Research On Structure Design And Performance Of Radiative Cooling Textile Based On PVDF Fiber Membrane

Radiative cooling utilizes the huge temperature difference between the earth’s surface and outer space to transfer thermal radiation.Compared with traditional cooling technology based on air compression,it has the advantages of green environmental protection and energy saving.If radiative cooling technology is applied to personal thermal management,it can significantly reduce the usage rate of air-conditioning and other high energy consumption cooling equipment,and provide an effective way for the adjustment of outdoor personal thermal comfort.In this paper,the structure design of radiative cooling textile based on Polyvinylidene fluoride（PVDF）fiber membrane was carried out.By combining the properties of the individual materials,the textiles achieve a synergistic enhancement that contributes to passive radiative cooling or radiative warming.The specific works were as follows:（1）The PVDF/SiO₂high emissive radiative cooling fiber membrane was prepared by electrostatic spinning with PVDF as polymer matrix,acetone and N,N-dimethyl formamide（DMF）as solvent,SiO₂as additive.The morphology and structure of SiO₂and fiber membrane were characterized by scanning electron microscopy（SEM）,energy dispersive X-ray spectrometer（EDS）,particle size measurement and pore size analysis;The mechanism of radiative cooling was studied by making use of solar reflectance and mid-infrared emissivity;The effects of measuring device,weather condition and SiO₂content on the radiative cooling performance of fiber membrane were studied by outdoor temperature measurement.At the same time,the thermal stability,tensile properties,hydrophobicity and air permeability of the fiber membrane were analyzed by thermogravimetric test,tensile strength test,contact angle measurement and air permeability measurement.The results shown that when the percentage of SiO₂mass to PVDF mass is 30%,PVDF/SiO₂fiber membrane had the best daytime radiative cooling performance,which was 2.0-10.1℃ lower than simulated skin（blank group）and 0.4-7.9℃ lower than pure PVDF fiber membrane;The cooling effect of PVDF/SiO₂fiber membrane on sunny days was better than that on cloudy days.In addition,with the increase of SiO₂content,the thermal stability of PVDF/SiO₂fiber membrane was basically unchanged,hydrophobicity and tensile properties were decreased,and air permeability become better.（2）The PVDF/SiO₂-PTFE（PFM）radiative cooling fiber membranes were prepared by laminated PVDF/SiO₂fiber membrane and polytetrafluoroethylene（PTFE）clothing film,and the related structures and properties were investigated.The results showed that when the percentage of SiO₂mass to PVDF mass is 30%,PFM had the best daytime radiative cooling performance;The cooling effect on sunny days was better than that on cloudy days;The temperature of 30%PFM was 2.5-9.2℃ lower than simulated skin and1.5-6.4℃ lower than 0%PFM on sunny days.Furthermore,with the increase of SiO₂content,the thermal stability of PFM was basically unchanged,the hydrophobic and tensile properties were decreased,and air permeability become better.（3）A sandwich structure of PTFE-PVDF/SiO₂-conductive fabrics with asymmetric emitter was designed and fabricated by lamination PFM and conductive fabrics,and adjusting its front and back sides can realize the dual function of radiative cooling and warming.The morphology and structure,optical properties,daytime radiative cooling/warming properties,thermal stability properties,tensile properties and air permeability properties of the bifunctional textiles were analyzed,and the following conclusions were obtained:When the PTFE layer faced outwards,the composite fabrics entered cooling mode,and 30%PFM-CF had the best daytime radiative cooling effect,which was 3.3-8.9℃ lower than simulated skin and 0.8-7.2℃ lower than 0%PFM-CF;When the conductive fabric layer faced outward,the composite fabrics entered warming mode,and 20%PFM-CF had the best daytime radiative warming effect,which was 5.7-15.2℃ higher than simulated skin and 4.9-12.3℃ higher than 0%PFM-CF.Moreover,with the increase of SiO₂content,the thermal stability of PFM was basically unchanged,with a decrease in hydrophobicity and air permeability.