Products · PBT
Polybutylene terephthalate (PBT) is a semi-crystalline polyester produced by polycondensation of 1,4-butanediol and terephthalic acid (or dimethyl terephthalate). The combination of high crystallinity, good electrical properties, dimensional stability, and chemical resistance makes PBT a workhorse for automotive sensors, lighting, electrical connectors, and appliance components. PBT is often compared to PA66: similar mechanical performance, but lower water absorption (better dimensional stability) and better electrical properties (higher CTI). Glass-fiber-reinforced and flame-retardant grades are the dominant commercial offerings. Reference grades from SABIC (Valox), BASF (Ultradur), and Celanese (Crastin) cover the full property range.
Section 1
A reference overview of the molecular architecture and the design variables that govern the performance of this polymer family.
PBT is a step-growth polyester of 1,4-butanediol and terephthalic acid. The semi-aromatic backbone (aromatic terephthalate + aliphatic butanediol) gives a melting point of 220-225°C, high crystallinity (up to 40-50% achievable with proper molding), and good chemical resistance. PBT is more dimensionally stable than PA66 in humid environments due to lower water absorption (0.1% vs 1.0% at saturation). PBT is susceptible to hydrolysis at high temperatures, requiring careful drying before processing.
Section 2
Typical property ranges across commercial grades. Test methods are listed in the rightmost column for traceability to public manufacturer data sheets.
PBT offers an excellent balance of high stiffness (especially with GF reinforcement), high HDT, low moisture absorption, good electrical properties (CTI > 400V for flame-retardant grades), and chemical resistance. The lower water absorption vs PA66 is the key advantage in humid environments.
| Property · 性能 | Unfilled PBT | 30% GF PBT | Test Method · 测试方法 |
|---|---|---|---|
| Density · 密度 | 1.30 – 1.32 g/cm³ | 1.50 – 1.55 g/cm³ | ASTM D792 |
| Melt Point · 熔点 | 220 – 225 °C | 220 – 225 °C | ISO 3146 |
| Tensile Strength · 拉伸强度 | 50 – 60 MPa | 130 – 150 MPa | ASTM D638 |
| Flexural Modulus · 弯曲模量 | 2.3 – 2.8 GPa | 8 – 10 GPa | ASTM D790 |
| Elongation at Break · 断裂伸长 | 100 – 200 % | 3 – 5 % | ASTM D638 |
| HDT (1.82 MPa) · 热变形 | 60 – 75 °C | 200 – 220 °C | ASTM D648 |
| Water Absorption (24h) · 吸水率 | 0.08 – 0.10 % | 0.05 – 0.08 % | ASTM D570 |
| CTI (Comparative Tracking Index) · 漏电起痕 | 400 – 600 V | 250 – 400 V | IEC 60112 |
Section 3
The major application areas for this polymer family, each illustrated with a brief description of how the material is specified and used.
PBT is widely used in automotive sensors (oxygen, knock, MAP, position sensors) and lighting (headlamp housings, fog lamp bezels, interior lighting reflectors). The combination of high HDT, low moisture absorption, dimensional stability, and good electrical properties is valued in these applications.
Flame-retardant PBT grades (UL94 V-0) are used in electrical connectors, IC sockets, and terminal blocks. The high CTI (> 400V for unfilled FR grades) and inherent flame retardance are valued in consumer and industrial electrical equipment.
PBT is used in appliance components (coffee machine boilers, dishwasher parts, hair dryer housings) where the combination of high heat resistance, dimensional stability, and chemical resistance to detergents is required. Common in small and large kitchen appliances.
Glass-fiber-reinforced and flame-retardant PBT grades are used in industrial switches, contactors, relays, and control housings. The combination of high CTI, flame retardance, and dimensional stability is valued in industrial electrical equipment.
Section 4
Key processing parameters and equipment considerations. Contact our business manager for grade-specific processing recommendations.
| Melt Temperature | 240 – 270 °C; mold temperature 60 – 100 °C |
| Drying | 120 – 130 °C for 4 – 6 hours (moisture < 0.02%) |
PBT is highly sensitive to hydrolysis at processing temperatures — wet resin rapidly loses molecular weight and becomes brittle. Aggressive drying (4-6 hours at 120-130°C) is mandatory. Mold temperature control is critical for crystallinity: too low results in amorphous skin and post-mold warping. Post-mold annealing at 150°C for 1-2 hours can improve dimensional stability in tight-tolerance parts.
Section 5
A summary of when this polymer family is the right choice and what to consider as alternatives. For project-specific grade selection, contact our business manager.
Choose PBT over PA66 when the application requires lower water absorption, better dimensional stability, or higher CTI. Choose PBT over PPS when the cost target is more aggressive and the application temperature is below 150°C. For very high temperature (above 180°C continuous) or better chemical resistance, PPS or PPA is preferred. For better impact strength, PBT/PC alloys or PC are alternatives.
Section 6
Reference grades from publicly available manufacturer catalogs. Complete catalog available on request.
| Grade | Manufacturer | Key Properties | Typical Use |
|---|---|---|---|
| Valox® 553 | SABIC | 30% GF · Heat stabilized | Automotive sensor · Lighting · Industrial |
| Ultradur® B 4300 G4 | BASF | 20% GF · Standard | Connector · Appliance · Industrial |
| Crastin® 6129 | Celanese | 30% GF · FR · High flow | SMT connector · FR applications |
| Valox® 420SE0 | SABIC | Unfilled · Flame retardant (UL94 V-0) | Connector · Industrial · Consumer |
Section 7
Cross-references to industry-specific applications and case studies.