# Polyethylene-Based Phase Change Materials Modified with Hexagonal Boron Nitride Nanoparticles with Enhanced Thermal Stability and Thermal Conductivity

## TL;DR

This paper explores how adding hexagonal boron nitride nanoparticles improves the thermal properties of polyethylene wax for energy storage.

## Contribution

The novel use of hexagonal boron nitride in polyethylene wax to enhance thermal conductivity and stability is presented.

## Key findings

- Adding h-BN reduces supercooling and broadens melting/solidification temperature ranges.
- Thermal stability increases with h-BN, raising the temperature of maximum mass-loss rate by 8 °C.
- Thermal conductivity increases from 0.30 to 0.40 mW/K with h-BN addition.

## Abstract

Polyethylene waxes (PEWs) are considered promising mid-temperature phase change materials (PCMs). However, their low thermal conductivity limits both applicability and efficiency. One of the more interesting inorganic additives for PCMs is boron nitride (BN), which exhibits high thermal conductivity while remaining electrically insulating, excellent chemical and thermal stability, and good oxidation resistance. In this study, PEW was modified with hexagonal boron nitride (h-BN) in the range of 0.025 to 0.5 wt.%. Differential scanning calorimetry (DSC) results revealed that the addition of h-BN significantly alters the phase-transition behavior of polyethylene wax, broadens the melting and solidification temperature ranges, and reduces supercooling from 11 °C to 9 °C. Thermogravimetric analysis (TGA) showed that the incorporation of h-BN improves the thermal stability of the material. The temperature corresponding to 5% mass loss increased by about 50 °C after incorporation of more than 0.025% h-BN. The temperature of maximum mass-loss rate (TDTGmax) was shifted about 8 °C toward higher temperatures. FTIR results indicate that h-BN does not change the chemical structure of polyethylene waxes, but does affect their morphology and physical properties by increasing the thermal conductivity from 0.30 to 0.40 mW/K. These effects enable the design of composites with tunable properties for energy-storage applications.