Diethyl terephthalate is primarily used as an intermediate in the production of polyethylene terephthalate (PET), a widely used polymer in the manufacture of plastic bottles, packaging materials, and synthetic fibers. Its role in the polymerization process is crucial for creating high-quality PET with desirable properties such as strength, durability, and transparency. Additionally, it finds application in the synthesis of certain polyesters and coatings, where it contributes to enhancing the material's thermal stability and chemical resistance. In the textile industry, it is utilized to produce fibers that are used in clothing, upholstery, and industrial fabrics. Its versatility also extends to the production of films and sheets for various industrial and consumer applications.