Polyetherimide varnish compositions, methods of manufacture, and articles prepared therefrom
View Patent ↗A varnish includes an isolated as-synthesized polyetherimide having a glass transition temperature of 180° C. or more, a solvent in an amount effective for the polyetherimide to remain in solution at a selected temperature, and an inorganic particulate composition wherein the amount of polyetherimide, inorganic particulate composition, and solvent total 100 wt %. Also disclosed is a method of manufacturing the varnish, articles prepared from the varnish, and methods of manufacturing such articles.
1. A varnish comprising
1 to 45 wt % of an isolated, as-synthesized polyetherimide having a glass transition temperature of 180° C. or more;
a solvent in an amount effective for the polyetherimide to remain in solution at a selected temperature;
0.5 to 40 wt % of an inorganic particulate composition, wherein the inorganic particulate composition comprises a thermally conductive filler having a thermal conductivity of more than 45 W/mK and an average particle size of greater than 10 nanometers to less than 20 micrometers;
wherein the amount of polyetherimide, inorganic particulate composition, and solvent total 100 wt %; and
wherein the varnish has
a viscosity greater than 100 cP at 23° C., or
a viscosity greater than 30 cP at 90° C.
2. The varnish of claim 1 , wherein the solvent is a polar, electron donating solvent optionally having a solubility parameter value of 8.5-13, a boiling point greater than 90° C., or both.
3. The varnish of claim 1 , wherein the inorganic particulate composition further comprises
one or both of
an additional thermally conductive filler having a thermal conductivity of 10 to 45 W/mK; and
a thermally insulating filler having a thermal conductivity of less than 10 W/mK.
4. The varnish of claim 1 wherein the varnish is disposed on a fibrous preform.
5. The varnish of claim 1 comprising
15 to 35 wt % of the isolated, as-synthesized polyetherimide having a glass transition temperature of 180° C. or more;
5 to 30 wt % of the inorganic particulate composition wherein the amount of polyetherimide, inorganic particulate composition, and solvent total 100 wt %; and
wherein the solvent is chlorobenzene, a dichlorobenzene, cresol, dimethyl acetamide, veratrole, pyridine, nitrobenzene, methyl benzoate, benzonitrile, acetophenone, n-butyl acetate, 2-ethoxyethanol, 2-n-butoxyethanol, dimethyl sulfoxide, anisole, cyclopentanone, gamma-butyrolactone, N,N-dimethyl formamide, N-methyl pyrrolidone, or a combination comprising at least one of the foregoing.
6. The varnish of claim 1 , wherein the thermally conductive filler having a thermal conductivity of more than 45 W/mK and an average particle size of greater than 10 nanometers to less than 20 micrometers comprises boron nitride.