then converted to the corresponding polyimide.

[Gerber Margaret K.(Newport News,VA), St. Clair Terry L.(Poquoson,VA), Pratt J. Richard(Poquoson,VA), St. Clair Anne K.(Poquoson,VA)] High performance, thermooxidatively stable polyimides are prepared by reacting aromatic diamines with pendant trifluoromethyl groups and dianhydrides in an amide solvent to form a poly(amic acid), followed by cyclizing the poly(amic acid) to form the corresponding polyimide, which has the following general structure: ##STR1##

[St. Clair Anne K.(Poquoson,VA), St. Clair Terry L.(Poquoson,VA)] An aromatic condensation polyimide film that is approximately 90% transparent at 500 nm, useful for thermal protective coatings and the like, and the processes for preparing same by thermal and chemical conversion are disclosed. An essential feature of the invention for achieving maximum optical transparency films requires utilizing recrystallized and/or sublimated specific aromatic diamines and dianhydride monomers and introducing phenoxy or thiophenyl separator groups and isomeric m,m'- or o,p'-oriented diamines into the polymer molecular structure. The incorporation of these groups in the polymer structure serves to separate the chromaphoric centers and reduce the formation of inter-chain and intra-chain charge transfer complexes which normally cause absorptions in the UV-visible range. The films may be obtained by hand, brushing, casting or spraying a layer of the polyamic acid solutions onto a surface and thermally converting the applied layer to the polyimide or the polyamic acid solution can be chemically converted to the polyimide, subsequentially dissolved in an organic solvent, and applied as a polyimide film layer with the solvent therein thermally removed.

[St. Clair Anne K.(Poquoson,VA), St. Clair Terry L.(Poquoson,VA)] An aromatic condensation polyimide film that is approximately 90% transparent at 500 nm, useful for thermal protective coatings and the like and the process for preparing same are disclosed. An essential feature of the invention for achieving maximum optical transparency films requires utilizing recrystallized and/or sublimated specific aromatic diamines and dianhydride monomers and introducing bulky electron-withdrawing groups and separator groups into the polymer molecular structure. The incorporation of bulky electron-withdrawing groups in the diamine portion of the polymer structure serves to reduce the formation of inter-chain and intra-chain charge transfer complexes which normally cause large absorptions in the UV-visible range. Incorporation of separator atoms into either the diamine or dianhydride monomers serves to reduce the amount of conjugation and inter-and intra-chain electronic interactions and thereby lessen charge transfer complex formation.

[St. Clair Anne K.(Poquoson,VA), St. Clair Terry L.(Poquoson,VA)] A rubber-toughened addition-type polyimide composition having excellent high temperature bonding characteristics in the fully cured state and improved peel strength and adhesive fracture resistance physical property characteristics is disclosed. The process for making the improved adhesive involves preparing the rubber-containing amic acid prepolymer by chemically reacting an amine-terminated elastomer and an aromatic diamine with an aromatic dianhydride with which a reactive chain stopper anhydride has been mixed, and utilizing solvent or mixture of solvents for the reaction.

[St. Clair Anna K.(Poquoson,VA), St. Clair Terry L.(Poquoson,VA)] The diamine, 1,3-diamino-5-pentafluorosulfanylbenzene (DASP), was reacted with various dianhydrides to form polyimides containing an SF.sub.5 moiety. These polyimides exhibit high glass transition temperatures, high density, low solubility, and low dielectric properties. These polymers were used to prepare semi-permeable membranes, wire coatings, and films and are useful for electronic, space and piezoelectric applications.

[Frosch Robert A. Administrator of the National Aeronautics and Space( Administration, with respect to an invention of,Poquoson), St. Clair Anne K.(Poquoson,VA), Taylor Larry T.(Blacksburg,VA), St. Clair Terry L.(Poquoson,VA)] A method for preparing an aluminum ion-filled polyimide adhesive wherein a meta-oriented aromatic diamine is reacted with an aromatic dianhydride and an aluminum compound in the presence of a water or lower alkanol miscible ether solvent to produce an intermediate polyamic acid; and thereafter converting the polyamic acid to the thermally stable, metal ion-filled polyimide by heating in the temperature range of 300.degree. C. to produce a flexible, high temperature adhesive.

[St. Clair Anne K.(Poquoson,VA), St. Clair Terry L.(Poquoson,VA)] High temperature polyimide film laminates and a process for fabricating large-area, void-free polyimide laminate structures wherein multiple-ply polyimide film laminates may be constructed without decreasing the individual film strength and wherein layers of metal foil may be laminated between polyimide film layers to yield a flexible high temperature resistant structure having capabilities for use as flexible electric circuits, in aerospace applications, and the like.

[St. Clair Anne K.(Poquoson,VA), St. Clair Terry L.(Poquoson,VA), Winfree William P.(Williamsburg,VA)] A structure which is effective as an electrical insulator or as a transmitter-receiver of electromagnetic energy is prepared by providing a suitable substrate and covering the substrate with an adhering layer of a low dielectric, high temperature, linear aromatic polyimide. This polyimide is prepared by: (1) selecting aromatic diamine and aromatic dianhydride reactants to meet at least two of the following three conditions: (a) a reactant must have minimal permanent or inducible electrical dipolar characteristics as a result of the presence of pendant or bridging groups therein; (b) a reactant must impart a high degree of free volume to the polymer caused by inefficient chain packing therein in the solid state as a result of the presence of pendant or bridging groups therein; and (c) a reactant must have fluorine atoms chemically attached thereto; and (2) chemically combining equimolar quantities of the aromatic diamine and aromatic dianhydride reactants in a solvent to form a high molecular weight polyamic acid solution, and converting the high molecular weight polyamic acid to the corresponding low dielectric, high temperature linear aromatic polyimide.