Waste cooking oil applicable phase change capsules to improve thermoregulation of foamed concrete

Phase change materials are used to reduce energy consumption in building systems due to their high latent heat and low ambient temperature fluctuation. In this study, phase change capsules (PCCs) deemed environmentally beneficial were developed using waste cooking oil derivatives as the basic material for the phase change process, and it was applied to foamed concrete to improve the thermal insulation performance. Results show that the derivative exhibits a phase transition temperature of 18.10 °C and an enthalpy of 148.3 J/g, which are suitable for temperature regulation of building walls. PCCs were prepared by emulsifying waste cooking oil derivative and combining it with the droplet microfluidic technology. The fluorescence experiment shows that 1 wt% surfactant Tween80 ensures the stability of the emulsion. Meanwhile, the microscopic morphology, thermal cycling and mechanical properties of PCCs were analyzed comprehensively. The prepared PCCs were spherical and intact, and the content of loaded phase change units was up to 51.62%. The PCCs exhibit excellent thermal stability even after undergoing 200 thermal cycles (change<3%). The PCCs maintain good mechanical strength above the phase change point of the waste cooking oil derivatives (>12.86 N). Most importantly, the mechanical properties of the foamed concrete containing 6 wt% PCCs still meet the strength requirements (>4.80 MPa), and it showed obvious thermal insulation properties under infrared images. The findings of this study have significant ramifications for the application of PCCs in low-density foamed concrete and help to promote the functional and green development of building materials.