Production of foamed polymer structures
AssigneeEthyl Corporation
InventorsH. Eugene Broemmelsiek, Raymond Lee, Carroll W. Lanier
Life of this patent
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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.
Claims28
A bun of cured polyimide foam produced by directing upon the top, sides and ends of a body of foamable polyimide precursor and of the foam structure as it is developing therefrom, microwave radiation of intensity sufficient to cause the development of a foamed polymer structure through the generation and evolution of gaseous material within the body of the precursor, but curtailing the extent to which microwave radiation impinges upwardly into the bottom of said body and said foam structure by maintaining a microwave radiation-curtailing shield underneath said body and said foam structure, and thermally curing the developed foam structure to form cured polyimide foam.
A bun of cured polyimide foam produced by placing a foamable polyimide precursor in the form of a powder on a heat-stable cloth positioned on a microwave-curtailing shield underneath said heat-stable cloth;
- directing upon the top, sides and ends of the body of said polyimide precursor and of the foam structure as it is developing therefrom, microwave radiation of intensity sufficient to cause the development of a foamed polymer structure through the generation and evolution of gaseous material within the body of the precursor, said microwave-curtailing shield curtailing the extent to which microwave radiation impringes upwardly into the bottom of said body and said foam structure;
- and thermally curing the developed foam structure to form cured polyimide foam.
Dependencies are inferred from the claim text.