What Is Polyester? + Why It's More Eco Than We Thought
Published: August 09, 2021Updated: September 24, 202214 min read4 Comments
Think of this blog post as Wicked, but for polyester. If you aren’t familiar with Wicked, it is a Broadway play that was written from the point of view of the Wicked Witch Of The East, you know, that evil green lady with the flying monkeys from The Wizard Of Oz. What happens in the show is that, when we hear the story from a different perspective our feelings and opinions about all the characters shift. What the show teaches us, is that we often cast judgments with limited information. And, that’s what the media has done to polyester. Does polyester have its problems? Absolutely. But, I think when you take the time to really learn about what is polyester, your opinions about this fashion industry villain, just like the witch in Wicked, will change.
The world of fashion news is chaotic. There is this oversimplistic world of publications like Fashionista where a credible news source is anyone with over 100k followers on Instagram.
The consequence of journalists getting quotes from people with the most likes instead of credible experts is that you, the consumer, end up getting left in the dark about what it is you are actually supporting when you buy something new. Whether it is polyester clothing, or something else.
That’s why it’s so important for me to take you on A Look Behind The Seams of the fashion industry. I want you to see the full picture, not just a snapshot.
The History Of Poly
Have You Heard Of Polymer Science?
To understand where polyester comes from, first, we need to take a quick peek into the world of polymer science.
Whenever I hear the world polymer science I always think about the character Rusty Cartwright from the early 2000's cult tv show Greek. Ok, maybe I am dating myself here. He was a polymer science major. And, what the show made very clear, in just about every episode, was that it was basically the hardest major at the college.
Anyway, polymer science is a really serious discipline. And, it requires an insane knowledge of science, specifically chemistry.
Not only are polymer scientists responsible for creating polyester. They are also responsible for other materials. Polymers can be plastics like kevlar (think, bulletproof vests), and Teflon (stick-free pans). Or, they can be all natural like rubber or even wood.
"By definition, polymers are large molecules made by bonding (chemically linking) a series of building blocks. The word polymer comes from the Greek words for “many parts.” Each of those parts is what scientists call a monomer (which in Greek means “one part”). Think of a polymer as a chain, with each of its links a monomer. Those monomers can be simple — just an atom or two or three — or they might be complicated ring-shaped structures containing a dozen or more atoms."
Fiber Invention History Is Like A Really Messy Family Tree (With Multiple Divorces)
Ok, now that we understand the type of seriously smart people who are responsible for plastic innovation (because that is what the invention of polyester really was - the development of a new type of plastic), we can dive into the history.
Dr. Wallace Carothers was a leading scientist at DuPont. And, is credited with inventing nylon. But, what much of modern textile history forgets, is that he laid the groundwork for polyester. The legend goes that DuPont made a strategic decision at the time to push forward with nylon research and abandon polyester.
Polyester was then picked up by J.R. Whinfield and J.T. Dickson both of Calico Printers Association in England. While polyester was able to be successfully produced, again it took second stage to nylon.
That is because during this time of textile innovation WWII was also happening. And, nylon, was a quick easy way to replace silk parachutes, and ultimately helped us to win the war. So, polyester was ignored for a while.
Now, I have Been Calling It Polyester But, During This Time, Polyester Did Not Go By The Name We All Know It As Today
It was around 1953, and the UK company Imperial Chemical Industries bought the British patent from Calico for the chemical technology and called the fibers produced Terylene. And, in the United States DuPont bought back the chemical patent and manufactured it under the name Dacron.
Kind of ironic right? DuPont had to buy back the patent for a fiber they basically created.
By 1958 Eastman Chemical Products created their own polyester called Kodel. And, the way they got around the patents was that they produced them using a slightly different method than Terylene and Dacron.
After that, in 1960 Imperial Chemical Industries (UK), teamed up with Celanese Corporation of America to produce yet another type of polyester - Fortrel.
And, finally, Beaunit released their version of poly, Vycron.
By the 1990s (when many of us reading this were alive, I know I was) there were a total of 13 companies that were making different versions of poly in the United States. They were - Albany International, Allied Fibers, Ametek, BASF Fibers, du Pont, Eastman Chemical Products, Firestone Fibers, Fuilford Fibers Division, Hoechst Calenese, Johnson Filaments, Monofilaments, Inc. Shakespear, and Wellant Industries.
Isn't that wild to think about? Only 30 years ago this country was a top producer of polyester! And, now we make none of it.
A Look Behind The Seams
Now that we know the soap opera level history of polyester production and all its patents, let’s talk about how it is actually made.
There are two common chemical mixes for polyester. The first is dimethyl terephthalate and ethylene. And, the second is terephthalic acid and other dihydric alcohols. Add a lot of heat to the mix, and a byproduct of the reaction is methanol.
Methanol is what is most problematic in this equation, not necessarily the dependence on petroleum (read crude oil and fossil fuel).
According to the CDC “Methanol may cause birth defects of the central nervous system in humans. Chronic poisoning from repeated exposure to methanol vapor may produce inflammation of the eye (conjunctivitis), recurrent headaches, giddiness, insomnia, stomach disturbances, and visual failure.”
The heated mixture is then filtered to remove any impurities. And then, the pure mixture passes through a spinnerette (basically a really tiny showerhead). When the liquid comes out of the other end it is cooled in the air forming a fiber.
It sounds pretty simple, right? And, it kind of is. The only problem is the byproducts of the process are pretty toxic, as I mentioned just a second ago. And, for some reason, no one is talking about it.
A few months ago I got in a disagreement with a rando in a sustainable fashion Facebook group that I am a part of. I was talking about how I didn't think that polyester deserved the terrible reputation the media gave it, and I had a few facts to back up my opinion… More on those in a second.
I went into the conversation thinking she was just another consumer with misinformation. So, why not hit her with some science? Because that's what this topic is really all about, textile science.
But, what I soon realized was that she had a hemp bathing suit company. Meaning, she had an agenda, to push her wares on people.
Now, I am sure she meant well. Even though she basically called me an earth-destroying goblin for even suggesting hemp was not the most sustainable choice.
Now, this girl was a bit unhinged - why does a civilized disagreement always need to result in name-calling on the internet? But, it did get me thinking about a major problem with startup supply chains and information.
Brands, or soon to be brands, you can't believe everything you are told.
Even from your suppliers. Even, if you really want to believe it.
Because, the truth is, suppliers are often going to tell you what it is that they think you want to hear.
The biggest example of this is all of the banana and lotus silk in India. It's all fake. Everyone that works in the industry knows it, but every day there is yet another wide-eye, a little too trusting newbie brand believing what anyone will tell them.
So, let’s get to the real facts.
Natural polyester fibers are slightly transparent and off-white. And, hemp fibers can range from cream to brown.
There are two advantages to adding color to polyester over hemp.
The first one might be a little obvious, especially if you are an artist or know a little about color mixing.
Polyester creates a better base than natural hemp. Think about it this way. If you wanted to paint your walls bright yellow. Would you start with a brown base, or a white one? A white one, because the brown would most likely show through the yellow paint and create a dirty-looking color.
So, to dye hemp effectively first you need to process it with a semi-bleach treatment. To get it closer to a white color.
The whole extra step of preparing hemp for dying involves tons of water, chemicals, and heat (read energy). Not exactly eco, right? For those of you keeping count. That’s one point for polyester.
The second thing we need to talk about when it comes to color is the dyeable color range. Synthetic fibers get their color with disperse dyes. And, hemp generally uses reactive dyes.
Here’s what they mean…
Disperse dyes require a crazy amount of heat to push the color into the fibers. But, once the colors are in there, they are pretty stuck. That is why polyester fabrics dyed with disperse dyes tend to have good very good colorfastness. Colorfastness is the industry way of saying how well color sticks onto a fabric. Generally, disperse dyes go well with polyester fibers, and other fibers with a petroleum base. They don't play well with plant fibers like cotton, or rayon. And, another benefit to disperse dyes is that you can literally hit any shade under the sun.
Reactive dyes work by creating a covalent bond (yes, I know, more science) with the fiber. These dyes are as simple as RIT dye that you can buy off of Amazon and use in your own bathtub. But, with a little extra heat, they do tend to perform better. These are easy to use, but they only really work on cellulosic fibers like cotton, rayons, and of course hemp. The downside to these easy peasy dyes is that they have a limited color range. Super brights like neons are impossible to achieve. And, reactive dyes are not as colorfast, meaning they fade easier than disperse dyes.
So, based on color performance, what is the better option to use?
Poly will leave you with a brighter longer lasting color. But, if you are looking to lower your footprint, and use less electricity/heat, or even dye at home, hemp might be the way to go.
Remember, I am never going to tell you this is right and this is wrong. All I can do for you is tell you the facts, and let you make your own decisions.
In the textile industry, tenacity is a term we use to describe the strength of a fiber. A common unit of measure to describe the strength of a fiber is g/d or grams of breaking force per denier (denier is how we measure the width of a synthetic yarn). Generally, the stronger the fiber the better, because that means the fabrics and garments should be strong too.
Polyester, depending on what type you use has a tenacity of 2.5-9.5 g/d. That is a huge range. But, most apparel uses polyester that has a tenacity of 4.5g/d.
In comparison, hemp has a tenacity of 5.8-6.8 g/d. So, while we can manufacturer polyesters that are stronger than hemp, generally, in most of the apparel in our closets the hemp we find is stronger than the polyester.
This seams promising for our perfect swimsuit doesn’t it?
But, The Next Thing We Need To Ask Is. How Strong Is The Fiber When It Is Wet?
Many fibers (like cotton) become weaker when they are wet. And swimsuits are meant for the water, so this is important to think about.
Quick side note. Fiber strength when wet is part of the reason why laundering clothes will make them wear out quicker. They are in an already weakened state, being bashed around a washing machine.
Anyway. Polyester keeps about the same amount of strength when wet. But, get this. Hemp actually gets stronger when wet.
So, for a bathing suit this is actually starting to sound like the perfect fiber option, strong, and then ever stronger when wet!
But, there hold off on making any decisions, there are a few more things we need to think about.
Moisture Regain + Saturation Regain
Moisture regain is the percent of moisture in a fiber under normal conditions. Saturation regain is the percent of moisture absorbed by a fiber with 95-100% humidity.
And, FYI, 100% humidity means that the air is totally saturated with water, and even just the littlest bit more humidity will push it over the edge and create rain.
So, what does this have to do with picking the perfect textile for a swimsuit?
Polyester has very low moisture regain at only about 0.4% and 0.6-0.8% for saturation regain. This means polyester does not really like water, and it’s very quick drying.
But on the negative side, very dry fibers tend to build up a lot of static electricity. Basically poly is not your friend if you are trying to create long flowy gowns for the desert. The try conditions will make the fabric crumple right up and the fabric sticks to itself.
But, this is perfect for a swimsuit. For comfort, when you go swimming you don’t want your bathing suit to absorb a lot of water, because when it does it becomes heavy, stretches out, and is not just uncomfortable, but also a hazard to swim in.
Hemp has a moisture regain of 12% and saturation regain of 30%. Hemp really likes water, and it will absorb a lot of moisture.
Loving to absorb water is part of what makes hemp so comfortable to wear in hot climates, it is able to absorb sweat from the body creating a cooling sensation. Where polyester in the heat literally feels like you are wearing a plastic bag (because you technically are).
So, while hemp is great for a hike through the jungle. It’s not very comfortable to swim in. And, once you get it wet, be prepared to be damp for a while.
For this reason, if you are planning to swim in your swimsuit (did you know some companies are making swimsuits for fashion only that can’t get wet) polyester is probably a better choice over hemp.
Swimsuits are meant to be worn in the warm weather, and part of swimsuit culture is being a beach bum - always out in the sun.
Polyester has very good sun resistance in and so does hemp.
Now, when you think of sun resistance you might actually be getting the concept confused with colorfastness. Colorfastness means how much color will fade in the sun. Sun resistance, measure if a fabric will degrade from sun exposure.
Many natural fibers tend to start to break down when they are left in the sun for prolonged periods of time. Luckily, hemp is not one of those types of natural fibers.
What about pests and mold?
Insects and microorganisms don’t really like to eat polyester (part of the reason it lasts so long in the landfill).
And, another benefit of poly is that mold does not really affect it. Even if the fabric does grow mold, it will rarely affect the strength of the garment. All you need to do is clean the mold off (in Goa we just throw our clothes in the sun and the UV light will kill it), and it’s basically as good as new.
Hemp isn’t as resilient to pests, but overall compared to a lot of other natural cellulosic fibers pests don’t really love it.
But, hemp does create a nice habitat for mold to grow.
So, if you are thinking about using hemp for a swimsuit, that could be a problem. Mold loves moist environments, and a swimsuit that naturally has trouble drying out creates the perfect place for mold to grow.
When it comes to keeping your swim gear mold-free, I think polyester has an advantage.
Microplasticity basically means that you can mold the fabric by melting it down and then re-setting it in a shape. An example of this technique in use are pleats and permanent presses. Now, I am not sure where that would come in helpful designing a swimsuit, but it’s a cool textile function to know about.
So What Would You Make A Swimsuit Out Of?
By now I hope you are starting to realize, fibers are not one size fits all.
When you are designing something it is important to look at the end-use. Not, just the fibers pros and cons in a vacuum. Some fibers are better for certain products (like poly for swim). While others are better in different categories (like hemp for denim).
A Few More Things I Think You Should Know About Polyester
How Polyester Has Improved Through The Years
HIGGS Index Says It's More Sustaianble Than Silk And Other Natural Fibers
The HIGG Index (an offshoot of the Sustainable Apparel Coalition) ranks the environmental impact of everything fashion. And, is basically the gold standard for both small and large brands alike.
If you didn't hear, some of the craziest conscious fashion news of 2020, was the HIGGs Index proclaiming as polyester one of the most sustainable fibers to use.
"Figures from the all-new fibre scoring tool show the environmental impact of polyester according to the MSI has fallen from 44 to 36 – making it by far and away the most sustainable fibre on the planet. Meanwhile, Higg’s completely unwarranted attack on the silk industry (and other natural fibres) continues – silk’s impact per kilo has risen from 681 to 1086 per kilo."
Unpacking the HIGG index will need to be a post for another day. But I encourage you to start doing your own research into what they are saying about polyester.
So, Is Recycled Polyester More Eco-Friendly?
Yes and no. Like I am constantly preaching, the answers to fast fashion problems are not black and white.
While it’s great that polyester can be made from old plastic, like from water bottles, fishing nets, and industrial waste. The process to make new fibers isn’t exactly chemical-free.
"Methanolysis is a process through which scrap PET is heated and treated with methanol. The process breaks down the plastic into its component monomers, dimethyl terephthalate (DMT), and mixing ethylene glycol (EG), which are purified and used to make new plastic. Eastman calls its technology “polyester renewal technology.”
So, dangerous methanol is still part of the equation.
Not All Polys Are The Same, There Are Actually Many Different Qualities Depending On Use
What is polyester material like? When polyesters first hit the market, they were round, bouncy, and created very distinct-looking fabrics. Today they come in all shapes and sizes. From brushed knits that are super cozy to fabrics that are almost identical to silk, to high-performing outdoor apparel.
Microplastics (ps...I was the first to report on this, before any MSM)
Speaking of all polyesters being different, listen to this.
I know the confused media has taught us all to believe that all polyesters are evil because they release microplastics. But, the actual reality is that they all don’t. Some fabrics release them, and some hardly do.
So how do you know which are polluting the oceans, and which are ok to buy? Well, that’s the hard part.
IMO, it should be the job of companies to do the necessary testing to find out if the polys they are using are contributing to damaging the oceans, or if they are using safe polyesters.
There is actually a test by the AATCC to find this out (although it does cost a pretty penny).
Finally, Let's Have An Open Discussion
There are no wrong answers here.
Here are my two cents. It’s important to consider the end-use of the garment. Yes, polyester is often used to cheapen products and increase bottom lines. But, sometimes when used correctly, like in the case of swim, or performance apparel. Or, if it is being used to add a little bit of strength it helps make cotton clothes last longer, it really could be the best, dare I say, more sustainable option.
I think it’s important to look holistically at the garment design, and also what is important to you, and then decide if using polyester really is, that bad.