Waterproof and breathable membranes come in three forms

1 microporous membrane

In a microporous membrane, the size of the micropores is 0.1 to 50 μm, which determines that only air or water vapor can pass through the membrane but liquid cannot. Electrospinning technology has low cost, easy operation and high applicable value. This technology can prepare waterproof and breathable microporous films from natural polymers, synthetic polymers, etc.

2 hydrophilic membrane

Hydrophilic polymers are composed of copolymers. Generally, hydrophilic membranes are airtight, but breathable effects can also be achieved by adding humectants to the molecular chains. In addition, when the hydrophilic membrane comes into contact with liquid or is under a high saturated vapor pressure, it will undergo a swelling process. Through this process, the water vapor permeability of the hydrophilic membrane is also enhanced. Therefore, membrane layers composed of hydrophilic polymers are a good choice for making breathable protective clothing.

3 Microporous hydrophilic composite membrane

In the study of Wu et al., they used electrospinning to coat the PU microporous membrane layer directly on the prepared hydrophilic membrane layer (Figure 1). The prepared composite membrane contained a hydrophobic PU membrane layer and a hydrophilic membrane layer. Water polyvinyl alcohol (c-PVA) film layer. In the composite membrane, the hydrophobic section is waterproof, and water can spontaneously move from the hydrophobic section to the hydrophilic section; water vapor can pass through the hydrophilic section. At present, microporous hydrophilic membranes have not been widely used in protective clothing, but this kind of composite membrane with special properties has great development prospects.