Effect of Tourmaline Nanoparticles on Thermal, Mechanical, and Electrical Properties of Epoxy Resin Nanocomposites

Tourmaline nanoparticle-reinforced DGEBA/MTHPA epoxy nanocomposites were developed to obtain mechanically robust insulating materials with reduced dielectric loss. Composites containing 0-20 phr tourmaline were prepared by mechanical mixing, vacuum degassing, and stepwise curing, and FTIR verified successful curing and network formation. Tourmaline delivered stiffness-dominated reinforcement, increasing the flexural modulus from 2.585 to 4.07 GPa. At 5 phr, the composites reached simultaneous maxima in flexural strength and impact strength, corresponding to improvements of 5.02% and 57.4% over the unfilled resin, respectively. Moreover, the modified epoxy thermosets still maintained excellent <i>T</i>_g and thermal decomposition temperature. Electrical insulation improved concurrently, as volume resistivity increased from 1.36 × 10¹⁶ Ω·cm for EP-0 to 1.89 × 10¹⁶ Ω·cm for EP-20, and surface resistivity rose from 1.72 × 10¹⁵ to 2.49 × 10¹⁵ Ω, giving 9.6-39.0% and 14.2-44.9% gains for EP-5 to EP-20. Notably, at 50 Hz, 5 phr tourmaline preserved a low permittivity of 4.360 while reducing dielectric loss tangent (tan δ) from 0.0270 to 0.0190, a 29.6% decrease. Collectively, these improvements reduce dielectric heating and support reliable operation of epoxy-based insulation in power equipment.