GPO-3
ASTM D709 Grade GPO-3
GPO-3 is a flame-retardant polyester glass-mat laminate to ASTM D709 Grade GPO-3 (similar to EN 60893 UP GM 203), filled with alumina trihydrate to give arc and track resistance.
Reference datasheet — GPO-3 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.
GPO-3 grades and fills
GPO-3 is supplied in 5 conditions, soft to hard.
Compare all 5 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
UL94 5VA rated high-flame-resistance grade | Use where enclosure-level 5VA burn performance is required (typically ≥3 mm sheet). | 65 | 1 | 108 HRM | |
UL94 V-0 flame-rated stock (thin sections from ~1.5 mm) | Pick when the UL Yellow Card V-0 rating must be held down to thin barrier thicknesses. | 68 | 1.2 | 106 HRM | |
Enhanced track/arc-resistant grade | Pick for medium-voltage phase barriers where surface tracking and arc erosion dominate the design. | 68 | 1.2 | 108 HRM | |
High-temperature grade | Choose for arc chutes and coil insulation running continuously above 130 °C. | 70 | 1.1 | 108 HRM | |
High-mechanical grade | Use for load-bearing barriers and machined structural parts where standard GPO-3 stiffness is marginal. | 95 | 1.5 | 100 HRM |
Supply forms, finishes and certifications
Ways GPO-3 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
STDDefault | Standard GPO-3 sheet | Standard supply |
What is GPO-3?
GPO-3 is a flame-retardant polyester glass-mat laminate to ASTM D709 Grade GPO-3 (similar to EN 60893 UP GM 203), filled with alumina trihydrate to give arc and track resistance. It is the standard insulation board for high-voltage switchgear and arc chutes, supplied as sheet, rod and tube at 1.85 g/cm³ density, 70 MPa tensile strength and 130 °C maximum service temperature, with V-0, 5VA, high-temperature, high-mechanical and tracking-optimised conditions on file. Strength is well below glass-fabric epoxy grades such as G-10/FR-4, and the ATH plus glass content is highly abrasive to tooling. GPO-3 has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades. GPO-3 has a tensile strength of 70 MPa (10.2 ksi), weaker than 81% of composite grades. Elongation at break is 1.2% and the elastic modulus is 9 GPa (1.31 Msi).
What is GPO-3 used for?
- switchgear arc chutes
- high-voltage insulation barriers
- circuit breaker components
- bus supports
Advantages
- Low embodied carbon — 4.2 kg CO₂/kg, better than 88% of composite grades
Limitations
- Hard to polish — 20/100, worse than 90% of composite grades
GPO-3 properties
Typical room-temperature values; bars are the position among composite grades.
Physical3
GPO-3 has a density of 1.85 g/cm³ (0.0668 lb/in³), heavier than 67% of composite grades.
Mechanical11
GPO-3 has a tensile strength of 70 MPa (10.2 ksi), weaker than 81% of composite grades. Elongation at break is 1.2% and the elastic modulus is 9 GPa (1.31 Msi).
Thermal8
GPO-3 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 22 µm/m·K (12.2 µin/in·°F).
Electrical7
GPO-3 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 very good (75/100), worse than 55% of composite grades. UV resistance is good.
Sustainability4
Producing a kilogram of GPO-3 takes about 70 MJ of energy and emits 4.2 kg of CO₂ — less than 93% of composite grades. Typical recycled content is 0%.
Manufacturability2
GPO-3'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. GPO-3 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with GPO-3
Is GPO-3 easy to machine?
Very abrasive (ATH + glass): use carbide or PCD tooling, high speed / moderate feed, sharp positive rake and dust extraction — the dust is a respiratory irritant.
Can GPO-3 be welded?
Thermoset — cannot be welded or thermoformed; join by bolting, riveting or epoxy/polyurethane bonding after abrading and cleaning.
Can GPO-3 be formed, bent or molded?
Supplied as flat compression-molded sheet, rod or tube; net shapes are made by matched-die molding of the polyester/glass mat charge at roughly 140–160 °C, not by reheating stock.
GPO-3 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 |
|---|---|---|
| unsaturated polyester resin (matrix)styrene-crosslinked UP; some grades use vinyl ester or DAP-modified resin | 20 – 32 | 26 |
| glass fiber (chopped strand mat)random mat, gives quasi-isotropic in-plane properties | 20 – 35 | 28 |
| pigment / process additivestypically red, orange or natural sheet color | 0.5 – 3 | 1 |
| aluminum trihydrate / mineral fillerATH provides flame retardance, arc and track resistance | ≥ 35 (balance) |
What surface finishes work on GPO-3?
Machined edges should be deburred and sealed with polyurethane or epoxy varnish for humid/tracking-critical service; the sheet takes no plating and needs an adhesion primer before painting.
Equivalent designations
Standards and trade names that resolve to GPO-3 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- D709 Grade GPO-3
- Other
- D709
How much does GPO-3 cost?
GPO-3 is a premium-cost composite ($$$), cheaper than about 51% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
GPO-3 — frequently asked
What is GPO-3 used for?
GPO-3 is typically used for switchgear arc chutes, high-voltage insulation barriers, circuit breaker components and bus supports. In short: arc- and track-resistant; switchgear standard laminate; V-0 and 5VA conditions.
What is the tensile strength of GPO-3?
GPO-3 has a typical tensile strength of 70 MPa (10.2 ksi) — weaker than 81% of composite grades. Strength varies by condition: see the 5 listed tempers.
Is GPO-3 easy to machine?
Reasonably — machinability is rated fair (45/100, better than 63% of composite grades). Very abrasive (ATH + glass): use carbide or PCD tooling, high speed / moderate feed, sharp positive rake and dust extraction — the dust is a respiratory irritant.
Can GPO-3 be welded?
Thermoset — cannot be welded or thermoformed; join by bolting, riveting or epoxy/polyurethane bonding after abrading and cleaning.
What surface finishes work on GPO-3?
Machined edges should be deburred and sealed with polyurethane or epoxy varnish for humid/tracking-critical service; the sheet takes no plating and needs an adhesion primer before painting.
Can GPO-3 be formed, bent or molded?
Supplied as flat compression-molded sheet, rod or tube; net shapes are made by matched-die molding of the polyester/glass mat charge at roughly 140–160 °C, not by reheating stock.
What is the maximum service temperature of GPO-3?
GPO-3 is rated for continuous use to about 130°C (266 °F), and briefly to 180°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does GPO-3 cost?
GPO-3 is a premium-cost composite ($$$), 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 (Grade GPO-3) — ASTM International (2023)
- EN 60893-3-2 — Industrial rigid laminated sheets, thermosetting resins, type UP GM 203 — CENELEC/IEC (2013)
- IEC 60112 — Method for determining proof and comparative tracking indices — IEC (2020)
- GPO-3 polyester glass mat laminate sheet datasheets — Von Roll / Glastic / Norplex-Micarta (2023)
- Engineered Materials Handbook Vol. 1 — Composites — ASM International (1987)
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.