Poly(vinylidene fluoride) foams: a promising low-k dielectric and heat-insulating material†
In this study, we used a batch-foaming method to prepare closed-cell poly(vinylidene fluoride) (PVDF) foams with tailored microcellular structures. This is a simple, cost-effective, and environmentally-friendly method, and it offers a wide range of tunable microcellular structures. The cell size and porosity volume of PVDF foams can be effectively monitored at their saturation temperatures. The PVDF foam prepared at 169.5 °C possesses an ultra-low dielectric constant of k ∼ 1.1 and a thermal conductivity of 0.027 W m−1 K−1. We used numerous theoretical models to predict the effective dielectric permittivity of the microcellular PVDF foams, and found that the Bruggeman model was very close to the measured results. The ultra-low thermal conductivities of the PVDF foams were the result of a large number of air pockets in the microcellular structure. Based on these results, we concluded that this PVDF foam would be a promising low-k dielectric and heat insulating material.