PBT compounds
Flame-retardant glass-fiber-reinforced PBT for electrical insulation and tracking resistance.
Example grade / typical values — to be corrected by GREENPOLYMER
Selection criteria
- Electrical insulation
- CTI
- Flame retardancy
- Stiffness
- GRN-PBT-E510Connectors
PBT (polybutylene terephthalate) is a semi-crystalline polyester. It absorbs little moisture, is dimensionally stable, insulates well and has short molding cycles. With glass fiber and flame retardant, PBT is often used for connectors, coil bobbins, relay bases, switch parts and insulating parts inside power supplies.
GREENPOLYMER PBT grades
Full list · 1 grade
| Grade | Key features | Suitable parts |
|---|---|---|
| GRN-PBT-E510 | Flame-retardant glass-fiber-reinforced PBT, high CTI | Connectors, terminal blocks, coil bobbins, insulating parts inside charging and energy storage equipment |
Recycled-content versions (-R) can be customized.
Key properties
Typical values. Refer to the actual TDS.
| Item | Test standard | GRN-PBT-E510 |
|---|---|---|
| Density | ISO 1183 | 1.55–1.70 g/cm³ |
| MFR | ISO 1133 | 10–25 g/10 min (250 °C / 2.16 kg) |
| Tensile strength | ISO 527 | 100–130 MPa |
| Flexural modulus | ISO 178 | 8–10 GPa |
| Notched impact (23 °C) | ISO 179/1eA | 6–10 kJ/m² |
| HDT (1.80 MPa) | ISO 75 | 200–215 °C |
| CTI (design target) | IEC 60112 | ≥ 600 V |
| Flammability (design target) | UL 94 | V-0 @ 1.5 mm |
Flammability rating and CTI are design targets, tested to the standard methods (to be verified by GREENPOLYMER). Certificate to be uploaded.
Why electrical parts often use PBT
Low moisture absorption
Electrical properties and dimensions are little affected by humidity.
High CTI possible
Suits parts with tight creepage distances.
Fast molding
Crystallizes quickly with short cycles, suiting high-volume small parts.
Heat resistance
With glass fiber its heat deflection temperature is high, so it withstands most assembly temperatures other than reflow soldering (refer to the TDS).
Hydrolysis: a point to watch with PBT
PBT is a polyester. At high temperature and humidity it hydrolyzes and its strength gradually drops.
- It must be dried thoroughly before processing, or it hydrolyzes in the barrel.
- For parts working long-term in damp heat (such as portable power stations and energy storage equipment), tell us the damp heat conditions. We will evaluate hydrolysis-resistant formulations and recommend tests such as 85/85 (85 °C / 85 % RH).
Processing advice
Typical values. Refer to the actual TDS.
- Drying120 °C, 3–4 h (desiccant dryer); moisture content ≤ 0.02 %
- Melt temperature240–270 °C
- Mold temperature60–90 °C; upper end when surface and dimensional stability matter
- Injection speed
- Relatively fast
- Residence time
- As short as possible; avoid long times at high temperature for flame-retardant grades
- Mold
- Improve venting; glass fiber is abrasive, so hardened mold steel is recommended
Full table
| Item | Recommended |
|---|---|
| Drying | 120 °C, 3–4 h (desiccant dryer); moisture content ≤ 0.02 % |
| Melt temperature | 240–270 °C |
| Mold temperature | 60–90 °C; upper end when surface and dimensional stability matter |
| Injection speed | Relatively fast |
| Residence time | As short as possible; avoid long times at high temperature for flame-retardant grades |
| Mold | Improve venting; glass fiber is abrasive, so hardened mold steel is recommended |
Design points
Avoid sharp corners
PBT is notch sensitive; add fillets at corners.
Keep walls even
Crystallization shrinkage is high, so uneven walls warp easily.
Keep snap-fit strain low
Glass-fiber PBT has low elongation at break; leave margin in snap-fit design.
Watch fiber orientation and weld lines
Design clearance and creepage distances to the product standard
FAQ
PBT or PA66?
When low moisture absorption, high CTI and dimensional stability are needed, consider PBT first; when higher toughness and heat resistance are needed, consider PA66.
Can you make a low-warpage version?
Yes, warpage can be reduced by adjusting the combination of glass fiber and fillers. Send us the part drawing and we will evaluate it together.
What does CTI 600 V mean?
CTI is the comparative tracking index, tested to IEC 60112. The higher the value, the harder it is for a tracking path to form on the material surface. Product standards set creepage distances by CTI class.
Related content
- Applications: New energy and energy storage | ICT and security | Home appliances and cleaning
Contact us
Tell us the part name, applicable standards (UL 94 rating and thickness, CTI, glow-wire), damp heat conditions and the expected volume. Phone +86 18822892298 | Email hello@greenpolymer.com