LE FR
Flame-retardant grade
ASTM D709 Grade LE
FR = flame-retardant modified LE-type cotton phenolic
Choose when a UL 94 V-0/V-1 rating is required in enclosures or switchgear; slightly lower impact strength.
Values for the FR condition
Other LE grades and fills
LE is listed in 2 conditions; see the grade overview at LE.
- MoS2
- FR
Compare all 2 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
MoS2/graphite-filled bearing-grade cotton phenolic | Choose for water-lubricated bearings, wear pads and low-friction bushings; electrical properties are degraded. | — | 75 | 1.2 | 100 HRM |
FRThis page Flame-retardant modified LE-type cotton phenolic | Choose when a UL 94 V-0/V-1 rating is required in enclosures or switchgear; slightly lower impact strength. | — | 85 | 1.4 | 105 HRM |
What is LE FR?
LE FR is LE in the FR grade — choose when a UL 94 V-0/V-1 rating is required in enclosures or switchgear; slightly lower impact strength. LE FR has a tensile strength of 85 MPa (12.3 ksi), weaker than 75% of composite grades. Elongation at break is 1.4% and the elastic modulus is 7.3 GPa (1.06 Msi). LE FR has a density of 1.36 g/cm³ (0.0491 lb/in³), lighter than 70% of composite grades. Its glass-transition temperature is 155°C (311 °F).
Advantages
- Easy to machine — 85/100, better than 90% of composite grades
- Polishes to a fine finish — 55/100, better than 83% of composite grades
- Low embodied carbon — 4.5 kg CO₂/kg, better than 79% of composite grades
Limitations
- Limited service temperature — 115°C (239 °F), worse than 84% of composite grades
- Absorbs moisture — dry before molding — 1.5%, worse than 81% of composite grades
- Needs corrosion protection — 62/100, worse than 75% of composite grades
LE FR properties
Typical room-temperature values for LE FR; 18 are specific to this condition. Other listed values are LE reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
LE FR has a density of 1.36 g/cm³ (0.0491 lb/in³), lighter than 70% of composite grades. Its glass-transition temperature is 155°C (311 °F).
Mechanical12
LE FR has a tensile strength of 85 MPa (12.3 ksi), weaker than 75% of composite grades. Elongation at break is 1.4% and the elastic modulus is 7.3 GPa (1.06 Msi).
Thermal9
LE FR is rated for continuous service to 115°C (239 °F). It conducts heat at 0.3 W/m·K (0.173 BTU/hr·ft·°F), worse than 63% of composite grades. Thermal expansion is 25 µm/m·K (13.9 µin/in·°F).
Electrical7
LE FR is an electrical insulator with a dielectric strength of 15 kV/mm (381 V/mil) and a resistivity of 1×10⁹ Ω·m.
Chemical & Environmental3
Corrosion resistance is good (62/100), worse than 75% of composite grades. UV resistance is fair.
Sustainability4
Producing a kilogram of LE FR takes about 78 MJ of energy and emits 4.5 kg of CO₂ — less than 87% of composite grades. Typical recycled content is 0%.
Manufacturability2
LE FR's machinability is excellent (85/100, better than 90% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with LE FR
Is LE easy to machine?
Machines like hard wood/brass with carbide tooling — sharp positive rake, high speed, dust extraction (abrasive, respirable phenolic/cellulose dust); drill with slow feed to avoid delamination and exit chipping.
Can LE be welded?
Not weldable — a thermoset; join by bonding (epoxy/phenolic adhesive after abrading) or mechanical fasteners with washers to avoid crushing.
Can LE be formed, bent or molded?
Supplied as press-cured sheet/rod/tube; cannot be reformed. Thin sheet (<1.5 mm) can be cold-punched or hot-punched at 90–120 °C; blank dies must be sharp to prevent cracking.
What surface finishes work on LE?
Sand and buff for a smooth matt surface; seal machined edges with varnish or epoxy to limit moisture pickup; can be painted, but bare surfaces darken under UV. Bake dry before high-voltage testing.
LE 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 |
|---|---|---|
| cotton fabric (fine weave, cellulose)fine-weave cloth, typically <4 oz/yd² substrate | 42 – 55 | 50 |
| residual moisture/volatiles | 0.5 – 2.5 | 2 |
| phenol-formaldehyde (resole/novolac) rescured thermoset matrix | ≥ 42 (balance) | — |
LE FR — frequently asked
What is LE FR used for?
LE FR is typically used for precision insulating bushings, electrical mounting components and terminal insulators. In short: best-machining cotton phenolic; electrical version of Grade L; fine weave for detail parts.
What is the tensile strength of LE FR?
LE FR has a typical tensile strength of 85 MPa (12.3 ksi) — weaker than 75% of composite grades. Strength varies by condition: see the 2 listed tempers.
Is LE FR easy to machine?
Yes — machinability is rated excellent (85/100, better than 90% of composite grades). Machines like hard wood/brass with carbide tooling — sharp positive rake, high speed, dust extraction (abrasive, respirable phenolic/cellulose dust); drill with slow feed to avoid delamination and exit chipping.
Can LE FR be welded?
Not weldable — a thermoset; join by bonding (epoxy/phenolic adhesive after abrading) or mechanical fasteners with washers to avoid crushing.
What surface finishes work on LE FR?
Sand and buff for a smooth matt surface; seal machined edges with varnish or epoxy to limit moisture pickup; can be painted, but bare surfaces darken under UV. Bake dry before high-voltage testing.
Can LE FR be formed, bent or molded?
Supplied as press-cured sheet/rod/tube; cannot be reformed. Thin sheet (<1.5 mm) can be cold-punched or hot-punched at 90–120 °C; blank dies must be sharp to prevent cracking.
What is the maximum service temperature of LE FR?
LE FR is rated for continuous use to about 115°C (239 °F), and briefly to 150°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- ASTM D709 — Standard Specification for Laminated Thermosetting Materials — ASTM International (2017)
- NEMA LI 1 — Industrial Laminated Thermosetting Products — NEMA (1998)
- ASTM D2517 / D2518 — Laminated Thermosetting Rods and Tubes — ASTM International (2020)
- Engineered Materials Handbook Vol. 2: Engineering Plastics (phenolic laminates) — ASM International (1988)
- Canvas/cotton phenolic laminate grade LE datasheets — industrial laminate producers (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.