Designing high thermal conductivity of polydimethylsiloxane filled with hybrid h-BN/MoS2 via molecular dynamics simulation

YF Wang and ZC Chang and K Gao and ZW Li and GY Hou and J Liu and LQ Zhang, POLYMER, 224, 123697 (2021).

DOI: 10.1016/j.polymer.2021.123697

With the rapid development of modern electronic technology, addressing the heat dissipation problem of devices has become more and more urgent. Herein, the effects of molybdenum disulfide (MoS2) and hybrid hexagonal boron nitride (h-BN)/MoS2 fillers on the thermal conductivity of polydimethylsiloxane (PDMS) were investigated by reverse non-equilibrium molecular dynamics (RNEMD) simulation with fully atomistic model. Firstly, we simulated the thermal conductivity of MoS2 and BN fillers. It was found that the thermal conductivity of the two fillers enhanced with the increase of their sizes. The intrinsic thermal conductivity of MoS2 and BN obtained via the extrapolation were 52 W/(m?K) and 606 W/(m?K) separately. For 1?5 layers, the number of layers has almost no effect on the thermal conductivity of MoS2, but as the number of layers increase, the thermal conductivity of BN first decreases and then reaches a plateau. Then, we studied the thermal conductivity of the PDMS-based composites. Due to the existence of holes in the PDMS/MoS2 system, the thermal conductivity of PDMS/MoS2 composites is not much improved compared with that of PDMS. Therefore, we then introduced a hybrid BN/ MoS2 filler into the composite to solve the void problem in the system. The results proved that this method was effective. The introduction of the hybrid BN/MoS2 filler effectively promoted the dispersion of the two fillers in the PDMS matrix and greatly reduced the holes in the composites. Compared with the composites filled with only one kind of filler, PDMS/BN/MoS2 composites possess better thermal conductivity. The most surprising finding is that there exists an optimal loading ratio of the two fillers, and the thermal conductivity of the composite reached the maximum when the mass ratio of the two fillers is approximately 1:1, attributed to the change of the volume fraction of holes (?). In addition, with the increase of hybrid BN/MoS2 filler content, the thermal conductivity of the composites is also increasing. The oscillating shear can also promote the orientation of the filler along the shear direction and improve the thermal conductivity of composites along that direction. Therefore, composites based on hybrid BN/MoS2 nano-fillers can be used to improve the thermal conductivity of insulating polymer materials. The findings should shed some light on the design and preparation of polymer composites with excellent thermal conductivity and electrical insulation properties.

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