Nanofibrous Waterproof Breathable Protective Clothing

Waterproof breathable membranes allow water vapor to pass through and prevent liquid water from penetration. They have a wide range of applications (e.g., skiwear, sleeping bag, water purification, wound healing, gas... [ view full abstract ]

Waterproof breathable membranes allow water vapor to pass through and prevent liquid water from penetration. They have a wide range of applications (e.g., skiwear, sleeping bag, water purification, wound healing, gas diffusion, etc.). In this study, several nanofibrous membranes were electrospun by changing different effective parameters (e.g., polymeric concentration, voltage, feed flow, etc.). The physical-chemical properties of the membranes (i.e., average fiber diameters, thickness, areal density, porosity, contact angle, waterproofness, air permeability, water vapor transmittance and aerosol filtration) were studied based on the standard test methods.

 The beads-free webs with average fiber diameter as small as 200 nm were achieved from electrospinning of 10wt.% polyurethane in dimethylformamide, at feed rate of 0.5 ml/h, applied voltage of 25kV, and tip to collector distance of 15 cm (Figure 1). The thickness and areal density of the membranes increased linearly by time of electrospinning (Figure 2). By optimization of the electrospinning parameters, a web with high level of waterproofness, high air permeability (AP), and high water vapor transmission rate (WVTR) was obtained (Figure 3). A linear empirical equation was found for the estimation of AP and WVTR based on the average pore size diameter, the membrane thickness, and the porosity with very high regression coefficients (R²>0.97).

 The selected membrane ,with thickness=60 mm, and average pore size diameter=3mm, showed very good air permeability of  9 mm/s, hydrostatic pressure resistance of 155 cm H₂O, and WVTR of 42.5 g/m²/h.  This membrane could remove the particles larger than 0.6 µm completely (100%) from the air stream while it efficiently reduced the concentration of the smaller particles by minimum 92% (Figure 4).