What Is Polyester, Actually? A Breakdown of the Plastic in Your Closet

Pick up any piece of clothing in your house and check the tag. There's a good chance it says polyester, nylon, acrylic, spandex, or some blend of them. Those words sound like fabric types. They're not. They're types of plastic.

Every one of those materials is derived from petroleum. The same crude oil used to make gasoline, plastic bottles, and shopping bags. The textile industry just gave them softer names.

Polyester: Literal Plastic Bottles in Shirt Form

Polyester is polyethylene terephthalate, or PET. The exact same polymer used to make plastic water bottles and food packaging. It's produced by reacting petroleum-derived ethylene glycol with terephthalic acid at high temperatures, then extruded into thin fibers and woven into fabric.

Polyester accounts for 59% of all fiber produced globally. Roughly 78 million tonnes in 2024 alone. It's in fast fashion, athletic wear, bedsheets, couch cushions, and children's clothing. If a garment is cheap and stretchy, it's almost certainly polyester or a polyester blend.

The marketing pitch has always been convenience. When DuPont introduced polyester to the American market in 1951, they sold it as a "miracle fabric." Wrinkle-resistant, easy to wash, no ironing needed. After World War II, consumers wanted affordable, low-maintenance clothing, and synthetic fibers delivered. The fact that those fibers were petroleum byproducts wasn't part of the sales pitch.

Polyester fell out of favor in the 1970s when overproduction flooded the market with cheap, low-quality versions and the fabric earned a reputation for being tacky and uncomfortable. But the industry rebranded. By the 1990s and 2000s, polyester came back as "performance fabric," "moisture-wicking technology," and "athletic wear." Same plastic, better marketing.

Think about that next time you're shopping for a new ski base layer or a pair of mountain biking shorts. "Performance blend" sounds technical. "Petroleum plastic pressed against your sweating skin" doesn't sell as well.

Source: textileexchange.org/knowledge-center/reports/materials-market-report-2025 Source: tandfonline.com/doi/full/10.1080/17569370.2023.2196158

Nylon: DuPont's First Synthetic Hit

Nylon was the original synthetic fiber, developed by DuPont chemist Wallace Carothers in the 1930s. It's a polyamide, another petroleum-derived plastic, created through a chemical reaction between adipic acid and hexamethylenediamine.

DuPont introduced nylon stockings in 1940 and sold 64 million pairs in the first year. The fiber became a wartime material (parachutes, ropes, tire cords) before returning to consumer fashion after the war.

Today, nylon shows up in leggings, swimwear, activewear, windbreakers, and tights. Like polyester, it's treated with chemical additives during production, including BPA, phthalates, and various dye fixatives, that can migrate out of the fabric during wear.

Acrylic: The Wool Impersonator

Acrylic fiber is made from acrylonitrile, a petroleum-derived chemical classified as a probable human carcinogen by the EPA. The fiber is designed to mimic the look and feel of wool. Soft, warm, lightweight. At a fraction of the cost.

You'll find acrylic in sweaters, hats, scarves, blankets, and fake fur. It's one of the worst offenders for microplastic shedding. Research has found that acrylic releases significantly more microfibers during washing than polyester or nylon. So every time you wash that cozy acrylic sweater, you're sending a wave of plastic microfibers into the water supply.

Spandex (Lycra/Elastane): The Stretch Chemical

Spandex is a polyurethane fiber. Yes, the same chemical family as foam insulation and industrial coatings. DuPont invented it in 1958 and branded it Lycra. It's what gives athletic wear, jeans, and underwear their stretch.

Spandex is almost never used alone. It's blended into cotton, polyester, and nylon at 2-20% to add elasticity. So even a shirt labeled "95% cotton" often contains spandex, which means it's not fully natural and can't biodegrade the way pure cotton would. This one is hard to avoid completely, and I'm not going to pretend I own zero spandex. But knowing it's there changes how I shop.

Rayon and Viscose: The Tricky In-Between

Rayon deserves its own section because it confuses people. It starts as a natural material, wood pulp, usually from trees. But the manufacturing process is so chemically intensive that the end product has more in common with synthetic fabric than natural fiber.

The standard viscose process involves dissolving wood cellulose in sodium hydroxide (a highly corrosive chemical), then treating it with carbon disulfide. Carbon disulfide is a neurotoxin linked to coronary heart disease, nervous system damage, reproductive harm, and possibly Alzheimer's disease, according to a review published in the International Journal of Occupational and Environmental Health. Workers in viscose rayon factories have experienced devastating health effects for over a century. And while the factories have largely moved from the US and Europe to South and East Asia, the process hasn't fundamentally changed.

The end product, rayon or viscose, is often marketed as a "natural" or "plant-based" fabric. Technically the raw material is plant-based, but calling viscose "natural" is like calling high-fructose corn syrup "natural" because it started as corn.

There are cleaner alternatives within this category. Tencel (lyocell), made by the Austrian company Lenzing, uses a closed-loop process that recovers and reuses 99% of its solvents. Modal, also from Lenzing, is similar. If you're going to buy anything in the rayon family, look for Tencel or lyocell specifically, and check that the brand names the actual fiber rather than just "rayon."

Source: pmc.ncbi.nlm.nih.gov/articles/PMC6137800

How We Got Convinced This Was Normal

The synthetic takeover wasn't accidental. After World War II, petrochemical companies had massive production capacity and no more military contracts. They pivoted to consumer goods, and textiles were a perfect outlet for petroleum byproducts.

The fashion industry cooperated because synthetics were cheap to produce, easy to dye, and allowed for faster manufacturing cycles. When fast fashion exploded in the 2000s, polyester became the backbone of the business model. You can't sell a $5 t-shirt made from organic cotton. You can sell one made from polyester.

The language helped, too. Tags don't say "petroleum-based plastic fiber." They say "polyester" or "performance blend" or "moisture-wicking." Activewear brands built entire identities around synthetic fabrics, positioning them as high-tech and aspirational. Nobody markets a polyester shirt by saying "this is made from the same material as a soda bottle."

I fell for it for years. I bought the cute workout sets, the cozy fleece pullovers, the "performance" everything. I didn't know what I was putting on my body because nobody told me to flip the tag.

Reading a Clothing Tag Like an Ingredient List …

Here's the framework I use now. It takes two seconds once you get used to it.

Wear freely: Organic cotton, hemp, linen, wool, merino, silk

Proceed with caution: Conventional cotton (pesticide-heavy but not plastic), modal (better process than viscose), bamboo lyocell (not bamboo rayon)

That's plastic: Polyester, nylon, acrylic, spandex/elastane/Lycra, standard rayon/viscose

Once you know what to look for, it changes how you see every store, every online listing, every tag. The hard part isn't identifying the plastic. It's finding clothes without it. Which is exactly what the next post in this series covers.

Cailin + Whitley (the cat)