Triple Thermal Management Wood–Plastic Composite Plate with Excellent Waterproof and Mechanical Properties

Wood–plastic composite (WPC) possesses the advantages of both plastic and wood materials and has been widely applied to replace solid wood both outdoors (floor and railing of park and garden) and indoors (floor, wallboard, furniture, etc.). However, there will be high surface temperature (more than 55 °C) for outdoor applied WPC plates in the summer, which seriously affects the thermal comfort of human. Herein, we propose a triple thermal management strategy to solve the above problem of WPC plates by combining heat conduction, high solar reflection, and radiation cooling to quickly dissipate heat while blocking solar absorption, and fabricate a trilayer WPC plate with excellent comprehensive properties. The embedded titanium dioxide (TiO2) nanoparticles not only significantly improve the solar reflectance (53.8%) and mid-infrared emissivity (89.2%) of the colored top layer but also endow the surface with good hydrophobicity and abrasion resistance. By incorporating hexagonal boron nitride (h-BN) and short-cut glass fibers (GF) into the core layer of the WPC to enhance the thermal conductivity (0.9–1 W/(m·K)) and impact strength (8.7 kJ/m2), the heat accumulation of the surface and the overall mechanical strength are improved. For the bottom layer, addition of h-BN increases its thermal conduction and improves downward thermal transfer from the surface besides the water-proof function. Notably, the outdoor tests show that the trilayer WPC plate can keep around 45 °C, about 10 °C lower than the ordinary WPC plate under direct sunlight. This strategy of combining thermal conduction, high solar reflection, and radiation cooling offers promising avenues for developing advanced thermal management WPC plates and cooling designs for other outdoor facilities.