Preparation And Performances Of Polytetrafluoroethylene Based Photothermal Conversion Composite Fiber Membranes

Energy utilization is one of the hot topics of today’s world.Non-renewable energy reserves are decreasing and often cause environmental pollution.Solar energy has been used as a clean energy source for photovoltaic power generation.However,the utilization of solar energy is still in its early stages.Solar thermal conversion materials can effectively utilize solar energy to produce heat.Among them,the photo-thermal conversion fiber membranes are more suitable to people’s daily use with their lightweight,convenience to use,easy to fabricate,high photo-thermal conversion efficiency and good physicochemical properties.Polytetrafluoroethylene（PTFE）is a highly crystalline robust unique plastic with a high melting point.It has been widely used in aerospace and daily commodities because of its excellent chemical stability,anti-atmospheric aging,high temperature resistance,moisture-proof and waterproof properties.In this study,PTFE fiber membranes were selected as the substrate material to prepare composite fiber membranes with high photothermal conversion efficiency.The prepared photothermal fiber membranes can be used for photothermal purification of water and photothermal power generation.The microstructure and photothermal performance of the prepared PTFE-based photothermal fiber membrane was investigated.The main research includes the following two parts:1.The PTFE-based composite nanofiber membranes with high photo-thermal conversion performance were prepared by using electrospinning,hot pressing and sintering treatment techniques.By scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XPS）,X-ray diffraction（XRD）and tensile analysis,the morphology and structure of the PTFE-based composite nanofiber membrane were studied.and the relationship between structural changes and photo-thermal conversion was explored in this thesis.The results showed that the tensile strength and deformation rate of the PTFE-based composite membrane were 11.5 MPa and 482%,respectively.This is due to the effect of high temperature and pressure,which promotes diffusion and cross-linking reactions between molecules in the film,resulting in optimization of the mechanical properties of the membrane.In addition,a small water purification unit was designed to use solar energy for simple and sustainable water purification.The photothermal performance under different light intensities was analyzed.And the feasibility of photothermal conversion membranes in water purification was further explored.The photothermal conversion efficiency and water evaporation efficiency of this PTFE-based photothermal conversion fiber membrane can reach about 91.4%and2.3 kg·m²·h^-1,respectively,under a single light exposure.This is caused by the"island"microstructure of its surface and the large number of unobstructed rotating-CH₃ groups induced by the sintering treatment.In summary,this study confirmed the good photo-thermal performance of the composite fiber membrane by in-depth investigation of its microstructure and solar light purification water capacity.2.PTFE fiber membranes were used as the substrate material to prepare Cu/PP/PTFE composite fiber membrane（Copper/Polypropylene/PTFE fiber membrane）with high photothermal conversion efficiency.The method utilizes magnetron sputtering technique to sputter copper onto the plasma pretreated PP/PTFE fiber membrane.This Cu/PP/PTFE composite fiber membrane is excellent with flexibility and stability.It can adapt to multiple forms and usage scenarios.In this study,the microstructure,photothermal performance and thermoelectric effect of composite fiber membrane was thoroughly investigated.Their excellent photothermal conversion performance was confirmed.At the same time,an efficient and flexible"photo-thermal"conversion device has been designed.The device combines a fiber membrane with photothermal conversion effect and a thermoelectric power generation sheet.It is designed to generate electricity without any additional heat source by directly using the sunlight to heat one side,creating a temperature difference.The temperature of the device could reach 72℃under simulated sunlight.In the area of power generation,the"photo-thermal-electric"conversion device based on Cu/PP/PTFE flexible composite fiber membrane could achieve a power generation efficiency of 2.6 m V·K^-1.It indicated that the device could convert light energy into thermal energy and electrical energy with high power generation efficiency.Finally,the actual applicability of the thermoelectric generation sheet was verified by observing the lighting of small bulbs and the rotation of small fans.