# Tailoring Flame Retardance and Thermal Conductivity of Epoxy/Benzoxazine Mixtures via Aluminum Trihydrate and Ceramic Hybridization

## TL;DR

This paper shows how adding specific ceramic fillers to epoxy/benzoxazine mixtures can improve flame resistance and thermal conductivity while managing other material properties.

## Contribution

The study introduces a novel hybridization approach using aluminum trihydrate and ceramics to optimize flame retardance and thermal conductivity in polymer composites.

## Key findings

- Trimodal composites with 40 wt% Al2O3 and BN achieved a thermal conductivity of 1.64 W/m∙K.
- Composites with 7.5 wt% BN showed the lowest water absorption at 0.69%.
- Shear strength decreased with higher ceramic filler content but remained stable after thermal cycling.

## Abstract

A composite meeting the UL94 V-0 rating was produced by adding 30 wt% epoxy silane-modified aluminum trihydrate (EPATH) to a 60/40 epoxy/benzoxazine matrix. Various bimodal and trimodal composites containing 20–40 wt% of three types of ceramic fillers, i.e., aluminum oxide (Al2O3), boron nitride (BN), and magnesium oxide (MgO), were prepared to simultaneously achieve flame-retardant and thermal conductive properties. The bimodal composites with 40 wt% of Al2O3 and MgO exhibited thermal conductivities of 1.22 W/m∙K and 1.29 W/m∙K, respectively, which were superior to that of the composite containing the same amount of ATH (1.0 W/m∙K). In contrast, both the coefficient of thermal expansion (CTE) and shear strength decreased with increasing ceramic filler content. For agglomerated BN, the filler loading was constrained above 30 wt% because its high specific volume caused a significant rise in the viscosity. In the trimodal composites with a total filler content of 40 wt% of Al2O3 and BN, a BN fraction of 7.5 wt% yielded the highest thermal conductivity of 1.64 W/m∙K and the lowest water absorption of 0.69%. When the trimodal composites were exposed to −55 °C and 150 °C for 1000 h, they exhibited a reduction in shear strength of less than 30% compared to their initial values.