Enhanced thermal conductivity of epoxy–matrix composites with hybrid fillers

Abstract

The results of thermal conductivity study of epoxy-matrix composites filled with different type of powders are reported. Boron nitride and aluminum nitride micro-powders with different size distribution and surface modification were used. A representative set of samples has been prepared with different contents of the fillers. The microstructure was investigated by SEM observations. Thermal conductivity measurements have been performed at room temperature and for selected samples it was also measured as a function of temperature from 300 K down to liquid helium temperatures. The most spectacular enhancement of the thermal conductivity was obtained for composites filled with hybrid fillers of boron nitride-silica and aluminum nitride-silica. In the case of sample with 31 vol.% of boron nitride-silica hybrid filler it amounts to 114% and for the sample with 45 vol.% of hybrid filler by 65% as compared with the reference composite with silica filler. However, in the case of small aluminum nitride grains application, large interfacial areas were introduced, promoting creation of thermal resistance barriers and causing phonon scattering more effective. As a result, no thermal conductivity improvement was obtained. Different characters of temperature dependencies are observed for hybrid filler composites which allowed identifying the component filler of the dominant contribution to the thermal conductivity in each case. The data show a good agreement with predictions of Agari-Uno model, indicating the importance of conductive paths forming effect already at low filler contents. Figure 3. SEM images of the: a) the composite filled with 45 vol.% hybrid filler Millsil W12 and BN PT100 (90:10), b) filled with 45 vol.% hybrid filler Millsil W12 and BN PT100 (80:20).

Influence of magnetic field-aided filler orientation on structure and transport properties of ferrite filled composites

“…However, pure polymers do not exhibit the required physical properties such as high thermal or electrical conductivity and they are usually classified as thermal and electrical insulators. So far, many studies have been carried out in order to improve these properties by incorporation of conductive particles, such as metal or ceramic particles [2,3] into polymer [4,5] matrix. Recently, much attention of leading research centers dealing with heat transport in thermally conductive composites has been focused on various fillers and methods of arrangement of their particles that could improve the thermal conductivity of polymeric formulae.…”

Functional composites with core–shell fillers: I. Particle synthesis and thermal conductivity measurements

“…Several studies investigating the thermal properties of polymer composites have been carried out by applying hybrid fillers. Application of fillers with different shapes, such as, plate-like shaped and spherical particles, or rods mixed together, can create efficient conductive paths [16,17]. Moreover, one of the strategies with the aim of increasing the thermal conductivity of the filled composite materials is to modify the surface of the filler particles [12,14,18,19].…”

An Investigation into the Influence of Filler Silanization Conditions on Mechanical and Thermal Parameters of Epoxy Resin-Fly Ash Composites

“…Acoustic mismatch of two mixed materials results in additional phonons scattering at the boundaries, as they are transported through the interface between the filler and the matrix. As a consequence, interfacial thermal resistance can occur [4,7]. This problem may be solved through enhanced coupling between a filler and a matrix [16].…”

“…It has been shown, that this type of filler provides enhancement of the mechanical properties of composites [11], especially for highly packed systems [13,14]. Thermal conductivity can also be improved through the addition of greater amounts of the filler into composites based on epoxy resin [6,7]. With higher packing and proper arrangement of filler particles, there is a higher possibility that heat transfer paths may be created in the composite [15], resulting in better heat dissipation.…”

“…In order to improve mechanical properties, whilst also ensuring enhanced thermal conductivity, various fillers may be incorporated into the polymer matrix. Examples of filler that may be used include silica, which with a thermal conductivity of up to 10 W/mK [3][4][5][6] is the most popular filler material, or boron nitride which represents a more sophisticated (with a thermal conductivity of up to 600 W/ mK) but costly solution [7,8]. One can find attempts to add carbon nanotubes or graphene [9,10], however such fillers are electrically conductive and cannot be applied for composites used as electrical insulation.…”