Is Polyester Breathable? (Scientifically Explained)

Categorized as Polyester

If we’re talking about polyester as material then polyester fibers are not breathable because it is made up of PET (Polyethylene Terephthalate) which is plastic, however, the polyester fabrics are always breathable though not all polyester clothing provides an equal amount of breathability.

Because the breathability of polyester fabric will depend upon the yarn structure, fabric structure, and weave construction (loose or tight).

We all know that polyester is something that can be easily found in clothing either as 100% polyester or in the form of poly-blend.

But, the main question – is polyester breathable? always comes in newbies before they want to take their polyester-made clothing to camp, hiking, beach, or in a long marathon.

If you also have that question then bear with me because I am going to scientifically explain how breathable polyester is and how good is in real-life situations.

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How Breathable Is Polyester? (Explained)

To know how breathable typical polyester fabric is, we have to know what exactly the word ‘breathable’ means in the world of textiles.

The breathability of polyester does not merely mean the flow of air through the fabric but it means how easily the fabric allows the water vapor permeation.

In science, the breathability of any fabric is measured using the Thermal Evaporative Resistance (RET) coefficient. RET tells us the capacity of a fabric to stop water vapors to penetrate to go out in surroundings.

Meaning, the lower the value of RET the more breathable the fabric will be.

And according to scientific studies, the RET score 0-6 shows extreme breathability, and 30+ means not breathable at all.

Now, you may ask what is the RET of polyester. The RET of polyester fiber when it is not fabricated is obviously 30+ because plastic is not breathable at all and as you polyester is made up of plastic.

Read Also: Can Polyester Be 100% WIndproof?

Ok what about polyester fabric, honestly, I can not give the exact value because as it is man-made fiber the value of this fabric can go anywhere from 6 to 30 but one thing is quite clear that no matter polyester will show some sign of breathability.

There are many ways to get the RET value but the most common are – the upright cup test, the inverted cup test, and the sweating hot plate test.

Upright Cup Test: The objective of this test is to measure the rate of moisture vapor transmission through the garment.

Inverted Cup Test (ICT): The ICT aims to measure how much water is absorbed.

Sweating Hot Plate Test: It is quite different from the previous two tests because in this the evaporative resistance of the fabric and the moisture lost by the garment when heat is applied are measured.

For general people, there is no need to look at how these tests are performed because it is not the chemistry/physics lab.

So now I am going to explain the factors affecting the breathability of polyester understandably.

Let’s look at this through a microscope.

For polyester to be breathable, the pores between the fibers, between the yarn, and inside the yarn must be big enough for water vapor to escape.

And pores size is directly related to the thickness, density, filament fineness, weft sett values, and weaving tightness.

Now it does not mean that you need to get a fabric where you can see through it.

That’s not what I meant. Their pores can be as small as possible but they need to be big enough for a water vapor molecule to pass from one side of the fabric to another side of the fabric.

So the sweat or vapors can evaporate because the necessary heat of absorption is extracted from the sweat itself, which leads to a heat transfer from liquid to a gaseous state, this result in the cooling effect which helps the body to maintain temperature and cool down when it gets too hot. [source]

Polyester fabrics produced from microfilament are more breathable than conventional fiber fabrics.

If you’re seeking a highly breathable polyester fabric then always go for microfibers because the surface area of microfiber is 10-15% larger than ordinary yarn.

And, the larger surfaces area means more pores and air gaps are there, but they are small enough to provide some good water resistance too.

Similarly, the polyester tends to get more and more breathable as its filament fineness increases because now there is less filament in the yarn cross-section which results in bigger size pores to provide more air to pass through.

As a general rule of thumb, ask for loosely woven polyester clothing if you want a material to be highly breathable in terms of both airflow and water vapor permeability.

For a closely woven polyester fabric, the surface area and concentration of inter yarn spaces should be as high as possible to maximize the water vapor transmission through the woven fabric.

From a manufacturing perspective, you need polyester fabric that has a high number of pores between the fibers no matter they are smaller in size because if you have a good density of pores then the water vapor permeation will happen more successively across the length than having big sized pores in an only particular area.

However, you need to make sure that pores between fibers must be greater than 10-15 microns in mean diameter because it is the size of a water vapor molecule.

If you’re feeling sweaty in your polyester clothing then it is for sure less breathable because the fabric is tightly woven, has high filament fineness, higher yarn count, and density. Meaning the fabric is closely constructed.

Can polyester be waterproof, windproof & breathable at the same time?

Yes, it is 100% possible for polyester-made clothing to be waterproof, windproof, and breathable at the same time.

This can be achieved if the fabric is produced from microfilament because they are more superior to conventional fibers and thus provide waterproofness, windproofness, and breathability.

But the microfilament yarn must be woven in high densities.

Also, the micro denier polyester fabric yarns can provide water tightness, reduced air permeability while enabling it to breathe better.

Waterproofing breathable fabric can be categorized based on the design as closely woven fabric, hydrophilic membranes and coating, microporous membranes and coating, and lastly, the combination of hydrophilic and microporous membranes and coatings.

Read Also: How Much Water Can Polyester Resist? (Technical Answer)

If you’re looking for breathable polyester fabric then you should go for microfiber because they can lot of very tiny pores that are big enough for water vapor to escape but small enough to make the water and wind penetration hard.

However, polyester fibers alone can not do this because it is very hard to make the pores smaller than the size of a water droplet but bigger than water vapor.

So, let’s be practical here if you are a buyer who wants a fabric that is excellent in waterproofing, windproofing, and also breathability then you should go for the Gore-Tex.

Because this fabric is made of Teflon that contains 9 billion microscopic pores where each pore is 20,000 times smaller than a water droplet but 700 times bigger than a molecule of moisture or water vapor.

Which makes it the best breathable, windproof, and fully waterproof fabric at the same time.

Is 100 polyester breathable?

As described in depth that if is 100% polyester fiber then it is not breathable but if it is 100% polyester clothing then it has some amount of breathability.

But the amount of breathability a 100% polyester fabric will provide depends on the structure of fabric structure and the yarn structure.

So, a 100% polyester fabric will provide a good amount of breathability if it’s loosely constructed and woven because this will result in bigger gaps between the fibers which will be big enough for air to come inside and moisture or water vapor to go out.

You need to understand here it like this, If you’ve installed a 100% iron fence in your backyard, would it block the airflow? Obviously not because there are gaps between the two iron lines.

However as you know if your home is made up of 100% iron without any window or a hole, just a cube, would it be 100% breathable? No.

The same you need to understand here if the 100% polyester does not contain pores then it would not be considered as fabric or a ‘fence of polyester’. Meaning it would be not breathable.

But if it has pores or gaps between the fibers, inside the yarn, and between the yarns itself then it would definitely have breathability which will get reduced or increased depending on the dimensions of the pores which are directly proportional to the structure and the construction of the fabric.

Is polyester more breathable than cotton?

No, polyester is not breathable than cotton because cotton is a natural fiber that has much better fine pores to allow air to pass through and moisture to escape.

However because cotton is not water-resistant it absorbs your sweat first and then it will evaporate which is a much slower process as compared to polyester which is moisture-wicking material.

That’s the reason why cotton is a more preferred fabric to wear in hot hiking or camping day because it is one of the most breathable fabric that known for its cooling abilities.

In a nutshell, cotton will absorb your sweat in its fiber which will act as a cooling agent because it will let the heat escape while polyester will not absorb your sweat in fact it will let it pass through the fabric to the surrounding which results in it to dry quicker than cotton but it will try to resist the body heat to escape which may result in access sweating or a stingy feeling for a short period of time during outdoor activities.

Though still, the polyester will breathe sufficiently but not better than cotton.

So that’s the thing you need to keep in mind.

Is polyester more breathable than nylon?

Both polyester and nylon can be equally breathable if they are loosely woven and have lots of pores that are bigger than a water vapor molecule.

So yes, in this case, it hugely depends on the weave construction and fabric structure because nylon and polyester both are man-made fibers that can be altered depending on the consumer’s need or the manufacturer’s intent.

Is polyester more breathable than microfiber?

First of all, polyester is a type of microfiber but they are not the same.

Yes, polyester is not more breathable than microfiber because microfibers are created when the polyester or polyamide fibers are split into very fine strands which result in the microfiber being more porous and thus more breathable than the conventional polyester.

And as I’ve told earlier that if a fabric has more pores between the fibers, then it tends to be more breathable than the fabrics that are not that porous.

Is Poly Blend Breathable?

Poly Cotton Blend

Poly cotton blend comes in varying percentages like 50/50 but the most popular among the outdoor lovers are 65% cotton and 35% polyester especially on hot days.

So, technically, the more the percentage of cotton in the poly blend, the more breathable it will be.

However, the polyester will help the garment to dry much quicker and that is the reason why poly-cotton blend is very famous activewear because of the combo of improved breathability and quick drying.

Poly Spandex Blend

Both polyester fibers and spandex fibers are not breathable so if it is a poly-spandex blend then the breathability of that particular garment will depend on the structure of the fabric.

Meaning, if it is loosely woven then the poly-spandex blend will be porous and offer breathability.

And, if they are tightly woven then you’re going to end up in a sweat because both fibers do not absorb sweat.

Poly Crepe Blend

It depends on the Crepe fabric type.

Meaning, the original crepe fabric is the most breathable among all it’s type thus if you’re clothing is using poly crepe blend then it will be breathable.

However, the more will depend on the weave type itself.

Poly Viscose Blend

Yes, the poly-viscose blend is breathable because viscose absorbs the sweat and does not trap the heat which makes it ideal activewear for a hot day.

Poly Satin Blend

First of all, there is no poly satin blend as the manufacturer describes because satin is not a fiber it is a weave type that polyester can be.

A satin weave polyester gives a glossy look thus the breathability here will depend on the construction of the weave and structure of the fabric and yarn.

Is polyester breathable for masks?

As told it depends on the weave construction if it is loosely woven then you can breathe through your polyester mask.

But breathing through a polyester mask take effort because you’re relying on the tiny pores between the fibers for the air to pass through as polyester fibers themselves are not breathable on their own.

That’s why CDC recommends having a mask that is breathable and according to our research silk and cotton, masks are much better in terms of breathability as compared to face masks made up of polyester.

And because of that, it is not recommended by the health experts to wear 100% polyester masks because it can increase the local humidity which can create a conduit for viral transmission.

According to PLOS Global Public Health, it saw that the silk is a hydrophobic barrier which results in the silk face masks to be more breathable than other fabric that traps the humidity.

As an addon, silk face-covering possesses the properties that make them capable of repelling water droplets.

Is polyester breathable for bedding?

Yes, polyester is breathable for bedding but because it does not absorb moisture, may feel too hot or stiff at night.

But if polyester bedding is made up of microfibers then it would be more breathable than ordinarily polyester.

However, I would not recommend you to use polyester for bedding on hot summer days because there are natural fibers like cotton which tend to be the most breathable and cooling fabric.

Is polyester breathable for underwear?

Polyester underwear is not much breathable because for underwear it is good that the fibers absorb the sweat so that it won’t cause any infection or gave room to bacterias in the genitals.

That’s why Healthline recommends cotton-made underwear because it is the most breathable fabric and also absorbs moisture which can help prevent yeast infections.

Are polyester socks breathable?

Yes, polyester-made socks are breathable because generally, the socks feature mesh fabric instead of a tight weave. But still, for hot summer days, I would recommend you to go for cotton socks because they are more breathable and cooler than polyester.

And this mesh fabric will have lots of gaps that will allow the air to touch your feet and because the pores are pretty big they will also let the moisture and sweat wick quickly.

But, I am quite certain, that if you wear polyester socks on hot days then you may feel a bit sweaty in your feet because the polyester fibers are water-resistant and thus don’t absorb moisture.

But don’t worry all your sweat will despair quickly as soon as you pull out your shoes because polyester is a quick-drying breathable fabric.

Though cotton socks always breathe better than polyester because they will absorb the sweat and allow the heat to escape which may feel like there’s sweat at all.

Are polyester hats breathable?

For hats, I would not recommend polyester because they are great insulators meaning if you wear a polyester hat in summer you’re going to sweat more and feel more heat in your heat. Though polyester hats can be a great companion in the winter season when you want your head to remain warm.

The other reasons are polyester fibers don’t absorb sweat meaning you can literally feel your head sweaty till it gets wicked outside the surface.

But, in that short period of stinginess, infections can occur.

So, better go with wool or cotton hats because they are naturally breathable and will keep your head cool on hot days.

Are polyester pants breathable?

Again it depends on the weave construction, a tightly woven polyester pant is way less breathable than a loosely woven polyester pant.

In my case, I like to wear polyester pants in winter because of their insulating properties and cotton or natural material pants in summer because they are more breathable and way less stingy.

Are polyester shirts breathable?

Like polyester pants, polyester shirts can also be breathable if they are loosely woven and better made with microfiber because a microfiber polyester shirt will breathe much better than ordinary polyester.

But again polyester shirts are not recommended on generally warmer and hot days because they are not moisture-absorbent thus it is guaranteed that the sweat won’t go public but you will be damp in sweat for some time till the polyester wick the sweat which it will.

So consider polyester clothing in winter for warmth and breathability.

Are polyester leggings breathable?

Polyester leggings are highly popular because they are breathable, sweat-wicking, and water-resistant.

All thanks to its hydrophobic nature.

Is polyester breathable for comforter?

Polyester is not breathable enough for comforters in summer but comfort-loving people will love the polyester clothing in the winter season because it wicks the moisture, trap the body heat, and is breathable enough for winter conditions

Is polyester breathable for babies?

No polyester is not breathable enough for babies because this fabric does not absorb the moisture and its fibers don’t breathe at all.

Also if you’re baby is under a polyester blanket, please remove it because the polyester tends to get hotter which may increase the body temperature and cause excess sweat on already high-temperature nights.

Thus, instead of polyester, you should go for natural fibers for your baby like cotton, silk, merino wool bamboo, etc because they can absorb the sweat of your body and have high heat conductivity meaning your baby will remain cooler on hot days.

Though you can absolutely go for a poly-cotton blend if you want the breathability and coolness of cotton and the quick-drying and moisture-wicking quality of polyester for your baby.

In short for babies’ bedding you should always go for natural fibers while for winter wear you can go for poly-cotton blend or clothing made from wool or cotton are good.

But please make sure that the layer is not thick enough to block the breathability.

Refrences

  • Dr. S. K.Chinta (professor), Darbastwar Satish (research scholar) – Studies in waterproof breathable textile – research pulished on IJRDET
  • Padleckiene, Ingrida & Petrulis, Donatas & Rubeziene, Vitalija & Valiene, Vitalija & Abraitiene, Ausra. (2009). Breathability and Resistance to Water Penetration of Breathable-Coated Textiles after Cyclic Mechanical Treatments. Medziagotyra. 15. 69-74.
  • L. Hunter, J. Fan. Waterproofing and breathability of fabrics and garments, In Woodhead Publishing Series in Textiles, Engineering Apparel Fabrics and Garments, Woodhead Publishing, 2009, Pages 283-308, ISBN 9781845691349
  • Mukhopadhyay, Arunangshu, and Vinay Kumar. “A Review on Designing the Waterproof Breathable Fabrics Part I: Fundamental Principles and Designing Aspects of Breathable Fabrics.” Journal of Industrial Textiles, vol. 37, no. 3, Jan. 2008, pp. 225–262, doi:10.1177/1528083707082164.
  • Influence of textile property on thermal comfort. A Marolleau et al 2017 IOP Conf. Ser.: Mater. Sci. Eng. 254 182007