Preparation and properties of imide/Pyrrone copolymers
Preparation and properties of imide pyrrone copolymers
Bell, V. L.↗
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The development of autoclave processable, thermally stable adhesives for titanium alloy and graphite composite structures
The A-type polyimide adhesive resin P11B was modified by use of mixed diamines (thio-dianiline and meta phenylene diamine) which provided the desired autoclave processability. This new resin was termed P11BA. It was shown that copolymeric blends of P11BA and Amoco AI-1137 amide-imide resin provided improved adhesive properties when autoclave processed over the properties obtained previously by press bonding with P11B based copolymeric blended adhesives. Properties of bonded assemblies are presented for long-term aging at both elevated and low temperatures, and also stress-rupture tests at elevated temperature.
Vaughan, R. W.↗
Polyimidazopyrrolone model compounds.
Study of model reactions between phthalic anhydride and o-phenylenediamine under conditions analogous to the polymerization and post cyclization of dianhydrides with bis(o-diamines) to form polyimidazopyrrolones (Pyrrones). Solid-state thermal conversion of the amide-acid-amine affords a unique dimeric species containing amide, imide, and benzimidazole functions. It was confirmed that melt techniques lead to disproportionation products. The application of these findings to related polymer syntheses is discussed.
Young, P. R.↗
Solid state polymerization and crystallography of polyimide precursors
Although the production of crystallinity in a polymeric system has historically led to commerically useful properties, the polyimides, prized for their high temperature characteristics, as customarily synthesized by melt or solution casting, are amorphous. It is shown that polymide containing residual crystallinity can be synthesized by isothermal annealing of crystals of the salt of the diisopropyl ester of pyromellitic acid and phenylene diamine. The reaction is topochemical in that the geometry of the polymer product is dependent upon that of the crystalline precursor. Infrared spectroscopy reveals the presence of imide absorption in the polymer, while powder diffractometry suggests residual crystallinity. Single crystal X-ray analysis of the monomer yields a structure of chains of alternating acid and base suggesting that the monomer is amenable to polymerization with a minimum of geometrical disruption.
Wakelyn, N. T.↗
The hydrolysis of polyimides
Thermal polymerization of aspartic acid produces a polysuccinimide (I), a chain of aspartoyl residues. An investigation was made of the alkaline hydrolysis of the imide rings of (I) which converts the polyimide to a polypeptide. The alkaline hydrolysis of polyimides can be expected to be kinetically complex due to increasing negative charge generated by carboxylate groups. For this reason, a diimide, phthaloyl-DL-aspartoyl-beta-alanine (IIA) was synthesized for a progressive study of the hydrolysis of polyimides. In addition, this diimide (IIA) can be related to thalidomide and might be expected to exhibit similar reactivity during hydrolysis of the phthalimide ring.
Hoagland, P. D.↗
Isomer effects on polyimide properties
The effect of structure variation on the solubility and glass-transition temperature of polyimide polymers is investigated. The addition of alkyl substituents to an aromatic ring in the polymer molecule, the reduction in the number of imide rings per average polymer chain-length, and a variation in the symmetry of the polymer molecule are studied. The synthesis of key intermediates for the preparation of the monomers required in this investigation is reported along with progress made in the synthesis of polyimide-precursor amines that contain functional groups to allow for post-cure cross-linking.
Stump, B. L.↗
Novel aminobenzyl and imidobenzyl benzenes
Compounds are useful as intermediates for several classes of polymers. Amines can function as cross-linking agents for epoxide and urethane polymers, as well as intermediates for synthesis of thermally-stable addition-type polyimides. Imide derivatives can be obtained by reacting amines with certain monoanhydrides containing olefinic unsaturation.
Bell, V. L.↗
Trimerization of aromatic nitriles
Triazine compounds and cross-linked polymer compositions were made by heating aromatic nitriles to a temperature in the range of about 100 C to about 700 C, in the presence of a catalyst or mixture of catalysts. Aromatic nitrile-modified (terminated and/or appended) imide, benzimidazole, imidazopyrrolone, quinoxaline, and other condensation type prepolymers or their precopolymers were made which were trimerized with or without a filler by the aforementioned catalytic trimerization process.
Hsu, L. C.↗
Isomer effects on polyimide properties
Thermally stable polyimide polymers were prepared. Parameters explored include asymmetry of substitution, addition of alkyl substituents to an aromatic ring, and an increase in the number of aromatic rings present in the diamine monomer. It is shown that the use of an asymmetrical diamine in the preparation of a polyimide produces a polymer with a markedly lowered glass transition temperature. This is achieved with little or no sacrifice of thermal stability. An alternate approach taken was to prepare imide monomers which are capable of addition-type polymerization.
Stump, B. L.↗
Feasibility demonstration for electroplating ultra-thin polyimide film
The effect of electrodeposition variables on film thickness was investigated using a dilute polyimide solution as a bath into which aluminum (as foil or as a vapor deposited coating) was immersed. The electrodeposited film was dried for 2 hours at 93 C (primarily to remove solvent) and cured for 18 hours at 186 C. Infrared studies indicate that imide formation (curing) occurs at 149 C under vacuum. From a conceptual viewpoint, satisfactory film metallized on one side can be obtained by this method. The cured ultra thin polyimide film exhibits properties equivalent to those of commercial film, and the surface appearance of the strippable polyimide film compares favorably with that of a sample of commercial film of thicker gauge. The feasibility of manufacturing approximately one million sq m of ultra thin film capable of being joined to fabricate an 800 m by 9 800 m square from starting material 0.5 to 1 m wide for space erectable structures was demonstrated.
Schneier, R.↗
Toxicity of pyrolysis gases from some cellular polymers
Various samples of cellular polymers were evaluated for toxicity of pyrolysis gases, using the screening test method developed at the University of San Francisco. The cellular polymer samples included polyimide, polymethacrylimide, polybismaleimide, polyurethane, polyisocyanurate, polyethylene, polychloroprene, polyvinyl chloride, polystyrene, polysiloxane, and polyphosphazene. The cellular polymers exhibited varying levels of toxicity under these test conditions. Among the rigid cellular polymers, times to death were shortest with the imide type foams and longest with polyvinyl chloride and polystyrene. Among the flexible cellular polymers, times to death were shortest with polyimide and polyester, and longest with polychloroprene and polysiloxane. Increased char yield was not necessarily associated with reduced toxicity.
Hilado, C. J.↗
Stability of PMR-polyimide monomer solutions
The stability of alcohol solutions of norborneyl capped PMR-polyimide resins was monitored during storage at ambient and subambient temperatures. Chemical changes during storage were determined spectroscopically using nuclear magnetic resonance. Resin processability and cured resin quality were determined by fabrication of unidirectional, graphite fiber composites using aged solutions and testing of selected composite properties. PMR-15 solutions exhibit nominally two weeks of useful life and PMR-2 solutions exhibit nominally two days of useful life at ambient conditions. The limiting factor is precipitation of imide reaction produces from the monomer solutions. Both solutions exhibit substantially longer useful lifetimes in subambient storage. PMR-15 shows no precipitation after several months storage at subambient temperatures. PMR-2 solutions do exhibit precipitates after extended subambient storage, however, the precipitates formed under these conditions can be redissolved. The chemical implications of these observations are discussed.
Lauver, R. W.↗
Synthesis of improved moisture resistant polymers
The use of difluoromaleimide-capped prepolymers to provide improved moisture resistant polymers was investigated. Six different prepolymer formulations were prepared by two different methods. One method utilized the PMR approach to polyimides and the second method employed the normal condensation route to provide fully imidized prepolymers. Polymer specimens cured at 450 F exhibited adequate long-term stability in air at 400 F. Moisture absorption studies were conducted on one polymer formulation. Neat Polymer specimens exhibited weight gains of up to 2% (w/w) after exposure to 100% relative humidity at 344K (160 F) for 400 hours.
Orell, M. K.↗
Synthesis of improved moisture resistant polymers
The synthesis and characterization of novel moisture resistant aliphatic polyimides are described. Several novel aliphatic imides of diversified functionalities were synthesized, purified, and characterized, they include: (1) N-(12-aminododecyl)-5-norbornene-2,3-dicarboximide; (2) N,N'-2,2,2-trifluoro-1-(trifluoromethyl)ethylidene bis (1,3-dioxo-5,2-iosoindolinediyl)dodecamethylene di-5-norbornene-2,3-dicarboximide; (3) N,N'-dodecamethylenedi-5-nobornene-2,3-dicarbonoximide; (4) N,N'-dodecamethylenebis 5,6-epoxy-2,3-norbornanedicarboximide ; and (5) N,N'-Bis 12-(5-norbornene-2, 3-dicarboximidido)dodecyl - 1,2,3,4- butanetetracarboxylic 1,2:3,4-diimide. The structures of these compounds were established by elemental analysis, IR, NMR, and mass spectra.
Scola, D. A.↗
Catalytic trimerization of aromatic nitriles and triaryl-s-triazine ring cross-linked high temperature resistant polymers and copolymers made thereby
Triazine compounds and cross-linked polymer compositions are made by heating aromatic nitriles to a temperature in the range of from about 100 C to about 700 C, and preferably in the range of from about 200 C to about 350 C, in the presence of a catalyst or mixture of catalysts selected from one or more of the following groups: (1) organic sulfonic and sulfinic acids, (2) organic phosphonic and phosphinic acids, and (3)metallic acetylacetonates, at a pressure in the range of from about atmospheric pressure to about 10,000 psi and preferably in the range of from about 200 psi to about 750 psi. Aromatic nitrile-modified (terminated and/or appended) imide, benzimidazole, imidazopyrrolone, quinoxaline, and other condensation type prepolymers or their precopolymers are made which are trimerized with or without a filler by the aforementioned catalytic trimerization process into triaryl-s-triazine ring containing or cross-linked polymeric or copolymeric products useful in applications requiring high thermal-oxidative stability and high performance structural properties at elevated temperatures.
Hsu, L. C.↗
Stability of PMR-polyimide monomer solutions
The stability of alcohol solutions of norbornenyl capped PMR-polyimide resins (both PMR-15 and PMR-II) has been monitored during storage at ambient and subambient (5 C and -18 C) temperatures. PMR-15 solutions exhibit nominally two weeks of useful life and PMR-II solutions exhibit nominally two days of useful life at ambient conditions. The limiting factor is precipitation of imide reaction products from the monomer solutions. Both solutions exhibit substantially longer useful lifetimes in subambient storage. PMR-15 shows no precipitation after several months storage at subambient temperatures. PMR-II solutions do exhibit precipitates after extended subambient storage (nominally three months at -18 C), however, the precipitates formed under these conditions can be redissolved. The chemical implications of these observations are discussed.
Lauver, R. W.↗
Electrically conductive palladium-containing polyimide films
Palladium addition makes light, flexible film with low resistivity to relieve space charging. Polyimide film is prepared in four steps: preparation of polyamic acid in polar solvent; addition of soluable palladium complex salt; fabrication of film of "palladium polyamic acid" solution; and thermal imidization of film to palladium-containing polyimide by 300 C heating. Lowered resistivities were achieved without loss in film flexibility or increase in film weight.
St.clair, A. K.↗
High char yield epoxy curing agents
Class of imide-amine curing agents preserves structural integrity, prevents fiber release, and is fully compatible with conventional epoxy resins; agents do not detract from composite properties while greatly reducing char yield. Materials utilizing curing are used in aerospace, automotive, and other structural components where deterioration must be minimized and fiber release avoided in event of fire.
Delvigs, P.↗