Preparation and properties of epoxy modified cyanate ester resin for solvent free winding

A solvent-free epoxy modified cyanate ester resin for winding is prepared by modifying bisphenol E cyanate ester/bisphenol A cyanate ester/acetylacetone copper blend with resorcinol diglycidyl ether （RDGE）. The influence of RDGE content on the processability of the resin and the mechanical，thermomechanical，dielectric，and moisture absorption properties of cured resin is investigated. The results show that the viscosity of the resin at is 430 mPa·s @ 25 ℃，which is suitable for solvent-free winding. The processing window lasts for up to one month. RDGE has a catalytic effect on the curing reaction of cyanate esters. The curing temperature of the modified resin is 180 ℃，and the post-treatment temperature is 240 ℃. The oxazolidinone ring generated by the reaction between RDGE and cyanate ester enhances the toughness of the cured resin，while reducing BECy by an equal amount to maintain the processability of the winding process partially offsets the toughening effect. The mechanical properties of the resin cured material reach their maximum at an RDGE content of 20%，with tensile strength and modulus of 78.45 MPa and 3.50 GPa，elongation at break of 2.77%，and bending strength and modulus of 152.49 MPa and 3.48 GPa，respectively. At this point， the moisture resistance of cured resin has improved，with a water absorption rate of 1.60% after 100 h of boiling at 100 ℃.However，the glass transition temperature and dielectric properties have decreased， with a Tg of 247 ℃. The dielectric constant in the frequency range of 7-15 GHz is 3.04-3.05，and the dielectric dissipation factor is 0.013-0.014.