A Study on the Thermal Conductivity and Energy-Storage Performance of Microencapsulated n-Octadecane/Wood–Plastic Composites for Floor Heating Panels

Building energy conservation is a critical component of the global sustainable energy transition. Floor radiant heating systems are widely valued for their thermal comfort and efficiency. In this study, microencapsulated phase-change materials (MicroPCMs) are incorporated into wood–plastic composites (WPCs) to develop panels capable of enhanced heat storage and improved thermal conduction. MicroPCMs with the polymethyl methacrylate (PMMA) shells and n -octadecane cores are synthesized via emulsion polymerization. The microstructure, thermal behavior, and mechanical performance of the composites are characterized via scanning electron microscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. MicroPCMs with a 1:1 core–shell mass ratio show a melting enthalpy of 118.31 J g −1 , a crystallization enthalpy of 121.31 J g −1 , and an initial thermal decomposition temperature of 150°C. When 15 wt% MicroPCMs are added to WPCs, the utilization rate of MicroPCMs reaches 65.47%, which shows latent heat storage capability. The thermal conductivity of the composite increases by more than 70%, which enhances heat transfer performance. The mechanical strength decreases slightly but still meets the basic needs for flooring. The MicroPCM/WPC composite, with its thermal storage and heat transfer properties, provides an innovative solution for achieving low-energy, high-comfort floor heating systems with strong practical potential.