Summary Passive thermal management of an object can be achieved by manipulating its optical spectrum. Here, we present a protocol to create a dual-mode Janus fabric (DMJF) with unique switchable thermal management properties. We describe steps for fabricating radiative cooling (RC), ultraviolet (UV) reflective, and long-wave infrared (LWIR) shielding layers. We then detail steps for optical characterization and permeability and thermal measurements for the fabricated samples. This protocol could be applicable to various dynamic passive thermal management scenarios under diverse climatic conditions. For complete details on the use and execution of this protocol, please refer to Pian et al. 1
Polyisoprene is widely used in the industrial production of tires, thermoplastic elastomers, pressure sensitive adhesives, coatings, plasticizers, lubricants, and other functional materials. However, due to the inherent molecular defect of containing many unsaturated double bonds, polyisoprene exhibits relatively weak environmental endurance, especially under extreme environmental conditions. To incorporate the excellent features of fluorinated polymer such as tough environmental endurance, a new type of fluorinated polyisoprene is tailored and a facile procedure of introducing fluoroalkyl side chains onto polyisoprene backbone is carried out via epoxidation and thiol–epoxy click chemistry under mild conditions. The results demonstrate that fluorinated alkyl side chains are successfully clicked onto backbone chains of polyisoprene and the corresponding film exhibits a microphase separation structure. As for the fluorinated polyisoprene film after the introduction of fluoroalkyl groups, the water contact angle enhances significantly from 79.4° to 114.8° and the UV reflectivity improves markedly. In addition, the surface chemical constituents confirm that the incorporated fluoroalkyl groups have a tendency to migrate and enrich spontaneously onto the film surface.
Mujia Feng,Zhilin Xia,Zhi Liu,Tu Zhou,Huajun Sun,Xiaofang Liu
Radiative cooling is a passive cooling strategy that requires no external energy input. It can provide continuous cooling for buildings and reduce energy consumption. In this study, a double-layer radiative cooling coating (DHRC) was designed with a bilayer structure. Fluorocarbon resins were used as film-forming substances for the coatings. Hollow rutile TiO 2 and 200 nm diameter ZrO 2 were used as fillers in the lower and upper layers, respectively. The cooling coating exhibited excellent reflective radiation performance, with a solar reflectance (R solar ) of 92.9 % and an emissivity (ε 8-13 μm ) of 95.13 %. In outdoor tests, the average and maximum temperature reductions relative to ambient conditions were 8.44 ℃ and 12.3 ℃, respectively. The water contact angle was 98°, and after 25 days of UV irradiation, the R solar only decreased by 1.09 %. The cooling power calculated using MATLAB was 123.44 W∙m −2 , which was 22.45 W∙m −2 more than that of the commercial cooling coating. The EnergyPlus building energy consumption simulation results showed that among 15 cities around the world, buildings using cooling paints achieved energy saving rates of more than 7 % in 10 cities. The results showed that the DHRC effectively reduced temperature, improved energy efficiency in buildings, and exhibited resistance to staining and aging. This coating provides new ideas for future research on the design and innovation of building cooling coatings.
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