BMI GR-PTFE
Additive grade
GR-PTFE = graphite / PTFE lubricated BMI
Self-lubricating high-temperature bushings, wear pads and seal rings running dry to about 230 °C.
Values for the GR-PTFE condition
Other BMI grades and fills
BMI is listed in 9 conditions; see the grade overview at BMI.
Compare all 9 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Silica / mineral filled BMI | Pick for high-Tg encapsulation, chip-carrier and dimensionally stable insulating parts where CTE must approach that of metal/ceramic. | — | 60 | 0.8 | — |
GR-PTFEThis page Graphite / PTFE lubricated BMI | Self-lubricating high-temperature bushings, wear pads and seal rings running dry to about 230 °C. | — | 60 | 1 | 88 Shore D |
NEATDefault Neat cured resin | Baseline cast/cured BMI used for property benchmarking, tooling resin, potting and small high-temperature parts. | — | 72 | 2 | — |
Low-viscosity RTM / infusion grade | Choose for resin transfer moulding or VARTM of thick high-temperature parts where injection viscosity below ~0.5 Pa·s at 120–140 °C is required. | — | 75 | 2.2 | — |
Toughened BMI | Pick when damage tolerance / CAI and hot-wet toughness matter (primary aerostructure prepreg) and a 20–40 °C Tg loss is acceptable. | — | 82 | 3.5 | — |
Chopped carbon-fiber BMI molding compound | For net-shape compression-molded brackets, fasteners, seals and bushing bodies at 200 °C+ where laminate lay-up is uneconomic. | — | 150 | 1 | — |
Glass-fabric reinforced BMI laminate (~60 vol% E-glass) | Use for high-temperature electrically insulating structures, radomes, motor/generator parts and high-Tg PCB substrates (BT/BMI laminate). | — | 450 | 1.8 | — |
Woven carbon-fabric/BMI laminate | Choose for drapeable, balanced-property high-temperature panels, ducts and hot tooling where UD tape is impractical. | — | 800 | 1.2 | — |
Unidirectional carbon-fiber/BMI laminate | The main structural form of BMI: hot engine nacelles, missile/hypersonic skins, supersonic aircraft structure needing 180–230 °C service. | — | 2,100 | 1.5 | — |
What is BMI GR-PTFE?
BMI GR-PTFE is BMI in the GR-PTFE grade — self-lubricating high-temperature bushings, wear pads and seal rings running dry to about 230 °C. BMI GR-PTFE has a tensile strength of 60 MPa (8.7 ksi), stronger than 68% of polymer grades. Elongation at break is 1% and the elastic modulus is 6.5 GPa (0.943 Msi). BMI GR-PTFE has a density of 1.55 g/cm³ (0.056 lb/in³), heavier than 91% of polymer grades. Its glass-transition temperature is 290°C (554 °F). NEAT is the default condition FabDigit quotes; GR-PTFE is available on request or by drawing note.
Advantages
- Conducts heat well — 0.8 W/m·K (0.462 BTU/hr·ft·°F), better than 99% of polymer grades
- Low, predictable mold shrinkage — 0.2%, better than 94% of polymer grades
- High service temperature — 230°C (446 °F), better than 91% of polymer grades
- Stiff — 6.5 GPa (0.943 Msi), better than 90% of polymer grades
Limitations
- Limited ductility — 1%, worse than 98% of polymer grades
- Difficult to weld — 0/100, worse than 98% of polymer grades
- Limited formability — 5/100, worse than 95% of polymer grades
- Low fracture toughness — 0.75 MPa·√m (0.683 ksi·√in), worse than 92% of polymer grades
- Heavy — 1.55 g/cm³ (0.056 lb/in³), worse than 91% of polymer grades
BMI GR-PTFE properties
Typical room-temperature values for BMI GR-PTFE; 24 are specific to this condition. Other listed values are BMI reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
BMI GR-PTFE has a density of 1.55 g/cm³ (0.056 lb/in³), heavier than 91% of polymer grades. Its glass-transition temperature is 290°C (554 °F).
Mechanical13
BMI GR-PTFE has a tensile strength of 60 MPa (8.7 ksi), stronger than 68% of polymer grades. Elongation at break is 1% and the elastic modulus is 6.5 GPa (0.943 Msi).
Thermal10
BMI GR-PTFE is rated for continuous service to 230°C (446 °F). It conducts heat at 0.8 W/m·K (0.462 BTU/hr·ft·°F), better than 99% of polymer grades. Thermal expansion is 40 µm/m·K (22.2 µin/in·°F).
Electrical7
BMI GR-PTFE is an electrical insulator with a dielectric strength of 20 kV/mm (508 V/mil) and a resistivity of 1,000,000 Ω·m.
Chemical & Environmental3
Corrosion resistance is excellent (88/100), better than 74% of polymer grades. UV resistance is fair.
Sustainability4
Producing a kilogram of BMI GR-PTFE takes about 190 MJ of energy and emits 9.5 kg of CO₂ — more than 88% of polymer grades. Typical recycled content is 0%.
Manufacturability7
BMI GR-PTFE's machinability is fair (45/100, worse than 78% of polymer grades); weldability not recommended (0/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with BMI GR-PTFE
Is BMI easy to machine?
Machine fully cured and postcured stock with PCD or diamond-coated carbide, high speed / low feed, sharp tools and vacuum dust extraction; fiber-reinforced laminates are highly abrasive and prone to delamination on drill exit — use backing plates and dagger/brad drills, coolant mist to keep the surface below Tg.
Can BMI be welded?
Not weldable — thermoset network; join by high-temperature adhesive bonding (BMI or polyimide film adhesive), co-cure/co-bond, or mechanical fasteners with titanium/A286 hardware to match CTE.
Can BMI be formed, bent or molded?
Processed as prepreg (autoclave 177–191 °C / 0.6–0.7 MPa), RTM/VARTM, or compression molding; ALWAYS requires a freestanding postcure at 227–250 °C to develop full Tg; exotherm and volatile control matter in thick laminates, and low-humidity prepreg storage/out-time control is required.
What surface finishes work on BMI?
Sand/abrade and solvent-wipe or peel-ply then prime with a high-temperature epoxy/BMI primer; polyimide or silicone-modified topcoats for 200 °C+ service; UV protection needed outdoors; electroless/vapor-deposited metallization possible for EMI shielding.
BMI 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 |
|---|---|---|
| 4,4'-bismaleimidodiphenylmethane (BDM/MDmain maleimide monomer; other backbones (BPA-BMI, m-phenylene-BMI, eutectic monomer blends) used to lower melt point | 50 – 75 | 65 |
| o,o'-diallylbisphenol A (DABA) co-reactaEne/Diels-Alder co-monomer; also aromatic diamine, bisallyl or vinyl co-reactants | 20 – 45 | 33 |
| toughener (thermoplastic PES/PEI, CTBN, only in toughened prepreg grades; lowers Tg | 0 – 15 | 0 |
| catalyst / inhibitor / processing aidsfree-radical initiator, hydroquinone-type inhibitor, release/flow aids | 0.1 – 2 | 0.5 |
| carbon fiber (structural laminate gradesvol% in UD prepreg laminate; not in neat resin | 0 – 68 | 60 |
| glass fiber (electrical / radome grades)vol% in woven-glass laminate | 0 – 65 | 60 |
BMI GR-PTFE — frequently asked
What is BMI GR-PTFE used for?
BMI GR-PTFE is typically used for aerospace composite structures, engine nacelle components and high-temp printed circuit substrates. In short: between epoxy and polyimide; 230 °C service matrix; postcure is mandatory.
What is the tensile strength of BMI GR-PTFE?
BMI GR-PTFE has a typical tensile strength of 60 MPa (8.7 ksi) — stronger than 68% of polymer grades. Strength varies by condition: see the 9 listed tempers.
Is BMI GR-PTFE easy to machine?
Reasonably — machinability is rated fair (45/100, worse than 78% of polymer grades). Machine fully cured and postcured stock with PCD or diamond-coated carbide, high speed / low feed, sharp tools and vacuum dust extraction; fiber-reinforced laminates are highly abrasive and prone to delamination on drill exit — use backing plates and dagger/brad drills, coolant mist to keep the surface below Tg.
Can BMI GR-PTFE be welded?
Not readily — weldability is rated not recommended (0/100). Not weldable — thermoset network; join by high-temperature adhesive bonding (BMI or polyimide film adhesive), co-cure/co-bond, or mechanical fasteners with titanium/A286 hardware to match CTE.
What surface finishes work on BMI GR-PTFE?
Sand/abrade and solvent-wipe or peel-ply then prime with a high-temperature epoxy/BMI primer; polyimide or silicone-modified topcoats for 200 °C+ service; UV protection needed outdoors; electroless/vapor-deposited metallization possible for EMI shielding.
Can BMI GR-PTFE be formed, bent or molded?
Processed as prepreg (autoclave 177–191 °C / 0.6–0.7 MPa), RTM/VARTM, or compression molding; ALWAYS requires a freestanding postcure at 227–250 °C to develop full Tg; exotherm and volatile control matter in thick laminates, and low-humidity prepreg storage/out-time control is required.
What is the maximum service temperature of BMI GR-PTFE?
BMI GR-PTFE is rated for continuous use to about 230°C (446 °F), and briefly to 300°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- CYCOM 5250-4 / 5250-4RTM BMI prepreg and resin data sheets — Solvay Composite Materials (formerly Cytec) (2022)
- MATRIMID / bismaleimide resin technical data — Huntsman Advanced Materials (2019)
- ASM Handbook Vol. 21: Composites — Bismaleimide resins — ASM International (2001)
- Engineered Materials Handbook Vol. 2: Engineering Plastics — ASM International (1988)
- CAMPUS / high-temperature thermoset property compilations — CAMPUS Plastics (2023)
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.