Surface modification and magnetic alignment of hexagonal boron nitride nanosheets for highly thermally conductive composites

Abstract

With the current development of microelectronic technology, thermally conductive and electrically insulating encapsulation materials are in urgent demand. Hexagonal boron nitride nanosheets (BNNSs) possess a highly anisotropic thermal property. Therefore, the thermal conductivity of the BNNSs-based composites can be dramatically increased through the orientation of fillers. However, it is still difficult to well align BNNSs at high loadings due to the intensive aggregation. Herein, highly ordered thermoplastic polyurethane elastomer (TPU)/BNNSs composites are successfully fabricated by the combination of filler modification and magnetic alignment. The effective covalent modification with 2,4-tolylene diisocyanate (TDI) greatly increases the dispersibility of fillers, thus making it easy to well orient BNNSs at high loadings. The highly aligned fillers result in much higher in-plane thermal conductivity than the composites filled with disordered or less-ordered unmodified BNNSs. The thermal conductivity is as high as 5.15 W m À1 K À1 at 30 wt% loading. Moreover, the composite simultaneously exhibits low dielectric constant, low dielectric dissipation factor and excellent thermomechanical properties. These results reveal the promising application of such highly-ordered composites in advanced electronic packing. Fig. 9 (a) Storage modulus and (b) tan delta of the blank TPU resin and different composites with 10 wt% fillers. 43388 | RSC Adv., 2017, 7, 43380-43389 This journal is

Chain Structure in a Cross-Linked Polyurethane Magnetic Elastomer Under a Magnetic Field

“…We developed a new class of magnetic soft materials that exhibited drastic and reversible changes in the dynamic modulus by weak magnetic fields [5,6,7]. In addition to the viscoelastic property, the magnetic field response of physical properties such as surface property [8,9], electric conductivity [10,11], thermal conductivity [12,13,14], have also been reported. These changes in physical properties by magnetic fields are confirmed results of the change of the inner structure of magnetic elastomers.…”

Effect of Sonication Time on Magnetorheological Effect for Monomodal Magnetic Elastomers

“…So far, we have developed a new class of magnetic soft materials that exhibit drastic and reversible changes in the dynamic modulus by weak magnetic fields [5,6,7]. In addition to the viscoelastic property, the magnetic-field response of physical properties such as surface property [8,9], electric conductivity [10,11], thermal conductivity [12,13,14], have also been reported.…”

Flexible polyurethane/boron nitride composites with enhanced thermal conductivity

“…Thermal dissipation is very important for increasing the performance, lifetime, and reliability of advanced electronic devices with increased power density, together with their miniaturization, integration, and the functionalization of traditional electronics. 1,2 Metals, carbon materials, ceramic materials, and polymer materials have been developed to meet the thermal requirements with the aim of improving heat dissipation. However, short circuits and electron magnetic shielding restrict the application of carbon-based, metal-based, and filled materials because of their electrical conductivity.…”