Thermal Conductivity of Polyvinylidene Fluoride Films with a Multi-Scale Framework

Abstract

The orientation of amorphous regions in pure polymers has been noted to be critical to the enhancement of thermal conductivity (TC), but the available reports are still rather few. Here, we propose to prepare a polyvinylidene fluoride (PVDF) film with a multi-scale framework by introducing anisotropic amorphous nanophases in the form of cross-planar alignments among the in-planar oriented extended-chain crystals (ECCs) lamellae, which show an enhanced TC of 1.99 Wm−1K−1 in the through-plane direction (K⊥) and 4.35 Wm−1K−1 in the in-plane direction (K∥). Structural characterization determination using scanning electron microscopy and high-resolution synchrotron X-ray scattering showed that shrinking the dimension of the amorphous nanophases can effectively reduce entanglement and lead to alignments formation. Moreover, the thermal anisotropy of the amorphous region is quantitatively discussed with the aid of the two-phase model. Superior thermal dissipation performances are intuitively displayed by means of finite element numerical analysis and heat exchanger applications. Moreover, such unique multi-scale architecture also results in significant benefit in the improvement of dimensional stability and thermal stability. This paper provides a reasonable solution for fabricating inexpensive thermal conducting polymer films from the perspective of practical applications.

Molecular perspective and engineering of thermal transport and thermoelectricity in polymers

“…Anharmonic interactions between surface and bulk phonons can reduce the overall in-plane thermal conductivity, 337 suggesting the challenges of designing polymers with high and isotropic thermal conductivity. Recent work by Wang et al 334 explored the thermal conductivity of polyvinylidene (PVDF) films by inducing amorphous nanophases via cross-planar arrangements among the in-plane extended chain crystal lamellae. It was achieved by applying pressures up to 100 MPa in the direction opposite to stretching.…”