Composition for bonding windings or core laminates in an electrical machine, and associated method

A method for bonding a winding or a core laminate of an electrical machine, comprising:

• impregnating the winding or the core laminate with a curable composition, comprising:
• (A) about 10 weight percent to about 25 weight percent of a polyfunctional cyanate ester having a structure (I)
• NCO—Ar1R1Y—R1nAr1—OCN, (I)
• wherein “n” is an integer equal to or greater than 1, Y has a structure (i) or (ii)
• *R2—Ar2—OCN, or (i)
• *Ar2—OCN, (ii)
• Ar1 and Ar2 are independently at each occurrence a C5-C30 aromatic radical, R1 and R2 are independently at each occurrence a C1-C3 aliphatic radical or a C3-C20 cycloaliphatic radical, and * represents the bonding site;
• (B) about 35 weight percent to about 65 weight percent of a first difunctional cyanate ester having a structure (II), or a prepolymer thereof
• NCO—Ar3—R3—Ar3—OCN, (II)
• wherein Ar3 is a C5-C30 aromatic radical, R3 is a bond or a C1-C2 aliphatic radical;
• and
• (C) about 15 weight percent to about 40 weight percent of a second difunctional cyanate ester having a structure (III), or a prepolymer thereof
• NCO—Ar4—R5—Ar4—OCN, (III)
• wherein Ar4 is a C5-C30 aromatic radical, and R5 is a C3-C10 aliphatic radical;
• applying a vacuum to the winding or the core laminate;
• and
• heating the winding or the core laminate of the electrical machine to cure the curable composition and form a bonding material comprising the cured composition, wherein the electrical machine is selected from the group consisting of a motor, a generator, a transformer, a toxoid;
• an inductor, and combinations thereof.