Forming techniques for shaping polyimide foams
OwnerJohn V. Long, John Gaglianiinventors
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Abstract
A method of re-shaping polyimide and modified polyimide foam sheets into selected shapes. Polyimide foam sheets can be made by any of a number of methods, some of which produce sheets of selected thicknesses directly and others of which produce blocks or buns of foam which are sliced into sheets. A sheet is placed in a mold having the desired configuration, such as a half-pipe. The sheet is compressed to about 0 to 99% of the original thickness with heating of one or both major surfaces of the sheet to a temperature of from about 250.degree. to 320.degree. C. for about 0.5 to 5 minutes. Upon removal from the mold, the polyimide foam is found to be self-supporting and to have taken on the mold shape. A moisture impervious densified skin is found on the heated side(s).
Claims15
The method of reshaping polyimide foam sheets which comprises the steps of:
- providing a sheet of polyimide foam;
- placing one major surface of said sheet into contact with a first mold surface;
- bringing a second mold surface at least into substantially complete contact with the second major surface of said sheet and compressing and reshaping the sheet;
- heating at least one major surface of said sheet to a temperature of from about 220.degree. to 320.degree. C. for about 0.5 to 5 minutes while allowing the balance of said sheet to remain at a lower temperature;
- and
- removing the reshaped foam sheet from the mold;
- whereby a self-sustaining foam structure having a higher density, moisture impervious, fire blocking and abrasion resistant skin on the heated foam surface results.
In the method of preparing polyimide foam sheets having a desired configuration, which comprises the steps of reacting a tetracarboxylic acid dianhydride with an oxoimine in a solvent, adding a diamine, drying the solution to a powder, heating the powder in a mold to cause the powder to foam and produce a foam bun and slicing said bun into sheets having desired thicknesses, the improvement comprising the further steps of:
- placing one major surface of one of said sheets into contact with a first mold surface;
- bringing a second mold surface at least into substantially complete contact with a second major surface of said sheet and compressing and reshaping the sheet;
- heating at least one major surface of said sheet to a temperature of from about 220.degree. to 320.degree. C. for about 0.5 to 5 minutes;
- and
- removing the reshaped foam sheet from the mold;
- whereby a self-sustaining foam structure having a higher density, moisture impervious skin on the heated foam surface results.
In the method of preparing polyimide foam sheets having a desired configuration, which comprises the steps of reacting a tetracarboxylic acid dianhydride with a caprolactam in a mole ratio less than 1:1.5 in a solvent to produce an imidocaproic acid monomer, reacting said monomer with a diamine in a substantially stoichiometric ratio, drying the solution to a powder, heating said powder in a mold to cause it to foam and form a polyimide foam bun, removing said bun from said mold and slice it into foam sheets of desired thicknesses, the improvement comprising the further steps of:
- placing one major surface of one of said sheets into contact with a first mold surface;
- bringing a second mold surface at least into substantially complete contact with a second major surface of said sheet and compressing and reshaping the sheet;
- heating at least one major surface of said sheet to a temperature of from about 220.degree. to 320.degree. C. for about 0.5 to 5 minutes;
- and
- removing the reshaped foam sheet from the mold;
- whereby a self-sustaining foam structure having a higher density, moisture impervious skin on the heated foam surface results.
Dependencies are inferred from the claim text.