PBT · grade · default condition
PBT Unfilled
Properties of the Unfilled condition, compared with the other PBT grades.
Pick for tough, low-friction, dimensionally stable parts where high stiffness and 1.8 MPa heat resistance are not required.
What is PBT Unfilled?
PBT Unfilled is PBT in the Unfilled grade — pick for tough, low-friction, dimensionally stable parts where high stiffness and 1.8 MPa heat resistance are not required. PBT Unfilled has a yield strength of 55 MPa (7.98 ksi) and a tensile strength of 55 MPa (7.98 ksi) — stronger than 59% of polymer grades. Elongation at break is 100% and the elastic modulus is 2.6 GPa (0.377 Msi). PBT Unfilled has a density of 1.31 g/cm³ (0.0473 lb/in³), heavier than 71% of polymer grades. Its glass-transition temperature is 55°C (131 °F).
Advantages
- Low moisture uptake — 0.09%, better than 79% of polymer grades
PBT Unfilled properties
Typical room-temperature values for PBT Unfilled — 12 properties are specific to this condition; the rest are grade-level values shared by every PBT grade. Each bar shows where the value sits among the polymer grades in FabDigit's library — further right is higher.
Physical5
PBT Unfilled has a density of 1.31 g/cm³ (0.0473 lb/in³), heavier than 71% of polymer grades. Its glass-transition temperature is 55°C (131 °F).
Mechanical17
PBT Unfilled has a yield strength of 55 MPa (7.98 ksi) and a tensile strength of 55 MPa (7.98 ksi) — stronger than 59% of polymer grades. Elongation at break is 100% and the elastic modulus is 2.6 GPa (0.377 Msi).
Thermal11
PBT Unfilled is rated for continuous service to 110°C (230 °F). It conducts heat at 0.25 W/m·K (0.144 BTU/hr·ft·°F), better than 71% of polymer grades. Thermal expansion is 80 µm/m·K (44.4 µin/in·°F).
Electrical7
PBT Unfilled is an electrical insulator with a dielectric strength of 23 kV/mm (584.2 V/mil) and a resistivity of 1×10¹⁴ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (82/100), better than 54% of polymer grades. UV resistance is fair.
Sustainability4
Producing a kilogram of PBT Unfilled takes about 105 MJ of energy and emits 5 kg of CO₂ — more than 54% of polymer grades. Typical recycled content is 5%.
Manufacturability8
PBT Unfilled's machinability is good (68/100, better than 71% of polymer grades); weldability very good (70/100); formability poor (20/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other PBT grades and fills
PBT is also supplied in 12 other conditions. The full side-by-side table is on the PBT overview.
- UnfilledDefaultPick for tough, low-friction, dimensionally stable parts where high stiffness and 1.8 MPa heat resistance are not required.55 MPa tensile
- GF40Maximum stiffness/strength PBT for metal-replacement structural parts; accept higher warpage, brittleness and tool wear.155 MPa tensile
- GF30The workhorse structural PBT: choose for stiff, creep-resistant, heat-resistant parts (connectors, housings, brackets) where warpage can be managed by gating.135 MPa tensile
- GF30 FR V-0Standard for connectors, coil bobbins and switchgear needing both V-0 and >200 °C HDT with high stiffness.125 MPa tensile
- GF15Mid-way grade when you need roughly double the stiffness and 200 °C HDT but want lower warpage and better surface than GF30.95 MPa tensile
- MINChoose for flat, dimensionally accurate covers and lids where isotropic shrinkage and good surface beat maximum strength.85 MPa tensile
- FR V-0Choose for electrical housings, relay bases and connectors that must carry a UL 94 V-0 listing at 0.8–1.5 mm wall.52 MPa tensile
- IMUse where notch sensitivity or cold (-30 °C) impact is the failure mode — snap fits, exterior clips, mirror housings.42 MPa tensile
Working with PBT Unfilled
Is PBT easy to machine?
Machines cleanly with sharp, positive-rake carbide tools and air cooling; glass-filled grades are abrasive and need diamond or coated tooling, and sharp internal corners must be avoided due to notch sensitivity.
Can PBT be welded?
Excellent for ultrasonic, hot-plate, vibration, spin and laser welding (with laser-transparent/absorbing pairs); no solvent bonding — use cyanoacrylate/epoxy on abraded, primed surfaces.
Can PBT be formed, bent or molded?
Dry to <0.02% moisture (120 °C, 3–4 h) to prevent hydrolytic MW loss; mold at 240–260 °C melt and 60–90 °C tool, fast fill, and expect anisotropic shrinkage in GF grades — gate to control warp.
What surface finishes work on PBT?
Takes pad printing and laser marking well; painting/metallizing needs plasma or primer pretreatment because of the low-energy, solvent-resistant surface; molded-in texture is usually preferred over polishing.
PBT chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| 1,4-butanediol (BDO) unitdiol comonomer of the polyester backbone | ≈ 40 | 40 |
| glass fiber0 for unfilled default; 15/30/40 wt% in GF variants | 0 – 40 | 0 |
| flame retardant + synergistbrominated or halogen-free P-based system + Sb2O3 in FR V-0 grades | 0 – 20 | 0 |
| stabilizers / nucleant / pigmentantioxidant, hydrolysis stabilizer, mold release, carbon black | 0.2 – 2 | 0.8 |
| terephthalic acid / DMT unitdiacid comonomer; balance of resin | balance | — |
PBT Unfilled — frequently asked
What is PBT Unfilled used for?
PBT Unfilled is typically used for automotive electrical connectors, relay and switch housings, coil bobbins and formers, automotive electronic control unit housings, appliance structural components and sensor bodies. In short: stronger precise PBT.
What is the yield strength of PBT Unfilled?
PBT Unfilled has a typical yield strength of 55 MPa (7.98 ksi) and a tensile strength of 55 MPa (7.98 ksi) — stronger than 59% of polymer grades. Strength varies by condition: see the 13 listed tempers.
Is PBT Unfilled easy to machine?
Reasonably — machinability is rated good (68/100, better than 71% of polymer grades). Machines cleanly with sharp, positive-rake carbide tools and air cooling; glass-filled grades are abrasive and need diamond or coated tooling, and sharp internal corners must be avoided due to notch sensitivity.
Can PBT Unfilled be welded?
Yes — weldability is rated very good (70/100). Excellent for ultrasonic, hot-plate, vibration, spin and laser welding (with laser-transparent/absorbing pairs); no solvent bonding — use cyanoacrylate/epoxy on abraded, primed surfaces.
What surface finishes work on PBT Unfilled?
Takes pad printing and laser marking well; painting/metallizing needs plasma or primer pretreatment because of the low-energy, solvent-resistant surface; molded-in texture is usually preferred over polishing.
Can PBT Unfilled be formed, bent or molded?
Dry to <0.02% moisture (120 °C, 3–4 h) to prevent hydrolytic MW loss; mold at 240–260 °C melt and 60–90 °C tool, fast fill, and expect anisotropic shrinkage in GF grades — gate to control warp.
What is the maximum service temperature of PBT Unfilled?
PBT Unfilled is rated for continuous use to about 110°C (230 °F), and briefly to 160°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in PBT Unfilled?
Yes — PBT Unfilled is available for injection molding with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ISO 7792-1/-2 Plastics — Thermoplastic polyester (TP) moulding and extrusion materials — ISO (2012)
- ASTM D5927 Standard Specification for Thermoplastic Polyester (TPES) Injection and Extrusion Materials — ASTM (2020)
- Ultradur (PBT) product range brochure and CAMPUS data — BASF (2023)
- Crastin PBT thermoplastic polyester resin product guide — Celanese (DuPont Performance Materials) (2023)
- Valox resin product data / processing guide — SABIC (2022)
- Pocan PBT technical information — LANXESS (2023)
- CAMPUS plastics database — PBT ISO 10350 single-point data — CWFG (2024)
- Engineered Materials Handbook Vol. 2: Engineering Plastics — ASM International (1988)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.