Abstract: A process of forming vias in a composition comprising (a) applying a layer of a composition containing (i) a cyanate ester, (ii) a bismaleimide, (iii) a co-curing agent having the structure R1—Ar—R2 wherein Ar is at least one aryl moiety, R1 is at least one unsaturated aliphatic moiety and R2 is at least one glycidyl moiety, (iv) an epoxy resin and, optionally, (v) a free-radical initiator; (b) covering the layer with a mask having windows through which radiation can be transmitted; (c) exposing part of the composition to radiation to at least partially cure it in the exposed areas; (d) removing the non-cured portions of the composition; and (e) completing the cure of the resin compositions.

Abstract: A composite structure is made by first furnishing a skin layer made of a composite material of quartz fibers embedded in an uncured cyanate ester-resin matrix. A transition layer of a first epoxy resin is applied to the skin layer. The skin structure including the skin layer and transition layer is cured at a first temperature and post cured at a second temperature greater than the first temperature. A bonding layer of a second epoxy resin is thereafter applied to the bonding surface of the transition layer, and a substrate is contacted to the exposed face of the bonding layer. The second epoxy resin is cured at a third temperature no greater than the first temperature.

Abstract: A thermosetting resin system including an epoxy resin, a bismaleimide, a cyanate ester and a co-curing agent that is an aromatic moiety having unsaturated aliphatic groups and glycidyl ether groups is provided. Preferred co-curing agents are 2-allylphenyl glycidyl ether and 2,2′-diallylbisphenol A diglycidyl ether. The resin system can be employed as an encapsulant for electronic components and as dielectric layers with microvias on printed circuits.

Abstract: A low-density, syntactic foam material is provided according to the invention. The syntactic foam material is prepared by mixing together a plurality of microballoons and a finely divided solid thermosetting resin. Fibers are also preferably incorporated into the material during processing to impart specific properties. The mixture is heated to allow the thermosetting resin to flow and wet the microballoons in the mixture. The mixture is then cured to set and crosslink the thermosetting resin to form the syntactic foam of the invention. The syntactic foam material has highly uniform properties and can be used in aerospace applications.

Abstract: A low-density, syntactic foam material is provided according to the invention. The syntactic foam material is prepared by mixing together a plurality of microballoons and a finely divided solid thermosetting resin. Fibers are also preferably incorporated into the material during processing to impart specific properties. The mixture is heated to allow the thermosetting resin to flow and wet the microballoons in the mixture. The mixture is then cured to set and crosslink the thermosetting resin to form the syntactic foam of the invention. The syntactic foam material has highly uniform properties and can be used in aerospace applications.

Abstract: A low-density, syntactic foam material is provided according to the invention. The syntactic foam material is prepared by mixing together a plurality of microballoons and a finely divided solid thermosetting resin. Fibers are also preferably incorporated into the material during processing to impart specific properties. The mixture is heated to allow the thermosetting resin to flow and wet the microballoons in the mixture. The mixture is then cured to set and crosslink the thermosetting resin to form the syntactic foam of the invention. The syntactic foam material has highly uniform properties and can be used in aerospace applications.

Abstract: A composite structure is made by first furnishing a skin layer made of a composite material of quartz fibers embedded in an uncured cyanate ester-resin matrix. A transition layer of a first epoxy resin is applied to the skin layer. The skin structure including the skin layer and transition layer is cured at a first temperature and post cured at a second temperature greater than the first temperature. A bonding layer of a second epoxy resin is thereafter applied to the bonding surface of the transition layer, and a substrate is contacted to the exposed face of the bonding layer. The second epoxy resin is cured at a third temperature no greater than the first temperature.

Abstract: A radome structure has an outer first layer of a fiber-reinforced composite material of quartz fibers in a noncrystalline cured oligomeric cyanate ester pre-polymer. A second layer of a syntactic foam underlies and is bonded to the first layer. A third layer of the same fiber-reinforced composite material (although possibly of different thickness) underlies and is bonded to the second layer. A fourth layer of the syntactic foam underlies and is bonded to the third layer. A fifth layer of the same fiber-reinforced composite material (preferably of the same thickness as the first layer) underlies and is bonded to the fourth layer. The structure is formed by layup of the first layer inside a female mold, and successively shaping the remaining layers and tacking them to each preceding layer. The shell produced in this manner can be joined to conforming shells.

Abstract: A radome structure has an outer first layer of a fiber-reinforced composite material of quartz fibers in a noncrystalline cured oligomeric cyanate ester pre-polymer. A second layer of a syntactic foam underlies and is bonded to the first layer. A third layer of the same fiber-reinforced composite material (although possibly of different thickness) underlies and is bonded to the second layer. A fourth layer of the syntactic foam underlies and is bonded to the third layer. A fifth layer of the same fiber-reinforced composite material (preferably of the same thickness as the first layer) underlies and is bonded to the fourth layer. The structure is formed by layup of the first layer inside a female mold, and successively shaping the remaining layers and tacking them to each preceding layer. The shell produced in this manner can be joined to conforming shells.

Abstract: A low-density, porous material is prepared by mixing together microballoons and an oligomeric precursor to a polyesterimide polymer. The oligomeric precursor has an initial viscosity sufficiently low that it can flow and wet the microballoons when first heated to a polymerization processing temperature, and thereafter polymerize. Fibers may be controllably incorporated into the material during processing to impart specific properties, and air may be controllably incorporated into the material during processing to further decrease its density.

Abstract: A low-density, porous material is prepared by mixing together microballoons and an oligomeric precursor to a polyetherimide polymer. The oligomeric precursor has an initial viscosity sufficiently low that it can flow and wet the microballoons when first heated to a polymerization processing temperature, and thereafter polymerize. Fibers may be controllably incorporated into the material during processing to impart specific properties, and air may be controllably incorporated into the material during processing to further decrease its density.

Abstract: A separable blade agitator has a glass coated drive shaft and a glass coated impeller interference fitted to the end of the shaft in a gasketless, glass surface to glass surface joint. The interference fitting of the impeller to the shaft is accomplished by super cooling the end of the shaft with nitrogen or the like so that it can be inserted into a glass coated bore in the impeller.

Abstract: A separable blade agitator has a glass coated drive shaft and a glass coated impeller interference fitted to the end of the shaft in a gasketless, glass surface to glass surface joint. The interference fitting of the impeller to the shaft is accomplished by super cooling the end of the shaft with nitrogen or the like so that it can be inserted into a glass coated bore in the impeller.

Abstract: Foamed cross-linked poly-N-arylenebinzimidazoles are prepared by mixing an organic tetraamine and an ortho substituted aromatic dicarboxylic acid anhydride in the presence of a blowing agent and then heating the prepolymer to a temperature sufficient to complete polymerization and foaming of the reactants. In another embodiment of the process, the reactants are heated to form a prepolymer. The prepolymer is then cured at higher temperatures to complete foaming and polymerization.