FR-6
ASTM D709 Grade FR-6
FR-6 is a flame-retardant polyester glass-mat laminate to ASTM D709 Grade FR-6, built from chopped mat rather than woven fabric.
Reference datasheet — FR-6 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
FR-6 grades and fills
FR-6 is supplied in 4 conditions, soft to hard.
Compare all 4 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Hot/cold punching grade | Choose for high-volume stamped insulating washers, slot liners and PCB blanks where crack-free punching matters more than peak strength. | 75 | 1.4 | 100 HRM | |
Enhanced flame/arc-resistant grade | Specify for arc chutes and switchgear barriers needing high ATI/CTI plus low smoke and V-0 at reduced thickness. | 80 | 1.1 | 108 HRM | |
Heat-resistant thermal class F/H polyester glass-mat board | Use where continuous service reaches 155–180 °C, e.g. motor and transformer insulation near windings. | 88 | 1.1 | 108 HRM | |
GPO-3 / UPGM 203 | The IEC/NEMA industrial equivalent, supplied in thick sheet and rod for switchgear arc barriers and transformer insulation. | 90 | 1.2 | 108 HRM |
Supply forms, finishes and certifications
Ways FR-6 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
CCL-1 | Single-sided copper-clad FR-6 | Surface finish |
STDDefault | Unclad FR-6 laminate sheet | Standard supply |
What is FR-6?
FR-6 is a flame-retardant polyester glass-mat laminate to ASTM D709 Grade FR-6, built from chopped mat rather than woven fabric. It is used as a low-cost, general-purpose insulating board where 85 MPa tensile strength and a 130 °C maximum service temperature are sufficient and the strength of glass-fabric epoxy grades is not required; conditions on file include standard sheet, punching stock, copper-clad (CCL-1), high-temperature and V-0/high-HTI variants. As a thermoset it cannot be welded or post-formed, and cut edges wick moisture unless sealed. Specify GPO-3 where arc and track resistance are needed. FR-6 has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades. Its glass-transition temperature is 120°C (248 °F). FR-6 has a tensile strength of 85 MPa (12.3 ksi), weaker than 75% of composite grades. Elongation at break is 1.2% and the elastic modulus is 10 GPa (1.45 Msi).
What is FR-6 used for?
- general electrical insulation
- low-cost terminal boards
- appliance insulation panels
Limitations
- Hard to polish — 20/100, worse than 90% of composite grades
- Needs corrosion protection — 62/100, worse than 75% of composite grades
FR-6 properties
Typical room-temperature values; bars are the position among composite grades.
Physical4
FR-6 has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades. Its glass-transition temperature is 120°C (248 °F).
Mechanical12
FR-6 has a tensile strength of 85 MPa (12.3 ksi), weaker than 75% of composite grades. Elongation at break is 1.2% and the elastic modulus is 10 GPa (1.45 Msi).
Thermal9
FR-6 is rated for continuous service to 130°C (266 °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
FR-6 is an electrical insulator with a dielectric strength of 14 kV/mm (355.6 V/mil) and a resistivity of 1×10¹¹ 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 FR-6 takes about 85 MJ of energy and emits 5 kg of CO₂ — less than 79% of composite grades. Typical recycled content is 0%.
Manufacturability2
FR-6's machinability is fair (45/100, better than 63% of composite grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the composite family
Yield strength against density for every composite grade FabDigit runs. FR-6 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with FR-6
Is FR-6 easy to machine?
Cut, drill and rout with carbide or PCD tooling at high speed / low feed; the glass mat and mineral filler wear HSS quickly and generate irritant dust requiring extraction.
Can FR-6 be welded?
Not weldable — thermoset; join by bonding with epoxy/polyurethane adhesives or by mechanical fasteners with generous washers.
Can FR-6 be formed, bent or molded?
Supplied as fully cured flat sheet or rod; it cannot be post-formed, but thin gauges punch cleanly (warm the sheet to 40–60 °C to avoid edge crazing).
FR-6 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 |
|---|---|---|
| E-glass fiber matrandom chopped-strand mat reinforcement | 25 – 40 | 32 |
| mineral filler (ATH / CaCO3)ATH also contributes flame retardancy | 20 – 40 | 30 |
| flame retardant / additivesbrominated or phosphorus FR, catalysts, pigments | 2 – 10 | 6 |
| unsaturated polyester resinmatrix, styrene cross-linked | ≥ 25 (balance) |
What surface finishes work on FR-6?
Edges should be deburred and sealed with varnish or epoxy to limit moisture wicking; surface takes conformal coating and screen printing, but polishing and plating are not practical.
Equivalent designations
Standards and trade names that resolve to FR-6 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- D709 Grade FR-6
How much does FR-6 cost?
FR-6 is a premium-cost composite ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
FR-6 — frequently asked
What is FR-6 used for?
FR-6 is typically used for general electrical insulation, low-cost terminal boards and appliance insulation panels. In short: low-cost flame-retardant board; punchable polyester laminate; economy alternative to FR-4.
What is the tensile strength of FR-6?
FR-6 has a typical tensile strength of 85 MPa (12.3 ksi) — weaker than 75% of composite grades. Strength varies by condition: see the 4 listed tempers.
Is FR-6 easy to machine?
Reasonably — machinability is rated fair (45/100, better than 63% of composite grades). Cut, drill and rout with carbide or PCD tooling at high speed / low feed; the glass mat and mineral filler wear HSS quickly and generate irritant dust requiring extraction.
Can FR-6 be welded?
Not weldable — thermoset; join by bonding with epoxy/polyurethane adhesives or by mechanical fasteners with generous washers.
What surface finishes work on FR-6?
Edges should be deburred and sealed with varnish or epoxy to limit moisture wicking; surface takes conformal coating and screen printing, but polishing and plating are not practical.
Can FR-6 be formed, bent or molded?
Supplied as fully cured flat sheet or rod; it cannot be post-formed, but thin gauges punch cleanly (warm the sheet to 40–60 °C to avoid edge crazing).
What is the maximum service temperature of FR-6?
FR-6 is rated for continuous use to about 130°C (266 °F), and briefly to 180°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does FR-6 cost?
FR-6 is a premium-cost composite ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM D709 — Standard Specification for Laminated Thermosetting Materials — ASTM International (2017)
- NEMA LI 1 — Industrial Laminated Thermosetting Products — NEMA (1998)
- IEC 60893-3-2 — Insulating materials, industrial rigid laminated sheets, type UPGM 203 — IEC (2003)
- IEC 60112 — Method for determining proof and comparative tracking indices — IEC (2020)
- GPO-3 / polyester glass-mat laminate technical datasheets — electrical laminate producers (2023)
- GPO-3/FR-6 (2025)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.