Novel flexible phase change materials with high emissivity, low thermal conductivity and mechanically robust for thermal management in outdoor environment

High summer temperatures will become the norm as global warming intensifies due to massive energy consumption and greenhouse gas emissions. High-temperature environments will seriously threaten the health of outdoor workers. It is urgent to adopt new technologies to solve the problem of reducing the thermal stress of workers in an extremely hot environment. Herein, phase change material (PCM) and radiative sky cooling technology were combined and prepared successfully a new kind of flexible composite phase change material (CPCM) with paraffin wax (PW), polypropylene hollow fiber (PP fiber) and Linear styrene-b-(ethylene-co-butylene)-b-styrene triblock copolymer with 30 wt% styrene (SEBS). Compared with the traditional end sealing technology, the melted SEBS can close the end of the fiber easily and cost-effectively. The novel material (10PP) has a high enthalpy of 180.01 J/g, and the thermal conductivity is as low as 0.26 W/ (m· K), the low thermal conductivity of CPCM reduces the transfer of heat from the outside to the inside. Tensile strength is 3.89 MPa, the maximum force that 10PP can withstand reaches 147 N, and the contact angle for the hydrophobicity test is 114.8°, which provides a guarantee for the wide application of the new material in an outdoor environment. Besides, the optical test shows an emissivity (atmospheric window) of 0.955, and the extremely high emissivity facilitates radiative cooling of the material at night. On a clear day, the average temperature difference and maximum temperature difference between 10PP and the environment are 6.403 °C and 13.414 °C respectively. In the simulation experiment of the tent, when the external temperature reaches 60 °C, the surface temperature of the tent with CPCM is about 22 °C lower than that without CPCM. This inspiring work offers a great contribution to flexible passive cooling materials for outdoor applications.