NEMA G11
NEMA G11 is the high-temperature glass-epoxy laminate — woven E-glass cloth bonded with a high-Tg epoxy resin system rated to 285°F (140°C) continuous service, retaining flexural strength and electrical properties at temperatures that cause NEMA G10 to soften and lose its mechanical integrity.
TL;DR
| Property | Value |
|---|---|
| Parent material | Glass phenolic (epoxy grades) |
| Primary use | High-temperature structural electrical insulation; G10 replacement above 266°F |
| Key spec | Tg ~170°C; flexural strength ≥ 60,000 psi (flatwise, RT) |
| Standards | NEMA LI 1 (Grade G11); MIL-I-24768/18; ASTM D709 |
Chemistry & Reinforcement
G11 and G10 are built on identical glass reinforcement — the difference is entirely in the epoxy resin chemistry:
- Reinforcement: Plain-weave woven E-glass cloth (same 7628-style fabric as G10)
- Resin: High-Tg epoxy system (often a multifunctional epoxy with anhydride or amine hardener); Tg ~170°C vs. ~130°C for G10
- Color/finish: Natural/green tint, same appearance as G10 and FR4
- Density: ~1.80–1.90 g/cc
The glass transition temperature (Tg) is the key distinction. Below Tg, the epoxy network behaves as a rigid glass; above Tg, it softens toward rubber-like behavior with sharply reduced modulus. G10's Tg of ~130°C means it begins losing stiffness around 266°F — a problem in motor control centers and transformer terminations operating at higher temperatures. G11's Tg of ~170°C pushes that transition point up to 338°F, extending the linear mechanical service range to 285°F continuous.
Critical note — G11 vs. FR4: G11 is NOT the same as FR4. FR4 is a flame-retardant grade (UL94 V-0, brominated epoxy resin) derived from G10. G11 is the high-Tg structural upgrade of G10 without the flame-retardant requirement of FR4. All three (G10, G11, FR4) use woven E-glass and epoxy chemistry but differ in Tg and flame-retardant treatment.
Key Properties
G11 has the highest room-temperature flexural strength in the standard NEMA glass-laminate family — 60,000–65,000 psi, matching structural aluminum. This combination of high Tg and high strength makes G11 the preferred structural insulation in high-temperature power conversion and motor drive equipment.
Typical Applications
G11 is the material specified when G10 would be the natural choice but operating temperature or thermal cycling exceeds G10's comfortable range:
- High-voltage bus bar supports in hot enclosures — motor drive cabinets and VFD enclosures where ambient plus heat rise reaches 130–140°C. G10 standoffs soften; G11 holds load.
- Dry-type transformer structural insulation — coil support cleats, clamping bars, and end-frame spacers in Class F and Class H transformers where winding temperatures exceed G10's Tg.
- Power converter mounting plates — high-density power electronics generate significant local heat; G11 sheets serve as mechanical mounting and bus bar isolation structures.
- Switchgear structural laminate at elevated temperature — G11 is specified in equipment rated to 40°C ambient with maximum temperature rise in Class F (155°C winding) insulation systems.
- High-temp jigs and fixtures — machined from G11 sheet for use in ovens and process environments up to 285°F where G10 would warp.
- CNC-machined precision parts — G11 machines like G10, with carbide tooling and good chip clearing; higher Tg means less gummy behavior during machining in warm shops.
Standard Sizes
| Form | Common sizes |
|---|---|
| Sheet thickness | 1/16, 1/8, 3/16, 1/4, 3/8, 1/2, 3/4, 1, 1-1/2, 2 in. |
| Sheet panel | 24 × 36 in., 48 × 96 in. |
| Rod diameter | 1/4 to 6 in. |
| Tube | Custom OD/ID |
G11 is less widely stocked than G10. Most industrial distributors carry G11 sheet in 1/8–1 in. thickness; rod may require laminator direct supply with 2–4 week lead time.
Standards Reference
- NEMA LI 1 — Grade G11 is defined with elevated-temperature mechanical retention requirements in addition to standard dielectric and mechanical tests. NEMA LI 1-2020 is current.
- MIL-I-24768/18 — Military high-temperature glass-epoxy specification. Type GEE-H (Glass-Epoxy, Elevated temperature). QPL certification for defense programs.
- ASTM D709 — test method standard; elevated-temperature flexural retention test underpins NEMA LI 1 G11 classification.
- IEC 60893 — International: HGW 2372.1 (glass-epoxy elevated temperature) corresponds to G11.
Comparison to Neighbor Grades
| Feature | G10 | G11 | FR4 | G7 |
|---|---|---|---|---|
| Resin | Epoxy | High-Tg Epoxy | Brominated Epoxy | Silicone |
| Tg | ~130°C | ~170°C | ~130–140°C | N/A |
| Flame retardant | No | No | Yes (V-0) | No |
| Max service temp | 266°F | 285°F | 266°F | 425°F |
| Flexural strength | 55,000–60,000 psi | 60,000–65,000 psi | 55,000–60,000 psi | 35,000–45,000 psi |
| Dielectric strength | ≥400 V/mil | ≥400 V/mil | ≥400 V/mil | ≥200 V/mil |
| Cost | Moderate | Higher than G10 | Similar to G10 | Highest |
Choose G11 when: your application exceeds G10's 266°F comfortable service range but 425°F (G7) is not required. Choose G10 for general glass-epoxy applications below 266°F. See the G10 material hub for practical buying guide. Choose FR4 when UL94 V-0 flame retardancy is required and temperature is below 266°F. Never conflate G11 and FR4 — they have different chemistries. Choose G7 for continuous service above 285°F.
Get a quote on G11 glass-epoxy sheet, rod, or tube — high-temp grade in stock
Request a Quote →More related guides
Glass-epoxy grades
High-temperature thermosets
All grades index