NOTEBOOK : Waterproof fabric

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In order to understand how waterproof clothing works, we have to understand what waterproof fabrics are and what they are made of. Waterproof fabrics, or breathable fabrics, as they are often called, are fabrics that have been treated to become resistant to penetration by water and wetting. What is special about them is that they keep water from passing through, but allow water vapor to evaporate. Usually they are natural or synthetic fabrics that are laminated or coated with waterproofing material, such as rubber, polyvinyl chloride (PVC) and polyurethane (PU). These are materials that are used in Mackintosh jackets, sauna suits, inflatable boats and even in footballs and glasses.

What is PVC and PU?

PVC clothing is shiny clothing made of the plastic polyvinyl chloride. PU clothing consists out of waterproof fabric, typically polyester, but may be cotton or a polyblend material that has been heat-laminated to a polyurethane layer. It is lightweight and extremely durable. These fabrics are used in several industries, from medical companies to the manufacture of diapers and active wear.

How can waterproof fabrics keep water from passing through, but allow water vapor to move through its fabric?

Making a material breathable and waterproof is often accomplished by using a membrane or substance that consists of many tiny holes. These pore-like holes are too small for a water droplet to pass through it, but are large enough for air molecules to evaporate. This allows a breathable waterproof jacket to protect underclothes from getting wet, while allowing sweat to pass through and escape from a person’s skin or clothes.

Detailed description

All in all there are three layers:

Inside

The interior or underside of WP/BR rainwear uses one of the following techniques and technologies to become waterproof and breathable:

Laminates are formed when a WP/BR membrane is bonded to the underside of a garment's face fabric, as if wallpaper was applied to a wall. In other words: membrane (or wallpaper) + fabric (or wall) = a laminate.

Coatings are liquid solutions that provide WP/BR characteristics when spread across the interior of a garment. It is like applying an ultrathin coat of paint to a wall.

All rainwear exteriors, also known as face fabrics are treated with a durable water repellent (DWR) finish. A DWR affects only the exterior of rainwear and is separate from the laminate or coating. Its purpose is to protect the face fabric from becoming saturated, weighing it down and causing any sensation of dampness. It (DWR) accomplishes this by causing water to bead up and roll off the garment's exterior. DWRs however do not inhibit fabric breathability.