Thermal conductivity and mechanical properties of polyimide composites with mixed fillers of BN flakes and SiC@SiO₂ whiskers

Abstract

Polyimide (PI) composites with mixed fillers of BN flakes and SiC whiskers exhibit enhanced thermal conductivity and mechanical properties. In order to improve dispersion and interaction of these mixed fillers within the PI matrix, BN flakes were modified by a titanate coupling agent while SiC whiskers were oxidized at 750 C for 60 minutes to produce SiC@SiO 2 followed by silane coupling agent modification. PI composites reached a maximum thermal conductivity of 0.95 W/m K at volume fraction of mixed fillers of 27.6 vol% when the weight ratio of BN flakes to SiC@SiO 2 whiskers was 1:4. The enhanced thermal conductivity is likely attributed to the formation of heat conductive networks constructed by BN flakes and SiC@SiO 2 whiskers and the improved interfacial affinity between fillers and matrix. The optimized Nielsen-mold confirms the distribution and morphology of fillers affect the thermal conductivity of PI composites. In addition, SiC whiskers enhanced the mechanical property of PI composites and the influence of fillers on the mechanical property was further elaborated.

Thermal and dielectric multiple percolation in α‐Si3N4 whiskers/silicone rubber

“…[1,4] Metal and C-related particles with high κ, such as Al, [5] Cu, [6] and graphite, [7,8] are commonly used effectively at a high filler volume fraction f of approximately 50 vol%. Since a large aspect ratio r for such fillers enables the formation of thermal pathways at low f, the use of one-or twodimensional materials, such as SiC whiskers (SiC w ), [9,10] carbon fibers (C f ), [11,12] especially multi-walled carbon nanotubes (MWCNTs) [13] and graphene, [14] has led to impressive results. Free electrons travel through the network of such fillers and act as major thermal carriers, which contribute much to thermal conduction.…”

Polyhedral oligosilsesquioxane-modified boron nitride enhances the mechanical properties of polyimide nanocomposites

“…To address this issue, it is generally effective to introduce functional llers into the polymer matrix. 8,9 Common functional llers include graphene, [10][11][12][13] carbon nanotubes, [14][15][16] boron nitride, 17,18 and metal materials. 19 However, graphene, carbon nanotubes, and metallic materials have high conductivity, dielectric constants and dielectric losses, 16,20,21 which are not suitable for electronic insulation materials and seriously hinder the transmission of electronic signals in electronic packaging materials.…”

Synergistic enhancement of thermal conductivity by addition of graphene nanoplatelets to three‐dimensional boron nitride scaffolds for polyamide 6 composites

“…It was suggested that this was due to the fact that there are not enough thermally conductive paths in the composite. In addition, BN is chemically inert, and therefore, challenging to be homogenously dispersed, [ 21 ] hence, further increase of the amount of fillers leads to poor dispersion and low grafting efficiency.…”