Copper flake-coated cellulose scaffold to construct segregated network for enhancing thermal conductivity of epoxy composites

This study reports about the enhanced thermal conductivity of epoxy composites fabricated by introducing relatively aligned structure of cellulose fibers with copper flakes embedded in their surface-layer. The obtained composite shows anisotropic thermal conductivity; in the parallel direction being higher than that in the perpendicular direction. With varying preparation conditions, a thermal conductivity of as high as 1.4 W m(-1) K-1 has been achieved at a low filler concentration of 36.4 wt%. A theory available in literature is modified by the introduction of resistivity factor to account for the loose connectivity at the flake-flake junctions and the effective thermal conductivity of epoxy composites filled by copper flakes coated cellulose fiber has been investigated. The theoretical prediction shows that the heat conduction along the fiber direction is mostly influenced by the thermal conductivities of cellulose fibers and copper flakes. Meanwhile, the thermal conductivity of polymer matrix and packing fraction of fiber affect strongly on the perpendicular thermal conductivity of the composites. The contact resistivity factor of at the flake-flake junction has been estimated to be 0.07 m K W-1. This report gives potential guidance exploiting recyclable cellulose fiber for further study in designing high thermal conductive composites for heat management applications.