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 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: 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 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 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 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.