G10 Properties — Mechanical, Electrical & Thermal Datasheet
G10 properties reflect its glass-cloth-epoxy construction: high dielectric strength (approximately 500 V/mil short time), excellent flexural and compressive strength, low moisture absorption, and reliable electrical insulation across a broad frequency range. G10 is classified as Thermal Class B, indicating suitability for continuous electrical insulation service at 130°C. This page compiles the full property set for NEMA G10 per standard conditioning, with tables covering mechanical, electrical, thermal, and environmental performance.
At a glance:
- Dielectric strength: ~500 V/mil (short time, in air); ~400 V/mil (step-by-step, in oil)
- Flexural strength: 60,000 psi (lengthwise) / 50,000 psi (crosswise)
- Compressive strength: 65,000 psi (flatwise)
- Thermal class: B — 130°C continuous (IEC 60085)
- Water absorption (24 hr, 1/8" specimen): 0.10% max
- Flame rating: UL94 HB (horizontal burn — not self-extinguishing)
- Density: 1.80–1.90 g/cc
Mechanical Properties
G10 is a structural laminate, not merely an insulator. Its glass-cloth reinforcement delivers flexural and compressive strength values that compete with many engineering thermoplastics at a fraction of the cost.
Tensile and Flexural Data
Compressive and Shear Data
G10 properties are anisotropic. Lengthwise values (parallel to warp direction of the glass cloth) are typically 15–25% higher than crosswise values. Always confirm the orientation when specifying G10 parts with critical directional load requirements.
Impact and Hardness
Electrical Properties
G10's electrical performance is the foundation of its use in PCB substrates, electrical insulators, and transformer components. The combination of high dielectric strength and moderate dielectric constant makes it suitable for both power-frequency and signal-frequency insulation duties.
Insulation and Dielectric Data
Conditioning and Moisture Effects
Electrical properties of G10 degrade modestly after moisture conditioning. The NEMA LI 1 specification defines two conditioning states:
- C-48/23/50: 48-hour conditioning at 23°C, 50% relative humidity (baseline)
- D-24/23: 24-hour water immersion at 23°C (wet condition)
Volume resistivity remains above 10⁸ Ω·cm after D-24/23 conditioning for standard 1/8" sheet — a characteristic that makes G10 reliable in humid environments where paper-phenolic laminates would degrade significantly more.
G10 is not waterproof. Prolonged immersion or cycling between wet and dry conditions will gradually degrade surface resistivity. For fully submerged electrical insulation, consult lot test data rather than relying on catalog minimums.
Thermal Properties
G10's in-plane CTE (14–18 ppm/°C) is governed primarily by the glass fiber, which has a CTE of approximately 5 ppm/°C, and the epoxy matrix, which runs 50–80 ppm/°C. The laminated composite value falls between these bounds and is relatively stable across the −40°C to +130°C operating range.
The through-thickness CTE (55–70 ppm/°C) is much higher — driven almost entirely by the neat epoxy resin — and must be accounted for in assembled structures where fasteners or inserts are loaded thermally through the laminate thickness.
Thermal Class B — What It Means
IEC 60085 and NEMA define Thermal Class B as rated for continuous electrical insulation service at 130°C. This does not mean the material will structurally fail above 130°C — the heat deflection temperature under load is in the same range — but it means the long-term dielectric performance has been validated to that temperature. Short-term exposure to 150°C is typically tolerable without permanent damage.
Environmental and Chemical Resistance
| Chemical | Resistance | Notes |
|---|---|---|
| Dilute acids (HCl, HNO₃, < 20%) | Good | No significant attack at room temperature |
| Concentrated H₂SO₄ | Poor | Attacks epoxy matrix |
| Dilute alkalis (NaOH, < 10%) | Good | Minor surface attack over extended time |
| Strong alkalis (NaOH, > 30%) | Moderate | Gradual degradation of epoxy/glass interface |
| Aliphatic solvents (hexane, heptane) | Excellent | No attack |
| Aromatic solvents (toluene, xylene) | Good | Some swelling on prolonged contact |
| Ketones (acetone, MEK) | Moderate | Softening possible at prolonged contact |
| Alcohols (IPA, ethanol) | Good | Limited effect |
| Motor oils, hydraulic fluid | Excellent | No attack |
| UV / outdoor exposure | Moderate | Epoxy will yellow and chalk; surface protection recommended |
Comparing G10 to Related Laminates
G10 and FR4 are essentially equivalent on mechanical and electrical performance — the differentiator is flame rating. G11 improves on G10 by using an epoxy resin system with a higher glass-transition temperature, offering modestly better retention of mechanical properties above 130°C. Cotton-epoxy (CE grade) is softer, lower in dielectric strength, and absorbs more moisture, but it machines more cleanly and costs less.
For a comprehensive grade comparison, see the G10 grades page.
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Frequently asked questions — G10 FAQ