Hybrid fillers of hexagonal and cubic boron nitride in epoxy composites for thermal management applications

Abstract

The synergistic effect of h-BN/c-BN/EP on the enhancement of thermal conductivity of polymeric composites has been demonstrated.

Thermal Conductivity and Cure Kinetics of Epoxy-Boron Nitride Composites—A Review

“…On the other hand, when the thermal conductivity is low (close to the lower trend line in Figure 9), a small absolute increase can translate into a significant percentage increase. This effect can be seen in the results of Lee et al [109], where for 10 wt.% BN the conductivity increases from 0.27 to 0.36 W/mK after sulphuric acid treatment and silanisation, and in the results of Zhang et al [155], where it increases from 0.37 to 0.43 W/mK at 15 wt.% BN after oxidisation in air and the addition of APTES. In contrast, again at a low BN content of only 10 wt.%, the non-covalent functionalisation with pyrenebutyric acid by He et al [85] results in a remarkable increase in thermal conductivity from 0.68 to 1.58 W/mK, well above the intermediate trend line.…”

“…Second, the scales are limited to 11 W/mK and 90 wt.% BN; in this way, it is possible to show more clearly the region in which most of the experimental data lie and to identify the effects of the parameters, namely the surface treatment and the particle size. In some instances, the effect of surface treatment is so small as to be virtually negligible [71,74,82,123,131,148,155]. On the other hand, when the thermal conductivity is low (close to the lower trend line in Figure 9), a small absolute increase can translate into a significant percentage increase.…”

“…These functionalised BN particles may be used directly in the epoxy-BN composite [69,71,85,124], or may additionally be treated with a coupling agent to further enhance the matrix-filler interface. Teng et al [57] used a zirconate coupling agent, but by far the most common are the silanes, of which numerous variants have been used, including (3-mercaptopropyl) trimethoxysilane, [97], (3-aminopropyl) triethoxysilane, APTES [88,109,138,155], epoxy-terminated dimethyl siloxane, ETDMS [101], and (3-glycidyloxypropyl) trimethoxysilane, GPTMS [66,138]. Jang et al [96] found that increasing the carbon chain length of the silane, from propyl trimethoxysilane to hexadecyl trimethoxysilane, improved the affinity of BN with epoxy and led to an increase in thermal conductivity.…”

“…One of the important parameters with respect to the use of these epoxy-BN composites in insulated metal substrates is the simplicity of the fabrication process, as mentioned in the Introduction, but many of the results discussed above make use of a solvent in the dispersion of the functionalised BN particles in the epoxy resin system, which is generally an undesired industrial practice. The solvents most widely used are acetone [57,74,85,113,131,141,148] and ethanol [68,82,97,155], but others include methyl ethyl ketone and dimethyl formamide [96], and tetrahydrofuran [71]. On the other hand, "dry" or "direct" mixing, which obviates the use of any solvents in this composite fabrication step, was adopted by many researchers [54,88,109,113,123,137,138,144,149,156].…”

Polydopamine-Modified Al2O3/Polyurethane Composites with Largely Improved Thermal and Mechanical Properties

“…In order to realize insulating composites with high thermal conductivity and mechanical properties, a high load of spherical Al 2 O 3 particles are required. However, if the filler cannot be uniformly dispersed in the matrix and has good compatibility with the matrix, accumulation and pores will be formed, which will reduce the mechanical properties of the composites [12,33,35]. Therefore, surface modification of the thermal conductivity filler under a high load can not only improve the thermal conductivity of the composites but also improve the mechanical properties.…”