Investigation of recycled materials for radiative cooling under tropical climate.

As a sustainable alternative to using virgin polymer, we propose the use of recycled polymer for the fabrication of passive radiative cooling materials to tackle both the increasing demand for cooling systems and to upcycle plastic waste. Using recycled acrylic sheets as the binder for BaSO thorough sol-gel method, a sustained 1.2 °C sub-ambient temperature during daytime and 3 °C sub-ambient temperature during nighttime was achieved under the hot and humid conditions of the tropical climate. The coating achieved 97.7 % solar reflectance and 95 % infrared emittance. Separately, when porosity is introduced to recycled acrylic sheets through a phase inversion method, a near-ambient temperature during noontime and sustained sub-ambient temperature of 2.5 °C during nighttime was achieved (with 96.7 % solar reflectance). Comparable performances are also obtained using recycled polyvinyl chloride (PVC) pipe and expanded polystyrene (EPS) foam.