Polyester Defined

What the Word Polyester Actually Means

Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term polyester as a specific material most commonly refers to polyethylene terephthalate, PET. Polyesters include naturally occurring chemicals, such as the cutin of plant cuticles, as well as synthetics made through step-growth polymerization such as polycarbonate and polybutylene terephthalate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not, a fact that shapes both their durability in use and their environmental discussion.

Depending on the chemical structure, polyester can be a thermoplastic or a thermoset; however, the most common polyesters are thermoplastics, as Rosato's plastics selection handbook notes. Thermoplastic behavior is the practical key to textile polyester: PET can be melted, extruded into filament, drawn for strength, heat-set into shape and, at end of life, melted again. Nearly everything polyester fabric does well, from permanent pleats to wrinkle resistance, traces back to that melt-processable chemistry.

Polyester Fabric in Apparel and Furnishings

Fabrics woven or knitted from polyester thread or yarn are used extensively in apparel and home furnishings, from shirts and pants to jackets and hats, bed sheets, blankets and upholstered furniture. Polyester fiber is also used as cushioning and insulating material in pillows, comforters and upholstery padding, where its resilience and resistance to moisture give it a long working life. Few fibers serve so many product categories at once, which is why polyester pricing and polyester definitions matter to almost every corner of the trade.

Synthetic clothing in general is perceived by many as having a less natural feel compared with fabrics woven from natural fibers such as cotton and wool, polyester fabrics can provide specific advantages over natural fabrics, such as improved wrinkle resistance, durability and high color retention. Synthetic fibers can also create materials with superior water, wind and environmental resistance compared with plant-derived fibers, which is why outerwear and performance clothing rely on them so heavily.

Blends: Polyester With Natural Fibers

As a result of that trade-off, polyester fibers are sometimes spun together with natural fibers to produce a cloth with blended properties. The classic blends pair polyester's strength, wrinkle resistance and color retention with cotton's softness and moisture absorption in shirts and sheeting, or with wool's warmth and drape in suiting. Blending is an engineering compromise in the best sense: each fiber covers a weakness of the other, and the blend ratio tunes the result toward comfort, durability or price as the product requires.

For buyers, blends carry a specification lesson. A blended fabric's price follows both fiber markets, its care instructions follow the more delicate component, and its hand and performance sit between the parents rather than matching either. When a supplier describes a cloth simply as a polyester blend, ask for the exact percentages and which polyester form, filament or staple, the blend uses. Those details, plus the construction, predict the finished garment far better than the single word polyester, however familiar it has become.

Beyond Clothing: Industrial and Technical Uses

Industrial polyester fibers, yarns and ropes are used in tire reinforcements, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements with high-energy absorption. Polyesters are also used to make plastic bottles, films, tarpaulin, canoes, liquid crystal displays, holograms, filters, dielectric film for capacitors, film insulation for wire and insulating tapes. Liquid crystalline polyesters are among the first industrially used liquid crystal polymers, valued for mechanical properties and heat resistance, including service as an abradable seal in jet engines.

Polyesters are even widely used as a finish on high-quality wood products such as guitars, pianos and vehicle and yacht interiors, where thixotropic spray-applied polyesters fill open grain quickly with a high-build film, and cured polyester can be sanded and polished to a high-gloss, durable finish. Polyester runs from a shirt to a jet engine and a piano. Understanding what polyester is, in all its forms, is the foundation for the fiber, yarn, fabric, resin and chip prices tracked in the companion pages, and for the wider textile glossary on Apparel Search.