Politereftalan

Politereftalan, known internationally as polyethylene terephthalate (PET), is a thermoplastic aromatic polyester used in a wide range of applications. It is typically produced from terephthalic acid (or dimethyl terephthalate) and ethylene glycol, and is commonly referred to by its shorthand PET. In Turkish contexts it is often called politereftalan.

The polymer consists of a repeating ester linkage between terephthalate units and ethylene glycol, forming a stiff yet processable chain. PET is generally semi-crystalline and exhibits a glass transition around 70°C with a melting point near 250°C. It offers high clarity when amorphous, excellent toughness, good chemical resistance, and a low permeability to water and gases, making it well suited for packaging and fiber applications.

Production occurs in two main stages: esterification or transesterification of the diacid (or dimethyl ester) with ethylene glycol, followed by polycondensation under reduced pressure to yield high-molecular-weight polymer. Catalysts are used to optimize reaction speed and polymer quality. PET can be synthesized from terephthalic acid or from dimethyl terephthalate, and its properties can be tuned through polymer processing and crystallization conditions.

Applications include beverage bottles, food and consumer packaging films, and textile fibers (polyester) used in clothing and industrial fabrics. PET fibers and films are valued for strength, durability, and recyclability.

Recycling and environment: PET is widely recycled through mechanical recycling into fibers and new bottles, and chemical recycling technologies exist to reclaim monomers. Recycling rates vary by region, and PET waste management is an area of ongoing environmental and policy focus to reduce pollution and resource use.

Historically, PET was discovered in the 1940s by researchers in the United Kingdom and later commercialized for fibers (Dacron) and, from the 1970s onward, for bottling applications, contributing to its status as one of the most versatile polymers worldwide.