Study On The Preparation Of Solar-To-thermal Conversion/Storage Nanofibers And Their Temperature Control,Stain Resistance And Breathable Properties

Photothermal conversion materials are a class of materials that directly and efficiently convert absorbed solar energy into heat energy.With the development of science and technology,photothermal conversion materials are widely used in chemical industry,energy,sensing and life and health fields.However,as an intermittent energy source,solar energy is easily affected by the season and climate.Therefore,the efficient storage of solar energy is of great importance for taking advantage of solar energy.Phase change materials(PCMs)have good prospects in the development of solar energy storage materials due to their high storage density and small temperature change during the phase change process.However,due to its prone to leakage during the phase change process and its own weak light absorption,it limits its application in solar thermal storage.In order to solve the shortcomings of the above-mentioned PCMs in solar thermal storage,this paper introduces nano-copper sulfide(Cu₇S₄)with photothermal function into polyvinylidene fluoride(PVDF)by uniaxial electrospinning technology to prepare photothermal fibers membrane.And use coaxial electrospinning technique to embed the PCMs into a single fiber to form the core-shell structure composite fiber.Realize the solar-to-thermal energy conversion and phase change temperature control ability of the nanofibers.On this basis,the hydrophilic/hydrophobic double-layer structure fiber membrane was prepared and used for temperature control,stain resistance and breathable properties research.The specific research contents are as follows:(1)PVDF/Cu₇S₄ nanofiber membranes with high-efficiency solar-to-thermal conversion effect are prepared by uniaxial electrospinning technology.In the wavelength range of 200?2500 nm,the optical absorption rate of PVDF/CU7S4 films maintained above 95%.Under simulated sunlight,the PVDF/Cu₇S₄ fiber membrane was heated up by 25? within 1.5 min,and the heating rate reaches up to 22.5?/min,which is nearly 5 times higher than that of pure PVDF fiber membrane(4.4?/min),showing good photothermal properties.The experimental results prove that when the loading capacity of Cu₇S₄ is 2.0 wt%,the fiber membrane has better comprehensive properties.(2)The core-shell structure n-eicosane@polyvinylidene fluoride/copper sulfide(PCM@PVDF/Cu₇S₄)composite fiber membrane was prepared by coaxial electrospinning technology.The phase transition temperature of the composite fiber membrane is 38.42? and the latent heat of phase transition is 71.72 J/g.Through the heat storage/release of the phase change process,the skin surface temperature is maintained at 32??33?,showing good temperature control performance.Moreover,the contact angle of the fiber membrane surface is kept above 140°,showing good hydrophobicity,ensuring the self-cleaning performance of the fiber membrane.(3)Using the above-mentioned fiber membrane as the substrate,continue uniaxial electrospinning of hydrophilic polyacrylonitrile(PAN)fibers to construct the PCM@PVDF/Cu₇S₄-PAN double-layer structure fiber membrane with good moisture absorption and air permeability.The fiber membrane can be folded,bent and cut at will,showing good flexibility.The permeability of the double-layer structure fiber membrane is 9.2 kg·m-2·-1,which can quickly absorb and evaporate sweat on the human body surface.In addition,after 120 hours of ultrasonic washing,the double-layer structure fiber membrane still maintains good temperature control,stain resistance and breathable properties.Therefore,the temperature regulating and pollution resistant breathable fiber membrane constructed in this paper has great application potential in the field of wearable thermal-regulating textiles.