Insulating and highly thermally conductive polyvinylidene fluoride multilayer composite film enhanced via CNT interleaf and electrospinning oriented BNNS

Abstract

The BNNS-CNT/PVDF composite film with high in-plane thermal conductivity and insulation was prepared by using the strategy of hybrid synergy and orientation enhancement of different thermally conductive fillers. The boron nitride nanosheets(BNNS)/polyvinylidene fluoride(PVDF) fiber film by electrospinning was first prepared, and then surface sprayed carbon nanotubes(CNT) and multi-layer film hot pressing were used. Electrospinning technology enables BNNS to achieve in-plane orientation in PVDF films. The sprayed CNTs build an efficient thermal conduction path between the film layers and bridge the BNNS in the adjacent fiber films, which promotes the construction of in-plane thermal conduction network, but still maintains good insulation performance. As a result of the optimization of film preparation conditions, the in-plane thermal conductivity of the BNNS-CNT/PVDF composite film with 30%(mass fraction, the same below) BNNS and 3%CNT content reaches 3.25 W∙m-1∙K-1, which is 1104% higher than that of pure PVDF. Meanwhile, the film has an ultralow out-of-plane conductivity of 2.09×10-12 S∙cm-1. It is found that BNNS and CNT synergistically build an efficient thermal conductivity network, and the enhancement efficiency of 3%CNT for BNNS/PVDF is as high as 52.2% at 5%BNNS filling. At the same time, the thin film has good tensile strength and flexibility.

Keywords

• polymer matrix composite
• thermal conductivity
• electrospinning
• carbon nanotube
• boron nitride nanosheet