Polybutylene Terephthalate
Polybutylene Terephthalate (PBT): High-Performance Engineering Plastic
Polybutylene Terephthalate (PBT) is a semi-crystalline thermoplastic polyester that offers exceptional mechanical strength, chemical resistance, and thermal stability. Widely used in automotive, electrical, and industrial applications, Polybutylene Terephthalate provides reliable performance under demanding conditions.
Key Features of Polybutylene Terephthalate
- High tensile strength and stiffness
- Excellent electrical insulation properties
- Superior dimensional stability
- Good resistance to chemicals, fuels, and oils
- Low moisture absorption
- UL 94 V-0 flammability rating (standard grade)
Technical Specifications
| Property | Value | Test Method |
|---|---|---|
| Density | 1.31-1.38 g/cm³ | ISO 1183 |
| Melting Point | 223-235°C | ISO 3146 |
| Tensile Strength | 50-60 MPa | ISO 527 |
| Flexural Modulus | 2300-3000 MPa | ISO 178 |
| Impact Strength (Izod) | 35-50 kJ/m² | ISO 180 |
| Dielectric Strength | 20-30 kV/mm | IEC 60243 |
Product Grades Available
| Grade | Characteristics | Applications |
|---|---|---|
| Standard PBT | Unfilled, general purpose | Electrical connectors, housings |
| Glass-filled PBT | 10-50% glass reinforcement | Structural components |
| Flame-retardant PBT | UL94 V-0/V-1 ratings | Electronic components |
| Impact-modified PBT | Enhanced toughness | Automotive parts |
Processing Guidelines for Polybutylene Terephthalate
- Injection Modling Temperature: 240-260°C
- Mold Temperature: 60-80°C
- Drying Conditions: 4 hours at 120°C
- Recommended Screw L/D Ratio: 18-22
Polybutylene Terephthalate FAQ
What are the main advantages of Polybutylene Terephthalate over other engineering plastics?
Polybutylene Terephthalate offers several advantages including excellent electrical properties that remain stable across varying humidity conditions, low warpage characteristics due to its crystalline structure, and superior resistance to automotive fluids compared to many other thermoplastics. Its fast crystallization allows for shorter cycle times in injection molding processes, making it a cost-effective choice for high-volume production.
How does glass fiber reinforcement affect the properties of Polybutylene Terephthalate?
Glass fiber reinforcement significantly enhances the mechanical properties of Polybutylene Terephthalate. Typically, 30% glass-filled PBT shows approximately 3 times higher flexural modulus and 2 times greater tensile strength compared to unfilled PBT. The fibers also improve heat deflection temperature by about 30-40°C while maintaining good electrical properties. However, fiber orientation can create anisotropic shrinkage in molded parts, requiring careful design considerations.
What are the typical applications for Polybutylene Terephthalate in the automotive industry?
In automotive applications, Polybutylene Terephthalate is commonly used for under-hood components such as ignition system parts, sensor housings, and connector systems due to its heat and chemical resistance. It's also used for exterior components like mirror housings and door handles where dimensional stability is critical. The electrical grade variants find application in fuse boxes, lamp sockets, and various electronic control units throughout modern vehicles.
Environmental Considerations
Polybutylene Terephthalate exhibits good recyclability characteristics and can be reprocessed multiple times with minimal property degradation. Many grades are available with recycled content, and some formulations meet RoHS and REACH compliance requirements for restricted substances.
Storage and Handling
- Store in original packaging in dry conditions (relative humidity < 50%)
- Recommended storage temperature: 15-30°C
- Typical shelf life: 12 months in unopened packaging
- Handle with gloves to avoid contamination