L-FR
Flame-retardant grade
ASTM D709 Grade L, D709 Type L · GB 5021
L-FR = l, flame-retardant modified
FR-modified cotton phenolic for enclosure and switchgear parts needing a UL 94 V-0 rating.
Values for the L-FR condition
Other L grades and fills
L is listed in 5 conditions; see the grade overview at L.
Compare all 5 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
L + MoS2/graphite | Use for unlubricated or marginally lubricated bushings, thrust washers and slide blocks where friction and stick-slip must be minimised. | — | 85 | 1.6 | 105 HRM |
L, oil-impregnated | Oil-impregnated fine-weave phenolic for water-lubricated or oil-fed bearings such as rolling-mill and pump bushings. | — | 85 | 1.7 | 100 HRM |
L-FRThis page L, flame-retardant modified | FR-modified cotton phenolic for enclosure and switchgear parts needing a UL 94 V-0 rating. | — | 88 | 1.7 | 106 HRM |
Fine-weave cotton fabric phenolic, electrical grade | Pick when the same machined cotton-phenolic part must also insulate at power frequency in dry conditions. | — | 90 | 1.7 | 105 HRM |
LDefault Fine-weave cotton fabric phenolic, mechanical grade | Standard choice for machined gears, bushings, wear pads and jigs where fine surface finish and dimensional stability matter more than electrical properties. | — | 95 | 1.8 | 108 HRM |
What is L-FR?
L-FR is L in the L-FR grade — fR-modified cotton phenolic for enclosure and switchgear parts needing a UL 94 V-0 rating. L-FR has a tensile strength of 88 MPa (12.8 ksi), weaker than 73% of composite grades. Elongation at break is 1.7% and the elastic modulus is 7.4 GPa (1.07 Msi). L-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). L is the default condition FabDigit quotes; L-FR is available on request or by drawing note.
Advantages
- Easy to machine — 78/100, better than 80% of composite grades
Limitations
- Low fracture toughness — 1.9 MPa·√m (1.73 ksi·√in), worse than 88% of composite grades
- Needs corrosion protection — 58/100, worse than 83% of composite grades
- Limited service temperature — 120°C (248 °F), worse than 78% of composite grades
- Absorbs moisture — dry before molding — 1.4%, worse than 78% of composite grades
L-FR properties
Typical room-temperature values for L-FR; 18 are specific to this condition. Other listed values are L reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
L-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).
Mechanical14
L-FR has a tensile strength of 88 MPa (12.8 ksi), weaker than 73% of composite grades. Elongation at break is 1.7% and the elastic modulus is 7.4 GPa (1.07 Msi).
Thermal9
L-FR is rated for continuous service to 120°C (248 °F). It conducts heat at 0.32 W/m·K (0.185 BTU/hr·ft·°F), worse than 55% of composite grades. Thermal expansion is 25 µm/m·K (13.9 µin/in·°F).
Electrical7
L-FR is an electrical insulator with a dielectric strength of 10 kV/mm (254 V/mil) and a resistivity of 1×10⁹ Ω·m.
Chemical & Environmental3
Corrosion resistance is good (58/100), worse than 83% of composite grades. UV resistance is fair.
Sustainability3
Producing a kilogram of L-FR takes about 90 MJ of energy and emits 4.6 kg of CO₂ — less than 75% of composite grades. Typical recycled content is 0%.
Manufacturability2
L-FR's machinability is very good (78/100, better than 80% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with L-FR
Is L easy to machine?
Machines readily with sharp carbide or PCD tooling at high speed and low feed; dust is abrasive and irritating, so use extraction and avoid heat build-up that scorches the resin.
Can L be welded?
Thermoset — cannot be welded or heat-formed; join by bolting, riveting, pinning or epoxy bonding after abrading the surface.
Can L be formed, bent or molded?
Supplied as fully cured pressed sheet, rolled tube or rod; shape only by cutting/machining, and pre-drill before tapping to avoid delamination or edge chipping.
What surface finishes work on L?
Cannot be plated or anodised; edges are usually sealed with varnish, epoxy or oil to limit moisture pick-up, and surfaces can be sanded and lightly polished to a matte dark-brown finish.
L 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, plain/twill)reinforcement, typically 100–160 g/m² fine-weave cloth | 45 – 60 | 55 |
| residual volatiles / moisture | 0 – 2 | 1 |
| phenol-formaldehyde (resol) resinmatrix, cured under heat and pressure | ≥ 38 (balance) | — |
L-FR — frequently asked
What is L-FR used for?
L-FR is typically used for precision gears, bushings, rollers and cam followers. In short: fine-weave mechanical cotton phenolic; quiet-running gear material; moS2 and oil-filled options.
What is the tensile strength of L-FR?
L-FR has a typical tensile strength of 88 MPa (12.8 ksi) — weaker than 73% of composite grades. Strength varies by condition: see the 5 listed tempers.
Is L-FR easy to machine?
Yes — machinability is rated very good (78/100, better than 80% of composite grades). Machines readily with sharp carbide or PCD tooling at high speed and low feed; dust is abrasive and irritating, so use extraction and avoid heat build-up that scorches the resin.
Can L-FR be welded?
Thermoset — cannot be welded or heat-formed; join by bolting, riveting, pinning or epoxy bonding after abrading the surface.
What surface finishes work on L-FR?
Cannot be plated or anodised; edges are usually sealed with varnish, epoxy or oil to limit moisture pick-up, and surfaces can be sanded and lightly polished to a matte dark-brown finish.
Can L-FR be formed, bent or molded?
Supplied as fully cured pressed sheet, rolled tube or rod; shape only by cutting/machining, and pre-drill before tapping to avoid delamination or edge chipping.
What is the maximum service temperature of L-FR?
L-FR is rated for continuous use to about 120°C (248 °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 Laminating Thermosetting Products — NEMA (1998)
- IEC 60893-3-4 Insulating materials — Industrial rigid laminated sheets — Phenolic cellulose (PF CL/CC/CP) — IEC (2013)
- Cotton fabric phenolic laminate (Grade L/LE) datasheets — Various 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.