Construction of low melting point alloy/graphene three-dimensional continuous thermal conductive pathway for improving in-plane and through-plane thermal conductivity of poly(vinylidene fluoride) composites.

As the temperature of hot spots increases in electronic devices, thermal management is a key issue for maintaining a device's reliability and performance. The usual approaches of quickly extracting the heat from the hot spots have focused on aligning two-dimensional filler along the in-plane orientation in the polymer matrix. Meanwhile, improving the through-plane thermal conductivity of polymer-based composites is as important as in-plane thermal conductivity. In this study, poly(vinylidene fluoride) composites with three-dimensional continuous thermal conductive pathways of a low melting point alloy (LMPA)/graphene were prepared through a two-step method. Poly(vinylidene fluoride)@graphene (PVDF@Gr) microspheres were firstly prepared by an in-situ water-vapor induced phase separation method. Subsequently, PVDF@Gr/LMPA composites were obtained by hot-pressing after mixing the LMPA with the PVDF@Gr microspheres. Attributed to the unique solid-liquid phase transition advantage of the LMPA and the good matching of the phonon power spectrum between the LMPA and the graphene, the PVDF@4.8Gr/10LMPA composites with 4.8 vol% graphene and 10.0 vol% LMPA exhibited an outstanding in-plane thermal conductivity of 9.41 W m K and through-plane thermal conductivity of 0.35 W m K, which was nearly increased by 245% and 130% compared to that of the PVDF@4.8Gr composites, respectively. The enhanced elasticity modulus and reduced thermal expansion coefficient were attributed to the LMPA constructing a three-dimensional continuous thermal conductive pathway along with the graphene and reducing interface thermal resistance. This study offeres a straightforward and repeatable method for fabricating highly thermally conductive polymer composites and widens the application of LMPAs in the fields of thermal management.