Polyester

Polyester is a category of polymers that contain ester functional groups in the main chain. The best-known polyester is polyethylene terephthalate (PET), which is used to produce fibers for clothing and containers for beverages and foods. Other polyesters include polytrimethylene terephthalate (PTT) and polybutylene terephthalate (PBT).

Most polyesters are formed by condensation polymerization, combining diols with dicarboxylic acids or by transesterification of dimethyl esters with diols. A common route for PET uses ethylene glycol and terephthalic acid, or dimethyl terephthalate with ethylene glycol in a transesterification sequence. Catalysts and vacuum conditions drive polymer growth and molecular weight.

Polyesters vary in crystallinity and can be melt-processed into fibers, films, and engineering plastics. PET fibers are strong, wear-resistant, and dimensionally stable, with excellent abrasion resistance; PET resins offer chemical resistance, clarity, and barrier properties for bottles. Polyester is relatively hydrophobic, dries quickly, and blends well with natural fibers.

Applications include textile fibers for clothing and home furnishings, packaging films and bottles, and engineering plastics such as PBT used in automotive parts and electronics.

PET is widely recycled through both mechanical and chemical processes. Recycled PET can be made into fibers, strapping, or new bottles. Concerns include resource use, energy demand, and microplastic pollution from synthetic textiles; ongoing advances aim to improve recycling rates and design for circularity.