Polyester is made from petroleum. Specifically, two chemicals derived from crude oil are combined: ethylene glycol (a type of alcohol) and terephthalic acid (an organic acid). When these two building blocks react together, they form long chains of a plastic polymer called polyethylene terephthalate, or PET. This is the same material used in plastic water bottles, just processed differently to create fibers for fabric.
The Two Building Blocks
Ethylene glycol is a colorless, odorless liquid produced from ethylene, a gas extracted during petroleum refining. Terephthalic acid is a white powder also derived from petroleum. These two substances serve as the raw ingredients for nearly all polyester fiber production worldwide. While it’s theoretically possible to source them from plant-based materials, petroleum remains the dominant starting point. Global synthetic fiber production accounts for roughly 1.5% of all crude oil consumption.
How Petroleum Becomes Fabric
Turning oil-based chemicals into soft, wearable fabric happens in two main stages. First, ethylene glycol and terephthalic acid are heated together in a reaction called esterification, where the two molecules link up and release water as a byproduct. This creates short chains and intermediate compounds.
In the second stage, called polycondensation, those short chains are heated further under vacuum conditions, which forces them to keep linking together into much longer molecular chains. The result is molten PET polymer. This molten material is then forced through tiny holes in a device called a spinneret (think of a showerhead) to form thin strands. As those strands cool, they solidify into fibers that can be stretched, crimped, and cut to mimic the feel of natural textiles like cotton or wool.
An alternative manufacturing route starts with dimethyl terephthalate instead of terephthalic acid. In this version, the first step is a transesterification reaction with ethylene glycol, followed by the same polycondensation process. Both routes produce essentially the same end product.
Types of Polyester Fiber
Not all polyester is identical. The fiber industry recognizes three main categories: PET fibers, modified PET fibers, and PCDT fibers. PET is by far the most common because it’s cheap to produce and easy to modify for different uses. Its molecular chains contain repeating ring-shaped structures that make the fiber stiff and strong.
PCDT polyester uses a slightly different alcohol molecule in place of ethylene glycol, which gives the resulting fiber more elasticity and resilience. It’s less common but shows up in applications where extra stretch matters, like heavy drapery fabrics. Modified PET fibers are standard PET that’s been chemically tweaked during production to change specific properties, such as improving dye absorption or reducing static cling.
Why Polyester Feels the Way It Does
The chemistry of polyester directly explains its familiar characteristics. Those stiff, repeating ring structures in the polymer chain make the fiber resistant to stretching and wrinkling, which is why polyester clothes hold their shape so well after washing. The fibers are smooth and rod-like, typically round in cross-section, which gives them a slightly slick feel compared to the irregular surface of cotton.
Polyester barely absorbs water. Its moisture regain rate is just 0.4%, meaning a polyester garment sitting in a humid room picks up almost no moisture from the air. For comparison, cotton’s moisture regain is around 7 to 8%. This is why polyester dries quickly but can feel clammy against skin during exercise: sweat sits on the surface rather than being absorbed into the fiber. The fiber is also remarkably tough, with tensile strength ranging from 500 to 1,147 MPa, and it won’t begin to break down until temperatures exceed 240°C (464°F). Add in strong resistance to sunlight, abrasion, and weather exposure, and you have a fiber that outlasts most natural alternatives.
Beyond Clothing
The same PET chemistry that makes clothing also produces films, resins, and rigid plastics used across dozens of industries. Thin polyester films provide electrical insulation in capacitors, transformers, and flexible circuits, where their resistance to moisture and ability to block electrical current make them ideal. In cars, polyester films appear in lighting components, interior trim, and protective surface layers. The construction industry uses polyester as barrier films in insulating glass and protective laminates that improve energy efficiency. Packaging, healthcare devices, printing substrates, and graphic arts all rely on polyester film as well. Plastic bottles remain one of the largest single uses of PET outside textiles.
The Microplastic Problem
Because polyester is plastic, it sheds tiny plastic fibers every time it’s washed, worn, or dried. Research on polyester knit fleece found that a single wash releases an average of 1.4 milligrams of microplastic fibers per gram of fabric during the first cycle. That rate drops somewhat over time, settling to about 0.59 milligrams per gram by the sixth through tenth washes. Tumble drying adds to the problem: the first drying cycle releases roughly 0.83 milligrams per gram, tapering to about 0.17 milligrams per gram in later cycles. These fibers are too small to be caught by most wastewater treatment systems and end up in rivers, oceans, and soil.
Polyester is also extremely slow to decompose. In a landfill, without the UV light and oxygen that help break down plastics on the surface, polyester fabric can persist for decades or longer. This durability, the same property that makes polyester so useful, is also what makes it an environmental concern.
Recycled Polyester
Recycled polyester (often labeled rPET) is made by melting down used plastic bottles or old polyester garments and re-forming them into new fibers. The chemical structure of the resulting fiber is the same as virgin polyester, so performance is comparable. The environmental benefit comes from skipping the petroleum extraction and initial chemical synthesis. A life-cycle analysis published in ACS Sustainable Chemistry & Engineering found that recycled PET bottles produced from fossil-fuel-derived sources cut greenhouse gas emissions by about 19% compared to virgin PET. When bio-derived feedstocks are included, reductions range from 12% to 82% for greenhouse gases and 13% to 56% for fossil fuel consumption, depending on the specific production pathway.
Recycled polyester still sheds microplastics during washing and still resists biodegradation, so it doesn’t solve every environmental issue. But it does reduce dependence on new petroleum and keeps existing plastic out of landfills, which is why it’s become increasingly common in outdoor gear, activewear, and everyday basics.