How Does Waterproof Fabric Work?

Waterproof jackets can be a lifesaver when it comes to the rain. But how does the fabric work exactly? Is it breathable at all? Find out all about waterproof fabric here!

The Science Behind Waterproof Fabrics

A waterproof jacket might seem like a simple piece of clothing, but beneath the surface, it’s a marvel of modern engineering.

The way they’re designed, the coated fabrics repel liquid water droplets while allowing moisture from sweat to evaporate, keeping you dry and comfortable even in challenging weather conditions.

So how does it work?

The secret lies in the fabric’s structure. It consists of many layers, which form a laminate – one that is both waterproof, thanks to a membrane, and breathable, due to its microporous structure.

The micropores in the membrane are small enough to prevent water droplets from penetrating but large enough to allow sweat vapor to escape.

This ingenious design, exemplified by materials like Gore-Tex, makes waterproof breathable fabrics a staple in outdoor gear.

Waterproof Membranes

Waterproof fabrics are typically made from materials like expanded polytetrafluoroethylene (ePTFE) or expanded polyethylene (ePE).

These membranes create a barrier that prevents wind and rain from penetrating the fabric, while their microporous structure allows perspiration to escape.

Take the ePTFE membrane used in Gore-Tex as an example, its extremely thin and tight weave blocks water while facilitating the evaporation of perspiration.

Another innovative technology, eVent, enhances PTFE fibers with an oleophobic protective solution, preserving the membrane’s microporous and air-permeable structure for superior breathability.

Popular Brands Known For Waterproof Fabric

Some well-known brands include:

• Gore-Tex, which uses a unique polytetrafluoroethylene membrane with 9 billion pores per square inch to achieve its waterproof and breathable properties
• eVent fabric, which offers a tightly woven, highly porous alternative that allows for breathability without relying on a polyurethane coating
• Marmot’s MemBrain, which offers waterproof breathable fabrics without a continuous PU layer, allowing immediate venting of water vapor for increased breathability
• Mountain Hardwear’s Dry.Q Elite, which also offers waterproof breathable fabrics without a continuous PU layer, allowing immediate venting of water vapor for increased breathability

Waterproof Jackets: Layers and Construction

Waterproof jackets are constructed with different layers and techniques, such as 2-layer, 2.5-layer, or 3-layer designs, with each offering varying levels of durability, breathability, and waterproofness.

A 3-layer jacket, for instance, consists of a face fabric, a waterproof/breathable membrane, and an inner lining.

On the other hand, 2.5-layer jackets enhance the waterproof membrane’s durability with a printed or sprayed inner material.

This also allows for a thinner waterproof membrane and face layer, which helps reduce the overall weight of the jacket.

Layer Functions

Every layer in a waterproof jacket has a designated role. The outer layer, typically made from nylon or polyester, provides durability and is typically coated with DWR to help shed water.

As far as the innermost layer goes, the function depends on the jacket type.

In 2-layer jackets, a mesh is used to protect the waterproof layer, while 3-layer jackets use a high-performance layer bonded to the membrane for breathability and protection against body oils and dirt.

Some laminates may even include an additional thin coating over the ePTFE membrane to prevent body oil contamination.

Seam Sealing Techniques

Techniques such as taping, welding, or gluing are used to prevent water from seeping through seams, ensuring complete waterproofness.

Seam taping involves the use of a heat-applied waterproof tape that covers the tiny holes made by the needle during sewing.

Keep in mind, however, that not every seam may be sealed in a waterproof jacket.

For example, ‘critically taped’ jackets have tape only on high-exposure areas such as the hood, neck, and shoulders.

‘Fully taped’ garments, on the other hand, have every seam covered.

Durable Water Repellent (DWR) Coatings

DWR coatings are applied to fabrics, such as nylon or polyester, to enhance their water resistance by creating a hydrophobic effect that causes water to bead up and run off the surface.

These water-resistant fabrics provide an additional layer of protection against moisture, making them ideal choices for waterproof coating applications.

How DWR Works

DWR coatings amplify the water-repellent properties of fabrics.

They work by creating a microscopically ‘spiky’ surface on the textile, which increases the contact angle of water, also known as ‘surface tension’.

A higher contact angle leads to water droplets forming more dome-shaped beads on the fabric, preventing them from spreading or seeping into the material.

Caring for DWR Coatings

DWR coatings, like any other material, require proper care and maintenance.

For one thing, it should be cleaned regularly to remove dirt and oils.

To reactivate the DWR finish after washing, place the garment in a dryer on low or medium heat for 20 minutes.

For areas where the DWR coating has worn off, you can re-apply it using an at-home spray.

Waterproof and Breathability Ratings Demystified

Waterproof Rating: Hydrostatic Head

The hydrostatic head test determines a fabric’s waterproof capability by applying water pressure to one side and identifying the point at which water begins to penetrate.

A higher hydrostatic head test value means the fabric can withstand greater water pressure before leaking.

Breathability Ratings: Moisture Vapor Transmission Rate (MVTR)

Breathability in waterproof garments is determined using the Moisture Vapor Transmission Rate (MVTR), measured in grams per square meter over a 24-hour period.

A higher MVTR value means the fabric allows for more moisture vapor to pass through, which translates to higher breathability.

For instance, a fabric rated at 15k MVTR will allow 15,000 grams of water vapor to pass through per square meter in 24 hours.

Choosing the Right Waterproof Garments for Your Needs

There are several things to consider when choosing a waterproof garment, including:

• Waterproofness
• Breathability
• Material composition
• Key features like ventilation and adjustable closures

How Does Waterproof Fabric Work – Overview

The science behind waterproof fabrics is both fascinating and complex.

From membranes and micropores to coatings and laminates, every aspect of a waterproof fabric’s design contributes to its ability to keep water out while allowing sweat to escape.

Understanding these principles can help you make informed choices when shopping for waterproof garments, ensuring you stay dry and comfortable in even the most challenging weather conditions.

Key Takeaways

• Waterproof fabrics utilize a laminated structure with a microporous membrane, such as Gore-Tex, that blocks liquid water while allowing moisture vapor from sweat to escape, balancing waterproofness with breathability.
• There are different types of waterproof materials and construction methods, including coated versus laminated fabrics, 2-layer to 3-layer jackets, and each offers varying levels of durability and breathability for specific uses and conditions
• Waterproof and breathability ratings provide insight into a fabric’s performance and are determined by tests like Hydrostatic Head for waterproofness and MVTR for breathability

Understanding Waterproof Clothing – FAQs

What about the fabric that makes it completely waterproof?

Waterproof fabrics are usually made of natural or synthetic materials and are coated with waterproof substances like rubber, PVC, PU, silicone elastomer, fluoropolymers, and wax.

What is the difference between waterproof fabric and water-repellent fabric?

The difference between waterproof fabric and water-repellent fabric lies in the degree to which they resist water.

Waterproof fabric completely repels water, while water-repellent fabric has an extra coating that improves its performance in repelling water.

How does Durable Water Repellent (DWR) coatings work?

DWR coatings work by creating a hydrophobic effect on fabrics, causing water to bead up and run off the surface, enhancing their water-repellent properties.

What do waterproof and breathability ratings mean?

Waterproof and breathability ratings measure a fabric’s ability to resist water and allow sweat to escape and are measured using tests like the hydrostatic head and Moisture Vapor Transmission Rate (MVTR). This helps determine how well the fabric will perform in different conditions.