A simple solvent-based sintering method for fabricating hierarchal porous UHMW polyethylene structures for high solar reflectivity and sub-ambient cooling

This study presents a novel o-xylene solvent-based sintering approach for fabricating hierarchal porous ultra-high molecular weight polyethylene structures, aimed at achieving high solar reflectance ( R solar ̅ ) and sub-ambient cooling. The bottom up, scalable method enables the fabrication of surfaces with high R solar ̅ while maintaining the possibility of easy installation on rooftop surfaces for space cooling applications in buildings. Fabricated ultra-high molecular weight polyethylene (UHMWPE) surfaces exhibit an R solar ̅ of 93 %, thermal conductivity of 0.1417 W/mK and an average sub-ambient cooling performance of ∼4.7 °C when exposed to direct sunlight. The high R solar ̅ of the fabricated samples are attributed to a hierarchal micro-nano porous structure due to the solvent-assisted sintering process. The high sub-ambient cooling performance may be attributed to a combinatory effect of solar reflectance, thermal conductivity and thermal emissivity of UHMWPE film. • Novel 2-step solvent method for porous UHMWPE hierarchical structures. • Hierarchical UHMWPE has micron pores and nano cabbage-leaf textures. • Exhibits high solar reflectance (93 %) and low thermal conductivity. • Achieved sub-ambient cooling of ∼4.7°C for radiative cooling purposes. • Simple, cost-effective process suitable for scalable PDRC applications.