C FR
Flame-retardant grade
ASTM D709 Grade C, D709 Type C · GB 4021
FR = flame-retardant modified cotton phenolic
Specify where rail, transit or enclosure fire codes demand a V-0 / low-smoke laminate rather than standard HB Grade C.
Values for the FR condition
Other C grades and fills
C is listed in 2 conditions; see the grade overview at C.
- GRAPH
- FR
Compare all 2 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Graphite / MoS₂ filled bearing grade cotton phenolic | Choose for dry or marginally lubricated bearings, thrust washers and marine stern-tube bushes needing a low, stable friction coefficient. | — | 60 | 1.2 | 88 Shore D |
FRThis page Flame-retardant modified cotton phenolic | Specify where rail, transit or enclosure fire codes demand a V-0 / low-smoke laminate rather than standard HB Grade C. | — | 70 | 1.3 | 89 Shore D |
What is C FR?
C FR is C in the FR grade — specify where rail, transit or enclosure fire codes demand a V-0 / low-smoke laminate rather than standard HB Grade C. C FR has a tensile strength of 70 MPa (10.2 ksi), weaker than 81% of composite grades. Elongation at break is 1.3% and the elastic modulus is 6.8 GPa (0.986 Msi). C FR has a density of 1.36 g/cm³ (0.0491 lb/in³), lighter than 70% of composite grades. Its glass-transition temperature is 160°C (320 °F).
Advantages
- Low embodied carbon — 4.5 kg CO₂/kg, better than 79% of composite grades
- Easy to machine — 68/100, better than 77% of composite grades
Limitations
- Absorbs moisture — dry before molding — 1.6%, worse than 84% of composite grades
- Low stiffness — 6.8 GPa (0.986 Msi), worse than 78% of composite grades
- Limited service temperature — 120°C (248 °F), worse than 78% of composite grades
C FR properties
Typical room-temperature values for C FR; 20 are specific to this condition. Other listed values are C reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
C FR has a density of 1.36 g/cm³ (0.0491 lb/in³), lighter than 70% of composite grades. Its glass-transition temperature is 160°C (320 °F).
Mechanical12
C FR has a tensile strength of 70 MPa (10.2 ksi), weaker than 81% of composite grades. Elongation at break is 1.3% and the elastic modulus is 6.8 GPa (0.986 Msi).
Thermal8
C FR 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
C 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 very good (70/100), worse than 64% of composite grades. UV resistance is fair.
Sustainability4
Producing a kilogram of C 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
C FR's machinability is good (68/100, better than 77% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with C FR
Is C 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 coolant soak that swells the cotton.
Can C be welded?
Not weldable — thermoset; join by bolting, riveting or epoxy bonding after light abrasion and degreasing.
Can C be formed, bent or molded?
Supplied fully cured as pressed sheet, rolled rod or wound tube; no post-forming except hot-bending of very thin sheet, so parts are produced by machining.
What surface finishes work on C?
Cannot be plated or anodised; edges are sealed with varnish or epoxy to limit moisture pick-up, and surfaces can be sanded/varnished rather than polished to a mirror finish.
C 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 |
|---|---|---|
| phenol-formaldehyde (phenolic) resinresole/novolac binder, fully cured thermoset | 42 – 55 | 48 |
| cotton fabric (coarse weave, ≥ 4 oz/yd² woven cellulose carrier defines Grade C vs fine-weave CE/L | ≥ 45 (balance) | — |
C FR — frequently asked
What is C FR used for?
C FR is typically used for gears and bearings, mechanical brackets, wear pads and structural insulation parts. In short: best-machining phenolic laminate; impact-tough cotton phenolic; low-cost gear stock.
What is the tensile strength of C FR?
C FR has a typical tensile strength of 70 MPa (10.2 ksi) — weaker than 81% of composite grades. Strength varies by condition: see the 2 listed tempers.
Is C FR easy to machine?
Reasonably — machinability is rated good (68/100, better than 77% 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 coolant soak that swells the cotton.
Can C FR be welded?
Not weldable — thermoset; join by bolting, riveting or epoxy bonding after light abrasion and degreasing.
What surface finishes work on C FR?
Cannot be plated or anodised; edges are sealed with varnish or epoxy to limit moisture pick-up, and surfaces can be sanded/varnished rather than polished to a mirror finish.
Can C FR be formed, bent or molded?
Supplied fully cured as pressed sheet, rolled rod or wound tube; no post-forming except hot-bending of very thin sheet, so parts are produced by machining.
What is the maximum service temperature of C FR?
C 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 (2023)
- IEC 60893-3-4 – Industrial rigid laminated sheets, phenolic resin (PF CC 201/203) — IEC (2013)
- NEMA LI 1 – Industrial Laminated Thermosetting Products — NEMA (2020)
- Engineered Materials Handbook, Vol. 2: Engineering Plastics — ASM International (1988)
- Cotton fabric phenolic laminate (Grade C / CE) datasheets — Norplex-Micarta / Franklin Fibre / Attwater (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.