In 1941, two British chemists invented polyester. Today, it is one of the most popular synthetic fabrics because it is durable, chemical-resistant, lightweight, and easily pigmented.
Besides those, many people also think that polyester is heat resistant. But a few others disagree. So, in this article, we’ll examine if polyester is indeed flammable.
Is Polyester Flammable?
Polyester is non-flammable but heat-resistant, as claimed. This is because the major compound in polyesters (Polyethylene terephthalate – PET) has a high melting point. However, when heated hot enough, the PET can melt and burn with a low-intensity flame.
However, once you remove the ignition source, the PET stops burning. Because of that, the United States Consumer Product Safety Commission classifies polyester as a Class-1 fabric. So, many polyester materials don’t need to undergo compulsory flame tests before using them.
For that reason, polyester is a good choice for fabric. But try not to wear polyester materials in areas exposed directly to high temperatures. Because if it melts onto your skin, you can suffer severe scalds and burns.
When compared, melted polyester can burn your skin more severely than other fabrics like cotton. So, manufacturers often make unique blends of polyester rather than materials with 100% polyester contents.
We call those materials poly blends. To make them, the producer’s mix thread fibers from other materials like silk, cotton, spandex, or wool with a premium polyester fabric.
The resulting poly blends have lower melting points than the premium polyester. But compared to most non-polyester components, poly blends still withstand more heat.
For instance, a silk poly-blend will not resist heat as a 100% polyester material. But compared to a 100% silk material, the silk poly blend should be more heat-resistant. Although without a proper flame test, you can’t say much.
What Happens When Polyester Catches Fire?
Because of certain factors that we’ll discuss later, polyesters resist heat inherently. Up to about 480°F, polyesters remain unwavering to heat. Above that, the material will melt.
If you keep heating the material to about 809°F and the molten polyester is large enough, it can burn with a low-intensity flame.
Most times, the melting rate and the intensity of the flame depending on how hot the fire is and the percentage of polyester in the material. If the polyester is 100%, you can expect it to melt more than a poly blend, which will burn more.
When polyester burns, it emits smoke, as we see in most combustion reactions. According to a research paper published in the National Library of Medicine, fumes from synthetic polymers can kill rats. What’s worse, it takes only bits of those materials to kill them.
Luckily, humans are bigger than rats, and tests on humans may not happen. But the reports from the research are reason enough to avoid the fumes that ooze while burning polyesters.
But to keep safe, all you have to do is keep your polyester away from a naked flame, right? Well… not really, because even under the wrong iron temperature or a high dryer setting can melt your polyester.
So, the trick is to keep polyesters from anything above 450⁰F as a whole. But if you need to iron your polyester fabric, there’s a way to it. In the recommendation section, we’ll drop you a few tips.
But on a general note, you can say that premium polyester fabrics and poly blends are quite a heat resistant. For that reason, the United States CPSC allows brand makers to produce kids’ sleepwear from polyester.
Why Is Polyester Heat-resistant?
The major reason polyester can resist high heat lies in its chemical nature and molecular structure. Structurally, synthetic polyesters contain high-melting semi-crystals.
Interestingly, these crystals connect in such a symmetrical way that they would require extreme heat to break down. Even if they break down, you can reshape some thermoplastic polyesters and cool them.
So, besides fabrics, polyesters also make good engineering thermoplastics and films. That said, let’s discuss the flammability and the heat-resistant ability of a few polyester materials below:
- Polyester Resin.
Polyester resins are liquid unsaturated polyesters. They can only withstand a temperature of about 162⁰F.
As a liquid, polyester resins have a flash point (which is the minimum temperature at which liquids form ignitable vapors).
For polyester resins, the flash point value is approximately 90⁰F. So, polyester resins are flammable and you should handle them with extreme caution.
- Polyester Insulation Materials
Polyester Insulation Materials contain aromatic polyesters that are highly heat resistant. So, they are non-flammable and behave just like any standard polyester as we’ve discussed earlier.
Besides extreme heat, polyester insulation can resist water and corrosive chemicals as well.
- Polyester Batting and Fiberfill.
Polyester battings are petroleum products used in textile industries. Producers prefer polyester battings because they hold their shape and thickness compared to other fibers.
They are non-breathable. But they are quite resistant to both mold and mildew, which is why they make a good choice.
However, like most petrochemicals, polyester batting catches fire easily compared to other polyester products. But it performs better when treated with a flame retardant chemical.
For fabrics, the heat-resistant ability of polyesters also depends on the fibers and the weaves of the fabric.
Summarily, a 100% polyester material can withstand more heat than a poly blend. Then, the more loosened the weave is, the lesser its ability to withstand heat.
In this article, we clarified polyesters are non-flammable because they contain PET. PET is inherently heat resistant, and that’s why the US product safety body classifies it as a Class-1 fabric.
However, when the heat is hot enough (*even iron or dryer temperature), polyesters melt. This molten form can burn. But the intensity depends on the percentage of polyester in the material.
So, 100% polyester fabrics melt more but burn less than poly blends.
Before we go, we promised to give you a few tips on how to iron polyesters. Here are a few lines:
- Always set your iron correctly. You can always check for the correct heat dial setting for cotton, polyesters, and other highly resistant clothes like Kevlar.
- Try not to skip the manufacturer’s label on your clothes. Check for the recommendation for iron temperature, and stick to it.
- It is always safer to place a thin, pressing cloth between the hot iron and the polyester fabric. This will put you more at ease while ironing.
We’ll wrap things up with that. If you want to learn about flammable and non-flammable materials, check out other Flamevenge articles here.