Preparation and characteristics of CuS-CNTs modified PVDF-based flexible composite phase change films

It is indisputable that the impact of buildings on global energy demand. To address the issue of excessive energy consumption in buildings, this manuscript proposes the preparation of a flexible composite phase change films with excellent solar energy absorption conversion and thermal management capabilities. In this paper, composite phase change material was obtained by adsorbing paraffin into expanded graphite (EG) using vacuum adsorption method. The photothermal material copper sulfide‑carbon nanotubes (CuS-CNTs) was synthesized by hydrothermal reaction. The dispersion of EG and carbon nanotubes (CNTs) in polyvinylidene fluoride (PVDF) matrix was enhanced under the influence of polyvinylpyrrolidone (PVP). The flexible and bendable films were finally prepared by using the non-solvent-induced phase separation method. The latent heat of the film reaches 63.63 J/g, and the thermal conductivity of the film system approaches to 0.53 W/(m·K) through the adsorption of the high thermal conductivity enhanced phase EG and the intervention of CNTs. The photothermal conversion ability of CuS-CNTs improves the photothermal performance of the film, and the solar energy utilization reaches 46.2 % under simulated sunlight. The experimental results show that the prepared films can effectively convert solar energy into thermal energy and store it in the form of latent heat, and the films can release the energy in the form of heat again at low temperatures. Utilizing this property, the film can be applied to the field of building materials, which demonstrates great potential and prospect in reducing energy consumption and carbon emission in buildings. The prepared composite phase change film for photothermal conversion provides a new idea for modern building thermal management materials.