Thermally conductive boron nitride/SEBS/EVA ternary composites: “Processing and characterization”

Abstract

AbstractThe aim of this study is to investigate the effect of hexagonal boron nitride (BN) particle shape/size and loading level on the thermal, mechanical, electrical properties, and morphology of styrene‐ethylene‐butylene‐styrene terpolymer (SEBS)/poly(ethylene‐co‐vinyl acetate) (EVA) blends to be used as thermal interface materials (TIM). It is observed from the scanning electron microscopy (SEM) of BN powders that each type has a characteristic particle size distribution and particle shape. SEM analysis conducted on matrices (i.e. SEBS/EVA blends) does not indicate any sign of interfacial delamination or phase separation between components. The surface energy measurements and subsequent wettability coefficient calculations point out that the dispersion of BN in SEBS is thermodynamically more favorable than that of BN in EVA. In other words, SEBS tends to encapsulate BN particles in comparison to EVA. Thermal conductivity of composites increases with increasing filler loading level regardless of filler size and shape. It is found that the composites with smaller BN particles (i.e. high aspect ratio and plate‐like particles) shows higher thermal conductivity than that of the composites with larger particles at the same filler content. The tensile strength of the composites reduces with the incorporation of BN regardless of BN content and matrix composition. The increasing content of BN in the matrix gradually improves the moduli of the composites. The hardness of composites enhances with BN loading level and SEBS/EVA ratio regardless of filler type. The increasing amount of EVA in the composites results in a decrease in dielectric constant of neat matrices and composites. POLYM. COMPOS., 31:1398–1408, 2010. © 2009 Society of Plastics Engineers