The Influence of Fibers Diameter on Water Vapor Permeability, Waterproof and Windproof Properties of Electrospun Poly(vinylidene fluoride) Membrane

Hypothesis:

 Waterproof breathable membranes are used in different fields such as protective clothing, hospital textiles and sport wears. Breathability is an important factor in clothing comfort.

The influence of fiber diameter on breathability, waterproof and windproof properties of poly(vinylidene fluoride) membrane was investigated in this study. Hence, membranes composed of fiber with diameters of 133, 203, 551 and 1018 nm were produced through electrospinning process. It was attempted to use dimethyl sulfoxide as a green solvent in this process. Porosity, pore size, water contact angle, air permeability and hydrostatic pressure of the membranes were assessed. Thermogravimetric analysis (TGA) was employed to measure the water vapor permeability of the membranes.

The hydrostatic pressure of the membranes increased from 10 kPa to 100 kPa by reducing the fibers' diameter (from 1018 nm to 133 nm) and subsequently the pore size of the membranes. The air permeability of the samples decreased from 9 mL/s.cm2 to 1.4 mL/s.cm2 (at pressure drop of 500 Pa) with decreasing fiber diameter. The results showed that the membranes composed of finer fibers have better waterproof and windproof properties. This is while the reduction in fiber diameter and subsequently reduction in the pore size have not led to reduction in the breathability, and the amount of water vapor permeability remained approximately 12.7 kg/m2.day. Hence, it seems that the ordinary diffusion (molecular diffusion) is the dominant mechanism of water vapor diffusion in pore size ranging from 761 nm to 3860 nm and it is independent of the fiber diameter in the membranes