Polybutyleeniglytereftalaatti

Polybutyleeniglytereftalaatti, known in English as polybutylene terephthalate (PBT), is a semi-crystalline thermoplastic polyester. It is widely used as an engineering plastic due to a balance of stiffness, toughness, and chemical resistance. PBT is typically prepared by polycondensation of terephthalic acid (or dimethyl terephthalate) with 1,4-butanediol, yielding long chains of terephthalate units linked by butylene glycol segments.

Chemically, PBT is a polyester whose repeating unit comprises a terephthalate group connected through butylene glycol residues. The material can be produced as neat resin or reinforced with glass fibers to increase stiffness and dimensional stability. It is often available in flame-retardant grades and in blends with other polymers.

Key properties include good mechanical strength and wear resistance, excellent dielectric properties, and good resistance to many chemicals and fuels. It exhibits low water absorption compared with some other plastics, though moisture uptake can still affect dimensional stability and mechanical performance. The glass transition temperature is typically well below room temperature, while the melting temperature lies in the range of roughly 220 to 235°C. These characteristics make PBT suitable for high-precision, thermally stable parts, though continuous use temperatures are limited compared with higher-temperature engineering polymers.

Processing of PBT is well established by injection molding and extrusion, enabling a wide range of components such as electrical connectors, housings, relays, gears, and automotive parts. Reinforced grades (PBT-GF) and flame-retarded variants expand its application portfolio. Recyclability is supported within engineering-plastics recycling streams, although lifecycle impacts depend on formulation and use conditions.