Improved out-of-plane thermal conductivity of boron nitride nanosheet-filled polyamide 6/polyethylene terephthalate composites by a rapid solidification method

Abstract

High thermal conductivity of insulating polymer composite material can effectively solve the heat dissipation problem associated with electronic equipment. In this work, we obtained modified boron nitride nanosheets (m-BNNSs) by ultrasonic exfoliation and modification. The surface was successfully grafted with organic functional groups that promoted the compatibility between filler and matrix. Orienting them along the in-plane during the preparation process was facilitated by the anisotropy of BNNSs, which resulted in poor out-of-plane thermal conductivity. Herein, m-BNNSs were uniformly and randomly orientated in the polyamide 6/polyethylene terephthalate (PET/PA6) matrix by a simple strategy of a rapid solidification method including solution mixing, rapid solidification, and hot pressing. The randomly orientated m-BNNSs increased the thermal conductivity of the PA6/PET composite film as high as 3.28 W (m⁻¹ K⁻¹) at a filler loading of 55 wt%, which is 64% higher than that of directly hot-pressed h-BN/PA6/PET composite film. With the increase in filler, the m-BNNS/PET/PA6 composite film exhibited excellent thermal stability as compared to pure PET/PA6 matrix. Such excellent performance indicates that there is a great deal of potential for this composite to be used in thermal management. Non-equilibrium molecular dynamics (NEMD) simulations showed that the increase in the numbers of boron nitride nanosheet (BNNS) layers and the orientation change from vertical heat flow to parallel heat flow can effectively increase the phonon density of states overlap area of BNNSs and PA6/PET, thereby enhancing the interfacial thermal conductance (G_k).