Polybutylene Terepthalate (PBT)
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Polybutylene Terephthalate (PBT) is a crystalline, high molecular weight polymer that has excellent balance of properties and processing characteristics. In general, PBT materials exhibit higher tensile, flexural and dielectric strength and faster, more economical molding characteristics than many thermosets. Compared to polyethylene terephthalate (PET), PBT has slightly lower strength and rigidity, slightly better impact resistance, and a slightly lower glass transition temperature.
Properties of Polybutylene Terepthalate
- Excellent stain resistant and machining characteristics
- Efficient use of material to reduce weight cost
- Deliver excellent short-term mechanical properties, such as high strength, toughness and stiffness as well as good practical impact
- Good durability under thermal stress and/or harsh chemical environments
- PBT’s high heat-deflection temperatures and high temperature index ratings help component withstand both short term thermal excursions and long-term heat exposure
- Good creep resistance over steady and elevated temperatures
- Block UV radiation and excellent heat aging behavior
- PBT is manufactured using similar principle of PET manufacturing
- The main raw materials used to manufacture PBT are 1,4-butanediol (BDO), dimethyl terephthalate (DMT), purified terephthalic acid (PTA) and catalysts. There are different design variations that go from a 5-Reactor (5-R) to a compact 2-Reactor (2-R) configuration. Recent technologies propose a 2-R design by combining the esterification and pre-polycondensation into one reactor, thus reducing the overall investment.
- In the first step, DMT or TPA was prepolymerized with BDO in the presence of catalyst at atmospheric pressure to afford oligomers containing hydroxybutyl ster end-groups.
- In the second stage, polycondensation was carried out until the torque measurement system of the batch reactor indicated a constant value.
- Finally, the PBT prepolymer was finally removed from the bottom of the batch reactor by applying nitrogen overpressure at the top of the reactor.
- Electrical and Electronic Application
Polybutylene terephthalate is used for housing in electrical engineering, such as connector, IC sockets, terminal blocks. PBT resin is used to make PBT fiber as well as electronic parts, electrical parts, and auto parts. Meanwhile, TV set accessories, motor cover sand motor brushes are some example of the use of PBT compound.
In automotive industry, PBT is used as wiper gear case, outer handle, distributor, coupler, ignition system parts, bumper, valve of exhaust, gas treating system, etc.
Polybutylene terephthalate can be found in showerheads or irons. It is also found processed into fibers in toothbrushes and false eyelashes.
PBT can also be made into yarn. Due to its chlorine resistance it is commonly found in swimwear. Recent studies have shown that PBT has superior UV properties to PET based fabrics such as T400