Abstract:
A heavy gauge, high temperature polyimide and polyamide-imide insulating film having a high fold endurance is made by: (1) depositing a solvent solution of a soluble polyamide precursor as a wet film on a substrate directly followed by (2) initially heating the wet film-substrate composite at a temperature of between about 80*C and 110*C, to partially remove solvent and water and form a tack free film-substrate composite directly followed by (3) heating the film-substrate composite to a temperature of at least about 130*C to further dry and semi-cure the film directly followed by (4) stripping the low solvent film from the substrate directly followed by (5) heating the stripped film at a temperature between about 200*C and 350*C and simultaneously stretching the film up to about 150 percent of its original length, to provide a solid, cured, stretched film.
Abstract:
A composite structure is disclosed which comprises a layer of glass cloth and a layer of mica paper impregnated and bonded together with a B-stage dephenyl oxide resin composition. The structure may be in the form of a tape or of a sheet and is used as insulation over electrical conductors. The dephenyl oxide composition preferably comprises a mixture of methoxy methyl diphenyl oxide and chloromethyl diphenyl oxide and a curing catalyst of finely divided silica containing a small amount of iron metal.