Is polyester waterproof? Well, it depends! Now, perhaps you’re expecting a straightforward yes or no answer. But, the thing is, there’s there’s no simple answer to the question.

Stay with me, and you’ll get to see why.


First, when do we say a material is waterproof?

Well, from our everyday experience, a material is said to be waterproof if it does not allow moisture pass through it to the other side.

This explanation is quite important especially if you’re the outdoorsy type – you see you don’t want to get drenched outside during a torrential rainfall or get soaked when caught in a snowstorm.

Often, fabrics are wrongly labeled as waterproof when in reality they are merely water resistant or just weatherproof.

So, identifying whether a material is waterproof or not goes a long way in helping you manage your expectations and also decide the appropriate weather conditions to use them.

You see, there’s a ton of misleading information out there; with many manufacturers erroneously claiming their product is 100% waterproofed – nothing can be further from the truth as you will well discover for yourself.

Strictly speaking, you’d be hard pressed to find a piece of fabric that is 100% waterproof except of course, in the rare case when the material undergoes a special treatment.

The thing is, to create something that could be thought of as waterproof depends on some factors such as the material used and the method used in making the fabrics.

So, these specially treated materials are not your regular run in the mill waterproof fabrics. And they don’t come cheap.

To create this kind of fabrics, they are often coated, laminated, or sprayed to make them waterproof then their seam is joined together using a method known as ultrasonic welding.

 

As you well know, during sewing, holes are made on the fabrics. These holes usually compromise the waterproof property of the material since water can pass through them.

So, to ensure that the apparel is 100% waterproof, ultrasonic welding is used – which is essentially joining two fabrics together without sewing.

The technique involves focusing a high-frequency sound on the spots that need joining; the heat from the ultrasonic welding melts the fabrics and seals them together without a need for sewing; hence, ensuring that the apparel produced is 100% waterproofed.

But wait, aren’t polyester and nylon waterproof?

Now, I can imagine you thinking – isn’t polyester supposed to be waterproof? So if you’re claiming there’s hardly any waterproof material what about nylon?

Hold on; I’m getting to all that in a bit.

Let’s go over the grounds we’ve covered again. You now know that material is waterproof if – regardless of the weather condition it is exposed to – it does not allow moisture through it – that is, the inside stays wholly dried.

You also know that, though there are many fabrics labeled as waterproof, they are in reality not so because when subjected to severe conditions they tend to absorb water which makes them not waterproof after all.

Finally, you’re aware now that creating a truly waterproof fabric depends on:

  1. The type of material used.
  2. The technique used to create the apparel.

Having said that, let’s go back to your question.


Is polyester waterproof?

Polyester in and of itself is waterproof. This, in a sense, means that when you pick, say, a single strand of it, might not absorb water like the other fabric strands such as cotton.

You can also think of it like this: in its truest nature as a single strand of synthetic fiber, polyester is waterproof.

However, it becomes an entirely different keg of fish when the strands are woven together to create a polyester fabric.

You see, unlike a single strand, the fabric is made of both polyester and air gaps. This mixture sure weakens the waterproofness of the material.

 

Now, there are several reasons for that, and I hope to do justice to them.

So, first, we start by looking at how tightly knitted the strands are. The thing is, between the strands, there are small gaps filled with air. It doesn’t even matter how tight the fibers are woven – there are still micro-spaces between the fabrics and between the yarns.

Unfortunately, air isn’t waterproof one bit and also considering that water molecules are really tiny, they squeeze themselves through these spaces between the strands when the material is exposed to extreme conditions.

Another factor that compromises the waterproof ability of polyester is capillary action – the ability of the fiber to pull moisture from one side of the material to the other. Remember those tiny spaces? Well, as it turns out, under immense pressure, like submerging the material underwater for a long time the strands give-in and begin to absorb water.

Thankfully, there’s an effective means to eliminate the effect of capillarity and make the material waterproof. A continuous coating of the material fills in the air spaces between the strands causing the fabric to resist water.

Remember, I mentioned the waterproof of a piece of fabric also depends on the construction technique used to make it?

Well, sewing polyester material together involves making holes in the material. These holes, regardless of how small they are, can allow water to penetrate the material.

So, from the above, one can see that polyester as a material is considered waterproof since it is a homogenous material.

However, a polyester fabric, on the other hand, is not waterproof since it is made of both the strands and air spaces.


Polyester vs. Nylon: Which one is more hydrophobic?

Another question, I often get asked is – between polyester and nylon which one is more hydrophobic?

It’s unsurprising that folks are often quite confused between whether to go for polyester or a nylon fabric.

Well, the thing is, both materials shares a lot of properties in common. For one, they are both made from petroleum and crude oil residue.

Also, they are both wrinkle-resistant, easy to care for, shrink-resistant, durable, lightweight, and extremely stretch strength.

However, even with all these similarities, there are distinct differences that make each material more appropriate for a certain use.

man wearing polyester-based water repellent tshirt

For instance, Nylon is softer and silkier which lends its use to the production of underwears, compared to its competitor. On the other hand, polyester is a rougher fabric than nylon and is more abrasion-resistant which of course, makes it more appropriate for making outer garments.

But, I’m guessing you’re itching to know which among the material is more hydrophobic, isn’t it?

Both fabrics act differently when exposed to water. Polyester, for instance, tends to repel water more than nylon. This ability can be attributed to the raw material and method used in their manufacture.

Though hydrophobic, polyester is oleophilic – that is, it can absorb oil. Now, this bit of information is essential when you’re considering purchasing a sweatshirt for your outdoor activities.

You see, body odors are oil based. Now, you may ask: what has it got to do with wearing a polyester fabric?

A lot, especially if you don’t like your shirts stinking.

During a workout or a strenuous activity, you sweat your body odor binds tightly to the polyester material and doesn’t let go. Even when you launder the material, it may smell nice for a while, but once you sweat again, the odor comes back.

However, nylon fabric is not oleophilic. They quickly lose the clinging body odor when you wash it, and the smell goes away.

An upside to the hydrophobic nature of polyesters is that they can handle moisture without getting wet. This means they come in handy when the consideration is to stay as dry as possible.

On the other hand, nylon as a moisture-loving material absorbs more water and tends to take longer to dry. This can be a bad thing in winter as the nylon fabric feels colder and wet.

However, for the tropics where the temperature could get pretty high, the cold nylon cloth is a welcomed relief from the heat as it helps keep the body cool.


In conclusion

Nylon and Polyester are both synthetic fabrics that share a lot of similarities, though polyester is more hydrophobic than nylon.

Both materials have unique attributes that lend them to specific uses. Nylon as a silkier, stronger, and oil resistant is often used in making foundation wears, lingerie, raincoats, hosiery, and underwear.

Polyester being rougher, more abrasion resistant and with a higher flammable temperature, is used more for outdoor gear.

Fair enough? Your turn now! If you got this far, make sure to leave a comment below and let us know what you think about the subject. Hopefully, the article made you a little bit more open-minded towards polyester or nylon – after all, it’s technology!

Nick Davis
Author

Technology blogs contributor, I love everything that's high-tech and super solid. While traveling, hiking and surfing, I make sure to put my gear to the toughest tests. Join me in my quest of discovering gadgets with superpowers!

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