Thermal conductive high-density polyethylene/boron nitride composites with high solar reflectivity for radiative cooling

Energy saving and environmental protection are the development themes in today's world, and exploring new cooling technologies that consume less energy or no energy at all to solve the problems of overheating of electronic devices and energy consumption of building cooling are new challenges in the process of technology development nowadays. In this paper, high-density polyethylene/boron nitride (HDPE/BN) composites with high thermal conductivity were prepared by melt blending method. BN has a strong scattering effect on sunlight and a characteristic infrared absorption peak in a mid-infrared band, which makes the composites exhibit strong sunlight reflectivity (>86%) and emissivity (>93%) at atmospheric window band (8-13 mu m). The subambient cooling capacity in direct sunlight is about 4-6 degrees C and it reduces the temperature of the substrate heater by about 10 degrees C compared to conventional polymers, making it suitable for practical electronic equipment or building radiative cooling applications. Using Energy Plus building energy software to model a typical building with HDPE/BN as the cladding material and simulate building energy savings in different climates, it is estimated to generate cooling energy savings of 5-11 MJ m(-2) per year, and about 8-20% of the whole yearly cooling energy consumption for these buildings.