CB6951 Polybutylene Terephthalate Plate (PBT Plate)

Polybutylene Terephthalate Plate (PBT Plate) Description

PBT Plates are semi‐crystalline thermoplastics that exhibit measurable mechanical anisotropy as a result of polymer chain orientation. Tensile strength measures 80–85 MPa parallel to the extrusion direction and 70–75 MPa perpendicular to it. The flexural modulus is 2 400 MPa with a 15% directional variation. Notched impact strength measures 70 J/m, which indicates brittle fracture behaviour. Shore hardness is D90.

Thermal properties include a glass transition between 40 °C and 60 °C and a melting point of 224 °C. Linear expansion differs by direction: 0.00008/K parallel to flow and 0.00010/K perpendicular to flow. Continuous service is limited to 100 °C (150 °C short‐term) because of hydrolysis risk. The heat deflection temperature is 110 °C at a load of 1.82 MPa. Thermal conductivity is 0.24 W/mK.

Electrical performance is characterised by a volume resistivity exceeding 1e15 Ohm‐cm and a surface resistivity above 1e14 Ohm. The dielectric strength is 22 kV/mm. The dielectric constant remains constant at 3.3 (1 MHz) with a loss factor of 0.015.

Chemical behaviour demonstrates low moisture absorption (0.1% at 23 °C/60% RH) but a susceptibility to hydrolysis above 60 °C in humid conditions. Resistance to weak acids, bases and hydrocarbons is satisfactory; however, strong acids (10% H₂SO₄) result in significant degradation. UV exposure causes yellowing when stabilisers are absent.

Processing induces residual stresses that require controlled cooling gradients below 10 °C/cm. Surface machining achieves a roughness of approximately 1.6 micron. Thermal decomposition commences at 280 °C with the release of tetrahydrofuran.

Polybutylene Terephthalate Plate (PBT Plate) Applications

PBT plates serve as machinable stock for precision components requiring electrical insulation, dimensional stability and chemical resistance. In electrical engineering, they are used to fabricate terminal blocks, circuit breaker isolators and relay housings. Their high volume resistivity (exceeding 1e15 Ω·cm) prevents current leakage in high‐voltage environments at temperatures up to 100 °C. In automotive applications, they are employed for sensor mounts and fuel system components, with low moisture absorption (0.1% at 23 °C/60% RH) ensuring dimensional integrity against biofuel blends.

Industrial implementations include wear pads, valve seats and conveyor guides that utilise a flexural modulus of 2 400 MPa and friction coefficients between 0.15 and 0.25. In chemical processing, PBT plates are machined into pump housings and laboratory equipment handles that resist hydrocarbons and dilute acids. Medical device grips and HVAC actuators comply with UL 94 V-0 flammability standards.

Critical limitations include prolonged exposure to temperatures above 150 °C, which leads to thermal degradation, and contact with strong mineral acids (exceeding 10% H₂SO₄), which accelerate hydrolysis. Performance is optimised when machining is conducted perpendicular to the extrusion direction given that anisotropic expansion is observed (0.00010/K ⊥ flow versus 0.00008/K ∥ flow). The combined attributes of machinability (achieving Ra ≤1.6 μm), creep resistance (less than 1% strain at 80 MPa over 1 000h) and cost efficiency render PBT plates suitable for replacing metals in electromechanical systems operating below 120 °C.

Polybutylene Terephthalate Plate (PBT Plate) Packaging

Our products are packed in customised cartons of various sizes based on the material dimensions. Small items are securely enclosed in PP boxes, while larger items are placed in custom wooden crates. Packaging procedures adhere to specific customisation requirements and appropriate cushioning materials are used to provide protection during transportation.

Packaging: Carton, Wooden Box, or Customised.

Kindly review the packaging details provided for your reference.

Manufacturing Process

1.       Testing Method

(1)    Chemical Composition Analysis – Techniques such as GDMS or XRF verify that the material complies with purity requirements.

(2)    Mechanical Properties Testing – This includes assessments of tensile strength, yield strength and elongation for performance evaluation.

(3)    Dimensional Inspection – The thickness, width and length are measured to ensure adherence to specified tolerances.

(4)    Surface Quality Inspection – Visual and ultrasonic examinations are conducted to identify defects such as scratches, cracks or inclusions.

(5)    Hardness Testing – Material hardness is determined to confirm uniformity and mechanical reliability.

Please refer to the testing procedures provided by SAM for detailed information.

Polybutylene Terephthalate Plate (PBT Plate) FAQs

Q1. How can warping be prevented during machining?

Cutting temperatures should be maintained below 120 °C by using air‐cooled carbide tools (feed rate 0.2–0.4 mm/rev, spindle speed ≤3 000 RPM). Pre‐dry the plates at 80 °C for 4 hours to achieve a moisture content of ≤0.05%. Clamp uniformly with low-pressure fixtures (below 0.5 MPa) to avoid stress-induced distortion.

Q2. What UV stabilisation methods prevent outdoor yellowing?

Incorporate 1–2% carbon black, which reduces UV transmission by approximately 90%, or add 0.3% benzotriazole as a UV absorber. Avoid TiO₂-filled grades as they accelerate photo-oxidation. Stabilised plates maintain a ΔYI below 5 after 2 000h of QUV-B exposure.

Q3. What is the maximum continuous temperature in wet environments?

The service temperature should be reduced to 80 °C when relative humidity exceeds 60%. Hydrolysis accelerates above this threshold; for example, tensile strength is reduced by 50% after 1 000h at 80 °C/85% RH compared to performance beyond 10 000h at 23 °C/60% RH.

Related Information

1.       Common Preparation Methods

PBT plates are produced by extruding dried polybutylene terephthalate pellets through a flat die, followed by controlled cooling and crystallisation. The raw PBT resin (intrinsic viscosity 0.9–1.1 dL/g) is vacuum-dried at 120–130 °C for 4–6 hours to reduce moisture below 0.02%, thereby preventing hydrolysis during melting. The dried pellets are fed into a single-screw extruder with heated zones at 230 °C (feed), 250 °C (compression) and 255 °C (metering), where shear homogenisation occurs at 50–150 s⁻¹. The molten polymer is filtered through screens of 100–150 μm and extruded through a T-shaped die maintained at 240–250 °C.

The extruded sheet enters a three-stage calibration system. First, chill rolls at 15–25 °C solidify the surface. Next, the sheet passes through a crystallisation oven at 90–110 °C for 2–4 hours to develop a uniform spherulitic crystallinity of 30–45% (with spherulite sizes of 5–50 μm). Finally, slow cooling to room temperature minimises residual stress. The plate is then stress-relieved at 130–140 °C for 1–2 hours to equilibrate crystalline phases before undergoing precision calibration with paired steel rollers. Surface finishing involves diamond grinding to achieve a roughness of Ra ≤1.6 μm and a parallel tolerance within 0.1 mm per metre. Critical process controls include maintaining transverse temperature uniformity (±2 °C across the die), managing the crystallisation gradient (less than 10 °C/cm) and real-time thickness monitoring via beta gauges to ensure dimensional stability of ±0.05 mm. Final inspection verifies crystallinity using DSC (melting enthalpy ≥45 J/g) and detects internal voids through ultrasonic scanning.