Method for preparing addition type polyimide prepregs
AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorTerry L. St. Clair
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Abstract
A novel addition polyimide based on the use of liquid monomers wherein the essentially solventless prepreg produced therefrom retains good drape, tack and other mechanical properties.
Claims5
A method for preparing a novel addition type polyimide prepreg comprising the steps of reacting equimolar quantities of benzophenonetetracarboxylic acid dianhydride and norbornene dicarboxylic acid anhydride in an excess of absolute ethanol while heating to 50.degree.-60.degree. C. until solution occurs, cooling the resulting solution of ethylesters to room temperature and adding the cooled solution to a vessel containing an equimolar solution of mixed dianilines, stirring the combined solution for approximately one hour to obtain a homogeneous ester-acid polyimide prepolymer adaptable for "hot-melt" prepreg applications as a liquid resin system, and including the further steps of applying the liquid resin system onto fibers after heating the resin to 50.degree.-70.degree. C. to lower the resin viscosity adqequately to permit prepregging in the absence of a carrier solvent and wherein the mixed dianilines are the isomers of methylenedianilines and in the following percentages:
- o,o'--MDA--3.20%
- o,p'--MDA--15.70%
- p,p'--MDA--66.00% ##STR6##
Dependencies are inferred from the claim text.