Are you looking for a new raincoat or purchasing waterproof fabric to sew your own jacket? You are probably wondering which waterproof fabric to choose. Polyester is a durable and affordable fabric popular in many styles of clothing. But is polyester fabric waterproof?
Polyester fabric is water-resistant, but on its own, it is not waterproof. Polyester is a polymer. Its individual fibers are waterproof, but once woven into a fabric, water can soak through the gaps in the fabric’s weave.
In this article, we’ll take a look at what makes polyester water-resistant, as well as what steps you can take to make polyester waterproof. We’ll also discuss how polyester lines up against other waterproof fabrics.
Waterproof vs Water-Resistant Fabric
What is Waterproof Fabric?
To be truly waterproof, a fabric must be able to hold water on its surface without any moisture seeping through. Most fabrics, in their natural states, are not fully waterproof. They are usually treated with a special coating or sealant to make them 100% waterproof.
The downside of these coatings is that they often make the fabric less breathable. We’ll take a look at the pros and cons of various treatments later in this article.
Whether or not a fabric product (such as a jacket or backpack) is waterproof depends on the fabric it is made of, but it also depends on the quality of any seams or closures in the product. For example, if your winter coat has a zipper in the front, and the wind blows rain through the zipper, your coat is not 100% waterproof.
What is Water-Resistant Fabric?
Water-resistant may sound less impressive than waterproof, but for most practical purposes, it can accomplish the same goals.
Water-resistant fabric repels water from its surface. However, with enough pressure or weight, that moisture will eventually soak through the fabric.
Lab tests are often performed to determine how many millimeters of water can rest on water-resistant fabric without any moisture soaking through.
Here’s the thing: most of the time, the water-resistant fabric is more than sufficient to keep you, your tent, or your outdoor patio cushions dry. How many times have you shoved your iPhone in the pocket of your rain jacket while you dashed across a rainy parking lot to get to your car? Nine times out of ten, the water-resistant fabric of your jacket probably kept you and your phone pretty dry.
Now, if you just survived a hurricane and you need to swim across a flooded parking lot, your rain jacket is not going to keep you dry for very long. Once enough millimeters of water weigh down on the water-resistant fabric, moisture will start to seep through. That is the difference between waterproof and water-resistant.
Is Polyester Fabric Waterproof?
One-hundred-percent polyester fabric, on its own, is not fully waterproof. However, it can be made waterproof in a variety of ways.
Unlike cotton or silk, which are derived from natural products, polyester is made in a factory from synthetic (man-made) chemicals that come from petroleum. This is important because the way polyester fabric is formed gives it unique water-resistant properties.
The process of making polyester begins with something called polymerization. In very basic terms, this means that single-molecule forms of alcohol are combined with an acid to create long ribbons of melted plastic. These ribbons dry and become hard, which makes it easy to break them into tiny bits.
These bits of brittle plastic are melted and spun out into a single, very long strand; this pulls all the polyester molecules into a consistent, straight structure that makes polyester strong and resilient.
These threads on their own are essentially waterproof since they are made of solid plastic. However, once they are woven together to make fabric, tiny spaces between the threads can allow water to pass through.
A very high thread count in a piece of polyester fabric makes it more water-resistant since there are fewer air gaps between the threads that water molecules can creep through.
Typically, though, a special coating is applied to polyester to increase its waterproof abilities.
Does Polyester Absorb Water?
On its own, 100% polyester fabric can resist quite a bit of moisture. Because of its plastic threads, polyester is slightly hydrophobic (which is just a fancy way of saying water-resistant).
If a piece of polyester fabric is left out in a gentle rain, the raindrops will bead on the surface of the polyester instead of soaking straight through. However, if the rainstorm turns into a thunderstorm and the raindrops begin to pelt into the polyester, the added pressure will force some water through those tiny gaps in the fabric’s weave.
If you have a fabric shower curtain at home, chances are pretty good it is made from polyester. You might notice that water from the shower forms tiny droplets on the curtain instead of soaking them into it in a large watery stain. You can easily shake the droplets off into the tub and the curtain will be dry in no time.
Polyester threads do not absorb water the way cotton threads would. But polyester fabric will hold water if enough moisture accumulates in the gaps between the polyester threads in the weave.
Popular Uses of Water-Resistant Polyester Fabric
Like most materials, polyester can be used in many ways. Polyester is popular because it is cheap, easy to mass-produce, and easy to work with. Polyester and nylon are the most commonly used water-resistant fabrics on the market.
Here are some of the most popular uses for water-resistant polyester:
- Outdoor furniture cushions
- Shower curtains
- Chair and sofa slipcovers
- Bean Bag chairs
Is Polyester Good for Rain?
Polyester is so water-resistant that it is often considered to be “everyday waterproof.” It is a popular material for windbreakers, raincoats, and winter coats. Brand names like Lands End and North Face sell polyester coats.
Polyester is designed to be durable and long-lasting. In fact, it is not biodegradable, which some people see as its greatest flaw. The good side of this is that polyester fabric is wind-resistant, stain-resistant, and mildew-resistant. Its strong plastic threads make it tear-resistant as well.
Polyester’s moisture-resistant surface makes it easy to wipe any mud or stains off its surface without damage to the fabric as well.
So, yes! Polyester is generally good in the rain. As a quick word of warning, it is not equally good with high heat. At high temperatures, polyester fabric will melt and can cause serious injuries.
How to Make Polyester Fabric Waterproof
There are two widely-used methods for making polyester either more water-resistant or fully waterproof. These methods are increasing the tightness of the weave in the polyester fabric and adding a seal or coating to the fabric.
You are probably familiar with the idea of thread count from things like bedsheets. You know that 1,000 count sheets are very soft and smooth, while 400 count sheets might be a bit rougher to the touch. Polyester works in a similar way, though its fabric thread count is measured in something called a denier.
If you see a polyester fabric described as “50d,” the “d” stands for denier. Denier is a term of measurement; it means the mass in grams per 9,000 meters of fiber. If that has you scratching your head, picture 9,000 meters of thread piled on top of a scale. The weight of that thread, in grams, equals the denier of the fabric that will be made from the thread.
Usually, a high denier means a thicker or closer woven fabric. Of course, as you know by now, more fibers woven more closely together means fewer air gaps in the weave for water to sneak through. So a higher denier polyester will be more water-resistant than a lower denier fabric.
Another way to close the weave in polyester is to layer fabric. This is not practical in every situation, but things like bean bag chairs can achieve a sturdy, waterproof finish by making a cover from multiple layers of polyester.
The most effective way to fully waterproof polyester fabric is to give it an additional, protective seal or coating. Several forms of polyester, like PUL and TPU, are made with these special coatings (which we’ll get into in just a moment!).
You can also effectively waterproof your polyester tent, backpack, or poncho by using a special silicone spray. Do a bit of research and make sure the spray is designed to adhere to polyester first, though!
Scotchgard Water and Sun ShieldOne of the most popular and effective spray coatings is Scotchgard 3M. This reputable brand has been around for quite a while; many outdoorsy people regularly treat their outdoor gear once a year with Scotchgard as a water repellent.
Many people also use this aerosol fabric protector for patio furniture, umbrellas, and even tents.
Scotchgard is easy to use. It can be lightly sprayed over many kinds of surfaces (including polyester) as a protective coat against UV rays, water, and dirt. It is also odorless and helps prevent yellowing.
Atsko Silicone Water-GuardHere is another example of a highly effective water repellent spray.
This is another silicone coating that works well on polyester, as well as on footwear, tents, and outdoor gear.
It does take a bit longer to dry–72 hours is suggested.
However, once dry, the coating is clear and odorless.
Types of Waterproof Polyester
There are also several polyester fabrics that are made waterproof by adding coatings to the fabric.
“PUL” (Polyurethane Laminate)
This fabric consists of a laminated layer on top of a thin knit polyester. The lamination is either glued onto the fabric or fused to it.
It is often used for things like upholstery, sports gear, and shower curtains. PUL is usually machine washable. It is fairly breathable and a tiny bit stretchy.
“TPU” (Thermoplastic polyurethane)
This fabric is similar to PUL. It is made by bonding a polyurethane membrane to polyester fabric. It is slightly softer than PUL, though some people consider it to be less durable.
TPU is often used for making waterproof cloth diapers, survival suits, and outdoor wear. This fabric is flexible, waterproof, and UV resistant.
This fabric is considered to be totally waterproof! It is made by coating poly-vinyl chloride on the back of polyester fabric.
Because of its backing, PVC-coated polyester is a bit stiff. However, it’s very useful for making raincoats, luggage, and banners. It typically has a high denier, so it is very strong and durable as well.
On its own, polyester fleece is strongly water repellent, but it is not actually waterproof unless you add a special spray. Despite that, it is often used to contain moisture in things like cloth diapers.
Polyester Blends: Are They Waterproof?
If you are familiar with polyester, you probably know that it is often blended with other fabrics to create different effects. Poly blends are usually made by spinning polyester fibers with natural fibers to make a blended thread that can then be woven into a fabric.
These blends are popular worldwide and have thousands of uses. But are they waterproof?
Poly Cotton Blend
This blend takes the breathability of cotton and the resilience of polyester and combines them into a stretchy, comfy fabric. A lot of t-shirts are made from this fabric.
The addition of highly absorbent material like cotton to the polyester does mean that this fabric is not super water-resistant, though.
Poly Wool Blend
This luxurious-feeling fabric is warm and soft. It is also water-resistant (both polyester and wool fibers are water-repelling). Many winter coats are made from this soft blend. However, it is not entirely waterproof.
Poly Spandex Blend
This is a light and stretchy fabric that is perfect for workout wear. Your yoga pants are probably made from poly spandex! It is also often used for things like compression tops and swimwear.
As you might guess from its swimwear applications, poly spandex can be a great water repellent.
Where to Buy Waterproof Polyester
By now, you have probably realized that polyester fabric is everywhere!
Waterproof Canvas Polyester FabricHere are a couple of examples of waterproof polyester fabric by the yard, in case you are interested in sewing your rain jacket or patio cushions!
Polyester fabrics that have been treated for waterproofing can usually be purchased at any major fabric retailer, such as the Amazon and Joann Fabric samples provided here.
Sharkborough NODLAND Hiking BackpackThis hiking backpack is made from durable and water-resistant polyester. It is lightweight for outdoor use.
It also features padded and adjustable straps for added comfort.
A lot of outdoor gear is made from polyester or a polyblend because it is strong and water, wind, and UV resistant.
This makes for sturdy gear that can withstand the rigors of hiking.
JASAMBAC Waterproof Long Raincoat Trench Coats WindbreakerThis stylish rain jacket is made of poly spandex. It might not withstand a dip in a swimming pool, but it is highly water-resistant.
It is also quick-drying and lined for additional warmth.
The jacket can be machine washed for easy care. It comes in a number of fun colors to suit your spring or fall wardrobe!
Now you will know all about denier, breathability, and water resistance when you search for just the right polyester fabric to suit your needs.
Which is More Waterproof, Polyester or Nylon?
Polyester and nylon are the top fabrics for any kind of waterproof clothing or gear. Both fabrics can be effective (which is why they are so popular!). However, polyester is naturally more waterproof than nylon.
Like polyester, nylon is a synthetic material. Both fabrics are wrinkle-resistant, stain-resistant, stretchy, and capable of holding their shape for long periods of time. Both fabrics are cheap and are mass-produced in any number of kinds of clothing.
Nylon is usually stretchier and softer than polyester and is used for things like underwear and stockings. Polyester is slightly more water repellent than nylon. However, nylon (or a variety of nylon blends) is often used for water-repelling uses, such as in umbrellas when it is correctly treated.
Both nylon and polyester are commonly used for rain jackets, tents, and swimwear. That said, nylon is much more absorbent than polyester. It is typically either blended with another fabric or treated in a special way to give it the water-repellent properties that polyester has naturally.
Next time you’re researching rain jackets, you know what to look for! Check the type of material, look at the denier of the fabric, and consider the special coating that may have been added to the fabric.
Let us know how you feel about water-resistant polyester in the comments!