Preparation And Properties Of Multifunctional Materials Based On In Situ Fiber Formation Technology

With the continuous progress of science and technology,the research of fiber fabric is no longer limited to single function application,but more and more attention to its multi-function development.The functional treatment of fabric by dip coating,chemical deposition,magnetron sputtering and in-suit polymerizations can endow them with self-cleaning,antibacterial,conductive and heating properties,making them widely used in various fields such as medical antibacterial,air filtration,seawater desalination,electromagnetic shielding and energy storage.However,the preparation of flexible and multifunctional fabrics is still a very challenging subject.Micro/nano-fiber fabrics are favored by researchers because of their unique flexibility,high mechanical strength and large specific surface area.Therefore,a PVA/PE blend fiber was prepared by melt blending extrusion based on in situ fiber forming technology.Subsequently,a polyethylene nanofiber fabric was obtained through weaving,water soluble stripping PVA and freeze-drying.Then,by surface functionalization treatment,the fiber fabric is endowed with excellent photothermal and electrothermal conversion capabilities,which makes it have broad development prospects in seawater desalination,flexible wearable heating fabric and other aspects.The main contents include:(1)Polyethylene nanofibers(PNBs)fabrics were prepared based on in-situ fiber formation technology.In this chapter,polyethylene glycol-200 and glycerol were used as a composite plasticizer to plasticize polyvinyl alcohol.Then,the plasticized polyvinyl alcohol(PVA)and polyethylene(PE)were used as raw materials to prepare polyethylene nanofibers(PNBs)fabrics by melt extrusion,weaving,water-soluble PVA and freeze-drying techniques.The results showed that the rheological properties of PVA were better when the concentration of PVA was 70 wt%and the content of plasticizer was 30 wt%(the mass ratio of glycerol and polyethylene glycol-200 was 20:10).At this time,the melting index of PVA was 7.18 g/10 min and the melting point decreased from 192℃ to 123℃.SEM results of melt extruded and drafted PVA/PE blended fibers showed that when the PE(dispersed phase)content reached 40 wt%,the fibers content were most abundant and showed an obvious two-phase structure.And the average diameter of the fibers prepared after removal of PVA was 300 nm nanofibers.(2)PDMS/PPy/AP-PNBs superhydrophobic photothermal fabrics with efficient interfacial evaporation capability were prepared by the strategy of interfacial polymerization of pyrrole and surface hydrophobic modification treatment.The polyethylene nanofibers(PNBs)fabric prepared in the previous chapter was used as the substrate,the surface modification was carried out by ammonium persulfate(APS)and dopamine(DA),followed by interfacial polymerization of pyrrole to obtain PPy/AP-PNBs fabrics.Then,the superhydrophobic PDMS/PPy/AP-PNBs fabrics were prepared by hydrophobic modification of the above fabrics with polydimethylsiloxane(PDMS).It has been shown that the hydrophilic PNBs fabrics were endowed with excellent light absorption ability(95.84%,2500-300 nm)and superhydrophobic properties(average water contact angle reached 152.1°)when pyrrole monomer was added in a volume of 200 uL and PDMS hydrophobic treatment for 40 min.The water evaporation rate and photothermal conversion efficiency of PDMS/PPy/AP-PNBs under a standard simulated sunlight(1 kW m-2)were as high as 1.478 kg m-2 h-1 and 86.5%,respectively,in the prepared suspension evaporation device.Even during a long time(12 h)and high salt concentration(21 wt%NaCl solution)evaporation process,this interfacial evaporation fabric showed no salt deposition on the surface and maintained a stable evaporation performance.The hydrophobic fabric has promising application in stable and efficient desalination.(3)CuS/AP-PNB fabric with excellent photothermal and electrothermal conversion properties was prepared by chemical deposition of copper sulfide(CuS).In this chapter,the effect of reaction concentration on the electrical heating performance of the composite fabric was investigated using the modified fabric as a substrate in Chapter 2.High conductivity(277 S m-1),excellent electric heating effect(0.8 V,85.7℃)and low voltage driving performance(0.2 V～0.8 V)were obtained when the mass fraction of copper sulfate was 4 wt%.In addition,the prepared CuS/AP-PNBs exhibited good light absorption with an average absorbance of 94.2%(2500-300 nm).The surface temperature of CuS/AP-PNB-4 wt%fabric could be increased to 92.1℃ under one standard simulated sunlight(1 kW m-2).Excellent photothermal conversion was demonstrated under both outdoor sunlight and infrared thermal therapy device.When used as an interfacial water evaporation material for a draped evaporation system,the CuS/APPNBs-4 wt%fabric achieved a water evaporation rate of up to 1.81 kg m-2 h-1 and an energy conversion rate of 95.1%.This new functional fabric provides a new idea for the field of energy harvesting and conversion,showing great advantages in the field of human thermal management and solar-driven water evaporation.