Thermally conductive PVDF-graphene coatings.
Hot pressing significantly improves coating thermal conductivity.
Coatings de-wet standard industrial aluminum surfaces.
De-wetting is eliminated by small roughness skewness and large kurtosis.
Coatings display very high thermal effusivity.
Hydrophobic polymeric coatings with high thermal conductivity have many important implications such as efficient surface heat dissipation in systems that heat up due to friction and as high thermal inertia interfaces in energy conversion or storage devices. In this work, we fabricated thermally conducting nanocomposite coatings from poly(vinylidenefluoride) or PVDF and graphene nanoplatelets (GnPs) having thermal conductivities as high as 13 W/mK. Coatings were made on commercial aluminum foils and plates by using ink spray deposition and subsequent hot pressing to compact the dispersed GnPs.
In order to eliminate coating deweting (coating inhomogeneity) during spray deposition, substrate surface skewness (Ssk) and kurtosis (Sku) values were changed to adjust substrate roughness profiles toward textures rich in microscale valleys. As sprayed coatings were hydrophobic (~130°) but their hydrophobicity declined to 110° due to hot pressing even for highly filled coatings (60 wt%. GnPs). Measured thermal effusivity, ε, of the coatings containing 40 wt% GnPs was close to 6000 Ws1/2/m2K indicating potential temperature sensing capability, and as functional coatings for dynamic capture and storage of ambient thermal energy.