Preparation of highly thermally conductive but electrically insulating composites by constructing a segregated double network in polymer composites

Thermally conductive but electrically insulating polymer composites have drawn much attention in various applications including thermal management, electronic packing, etc. Herein, a facile method of preparing polymer composites with both excellent thermal conductivity and electrical insulation is reported. To do this, nylon 6 (PA6)/Graphene nanoplatelets (GNPs) composites were firstly prepared via melt blending, then smashed into micron particles and coated with hexagonal boron nitride (h-BN) powder via VAE resin, finally hot compress molding to form composites. Thus depending on the content of GNPs inside PA6 particles and the content of hBN coated on the particles, the thermal and electrical conductivity of the composites could be well controlled. For instance, at the total content of fillers is 18.82 vol%, with 1.97 vol% GNPs insides PA particles and 16.85 vol % h-BN coated on the surface, almost ten times improvement of thermal conductivity (from 0.29 to 2.69 W m(-1)k(-1)) has been achieved, while still maintain an excellent electrical insulating (as low as 4.13 x 10(-9)S/m). It is proposed that this double segregated filler network could provide synergistic enhancement for the thermal conductivity, while the electrical conductivity caused by GNPs could be largely cut off by h-BN filler network. More importantly, this unique structure could be well preserved even after the sample thickness was decreased into a thin film, resulting in a further increase of thermal conductivity (up to 8.96 W m(-1)k(-1)) in the flow direction. Since various thermoplastic polymers can be chosen as matrix, and different filler combination can be adopted to construct thermal conductive synergistic and electrical insulating, we believe that this work provides a facial method to fabricate highly thermally conductive composites with a low electrical conductivity.