Polyamide precursor
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United States of America Patent
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Feb 15, 2000
Issued Date -
N/A
app pub date -
Nov 4, 1997
filing date -
Mar 21, 1996
priority date (Note) -
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Abstract
The service life of fiber-reinforced polyimide composites in a high temperature oxidative environment is extended by coating with a polyimide coating precursor solution that is synthesized by reacting an aromatic dianhydride with an aromatic diamine in a non-reactive solvent. The reactive solution is heated to a temperature sufficent to reduce its viscosity prior to its use as a coating. Preferably, a mixture of meta-phenylenediamine and para-phenylenediamine is reacted with biphenyldianhydride in n-methyl pyrrolidinone solvent and thereafter heated to between about 50.degree. C. (122.degree. F.) and 150.degree. C. (302.degree. F.) under nitrogen while stirring for a time sufficient to obtain a polyamic acid polyimide precursor coating solution having a Brookfield viscosity of from about 500 to about 5000 cP and a solids content of from about 5 to about 35 weight percent.
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