It can be synthesized through ester exchange method, which involves a ester exchange reaction between dimethyl terephthalate and ethylene glycol, followed by condensation polymerization under high temperature and vacuum conditions. In addition, it can also be directly esterified with terephthalic acid and ethylene glycol, and then prepared through condensation polymerization. After polycondensation, further solid-state polycondensation can increase molecular weight. The ester group in the molecular chain is conjugated with the benzene ring, making the molecular chain more rigid, slowing down the movement of the chain segment, and reducing the crystallization ability. Therefore, materials are mainly amorphous. The relative density of the polyester is 1.38 g/cm 3, The glass transition temperature is 67 to 80 ° C, the melting temperature is 250 to 265 ° C (related to the degree of crystallization), the thermal degradation temperature is 300 ° C, and the heat deflection temperature (at 1.82 MPa) is 65 ° C. It has excellent tensile properties, wear and friction resistance, excellent creep resistance, and good processing and electrical insulation properties. The heat resistance of PET materials reinforced with glass fiber is significantly improved, its heat deflection temperature can reach 220 to 240 ° C, and its long-term use temperature can reach 120 ° C. The main application of PET is in the production of fiber products, commonly referred to as polyester. PET fabric has excellent wrinkle resistance, heat resistance, light resistance, resilience and insulation, and is widely used in the manufacture of textiles, tire cord fabric and electrical insulation materials. In addition, PET can also be used to produce biaxially stretched films, stretch blown bottles, and so on. After glass fiber, carbon fiber reinforcement and alloy treatment, the products can be used in machinery, automobiles, electronic instruments and other fields.
Organic polymer materials -> Plastics