BMC LP-A
Grade
LP-A = low-profile / Class-A surface BMC
Choose for visible pigmented or painted parts (automotive lamp bezels, appliance fronts) needing near-zero shrink and smooth surface.
Values for the LP-A condition
Other BMC grades and fills
BMC is listed in 8 conditions; see the grade overview at BMC.
Compare all 8 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Thermally conductive mineral/ceramic-filled BMC | Use for LED heat-sink housings and encapsulations that need 1–3 W/m·K while staying electrically insulating. | — | 30 | — | — |
LP-AThis page Low-profile / Class-A surface BMC | Choose for visible pigmented or painted parts (automotive lamp bezels, appliance fronts) needing near-zero shrink and smooth surface. | — | 35 | 0.5 | 98 HRM |
Carbon/graphite-filled conductive BMC | Use where ESD dissipation or bulk electrical conduction is required (fuel-cell bipolar plates, static-safe housings) rather than insulation. | — | 35 | — | — |
Flame-retardant BMC, UL 94 V-0 / 5VA | Pick when a UL 94 V-0 or 5VA rating and glow-wire performance are mandatory (breakers, contactors, EV connectors). | — | 38 | 0.4 | 105 HRM |
High-whiteness reflector BMC | Choose for LED reflectors and lamp cups needing high initial reflectance with minimal yellowing after thermal/UV ageing. | — | 38 | 0.4 | 105 HRM |
Heat-resistant / high-CTI arc-resistant BMC | Specify for motor commutators, arc chambers and lamp bases running above 160 °C with arc/track exposure. | — | 40 | — | — |
Vinyl ester matrix BMC | Pick when the part sees acids, chlorides, hot water or steam that would hydrolyse standard orthophthalic polyester BMC. | — | 50 | 0.7 | 105 HRM |
High-strength BMC, 22–30% longer glass fiber | Use for load-bearing or pressure-containing mouldings (pump housings, structural brackets) where impact and flexural strength dominate. | — | 60 | 0.8 | — |
What is BMC LP-A?
BMC LP-A is BMC in the LP-A grade — choose for visible pigmented or painted parts (automotive lamp bezels, appliance fronts) needing near-zero shrink and smooth surface. BMC LP-A has a tensile strength of 35 MPa (5.08 ksi), weaker than 58% of polymer grades. Elongation at break is 0.5% and the elastic modulus is 10 GPa (1.45 Msi). BMC LP-A has a density of 1.95 g/cm³ (0.0704 lb/in³), heavier than 97% of polymer grades. Its glass-transition temperature is 120°C (248 °F).
Advantages
- Low, predictable mold shrinkage — 0.03%, better than 100% of polymer grades
- Conducts heat well — 0.65 W/m·K (0.376 BTU/hr·ft·°F), better than 99% of polymer grades
- Stiff — 10 GPa (1.45 Msi), better than 95% of polymer grades
- Low embodied carbon — 3 kg CO₂/kg, better than 83% of polymer grades
- Good UV / weathering resistance — 60/100, better than 80% of polymer grades
Limitations
- Limited ductility — 0.5%, worse than 100% of polymer grades
- Limited formability — 3/100, worse than 99% of polymer grades
- Heavy — 1.95 g/cm³ (0.0704 lb/in³), worse than 97% of polymer grades
- Difficult to weld — 3/100, worse than 95% of polymer grades
- Difficult to machine — 35/100, worse than 84% of polymer grades
BMC LP-A properties
Typical room-temperature values for BMC LP-A; 21 are specific to this condition. Other listed values are BMC reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
BMC LP-A has a density of 1.95 g/cm³ (0.0704 lb/in³), heavier than 97% of polymer grades. Its glass-transition temperature is 120°C (248 °F).
Mechanical12
BMC LP-A has a tensile strength of 35 MPa (5.08 ksi), weaker than 58% of polymer grades. Elongation at break is 0.5% and the elastic modulus is 10 GPa (1.45 Msi).
Thermal10
BMC LP-A is rated for continuous service to 140°C (284 °F). It conducts heat at 0.65 W/m·K (0.376 BTU/hr·ft·°F), better than 99% of polymer grades. Thermal expansion is 25 µm/m·K (13.9 µin/in·°F).
Electrical7
BMC LP-A is an electrical insulator with a dielectric strength of 14 kV/mm (355.6 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (70/100), worse than 78% of polymer grades. UV resistance is good.
Sustainability4
Producing a kilogram of BMC LP-A takes about 55 MJ of energy and emits 3 kg of CO₂ — less than 98% of polymer grades. Typical recycled content is 0%.
Manufacturability7
BMC LP-A's machinability is fair (35/100, worse than 84% of polymer grades); weldability not recommended (3/100); formability not recommended (3/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with BMC LP-A
Is BMC easy to machine?
Cured BMC is abrasive and brittle — use PCD or diamond-coated tooling, high speed / low feed, support the part and vacuum the dust; drill from the moulded side to avoid chip-out.
Can BMC be welded?
Thermoset: cannot be welded; join by mechanical fasteners, moulded-in inserts, or epoxy/MMA adhesives after light abrasion and solvent wipe.
Can BMC be formed, bent or molded?
Injection, injection-compression or compression mould with stuffer-feed screws at 20–45 °C barrel and 140–180 °C tool, ~30–60 s/mm cure; vent well for styrene and avoid fibre-degrading high shear gates.
What surface finishes work on BMC?
As-moulded surfaces take flash removal by tumbling or media blast; low-profile grades accept primer and 2K polyurethane paint, and vacuum-metallizing after a UV base coat for reflectors.
BMC 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 |
|---|---|---|
| unsaturated polyester resin (in styrene)ortho/iso-phthalic UP; vinyl ester in VE grades | 18 – 32 | 25 |
| glass fiber (chopped, 3–12 mm)higher in HS-GF25 structural grades | 10 – 30 | 18 |
| low-profile thermoplastic additivePS/PVAc shrink-control additive | 0 – 6 | 3 |
| internal mould release (zinc stearate) | 1 – 3 | 2 |
| peroxide initiator (TBPB/BPO) | 0.5 – 1.5 | 1 |
| thickener (MgO/Ca(OH)2), pigment, additi | 0.5 – 3 | 1 |
| calcium carbonate / mineral fillerreplaced partly by ATH in FR grades, by Al2O3/BN in TC grades | ≥ 35 (balance) | — |
BMC LP-A — frequently asked
What is BMC LP-A used for?
BMC LP-A is typically used for circuit breaker housings, appliance components, automotive under-hood parts and electrical insulators. In short: net-shape thermoset insulator; stable to 150 °C; V-0 flame-retardant grades.
What is the tensile strength of BMC LP-A?
BMC LP-A has a typical tensile strength of 35 MPa (5.08 ksi) — weaker than 58% of polymer grades. Strength varies by condition: see the 8 listed tempers.
Is BMC LP-A easy to machine?
Not especially — machinability is rated fair (35/100, worse than 84% of polymer grades). Cured BMC is abrasive and brittle — use PCD or diamond-coated tooling, high speed / low feed, support the part and vacuum the dust; drill from the moulded side to avoid chip-out.
Can BMC LP-A be welded?
Not readily — weldability is rated not recommended (3/100). Thermoset: cannot be welded; join by mechanical fasteners, moulded-in inserts, or epoxy/MMA adhesives after light abrasion and solvent wipe.
What surface finishes work on BMC LP-A?
As-moulded surfaces take flash removal by tumbling or media blast; low-profile grades accept primer and 2K polyurethane paint, and vacuum-metallizing after a UV base coat for reflectors.
Can BMC LP-A be formed, bent or molded?
Injection, injection-compression or compression mould with stuffer-feed screws at 20–45 °C barrel and 140–180 °C tool, ~30–60 s/mm cure; vent well for styrene and avoid fibre-degrading high shear gates.
What is the maximum service temperature of BMC LP-A?
BMC LP-A is rated for continuous use to about 140°C (284 °F), and briefly to 200°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM D1201 — Thermosetting Polyester Molding Compounds — ASTM International (2019)
- ISO 14526 / ISO 12114 — SMC and BMC compounds, cure and test methods — ISO (2018)
- Engineered Materials Handbook Vol.2: Engineering Plastics (thermoset molding compounds) — ASM International (1988)
- BMC / TMC compound datasheets (IDI Composites, Menzolit, Polynt-Reichhold, Bulk Molding Compounds Inc.) — various (2023)
- UL Yellow Card / Prospector data for thermoset polyester molding compounds — UL Solutions (2024)
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.