G10 Material — Glass-Epoxy Laminate Guide

G10 material is a NEMA-grade glass-cloth-reinforced epoxy laminate widely used as an electrical insulator, structural dielectric substrate, and precision mechanical component stock. It combines woven E-glass fabric with an epoxy resin binder, cured under heat and pressure into sheet, rod, and tube forms. G10 is not flame-retardant — it carries a UL94 HB (horizontal burn) rating, which is an important distinction from its close relative FR4. Both materials share the same glass-epoxy chemistry, but FR4 incorporates a brominated flame-retardant additive that G10 lacks, lifting FR4's rating to UL94 V-0.

At a glance:

• NEMA designation: G10 (per NEMA LI 1 and MIL-I-24768/2)
• Base chemistry: woven E-glass fabric + epoxy resin binder
• Flame rating: UL94 HB — not flame-retardant (vs. FR4's UL94 V-0)
• Dielectric strength: ~500 V/mil (short time); ~400 V/mil (in oil, step-by-step)
• Flexural strength: 60,000 psi (lengthwise), 50,000 psi (crosswise)
• Thermal class: B (130°C continuous per IEC classification)
• Color: natural green-tinted translucent to beige/olive; also available in black
• Available forms: sheet, plate, rod, tube

What Is G10 Material?

G10 is a thermoset composite laminate. Its structure begins with layers of woven E-glass cloth — a high-purity borosilicate glass fiber — which are then impregnated with an epoxy resin system. Multiple plies are stacked, then cured in a heated hydraulic press at elevated temperature and pressure. The result is a rigid, dimensionally stable laminate with directional anisotropy: properties are highest in the plane of the laminate (parallel to the glass cloth) and lower through the thickness direction.

Glass-Epoxy Chemistry

The "G" prefix in NEMA laminate designations always signals a glass-cloth reinforcement. The "10" distinguishes the epoxy resin system from other NEMA grades: G3 uses a melamine resin, G7 uses silicone resin, and G9 uses a melamine-glass binder. G10 specifically uses an epoxy resin without any flame-retardant additive, unlike FR4, which adds brominated compounds (typically tetrabromobisphenol A, TBBPA) to achieve its V-0 rating.

The epoxy system in G10 provides excellent adhesion to glass fiber, good electrical insulation across a broad frequency range, and superior mechanical strength relative to paper-phenolic or canvas-phenolic laminates. The cured laminate absorbs very little moisture — water absorption runs 0.10% at 24 hours in standard thickness sheet — which preserves electrical performance in humid environments.

NEMA G10 Standard

NEMA LI 1 (Industrial Laminated Thermosetting Products) is the primary governing document. It defines G10 as a glass-cloth-epoxy laminate meeting specified minimum values for flexural strength, dielectric strength, arc resistance, and water absorption. The military specification MIL-I-24768/2 (Type GEE) is the corresponding defense standard and is used when traceability to federal procurement requirements is needed. ASTM D709 is an additional testing standard commonly referenced in material qualification.

G10 Material Properties

G10's property profile positions it as a cost-effective high-performance insulator for both electrical and structural roles.

Mechanical Properties

Electrical Properties

Thermal Properties

For the complete datasheet including water absorption, chemical resistance, and environmental conditioning data, see the G10 properties page.

G10 vs. FR4: Key Distinctions

This distinction matters for specification, procurement, and compliance.

G10 and FR4 are functionally similar in mechanical and electrical performance. The material you choose depends on whether your application requires a UL94 V-0 flame spread rating. When it does not — such as knife handles, washer stock, outdoor structural insulators, or general machined parts — G10 is often the preferred choice because it avoids brominated additives.

For a complete technical and application comparison, read the G10 vs FR4 comparison.

Why G10 Is Not Flame-Retardant

A common misconception is that "glass-epoxy laminate" is inherently fire-resistant. In fact, epoxy resins and glass fiber will sustain combustion. NEMA G10 contains no flame-retardant additives, so the cured laminate will burn when ignited and will not self-extinguish. The UL94 HB rating means the material passes only the horizontal burn test — a far less stringent standard than the vertical burn tests (V-0, V-1, V-2) that FR4 passes.

This is deliberate. The absence of brominated flame retardants makes G10 suitable for:

• Applications where halogen content must be minimized (per RoHS or customer requirement)
• Food-preparation equipment where bromine off-gassing is a concern (though G10 is generally not FDA-cleared — see the G10 FDA page)
• Environments where the flame-spread risk is managed by other means (location, enclosure design, automatic suppression)

In applications requiring self-extinguishing behavior — electronics enclosures per IEC 60950, rail interiors, aircraft cabin components — FR4 or a specifically rated thermoset must be used instead.

Available Forms

G10 is produced and stocked in three primary forms. Each form follows the same base glass-epoxy laminate chemistry; the difference is geometry and manufacturing method.

G10 Sheet and Plate

Sheet stock runs from 0.005" to 0.250" in standard gauge thicknesses; heavy plate stock starts at 0.250" and extends to 4.0" and beyond. Standard sheet panels are 24" × 36", 36" × 48", and 48" × 96". Cut-to-size service is available for both sheet and plate. See the G10 sheet page and G10 plate page for full size tables and tolerances.

G10 Rod

Round rod stock is produced by compression molding or filament winding. Standard diameters run from 0.125" to 4.0" in 4-ft and 8-ft lengths. Tolerances on OD are typically +0.000" / −0.015" for small diameters. Full details at the G10 rod page.

G10 Tube

Tube is manufactured by filament winding glass cloth around a mandrel, then curing. This produces excellent hoop strength. Standard ID/OD ranges cover most sleeve, bushing, and standoff geometries. See the G10 tube page.

G10 Applications

G10 is specified across a wide range of industries wherever reliable electrical insulation combined with structural rigidity is required:

PCB substrates — G10 is the original material substrate for printed circuit boards, predating FR4. Because it lacks the V-0 flame rating, it is no longer the dominant PCB substrate for consumer electronics (where FR4 is mandated), but it remains used for specialized military and industrial boards built to older MIL specifications.

Electrical insulators and transformer parts — Slot liners, phase barriers, coil supports, and transformer spiders are machined or stamped from G10 sheet. The combination of high dielectric strength, dimensional stability, and machinability makes it the go-to for custom insulation components.

Knife handles — G10 is one of the most popular knife handle materials in the custom and production knife market. Its dimensional stability in wet environments, resistance to sweat and solvents, excellent grip texture when machined, and light weight make it highly preferred. G10 knife handles are produced in a wide range of colors (achieved by tinting the resin or the glass layer).

Aerospace structural insulators — Brackets, standoffs, and isolation mounts where electrical isolation is required alongside structural load-carrying, typically to MIL-I-24768/2.

Washers, standoffs, and spacers — High-volume machined or stamped components for electrical assemblies.

Precision mechanical structures — G10's high stiffness-to-weight ratio (relative to aluminum in thin cross-sections) and machinability make it useful for jigs, fixtures, and structural plates in controlled environments.

For a full application breakdown by industry, see G10 applications.

Machining G10

G10 machines readily on standard CNC equipment, but glass fiber reinforcement demands attention to tool selection and dust control. The abrasive glass fiber wears standard HSS tooling rapidly; carbide or PCD (polycrystalline diamond) tooling is required for any production-volume work. At the operator level, the dust generated from machining G10 contains respirable glass fiber particulate — an OSHA-regulated health hazard. Engineering controls (dust extraction, enclosures) and PPE (NIOSH-rated respirator, P100 filter) are mandatory.

Key parameters:

• Cutting speed: 500–700 SFM for carbide; 700–1,000 SFM for PCD
• Feed: 0.003–0.006 IPT; lower feeds reduce delamination at edges
• Drilling: Sharp carbide drill, 300–500 SFM, moderate feed to prevent fiber pullout at exit face
• Routing: Climb milling preferred at edges to minimize fraying

Full tooling specifications, setup tips, and dust control guidance are in the G10 machining guide.

Specifications and Standards

For detailed dimensional tolerances, standard thickness gauges, and surface finish specifications, see G10 specifications.

G10 Grades and Related Materials

Within the glass-epoxy laminate family, several NEMA grades share the same glass-cloth reinforcement but differ in resin system or additives:

• G10 — Standard epoxy, UL94 HB
• FR4 — Epoxy + brominated flame retardant, UL94 V-0
• G11 — Higher-temperature epoxy variant of G10, slightly improved thermal performance
• FR5 — High-temperature variant of FR4 (comparable to G11 but flame-retardant)

For grades outside the glass-epoxy family (cotton phenolic, paper phenolic, silicone-glass), see the G10 grades comparison.

More related guides

Cross-cluster suggestions for engineers and buyers exploring adjacent topics:

Applications

• Electrical Insulators
• Structural Insulators
• Washers and Spacers

Industries

• Aerospace
• Electronics
• Knife Making

Compare to other materials

• G10 vs FR4
• G10 vs Cotton Phenolic
• G10 vs G11

Forms

• G10 Sheet
• G10 Rod
• G10 Tube

Frequently asked questions — G10 FAQ