Effect of filler loading on polymer chain confinement and thermomechanical properties of epoxy/boron nitride (h-BN) nanocomposites

Abstract

This article examines the effect of the addition of hexagonal boron nitride (h-BN) nanopowder on the polymer chain confinement, thermal, morphological and mechanical properties of the epoxy system. A series of epoxy resin/h-BN (EPBN) nanocomposites with varying compositions (0.1, 0.25, 0.5 and 1 wt%) of h-BN was prepared using 4,4′-diaminodiphenyl sulfone (DDS) as the curing agent. The amount of epoxy chains confined at the h-BN nanofillers was determined and quantified using the results obtained by dynamic mechanical analysis (DMA). h-BN 0.5 wt%/epoxy (EPBN0.5) exhibited the highest volume fraction of the constrained region among the h-BN/epoxy nanocomposites and the presence of h-BN increases the glass transition temperature (T_g) of the epoxy matrix by 10 °C. Furthermore, h-BN/epoxy nanocomposites showed a higher storage modulus when compared to the neat epoxy. The incorporation of the h-BN nanopowder into the epoxy system resulted in an excellent improvement in the impact strength and tensile strength of the system, especially with 0.5 wt% h-BN concentration. This could be ascribed to the uniform distribution of the h-BN nanoparticle in the epoxy matrix. Although epoxy nanocomposites exhibited a higher activation energy (which is related to the thermal stability) compared to that of the neat epoxy, thermal analysis revealed that the incorporation of the h-BN nanopowder does not have much influence on the thermal stability of the system. However, fractured surface analysis of the nanocomposites indicated that the surface roughness increases with an increase in h-BN content.