Impregnated high voltage spacers for use with resin filled hose bracing systems

A fluid, gellable resin system impregnated into a porous substrate, said substrate being disposed between stator conductor coils in the end winding area of an electrical apparatus, wherein said resin system consists essentially of:

• (A) a liquid diallyl isophthalate mixture comprising the admixture of liquid diallyl isophthalate monomer and solid diallyl isophthalate prepolymer, where the ratio of monomer:prepolymer is between about 1.5:1 and about 3.0:1,
• (B) an amount of isocyanate terminated polyurethane prepolymer effective to provide between about 0.010 and about 0.020 equivalent of NCO group per 100 grams of liquid diallyl isophthalate mixture, where the isocyanate component is selected from the group consisting of 2,4-tolylene diisocyanate;
• 2,6-tolylene diisocyanate;
• mixtures of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate;
• and 4,4'-diphenyl methane diisocyanate,
• (C) a chain extender for the isocyanate terminated polyurethane prepolymer consisting of trimethylene glycol di-p-aminobenzoate when the isocyanate component contains tolylene diisocyanate;
• and selected from hydroquinone di-(.beta.-hydroxyethyl) ether;
• ethylene glycol;
• 1,2-propanediol;
• 1,3-propanediol;
• 1,5-pentanediol;
• 1,4-butanediol;
• 1,3-butanediol;
• 1,2-butanediol;
• 2,2-butanediol;
• 2,3-butanediol, mixtures thereof, and mixtures with triols when the isocyanate component contains 4,4'-diphenyl methane diisocyanate, and
• (D) a peroxide catalyst for the liquid diallyl isophthalate mixture, where the resin system is curable with the application of heat.