Polyester is the world's most widely produced synthetic fiber, manufactured from polyethylene terephthalate (PET), the same polymer used for plastic beverage bottles. Global polyester fiber production exceeds 60 million tonnes annually, accounting for more than half of all textile fiber production worldwide. Polyester's dominance stems from its combination of low cost, versatility, durability, and ease of care.
PET Polymer Chemistry
Polyester fiber begins with purified terephthalic acid (PTA) and monoethylene glycol (MEG), both petroleum derivatives. These monomers undergo polymerization at high temperature and under vacuum, forming long-chain PET molecules. The resulting polymer chips are melted and extruded through spinnerets with thousands of microscopic holes. As the filaments emerge, they are stretched up to five times their original length to align the polymer chains, increasing strength and reducing fiber diameter.
Standard polyester filaments range from 0.5 to 5 denier per filament. Microfiber polyester, defined as fibers finer than 1 denier per filament, can be as fine as 0.1 denier, approximately 100 times thinner than a human hair. These ultra-fine fibers create fabrics with exceptional softness, high surface area, and the ability to be tightly woven into windproof yet breathable textiles.
Performance Properties
Polyester is inherently hydrophobic, absorbing less than 0.5 percent of its weight in moisture, compared to 7 to 8 percent for nylon and higher for cotton. This property enables moisture-wicking fabrics where perspiration is drawn away from the skin through capillary action between fibers rather than absorbed into them. Polyester dries quickly, resists wrinkles, retains its shape, and resists stretching and shrinking.
The fiber has high tenacity (2.5 to 6.0 grams per denier depending on type), good abrasion resistance, and excellent resistance to acids, oxidizing agents, and UV degradation. Its melting point is approximately 250 to 260 degrees Celsius, and it softens at around 230 degrees Celsius, which limits ironing temperatures but enables heat-setting of pleats and shapes.
PET Recycling and rPET
Polyester is the most recycled plastic polymer globally. Recycled polyester (rPET) is produced primarily from post-consumer PET bottles. The recycling process involves collecting, sorting, and cleaning bottles, then grinding them into flakes. These flakes can be processed into fiber through mechanical recycling, where they are melted and extruded, or through chemical recycling, which breaks the polymer down to monomers for repolymerization.
The environmental case for rPET is substantial: producing rPET fiber uses roughly 50 percent less energy and 90 percent less water than virgin polyester, while reducing reliance on petroleum feedstocks and diverting plastic from landfills. Major brands including Patagonia, Adidas, and IKEA have committed to significant rPET usage. However, rPET still sheds microplastic fibers during washing, and recycling PET into fiber may be its last useful form before eventual disposal, since fiber applications typically preclude further recycling into high-clarity bottle-grade PET.
Microplastic Concern
Polyester fabrics, particularly fleece and other mechanically finished textiles, release microplastic fibers during home laundering. A single synthetic garment can shed hundreds of thousands of microfibers per wash. These fibers pass through wastewater treatment plants and enter aquatic ecosystems, where they have been found in marine organisms, drinking water, and even human blood and lung tissue. Washing machine filters, garment bags like Guppyfriend, and shifts toward woven rather than knit synthetics represent mitigation strategies, but the problem is inherent to the material. Research into biodegradable polyester alternatives and improved fiber construction is ongoing.