| Thin film composite (TFC) membrane is semi-permeable membrane, which consists ofporous membrane as support layer and hydrophilic non-porous membrane as separative layer.Therefore, The TFC membrane takes the advantages in both water-proof, permeable performanceand selective separation ability. Water droplet cannot penetrate into the composite fabrics laminatedby the TFC membrane and perspiration from human body can diffuse through the TFCmembrane-laminated fabric. Simultaneously, the TFC membrane establishing a comfortmicroclimate between skin and fabric arises from the need to avoid the direct contact of skin withharmful chemical agents. In the paper, electrospinning technology was utilized to prepare ahydrophilic-hydrophobic TFC membrane using the TPEE membrane as substrate and hydrophobicpolymer as spin materials. The membrane morphology and the surface structures were investigatedthrough Scanning electronic microscopy (SEM). Breathable and waterproof performance, surfacewettability, high temperature thermal stability and tensile strength were measured by uprightwater-cup method, contact angle tests, TG tests and stress-strain methods. Water vapor transferprocess was also modelled according to electrical resistance method. The feasibility of theapplication of electrospinning TFC membrane in thermal protective fabrics was investigated.It is difficult to prepare the TFC membrane with uniform porosity and surface smoothnessowing to the complex experimental condition. Firstly, orthogonal experimental method was used toinvestigate process parameters of the electrospinning system. The optimizing scheme for preparingporous membrane could be obtained based on the findings of impact of process parameters onfiber diameters. Results of statistical analysis indicated that solvent concentration executed animportant influence on the fiber diameter. Optimization program of preparation composite membrane were achieved as follow: Solution concentration at15%, voltage6Kv, solventDMAc:Ace=7:3(v:v), ACM0.4g/50ml, receiving distance14cm, the flow rate of solution1.0mL/h.A series of TFC membranes were prepared based on the above optimization scheme. Thesurface morphologies, chemical groups, water vapor permeability, surface wettability, mechanicalproperties and high temperature characteristics of composite membrane were studied in detail.The TFC membrane has a ambipolar capability with hydrophilicity and hydrophobicity. Thecontact angle of the hydrophobic layer is100o, and the contact angle of the hydrophilic layer is30o.Hydrostatic press is6240.3Pa. Water vapor permeability is3515.9g/m2·24h. The initial pyrolysistemperature is393.4℃in N2environment for the TFC membrane. Therefore, the TFC membranecan serve as a material for protective clothing.The total moisture resistance through the TFC membrane can be represented by the sum ofthe moisture resistance caused by the air gap between water surface and specimen inner surface,intrinsic diffusion resistance through specimen and boundary air layer diffusion resistance. Thewater vapor permeable mechanism was discussed in term of three steps experimental data andelectrical resistance model. Results showed that the mass transfer into the TFC membrane was inseries. The DGM model (Dusty-gas model) can be used describe the water vapor transfer process.That is to say, Knudsen diffusion resistance and Molecule diffusion resistance is in series, and inparallel with Poisseuille flow resistance. The numerical calculating values showed a goodagreement with the experimental results. The model can predict the moisture resistance ofcomposite membrane.At last, breathable and waterproof fabrics were prepared by utilizing laminating technology.The thermal protective performance and the liquid intrusion effectiveness were analyzedtheoretically. The thermal protective times were also estimated experimentally. |
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