Preparation and characterization of polymer matrix passive cooling materials with thermal insulation and solar reflection properties based on porous structure

Porous polymer materials achieve thermal insulation and solar reflection property at the same time because of their own porous structure, which makes the passive cooling property more superior so as to reduce the indoor temperature more effectively and achieve the purpose of energy saving. In this study, the pore structure was constructed in polyvinyl chloride (PVC) matrix by chemical etching with calcium carbonate (CaCO₃) particles as pore template. The effects of porosity on the structure and properties of PVC porous films were studied. The thermal insulation performance of PVC porous films improves with the increase of porosity, which is better than that of PVC films and PVC/CaCO₃ composite films. The thermal conductivity of sample with the porosity of 67 v% is 0.0868 Wm⁻¹K⁻¹. The total solar reflectance of sample 67 v% is 96.34%, which is 454.9% higher than that of PVC films. Although the thermal emissivity from 3 to 5 μm of PVC porous films is decreased, it still remains at a high level about 0.83 in the whole infrared region. In temperature test, the final temperature of sample with the porosity of about 67 v% is only 25.2 °C, 23.8 °C lower than that of PVC films, and 1.2 °C higher than the room temperature. The cooling property of PVC/titanium dioxide (TiO₂) composite films with 10 v% TiO₂ was also measured for comparation, and the final temperature is 29.1 °C, which is between that of samples with porosity of about 20 v% and 33 v%. The PVC porous material prepared in this study has the advantages of low thermal conductivity, good solar reflectance and simple preparation, which has potential application prospects in the field of passive cooling materials.