GPO-1 HT (H 180 °C GPO-1)
Heat-treated state
ASTM D709 Grade GPO-1
Pick the heat-resistant polyester/vinyl ester system when continuous service must reach Class H at 180 °C, as in motor and dry-type transformer insulation.
Values for the HT condition
Other GPO-1 grades and fills
GPO-1 is listed in 3 conditions; see the grade overview at GPO-1.
Compare all 3 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
hot/cold punching grade (thin sheet, 0.8–3 mm) | Use the thin sheet (≤3 mm) with adjusted resin/filler ratio when parts are punched cold or warm in high volume, such as insulating gaskets, instead of being machined from plate. | — | 60 | 1.7 | 100 HRM |
GPO-1UL94 V-0 | Choose the ATH-, halogen- or phosphorus-modified board when UL 94 V-0 is mandatory for insulation inside electrical cabinets; tensile strength falls to 65 MPa versus the standard sheet. | — | 65 | 1.4 | 105 HRM |
HTThis page H 180 °C GPO-1 | Pick the heat-resistant polyester/vinyl ester system when continuous service must reach Class H at 180 °C, as in motor and dry-type transformer insulation. | — | 68 | 1.3 | 108 HRM |
What is GPO-1 HT?
GPO-1 HT is GPO-1 heat treated to HT — pick the heat-resistant polyester/vinyl ester system when continuous service must reach Class H at 180 °C, as in motor and dry-type transformer insulation. GPO-1 HT has a tensile strength of 68 MPa (9.86 ksi), weaker than 81% of composite grades. The elastic modulus is 10 GPa (1.45 Msi). GPO-1 HT 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).
Advantages
- Low embodied carbon — 4.2 kg CO₂/kg, better than 88% of composite grades
Limitations
- Hard to polish — 25/100, worse than 76% of composite grades
GPO-1 HT properties
Typical room-temperature values for GPO-1 HT; 19 are specific to this condition. Other listed values are GPO-1 reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
GPO-1 HT 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).
Mechanical10
GPO-1 HT has a tensile strength of 68 MPa (9.86 ksi), weaker than 81% of composite grades. The elastic modulus is 10 GPa (1.45 Msi).
Thermal9
GPO-1 HT is rated for continuous service to 180°C (356 °F). It conducts heat at 0.33 W/m·K (0.191 BTU/hr·ft·°F), worse than 53% of composite grades. Thermal expansion is 25 µm/m·K (13.9 µin/in·°F).
Electrical7
GPO-1 HT 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 (78/100), worse than 52% of composite grades. UV resistance is fair.
Sustainability4
Producing a kilogram of GPO-1 HT 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-1 HT's machinability is fair (44/100, better than 59% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with GPO-1 HT
Is GPO-1 easy to machine?
Saws, mills, drills and turns without difficulty, but the glass and inorganic filler are strongly abrasive: use carbide or PCD tooling at high speed and low feed. Run dust extraction, as the dust is an irritant.
Can GPO-1 be welded?
Thermoset — not weldable. Join with epoxy or acrylic structural adhesive, or mechanically with bolts and rivets.
Can GPO-1 be formed, bent or molded?
Sheet is fully cured and cannot be reheated and formed; thin gauges punch cleanly. Finished thickness and shape are set during lamination, then trimmed by machining.
What surface finishes work on GPO-1?
Chamfer and seal edges with epoxy or varnish to limit moisture pick-up and surface tracking. Silk-screen marking is practical; plating and polishing are not.
GPO-1 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 resinThermoset matrix with styrene crosslinking | 20 – 35 | 28 |
| E-glass fiber (chopped strand mat)chopped strand glass mat reinforcement | 20 – 35 | 28 |
| pigment / release agent / catalystcolorant and curing additives | 0 – 3 | 2 |
| mineral filler (CaCO3 / ATH / clay)Inorganic filler; affects electrical and flame-retardant behavior | ≥ 30 (balance) | — |
GPO-1 HT — frequently asked
What is GPO-1 HT used for?
GPO-1 HT is typically used for general electrical insulation, low-voltage terminal boards and junction box liners. In short: lowest-cost GPO grade; economical insulating board; no arc-track rating.
What is the tensile strength of GPO-1 HT?
GPO-1 HT has a typical tensile strength of 68 MPa (9.86 ksi) — weaker than 81% of composite grades. Strength varies by condition: see the 3 listed tempers.
Is GPO-1 HT easy to machine?
Not especially — machinability is rated fair (44/100, better than 59% of composite grades). Saws, mills, drills and turns without difficulty, but the glass and inorganic filler are strongly abrasive: use carbide or PCD tooling at high speed and low feed. Run dust extraction, as the dust is an irritant.
Can GPO-1 HT be welded?
Thermoset — not weldable. Join with epoxy or acrylic structural adhesive, or mechanically with bolts and rivets.
What surface finishes work on GPO-1 HT?
Chamfer and seal edges with epoxy or varnish to limit moisture pick-up and surface tracking. Silk-screen marking is practical; plating and polishing are not.
Can GPO-1 HT be formed, bent or molded?
Sheet is fully cured and cannot be reheated and formed; thin gauges punch cleanly. Finished thickness and shape are set during lamination, then trimmed by machining.
What is the maximum service temperature of GPO-1 HT?
GPO-1 HT is rated for continuous use to about 180°C (356 °F), and briefly to 200°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)
- IEC 60893 / IEC 60112 (CTI) Insulating materials — industrial rigid laminated sheets — IEC (2020)
- GPO-1 / GPO-3 polyester glass laminate technical data — Glastic/Norplex-Micarta (2023)
- Handbook of Composites / Engineering Plastics — thermoset laminates — ASM International (2000)
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.