Polybutylene terephthalate
If a material with high strength, good dimensional stability, low wear and good chemical resistance is required for applications, polybutylene terephthalate (PBT) is the right choice.
Abbreviation
PBT
Molecular formula
C12H12O4
CAS no.
24968-12-5
General description
Partially crystalline structures cause the high stiffness, strength and toughness as well as the low creep tendency of the material polybutylene terephthalate (PBT).
PBT belongs to the group of polyesters. In addition to its convincing mechanical properties, the thermoplastic material is characterised by its high insulation resistance and low moisture absorption. The material is ideally suited for technical applications and, compared to the similar material polyethylene terephthalate (PET), can be better processed in injection moulding because it crystallises more quickly.
PBT has a high chemical resistance to many solvents, acids, greases, oils and chemicals. The typical temperature range for the use of this material lies between -50 and +150 °C.
Definition
Polybutylene terephthalate (PBT) is a thermoplastic used in technical applications for industry, in the field of household appliances, in the electronics industry as well as in automotive construction. It is a thermoplastic, semi-crystalline polymer that can be easily injection moulded, welded and bonded. The material belongs to the polyester group.
The plastic has excellent chemical resistance, is solvent resistant and shows low shrinkage. Its mechanical stability and impact strength are excellent, and wear is very low. The material has good heat resistance.
Production
Modification produces a wide range of PBT grades that are, for example, flame-retardant, easy-flowing or characterised by high impact strength. Reinforced or filled variants have an increased stiffness or strength, enable an increase in wear resistance or a reduction in the coefficient of sliding friction.
The material, which is primarily processed using injection moulding, is very adhesive and weldable.
Properties
PBT has excellent wear and sliding behaviour. The stiffness and strength are high, but slightly lower than that of PET. In contrast, PBT has a slightly improved toughness at low temperatures.
Chemical resistance
One of the most notable properties of polybutylene terephthalate is its chemical resistance. PBT has good chemical resistance to acids and very good resistance to caustic solutions and chlorine.
The material has low moisture absorption and good weather resistance.
Processing techniques
Injection moulding is the main process used for processing PBT. The melt temperatures are between 230 and 270 °C. Typically, mould temperatures are below 60°C. If an optimal surface finish is desired, temperatures of 110 °C are required.
The connection methods used are hot-gas and heating element and ultrasonic and friction welding. Gluing techniques are used for bonding with reaction resin adhesives.
Like polyethylene terephthalate (PET), PBT is a semi-crystalline thermoplastic and is very similar to the material PET in both its chemical structure and properties. PBT has the advantage over PET that it is easier to process, as the material crystallises faster and is better suited for injection moulding.
The granulate must be dried in a similar way to PET before use.