Improvement in Thermal Conductivity of Through-Plane Aligned Graphite Flake/Silicone Modified Epoxy Resin Composites

Abstract

We describe, here, our study of the thermal conductivity (TC) properties of silicone modified epoxy resin (SEP) films which were prepared by blending low molecular weight SH-023-7 silicone resin with Dow 332 epoxy resin as the matrix of composites using graphite flakes (GF) as a thermally conductive filler. The SEP/GF composites with different filler contents and SEP/vertically aligned GF (AGF) composites utilizing various magnetic field intensities were fabricated, and the TC, and thermal stability (TS) were characterized by thermal gravimetric analysis, and the morphology was observed by scanning electron microscopy (SEM). According to the experimental results, both the TC and TS increased with the increasing addition of filler. When the weight fraction of M (M = $\mathrm{ }\frac{\mathrm{GF}}{\mathrm{GF}\mathrm{ }+\mathrm{ }\mathrm{SEP}}\text{ × }100\mathrm{\%}$) was 60 wt%, the TC of the composites was 1.38 W/mk, which was 5.52 times higher than that of pure SEP (0.25 W/mK). In addition, the addition of graphite also increased the decomposition temperature of the composites. The vertically aligned GFs resulted in effective, vertical, thermally conductive pathways in the SEP matrix, and the SEP/AGF composites exhibited much higher through-plane TC compared to the non-orientated SEP/GF composites. The SEP/AGF reached 5.66 W/mK, which was approximately 4.1 and approximately 23 times higher than 60 wt% SEP/GF and pure SEP, when the nano-Fe₃O₄ content was 0.4 g, the strength of magnetic field was 0.65 T and the added amount of M was 60 wt%. In addition, by SEM observation, when the flake graphite was found in the direction of the magnetic field orientation, the graphite formed heat conduction channels touching each other in the magnetic field direction, improving the TC. Using XRD analyses the orientation degree of the graphite in the composite showed that the graphite obviously changed its internal orientation in the composite material when subjected to the magnetic field in the SEP melt.

Keywords:

• epoxy composites
• thermal conductivity
• vertically aligned-graphite

Additional information

Funding

This work was financially supported by the Cooperation Project of Guizhou Province (Grant No. LH [2016]7441).