G7
ASTM D709, D709 Grade G-7 · also Silicone Glass Laminate
G7 is a silicone-resin glass-fabric NEMA laminate (ASTM D709 Grade G-7, similar to EN 60893 SI GC 202) chosen for high arc resistance and dielectric strength at temperature.
Values for the Silicone Matrix condition
G7 grades and fills
G7 is supplied in one standard condition, Silicone Matrix. Silicone Matrix is the default FabDigit quotes; the values on this page are for it.
Supply forms, finishes and certifications
Ways G7 is supplied — form, process route, surface or paperwork — without a datasheet of their own. The property values above apply.
| Option | What it is | Type |
|---|---|---|
ROD-TUBE | Rolled rod / tube | Supply form |
What is G7?
G7 is a silicone-resin glass-fabric NEMA laminate (ASTM D709 Grade G-7, similar to EN 60893 SI GC 202) chosen for high arc resistance and dielectric strength at temperature. With about 170 MPa tensile strength and service to 220 °C it runs hotter than the epoxy grades G-10 and G-11, and is stocked as sheet, rod and tube for arc barriers, switchgear and thermal insulation. Trade-offs are lower mechanical strength than epoxy or melamine laminates, higher cost, abrasive machining, and a low-energy silicone surface from which paints and adhesives release poorly. Where 180 °C is enough, G-11 is the cheaper and stronger alternative. G7 has a density of 1.8 g/cm³ (0.065 lb/in³), heavier than 59% of composite grades. G7 has a tensile strength of 170 MPa (24.7 ksi), weaker than 55% of composite grades. The elastic modulus is 14 GPa (2.03 Msi).
What is G7 used for?
- Arc barriers in switchgear
- High-temperature electrical insulators
- Industrial spacers and washers
- Bus bar supports
- Coil forms and terminal blocks
- Heater and oven insulation components
- Welding and furnace fixture insulation
Limitations
- Hard to polish — 25/100, worse than 76% of composite grades
G7 properties
Typical room-temperature values for G7-Silicone Matrix; bars are the position among composite grades.
Physical2
G7 has a density of 1.8 g/cm³ (0.065 lb/in³), heavier than 59% of composite grades.
Mechanical10
G7 has a tensile strength of 170 MPa (24.7 ksi), weaker than 55% of composite grades. The elastic modulus is 14 GPa (2.03 Msi).
Thermal8
G7 is rated for continuous service to 220°C (428 °F). It conducts heat at 0.3 W/m·K (0.173 BTU/hr·ft·°F), worse than 63% of composite grades. Thermal expansion is 12 µm/m·K (6.67 µin/in·°F).
Electrical7
G7 is an electrical insulator with a dielectric strength of 15 kV/mm (381 V/mil) and a resistivity of 1×10¹¹ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (80/100), better than 54% of composite grades. UV resistance is very good.
Sustainability3
Producing a kilogram of G7 takes about 110 MJ of energy and emits 7 kg of CO₂ — less than 60% of composite grades. Typical recycled content is 0%.
Manufacturability2
G7's machinability is fair (35/100, better than 50% 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. G7 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with G7
Is G7 easy to machine?
Machines like other glass laminates but is abrasive and dust-forming — use carbide or PCD tooling, sharp positive rake, high speed/low feed, vacuum extraction and respiratory protection; back up thin sheet to avoid edge chipping/delamination.
Can G7 be welded?
Not weldable (thermoset); join mechanically or with high-temperature silicone/epoxy adhesives after abrasion and primer, since cured silicone surfaces bond poorly.
Can G7 be formed, bent or molded?
Supplied as fully cured flat sheet, rod and tube; no post-forming — cut, drill, punch (thin sheet, warm) or machine to shape.
Manufacturability
The process limits FabDigit's quote engine applies to G7. Design inside these and the part quotes instantly; outside them it routes to an engineer.
CNC machining
| Machinability | Better35 / 100 |
|---|---|
| Cutting speed (rough / finish) | — / — |
| Minimum wall | — |
| Minimum internal radius | — |
| Drill depth limit | |
| Best surface (machined / polished) | Ra — / — |
| Hardenable after machining | — |
Sheet metal
| Formability | Not Recommend5 / 100 |
|---|---|
| Weldability | Not Recommend5 / 100 |
G7 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 |
|---|---|---|
| E-glass woven fabriccontinuous-filament woven glass cloth reinforcement | 60 – 75 | 68 |
| silicone (polysiloxane) resinthermoset matrix, fully cured | ≥ 25 (balance) |
What surface finishes work on G7?
Edges deburred/sanded; surface can be sealed or coated only with silicone-compatible primers — paint and most adhesives release poorly from the low-energy silicone surface.
Surface treatments FabDigit runs on composite parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Equivalent designations
Standards and trade names that resolve to G7 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- ASTM
- D709D709 Grade G-7
- Trade names
- Silicone Glass Laminate
- Also called
- NEMA G-7
How much does G7 cost?
G7 is a premium-cost composite ($$$), pricier than about 58% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
G7 — frequently asked
What is G7 used for?
G7 is typically used for arc barriers in switchgear, high-temperature electrical insulators, industrial spacers and washers, bus bar supports, coil forms and terminal blocks and heater and oven insulation components. In short: silicone-glass thermal laminate.
What is the tensile strength of G7?
G7 has a typical tensile strength of 170 MPa (24.7 ksi) — weaker than 55% of composite grades.
Is G7 easy to machine?
Not especially — machinability is rated fair (35/100, better than 50% of composite grades). Machines like other glass laminates but is abrasive and dust-forming — use carbide or PCD tooling, sharp positive rake, high speed/low feed, vacuum extraction and respiratory protection; back up thin sheet to avoid edge chipping/delamination.
Can G7 be welded?
Not weldable (thermoset); join mechanically or with high-temperature silicone/epoxy adhesives after abrasion and primer, since cured silicone surfaces bond poorly.
What surface finishes work on G7?
Edges deburred/sanded; surface can be sealed or coated only with silicone-compatible primers — paint and most adhesives release poorly from the low-energy silicone surface.
Can G7 be formed, bent or molded?
Supplied as fully cured flat sheet, rod and tube; no post-forming — cut, drill, punch (thin sheet, warm) or machine to shape.
What is the maximum service temperature of G7?
G7 is rated for continuous use to about 220°C (428 °F), and briefly to 260°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does G7 cost?
G7 is a premium-cost composite ($$$), pricier than about 58% 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.
Can FabDigit make parts in G7?
Yes — G7 is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- NEMA LI 1 — Industrial Laminating Thermosetting Products (grade G7) — NEMA (1998)
- ASTM D709 — Standard Specification for Laminated Thermosetting Materials — ASTM (2017)
- Silicone glass laminate G7 technical data — Norplex-Micarta (2022)
- Garolite G-7 sheet/rod properties — Professional Plastics / McMaster-Carr (2024)
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.