Abstract: The invention relates to ultrasonic contrast agents composed of microparticles which contain a gas and polyamino-dicarboxylic acid-co-imide derivatives, to processes for their preparation and to their use as diagnostic and therapeutic agents.

Abstract: A method of forming complex polyimide foam shapes by impregnating a low density, open cell, reticulated form with polymide foam precursor, placing the combination in a mold, closing the mold, then heating the assembly to the foaming and curing temperatures of the precursor. As the powdered precursor expands, it spreads throughout the reticulated foam producing a product having substantially uniform density and polyimide foam characteristics. If desired, the reticulated foam can be removed from the product by using a material that outgasses and boils away at polyimide processing temperatures. Radar absorbing materials may be incorporated in the reticulated foam so that the final product will have uniformly distributed radar absorbing components with the desirable high temperature resistance and other properties of polyimide foams.

Abstract: A slurry is produced by adding to a polyimide precursor comprising carboxylic and diamine components at least one foam-enhancing polar, protic additive of the formula ROH, where R is hydrogen, or C.sub.1 to C.sub.12 linear or branched alkyl or cycloalkyl, affording a slurry. The slurry is then brought to a temperature in the range of about 40.degree. C. to about 105.degree. C., producing a homogeneous, transparent solution, opaque suspension, or melt. When heated to a higher temperature the melt foams and cures.

Abstract: Polyimide foam of desired density is produced by adding to a polyimide precursor comprising carboxylic and diamine components at least one foam-enhancing polar, protic additive of the formula ROH, where R is hydrogen, or C.sub.1 to C.sub.12 linear or branched alkyl or cycloalkyl, unsubstituted or substituted with halo, aryl, alkoxy or hydroxy, and heating the resultant slurry to a temperature that does not exceed about 105.degree. C. to form a homogeneous melt. When heated to a higher temperature the melt foams and cures. The density of the foam is affected by the amount of foam-enhancing additive which is utilized.

Abstract: Polyimide foam of desired density is produced by adding to a polyimide precursor comprising carboxylic and diamine components at least one foam-enhancing polar, protic additive of the formula ROH, where R is hydrogen, or C.sub.1 to C.sub.12 linear or branched alkyl or cycloalkyl, unsubstituted or substituted with halo, aryl, alkoxy or hydroxy, and heating the resultant slurry to a temperature that does not exceed about 105.degree. C. to form a homogeneous melt. When heated to a higher temperature the melt foams and cures. The density of the foam is affected by the amount of foam-enhancing additive which is utilized.

Abstract: A flavored synthetic monofilament useful for fishing is prepared by incorporating a flavoring agent throughout the mass of the monofilament. The monofilament can be either a homopolyamide or copolyamide having a breaking strength of at least 50 kg/mm.sup.2 for diameters less than or equal to 70/100 mm, of at least 30 kg/mm.sup.2 for diameters greater than 70/100 mm and less than or equal to 200/100 mm, and of at least 20 kg/mm.sup.2 for diameters greater than 200/100 mm and less than or equal to 300/100 mm and having a capacity to shrink in boiling water of greater than 1%.

Abstract: Described are ways of improving the yields of specification grade polyimide foam on a consistent basis from one run to the next, by use of improved microwave-based foaming processes. In one such process, prior to the application of the microwave radiation, the body of polyimide precursor is compressed at a pressure that will reduce the bulk volume of the precursor and heated to a temperature below that at which any substantial foaming occurs. to accomplish the foaming, one further embodiment of the invention employs microwave radiation directed upon the top, sides and ends of the body of above-treated polyimide precursor and of the foam structure as it is developing maintaining the developing foam under a substantially vapor-impermeable microwave compatible shroud. The extent to which the microwave radiation impinges upwardly into the bottom of said body and said foam structure is curtailed, preferably by means of a metallic shield located below the precursor and developing foam structure.

Abstract: A method of improving the flame resistance of foams, such as open cell polyimide foams, through the introduction of finely divided non-metallic inorganic particles which are gel forming and insoluble in water and polar organic liquids into the foam cells. A stable liquid suspension or gel, preferably aqueous is prepared using these particles. An opacifier such as finely divided titanium dioxide or tin oxide may also be added. An open cell foam product is placed in the gel until the cells fill with the gel. Excess gel is removed and the foam is dried, leaving the particles trapped in the cells. If desired, the foam may be post treated, such as by compression at the stabilizing temperature, resulting in a densified foam which further mechanically traps the particles and further improves the flame resistance.

Abstract: Expanded material obtained by heating a composition comprising at least one hermosetting nadimide resin, said heating being performed at a temperature and during a period which are sufficient to cause the expansion of said composition by release of cyclopentadiene. A nadimide resin of the polyimide type and having a number average molecular weight of 600 to 10,000 is preferably used. The composition further comprises preferably 1% to 50% by weight of a linear, preferably thermostable polymer.

Abstract: A low density, open cell polymeric body is formed by coating or filling a reticulated polymeric foam with a liquid-form polymer which is resistant to high temperatures, curing the liquid form polymer in and on the foam and then removing the foam skeleton by dissolving and leaching the foam out of the solid polymeric body which remains.

Abstract: Moldable shrunken foam beads comprising a foamable thermoplastic polymer, preferably a silane-crosslinked polyolefin foam, are produced by mixing a composition comprising a silane-modified polyolefin (such as a silane-grafted polyethylene) and a silanol condensation catalyst in an extruder to produce a melt, then projecting a blowing agent into the melt at a rate effective to produce a desired foam density in the extrudate; extruding and cutting the melt to form foam beads; allowing the beads to shrink; and exposing the foam beads to moisture to produce silane crosslinking of the polyolefin foam. In certain other embodiments the crosslinking of the thermoplastic polymer can be omitted, and/or shrinkage of the beads produced by vacuum treatment.

Abstract: A method of improving the flame resistance of foams, such as open cell polyimide foams, through the introduction of finely divided non-metallic inorganic particles which are gel forming and insoluble in water and polar organic liquids into the foam cells. A stable liquid suspension or gel, preferably aqueous is prepared using these particles. An opacifier such as finely divided titanium dioxide or tin oxide may also be added. An open cell foam product is placed in the gel until the cells fill with the gel. Excess gel is removed and the foam is dried, leaving the particles trapped in the cells. If desired, the foam may be post treated, such as by compression at the stabilizing temperature, resulting in a densified foam which further mechanically traps the particles and further improves the flame resistance.

Abstract: A method of improving the flame resistance of foams, such as open cell polyimide foams, through the introduction of finely divided metal oxide particles into the foam cells. A stable water suspension or gel is prepared using particles of metal oxides, such as aluminum oxide and silicon dioxide. An opacifier such as titanium dioxide may also be added. An open cell foam product is placed in the gel until the cells fill with the gel. Excess gel is removed and the foam is dried, leaving the metal oxide particles trapped in the cells. If desired, the foam may be post treated, such as by compression at the stabilizing temperature, resulting in a densified foam which further mechanically traps the particles.

Abstract: By compressing and heat curing a non-resilient, non-flexible recurable material formed by subjecting cured polyimide foam to the action of pressurized steam, a wide variety of useful articles may be produced. These include tough, flame-resistant plastic films, sheets, panels, boards, and shapes in general; composites (both reinforced and unreinforced); and laminates and other articles in which separate shapes or parts are bonded together by a new type of tough, flame-resistant adhesive. Additionally, heretofore worthless products such as the kerf cut away from buns of polyimide foam during the foam manufacturing process can be converted and vastly upgraded into any of such an array of new articles of manufacture such as those just mentioned.

Abstract: Foamed thermoplastic blends of Nylon 6,I/T and polycarbonate resin are provided which exhibit good chemical resistance. The foamed blends are useful for making foamed articles such as chemically resistant foamed sheet.

Abstract: A hole repair method and composition suitable for mufflers, and engine exhaust systems, and any situation where high temperature resistance is needed. A putty like mass of polyimide resin and from 28% to 35% of low boiling alcohol is used to fill the hole, then foamed by heating into a mechanically seated and adherent plug which is high temperature resistant and securely in place.

Abstract: A method of improving the flame resistance of foams, such as open cell polyimide foams, through the introduction of finely divided metal oxide particles into the foam cells. A stable water suspension or gel is prepared using particles of metal oxides, such as aluminum oxide and silicon dioxide. An opacifier such as titanium dioxide may also be added. An open cell foam product is placed in the gel until the cells fill with the gel. Excess gel is removed and the foam is dried, leaving the metal oxide particles trapped in the cells. If desired, the foam may be post treated, such as by compression at the stabilizing temperature, resulting in a densified foam which further mechanically traps the particles.

Abstract: A method of manufacturing lightweight shapes from polyimide foam in which density discontinuities such as cavities, varying cell size, or swirl marks are substantially eliminated. A block or bun of polyimide foam is prepared in a conventional manner which results in a high density rind and other discontinuities. The foam is chopped into fine flakes in a chopper with a continuous flow of air to prevent electrostatic attachment of the flakes to the chopper and ducting. The flakes are mixed with a quantity of polyimide precursor and then heated to cause the precursor to bond the flakes into a uniform mass having highly uniform and predictable density. This is a very economical process since portions of the original bun may be used which would ordinarily be discarded. An alternative method is described whereby the flakes can be bonded together by using the precursor in the form of a partially cured foam either as a binder, or by making the flakes of partially cured foam.

Abstract: A method of manufacturing lightweight shapes from polyimide foam in which density discontinuities such as cavities, varying cell size, or swirl marks are substantially eliminated. A block or bun of polyimide foam is prepared in a conventional manner which results in a high density rind and other discontinuities. The foam is chopped into fine flakes in a chopper with a continuous flow of air to prevent electrostatic attachment of the flakes to the chopper and ducting. The flakes are mixed with a quantity of polyimide precursor and then heated to cause the precursor to bond the flakes into a uniform mass having highly uniform and predictable density. This is a very economical process since portions of the original bun may be used which would ordinarily be discarded. An alternative method is described whereby the flakes can be bonded together by using the precursor in the form of a partially cured foam either as a binder, or by making the flakes of partially cured foam.

Abstract: Thermoplastic polyimide foams are provided which essentially consist of recurring units represented by the formula (I): ##STR1## wherein X is a bond, divalent hydrocarbon radical having from 1 to 10 carbon atoms etc. and R is an aliphatic radical having 2 or more carbon atoms, cycloaliphatic radical etc.The foams have an apparent density of from 0.02 to 0.2 g/cc, average cell diameter of 0.1 to 1 mm and a closed cell content of 50% or more.

Abstract: A method of making thermal insulating products comprising porous, lightweight, high temperature resistant inorganic particles in a polyimide foam matrix and the product thereof. A polyimide precursor powdered is mixed with about equal weight of flake-like porous inorganic particles to substantially uniformly coat the particles with powder. The mixture is placed in a mold and compressed slightly. The assembly is heated to the foaming temperature of the polyimide precursor for a period suitable to produce uniform foaming. Then the temperature is raised to the curing and crosslinking temperature of the precursor for a time period sufficient to produce complete cure. A high temperature and flame resistant, light weight, highly insulating product results. If desired, protective sheets of material may be bonded to selected product surfaces during or after the molding operation.

Abstract: A method of improving the flame resistance of foams, such as open cell polyimide foams, through the introduction of finely divided non-metallic inorganic particles which are gel forming and insoluble in water and polar organic liquids into the foam cells. A stable liquid suspension or gel, preferably aqueous is prepared using these particles. An opacifier such as finely divided titanium dioxide or tin oxide may also be added. An open cell foam product is placed in the gel until the cells fill with the gel. Excess gel is removed and the foam is dried, leaving the particles trapped in the cells. If desired, the foam may be post treated, such as by compression at the stabilizing temperature, resulting in a densified foam which further mechanically traps the particles and further improves the flame resistance.

Abstract: Described are flexible polyimide foams having enhanced compression characteristics and softness for use in the manufacture of seat cushions and methods for the production of such foams and precursors therefor. These foams are produced from novel polyimides prepared by reaction of at least one aromatic or heterocyclic primary diamine with a mixture of at least two organic tetracarboxylic acids or derivatives thereof, at least one of which is from 1 to 40 mol percent of a 2-(vicinal-dicarboxycyclohexenyl)succinic acid or derivative thereof and a second of which is an aromatic tetracarboxylic acid or derivative thereof.

Abstract: Compound having the formula ##STR1## wherein X is the residue of a polyoxyalkylene diamine or triamine having an average equivalent weight of at least 500, after having deleted the two or three amine groups,n is two if X is a residue of a diamine and three if X is a residue of a triamine, andR is the residue of a cyclic anhydride of a polycarboxylic acid having at least four carboxyl groups, after having deleted one group ##STR2## prepolymers comprising such compounds and polyimide foams prepared from such compounds and prepolymers. The foams have good mechanical-, fire retardant- and smoke emission properties.

Abstract: A copolyimide foam comprising the reaction product of one or more of an aromatic tetracarboxylic acid and a compound of the formula: ##STR1## where x is an integer from 1 to 12 and R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are the same or different and are hydrogen or C.sub.1 to C.sub.6 linear or branched alkyl a mixture thereof with two or more diamines at least one of which being a heterocyclic diamine having a nitrogen atom in the ring and the other being a para- or meta-substituted aromatic diamine free of aliphatic substitution.Processes for producing the above copolyimide foam are also disclosed.

Abstract: Cured polyimide foam is exposed to an atmosphere of steam at elevated temperature and pressure for a period of time sufficient to convert the foam into a non-flexible, non-resilient recurable cellular material. Preferably the process is conducted such that the cellular material is recurable to a flexible resilient foam having tensile strength properties similar to the tensile strength properties of the original cured polyimide foam subjected to the process. Before recuring, the non-flexible, non-resilient recurable cellular material may be shaped or contoured, and then recured. For example, by impressing shaped articles into the recurable material followed by recuring, shipping/storage containers for the articles are readily produced.

Abstract: Cured polyimide foam is exposed to an atmosphere of steam at elevated temperature and pressure for a period of time sufficient to convert the foam into a non-flexible, non-resilient recurable cellular material. Preferably the process is conducted such that the cellular material is recurable to a flexible resilient foam having tensile strength properties similar to the tensile strength properties of the original cured polyimide foam subjected to the process. Before recuring, the non-flexible, non-resilient recurable cellular material may be shaped or contoured, and then recured. For example, by impressing shaped articles into the recurable material followed by recuring, shipping/storage containers for the articles are readily produced.

Abstract: A method of improving the flame resistance of foams, such as open cell polyimide foams, through the introduction of finely divided metal oxide particles into the foam cells. A stable water suspension or gel is prepared using particles of metal oxides, such as aluminum oxide and silicon dioxide. An opacifier such as titanium dioxide may also be added. An open cell foam product is placed in the gel until the cells fill with the gel. Excess gel is removed and the foam is dried, leaving the metal oxide particles trapped in the cells. If desired, the foam may be post treated, such as by compression at the stabilizing temperature, resulting in a densified foam which further mechanically traps the particles.

Abstract: A hole repair method and composition suitable for mufflers, and engine exhaust systems, and any situation where high temperature resistance is needed. A putty like mass of polyimide resin and from 28% to 35% of low boiling alcohol is used to fill the hole, then foamed by heating into a mechnically seated and adherent plug which is high temperature resistant and securely in place.

Abstract: A method of making thermal insulating products comprising porous, lightweight, high temperature resistant inorganic particles in a polyimide foam matrix and the product thereof. A polyimide precursor powdered is mixed with about equal weight of flake-like porous inorganic particles to substantially uniformly coat the particles with powder. The mixture is placed in a mold and compressed slightly. The assembly is heated to the foaming temperature of the polyimide precursor for a period suitable to produce uniform foaming. Then the temperature is raised to the curing and crosslinking temperature of the precursor for a time period sufficient to produce complete cure. A high temperature and flame resistant, light weight, highly insulating product results. If desired, protective sheets of material may be bonded to selected product surfaces during or after the molding operation.

Abstract: A method of manufacturing lightweight shapes from polyimide foam in which density discontinuities such as cavities, varying cell size, or swirl marks are substantially eliminated. A block or bun of polyimide foam is prepared in a conventional manner which results in a high density rind and other discontinuities. The foam is chopped into fine flakes in a chopper with a continuous flow of air to prevent electrostatic attachment of the flakes to the chopper and ducting. The flakes are mixed with a quantity of polyimide precursor and then heated to cause the precursor to bond the flakes into a uniform mass having highly uniform and predictable density. This is a very economical process since portions of the original bun may be used which would ordinarily be discarded. An alternative method is described whereby the flakes can be bonded together by using the precursor in the form of a partially cured foam either as a binder, or by making the flakes of partially cured foam.

Abstract: A method of making thermal insulating products comprising porous, lightweight, high temperature resistant inorganic particles in a polyimide foam matrix and the product thereof. A polyimide precursor powdered is mixed with about equal weight of flake-like porous inorganic particles to substantially uniformly coat the particles with powder. The mixture is placed in a mold and compressed slightly. The assembly is heated to the foaming temperature of the polyimide precursor for a period suitable to product uniform foaming. Then the temperature is raised to the curing and crosslinking temperature of the precursor for a time period sufficient to product complete cure. A high temperature and flame resistant, light weight, highly insulating product results. If desired, protective sheets of material may be bonded to selected product surfaces during or after the molding operation.

Abstract: A polyamide dyed with a reactive dye capable of absorbing incident light of the excitation waveband of a fluorophore or light of the emission waveband of the polyamide is provided for use in assays in which the presence or quantity of an analyte is being detected by fluorescence as a result of excitation of a fluorescent material at an excitation waveband of light and in which the excitation waveband impinges upon the polyamide.

Abstract: By compressing and heat curing a non-resilient, non-flexible recurable material formed by subjecting cured polyimide foam to the action of pressurized steam, a wide variety of useful articles may be produced. These include tough, flame-resistant plastic films, sheets, panels, boards, and shapes in general; composites (both reinforced and unreinforced); and laminates and other articles in which separate shapes or parts are bonded together by a new type of tough, flame-resistant adhesive. Additionally, heretofore worthless waste products such as the kerf cut away from buns of polyimide foam during the foam manufacturing process can be converted and vastly upgraded into any of such an array of new articles of manufacture such as those just mentioned.

Abstract: A polyimide precursor mixture having a solids content of about 50 to about 77 (preferably about 65 to about 75) weight percent is subjected to a multistaged thermal treatment in which the precursor is heated to one or more temperatures sufficient to obtain a consolidated but friable cellular foam structure, and the resultant cellular foam structure is then subjected to one or more higher temperatures sufficient to cure the cellular material into a resilient polyimide foam. There is no need for use of time-consuming and expensive spray drying and microwave radiation apparatus.

Abstract: Described are ways of improving the yields of specification grade polyimide foam on a consistent basis from one run to the next, by use of improved microwave-based foaming processes. In one such process, the microwave radiation is directed upon the top, sides and ends of the body of polyimide precursor and of the foam structure as it is developing, but the extent to which such radiation impinges upwardly into the bottom of said body and said foam structure is curtailed, preferably by means of a metallic shield located below the precursor and developing foam structure. Mechanisms by which the shields function to provide the improvements of the process are discussed, and methods based thereon are set forth.

Abstract: By compressing and heat curing a non-resilient, non-flexible recurable material formed by subjecting cured polyimide foam to the action of pressurized steam, a wide variety of useful articles may be produced. These include tough, flame-resistant plastic films, sheets, panels, boards, and shapes in general; composites (both reinforced and unreinforced); and laminates and other articles in which separate shapes or parts are bonded together by a new type of tough, flame-resistant adhesive. Additionally, heretofore worthless waste products such as the kerf cut away from buns of polyimide foam during the foam manufacturing process can be converted and vastly upgraded into any of such an array of new articles of manufacture such as those just mentioned.

Abstract: Described are ways of improving the yields of specification grade polyimide foam on a consistent basis from one run to the next by use of improvements in microwave-based foaming processes. While a body of polyimide precursor is exposed to microwave radiation, the body of polyimide precursor and of the foam structure as it is developing therefrom are kept under a substantially vapor-impermeable microwave-compatible shroud that does not substantially restrict or impede development of the foam structure. For this purpose use may be made of a shroud composed of a polymer film. Mechanisms by which the shroud produces the improved results are discussed, and methods based thereon are set forth.

Abstract: Cured polyimide foam is exposed to an atmosphere of steam at elevated temperature and pressure for a period of time sufficient to convert the foam into a non-flexible, non-resilient recurable cellular material. Preferably the process is conducted such that the cellular material is recurable to a flexible resilient foam having tensile strength properties similar to the tensile strength properties of the original cured polyimide foam subjected to the process. Before recuring, the non-flexible, non-resilient recurable cellular material may be shaped or contoured, and then recured. For example, by impressing shaped articles into the recurable material followed by recuring, shipping/storage containers for the articles are readily produced.

Abstract: Described are ways of improving the yields of specification grade polyimide foam on a consistent basis from one run to the next, by use of improved microwave-based foaming processes. In one such process, the microwave radiation is directed upon the top, sides and ends of the body of polyimide precursor and of the foam structure as it is developing, but the extent to which such radiation impinges upwardly into the bottom of said body and said foam structure is curtailed, preferably by means of a metallic shield located below the precursor and developing foam structure. Mechanisms by which the shields function to provide the improvements of the process are discussed, and methods based thereon are set forth.

Abstract: This disclosure relates to a method for producing polyethylene open-cell foam materials, comprising a process step of pressurized heating at a temperature of 110.degree. to 135.degree. C. of a base compound consisting of polyethylene or a copolymer of polyethylene which has been compounded with an azodicarbonamide foaming agent and a bridging agent, in order to obtain a primary intermediate product with a cubical expansion coefficient of 1.0 to 2.0 times; a process step of heating the primary intermediate product under normal atmospheric pressure at a temperature of 150.degree..about.190.degree. C.

Abstract: By compressing and heat curing a non-resilient, non-flexible recurable material formed by subjecting cured polyimide foam to the action of pressurized steam, a wide variety of useful articles may be produced. These include tough, flame-resistant plastic films, sheets, panels, boards, and shapes in general; composites (both reinforced and unreinforced); and laminates and other articles in which separate shapes or parts are bonded together by a new type of tough, flame-resistant adhesive. Additionally, heretofore worthless waste products such as the kerf cut away from buns of polyimide foam during the foam manufacturing process can be converted and vastly upgraded into any of such an array of new articles of manufacture such as those just mentioned.

Abstract: A dye-containing porous plastic element, comprising a plastic body having interconnected capillary passageways, and a dry, water-soluble dye located within the passageways. The passageways extend to at least one surface of the body, and the size of the passageways are such that the body, when contacted with water, can absorb the water to wet the dye and make it soluble. The plastic body comprises fused granules of plastic interspersed with dry granules of dye. The plastic granules may have a diameter, prior to fusion, of between about 50 and 800 microns, preferably between about 100 and 300 microns. The dry dye comprises between about 5 percent and 35 percent of the element, by weight, and preferably between about 10 percent and 20 percent.

Abstract: A method of making thermal insulating products comprising porous, lightweight, high temperature resistant inorganic particles in a polyimide foam matrix and the product thereof. A polyimide precursor provided is mixed with about equal weight of flake-like porous inorganic particles to substantially uniformly coat the particles with powder. The mixture is placed in a mold and compressed slightly. The assembly is heated to the foaming temperature of the polyimide precursor for a period suitable to produce uniform foaming. Then the temperature is raised to the curing and crosslinking temperature of the precursor for a time period sufficient to produce complete cure. A high temperature and flame resistant, light weight, highly insulating product results. If desired, protective sheets of material may be bonded to selected product surfaces during or after the molding operation.

Abstract: Described are flexible polyimide foams having enhanced compression characteristics and softness for use in the manufacture of seat cushions and methods for the production of such foams and precursors therefor. These foams are produced from novel polyimides prepared by reaction of at least one aromatic or heterocyclic primary diamine with a mixture of at least two organic tetracarboxylic acids or derivatives thereof, at least one of which is from 1 to 40 mol percent of a 2-(vicinal-dicarboxycyclohexenyl)succinic acid or derivative thereof and a second of which is an aromatic tetracarboxylic acid or derivative thereof.

Abstract: A low density extruded structural foam of closed cell structure having good compressive strength comprising a engineered thermoplastic resin, alone, or containing a flame retarding agent and/or nucleating agent, optionally combined with a vinyl aromatic resin, and a blowing agent is produced by feeding said resin, or composition, into a primary extruder wherein mixing, adding a blowing agent which is essentially insoluble in the resin at room temperature but soluble in the melt and further mixing, then optionally passing the mixture to a second, cooling extruder, passing said extruded mixture through a die, then expanding and foaming said composition into a foam article.

Abstract: Described are flexible polyimide foams having enhanced compression characteristics and softness for use in the manufacture of seat cushions and methods for the production of such foams and precursors therefor. These foams are produced from novel polyimides prepared by reaction of at least one aromatic or heterocyclic primary diamine with a mixture of at least two organic tetracarboxylic acids or derivatives thereof, at least one of which is from 1 to 40 mol percent of a 2-(vicinal-dicarboxycyclohexenyl)succinic acid or derivative thereof and a second of which is an aromatic tetracarboxylic acid or derivative thereof.

Abstract: Described are ways of improving the yields of specification grade polyimide foam on a consistent basis from one run to the next, by use of improved microwave-based foaming processes. In one such process, during the application of the microwave radiation, the body of polyimide precursor and of the foam structure as it is developing therefrom are maintained under a substantially vapor-impermeable mmicrowave-compatible shroud that does not substantially restrict or impede development of the foam structure; and the microwave radiation is directed upon the top, sides and ends of the body of polyimide precursor and of the foam structure as it is developing, but the extent to which such radiation impinges upwardly into the bottom of said body and said foam structure is curtailed, preferably by means of a metallic shield located below the precursor and developing foam structure.

Abstract: Described are flexible polyimide foams having enhanced compression fatigue life and softness for use in the manufacture of seat cushions and methods for the production of such foams and precursors therefor. These foams are produced from novel polyimides prepared by reaction of an organic tetracarboxylic acid or derivative thereof, preferably an ester with (a) about 1 to about 50 mol percent of a diester of (i) a primary amino-substituted aromatic carboxylic acid, and (ii) a polymethylene glycol, and (b) at least one aromatic or heterocyclic primary diamine. Foams can be produced having (a) a fatigue life as determined by ASTM test procedure D 3574-81 using foam specimens from three to five inches in thickness of at least 15,000 cycles, or (b) an indentation force deflection as determined by ASTM test procedure D3574-81 on foam specimens of one-inch thickness of less than 40 pounds of force at 25% deflection and less than 180 pounds of force at 65% deflection, or both of (a) and (b).

Abstract: Disclosed herein are microporous polybenzimidazole articles prepared by the addition of a leachable additive to a polybenzimidazole polymer solution or dope and the subsequent leaching of the additive from the polybenzimidazole article. The microporous polybenzimidazole article may be formed into filaments or films. The micropores of the microporous polybenzimidazole article may be filled with an absorbent resin which will act to absorb chemicals or other harmful products. The microporous polybenzimidazole article with absorbent material may be formed into clothing which is highly resistant to both chemicals and heat.