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

## TL;DR

Tourmaline nanoparticles improve epoxy resin's mechanical strength and electrical insulation while reducing dielectric loss.

## Contribution

Tourmaline nanoparticles provide stiffness-dominated reinforcement and reduce dielectric loss in epoxy composites.

## Key findings

- Flexural modulus increased from 2.585 to 4.07 GPa with tourmaline addition.
- Tourmaline at 5 phr improved flexural and impact strength by 5.02% and 57.4%.
- Dielectric loss tangent decreased by 29.6% at 5 phr tourmaline.

## Abstract

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 Tg 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.