Nanodiamonds Shine as Heat-Conductive Fillers

Nanodiamonds (ND) might sound extravagant for use as thermally conductive fillers in plastics for electronics and LEDs, but Finland’s Carbodeon has refined its functionalized nanodiamonds for a performance increase of 20% to 100%, allowing up to 70% less ND use, greatly reducing the cost.

Carbodeon (U.S. rep. is SiliconSense of Nashua, N.H.) is now selling its “Ultra-Dispersed” uDiamond nanodiamonds in powder or liquid dispersions. In these, the ND is said to be fully dispersed into its primary particles without agglomeration, so the customer can benefit from the entire available ND surface area, giving better performance with less material and cost. While the company is not currently selling ND in masterbatch form, this is one future option. ND can be combined with other thermally conductive fillers such as boron nitride and alumina.

The performance achieved by uDiamond fillers is a combination of diamond’s extremely high thermal conductivity, Carbodeon’s ability to optimize the ND’s affinity to a range of thermoplastics and other thermal fillers, and its improvements in ND dispersion.

Says Carbodeon CTO Vesa Myllymaki, “With the ability to control these parameters, the nanotechnology key paradigm of ‘less gives more’ can truly be realized.” He notes that the active surface chemistry inherent in detonation-synthesized nanodiamonds has historically presented difficulties in utilizing the potential benefits of the 4-6 nm particles, making them prone to agglomeration. Carbodeon functionalizes the surface of NDs with a patented graphite-based coating so that the particles are driven to disperse consistently throughout the plastic matrix.

Late last year, the company published data showing the thermal conductivity of nylon 66 compounds could be increased by 25% by replacing 0.1% by wt. of the typically maximum effective level of boron nitride (45%) with ND. “While there are certain limits on, for example, boron nitride loadings, the overall performance can now be pushed forward with a minimum replacement of existing filler material with our NDs,” says Myllymaki. “If a customer wishes to reduce the standard filler concentration but retain certain thermal performance—either to reduce component weight or excess wear of production tools—it is cheaper to do this with NDs than with boron nitride.