G5 G9
Grade
ASTM D709, D709 Grade G-5 · also Melamine Glass Laminate
G9 = melamine glass-cloth laminate, improved humid-state electricals
Pick G9 over G5 when the part must hold dielectric strength and insulation resistance after humidity exposure while keeping melamine's arc/tracking resistance.
Values for the G9 condition
Other G5 grades and fills
G5 is listed in 2 conditions; see the grade overview at G5.
Compare all 2 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Melamine MatrixDefault G5 glass-cloth melamine laminate (NEMA G5 / MIL GME) | Standard choice when arc resistance, tracking resistance and inherent flame retardance matter more than humid-state electrical stability. | 220 | 1.5 | 115 HRM | |
G9This page Melamine glass-cloth laminate, improved humid-state electricals | Pick G9 over G5 when the part must hold dielectric strength and insulation resistance after humidity exposure while keeping melamine's arc/tracking resistance. | 240 | 1.5 | 118 HRM |
What is G5 G9?
G5 G9 is G5 in the G9 grade — pick G9 over G5 when the part must hold dielectric strength and insulation resistance after humidity exposure while keeping melamine's arc/tracking resistance. G5 G9 has a tensile strength of 240 MPa (34.8 ksi), weaker than 51% of composite grades. Elongation at break is 1.5% and the elastic modulus is 18 GPa (2.61 Msi). G5 G9 has a density of 1.95 g/cm³ (0.0704 lb/in³), heavier than 75% of composite grades. Melamine Matrix is the default condition FabDigit quotes; G9 is available on request or by drawing note.
Advantages
- Low embodied carbon — 4.5 kg CO₂/kg, better than 79% of composite grades
Limitations
- Needs corrosion protection — 60/100, worse than 79% of composite grades
G5 G9 properties
Typical room-temperature values for G5 G9; 21 are specific to this condition. Other listed values are G5 reference data and may not represent this condition. Bars are the position among composite grades.
Physical3
G5 G9 has a density of 1.95 g/cm³ (0.0704 lb/in³), heavier than 75% of composite grades.
Mechanical13
G5 G9 has a tensile strength of 240 MPa (34.8 ksi), weaker than 51% of composite grades. Elongation at break is 1.5% and the elastic modulus is 18 GPa (2.61 Msi).
Thermal9
G5 G9 is rated for continuous service to 155°C (311 °F). It conducts heat at 0.35 W/m·K (0.202 BTU/hr·ft·°F), better than 50% of composite grades. Thermal expansion is 14 µm/m·K (7.78 µin/in·°F).
Electrical7
G5 G9 is an electrical insulator with a dielectric strength of 16 kV/mm (406.4 V/mil) and a resistivity of 1×10¹² Ω·m.
Chemical & Environmental3
Corrosion resistance is good (60/100), worse than 79% of composite grades. UV resistance is fair.
Sustainability3
Producing a kilogram of G5 G9 takes about 75 MJ of energy and emits 4.5 kg of CO₂ — less than 91% of composite grades. Typical recycled content is 0%.
Manufacturability4
G5 G9's machinability is poor (25/100, worse than 65% of composite grades); weldability not recommended (0/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with G5 G9
Is G5 easy to machine?
Machine dry with sharp carbide or diamond tooling, high speed / moderate feed, backing plate to avoid edge chipping and delamination; provide dust extraction (glass + melamine dust is irritant).
Can G5 be welded?
Not weldable — thermoset laminate; join by bolting, riveting or epoxy bonding after abrading and solvent-cleaning the surface.
Can G5 be formed, bent or molded?
Supplied as fully cured flat sheet, rod or tube; no post-forming possible, all geometry by machining, punching (thin sheet, warm) or waterjet.
What surface finishes work on G5?
Edges should be deburred and sealed with varnish or epoxy to limit moisture pickup; can be sanded but not polished to gloss; paint only over abraded, dry surfaces.
G5 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 fabricreinforcement, plain/twill weave cloth | 50 – 65 | 58 |
| melamine-formaldehyde resinmatrix; may be modified with phenolic for toughness | ≥ 35 (balance) |
G5 G9 — frequently asked
What is G5 G9 used for?
G5 G9 is typically used for arc barriers, switchgear insulators, terminal blocks and boards, punched washers and spacers, contactor and circuit breaker components and bus bar supports. In short: melamine arc-resistant laminate.
What is the tensile strength of G5 G9?
G5 G9 has a typical tensile strength of 240 MPa (34.8 ksi) — weaker than 51% of composite grades. Strength varies by condition: see the 2 listed tempers.
Is G5 G9 easy to machine?
Not especially — machinability is rated poor (25/100, worse than 65% of composite grades). Machine dry with sharp carbide or diamond tooling, high speed / moderate feed, backing plate to avoid edge chipping and delamination; provide dust extraction (glass + melamine dust is irritant).
Can G5 G9 be welded?
Not readily — weldability is rated not recommended (0/100). Not weldable — thermoset laminate; join by bolting, riveting or epoxy bonding after abrading and solvent-cleaning the surface.
What surface finishes work on G5 G9?
Edges should be deburred and sealed with varnish or epoxy to limit moisture pickup; can be sanded but not polished to gloss; paint only over abraded, dry surfaces.
Can G5 G9 be formed, bent or molded?
Supplied as fully cured flat sheet, rod or tube; no post-forming possible, all geometry by machining, punching (thin sheet, warm) or waterjet.
What is the maximum service temperature of G5 G9?
G5 G9 is rated for continuous use to about 155°C (311 °F), and briefly to 200°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Can FabDigit make parts in G5 G9?
Yes — G5 G9 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 Laminated Thermosetting Products — NEMA (1998)
- MIL-I-24768/9 (Type GME) and /8 (Type GMG) — Plastic Sheet, Laminated, Thermosetting — US DoD (1994)
- ASTM D709 — Laminated Thermosetting Materials — ASTM (2017)
- Melamine glass-cloth laminate (G5/G9) sheet datasheet — industrial laminate producers (2023)
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.