Some basic knowledge of waterproof fabrics!
Generally speaking, ordinary rainproof work uniforms can be made easily. However, it is relatively difficult to make work uniforms that are both waterproof and can evaporate human sweat. In fact, all waterproof fabrics work the same: diffusion. Our molecules move from areas of high concentration to areas of low concentration. This means that when you wear a raincoat (or other waterproof fabric clothing), your body sweats and as the human body continuously emits heat and produces moisture, this moisture will pass through the raincoat (or other waterproof uniform) to the outside low concentration area. Different waterproof fabrics implement this principle in different ways. We generally commonly use ePTFE Membranes with a PU coating and ePTFE Membranes without a PU coating. In the following we will briefly introduce the basic characteristics of these two and the main ways to realize the working principle.
ePTFE Membranes with a PU coating (eg. GORE-TEX )
The traditional GORE-TEX (introduced in 1978) uses a stretched PTFE membrane containing 9 billion micropores per square inch to realize the diffusion principle. These pores are 20,000 times smaller than the external water droplets, but 700 times larger than water vapor, which is why rainwater cannot penetrate but water vapor can escape. This kind of microporous "sieve" is supported by an ultra-thin oleophobic polyurethane coating, which can prevent human body oil pollution. PU coating can also block the wind.
When you sweat, steam will condense on the lining and pass through the polyurethane coating as a liquid, reach the ePTFE membrane, and evaporate through the microporous "sieve". The difference between a warm and humid internal climate and a cool and dry external climate encourages steam to pass through the pores of the fabric away from your skin. So the harder you work, the warmer you will be.
ePTFE Membranes without a PU coating (eg. eVent / NeoShell)
This type of fabric uses ePTFE membrane, no protective PU membrane (or some use PU membrane to surround the pores, so that they are not completely covered). Since the pores are not covered, the membrane can breathe and breathe more effectively. In this way, this type of fabric can be both breathable and able to discharge water vapor. This is a two-way air flow that disperses moisture through convection (air circulation) and diffusion (pressure gradient).
However, the disadvantage of this type of fabric is that the membrane is more susceptible to contamination (because there is no PU coating). This can be treated with oleophobicity in the membrane, but this is not as effective and durable as the traditional GORE-TEX. Although the pores have better ventilation and breathing without membranes, they are also more likely to be blocked by human body grease and other dirt. Therefore, if you want to use it effectively, you must clean it frequently.