Towards Thermoconductive, Electrically Insulating Polymeric Composites with Boron Nitride Nanotubes as Fillers

Abstract

Ultilizing boron nitride nanotubes (BNNTs) as fillers, composites are fabricated with poly(methyl methacrylate), polystyrene, poly(vinyl butyral), or poly(ethylene vinyl alcohol) as the matrix and their thermal, electrical, and mechanical properties are evaluated. More than 20‐fold thermal conductivity improvement in BNNT‐containing polymers is obtained, and such composites maintain good electrical insulation. The coefficient of thermal expansion (CTE) of the BNNT‐loaded polymers is dramatically reduced because of interactions between the polymer chains and the nanotubes. Moreover, the composites possess good mechanical properties, as revealed by Vickers microhardness tests. This detailed study indicates that BNNTs are very promising nanofillers for polymeric composites, allowing the simultaneous achievement of high thermal conductivity, low CTE, and high electrical resistance, as required for novel and efficient heat‐releasing materials.

Thermal Conductivity of Nanoparticles Filled Polymers

“…As a few examples, HDPE filled with 7 vol.% nanometer size expanded graphite has a thermal conductivity of 1.59 W/m K, twice that of microcomposites (0.78 W/m K) at the same volume content (Ye et al, 2006). Poly(vinyl butyral) (PVB), PS, PMMA and poly(ethylene vinyl alcohol) (PEVA) based nanocomposites with 24 wt.% boron nitride nanotubes (BNNT) have thermal conductivities of 1.80, 3.61, 3.16 and 2.50 W/m K, respectively (Zhi et al, 2009). Carbon nanofiber was also reported to improve the thermal conductivity of polymer composites (Sui et al, 2008) and (Elgafy & Lafdi, 2005).…”

“…In order to take into account fluctuations in thermal conductivity in the composites, Zhi et al (Zhi et al, 2009) proposed the concept of heat-transfer passages, to model the conduction in regions where interparticle distance is low, applying the series model to "packed-belt" of conductive particles.…”

Recent research developments in polymer heat exchangers – A review

“…The optimal thermal conductivity with BNNTs of 10% volume content was 0.54W/mK, which showed good agreement with Nielsen's model. Another attempt has been made by Zhi et al 35 with a higher BNNTs fraction (>10wt%). …”

Edge‐Hydroxylated Boron Nitride Nanosheets as an Effective Additive to Improve the Thermal Response of Hydrogels

“…We have also found that OH-BNNS can effectively improve the thermal conductivity of the NIPAM/water mixture and even pure water (Supporting Information, Table S3), which is critical, since the hydrogel contains a large amount of water (> 80 % by weight). The improvement is likely due to the high phonon transport along the OH-BNNS basal planes [6,28] . The interfacial thermal contact resistance is minimized due to the large contact area between the OH-BNNS and the polymer, as well as the water.…”