L
Grade · default condition
ASTM D709 Grade L, D709 Type L · GB 5021
L = 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.
Values for the L 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, 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 |
LDefaultThis page 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?
L is L in the L grade — standard choice for machined gears, bushings, wear pads and jigs where fine surface finish and dimensional stability matter more than electrical properties. L has a tensile strength of 95 MPa (13.8 ksi), weaker than 69% of composite grades. Elongation at break is 1.8% and the elastic modulus is 7.5 GPa (1.09 Msi). L 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 — 80/100, better than 85% of composite grades
Limitations
- Low fracture toughness — 2 MPa·√m (1.82 ksi·√in), worse than 87% of composite grades
- Needs corrosion protection — 55/100, worse than 87% 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 properties
Typical room-temperature values for L; 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 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 has a tensile strength of 95 MPa (13.8 ksi), weaker than 69% of composite grades. Elongation at break is 1.8% and the elastic modulus is 7.5 GPa (1.09 Msi).
Thermal9
L is rated for continuous service to 120°C (248 °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
L 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 (55/100), worse than 87% of composite grades. UV resistance is fair.
Sustainability3
Producing a kilogram of L 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's machinability is very good (80/100, better than 85% of composite grades).
Common Calculations4
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with L
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 — frequently asked
What is L used for?
L 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?
L has a typical tensile strength of 95 MPa (13.8 ksi) — weaker than 69% of composite grades. Strength varies by condition: see the 5 listed tempers.
Is L easy to machine?
Yes — machinability is rated very good (80/100, better than 85% 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 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?
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 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?
L 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.