Glass-Fiber Reinforced Melamine Laminate (NEMA G-9)
G5/G9 glass melamine offers flame resistance, strong mechanical performance, and reliable electrical insulation for components used in switchgear, motors, and industrial equipment.
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Material Overview
G5/G9 sheet is the flat-panel form of NEMA G-5 / G-9 glass-melamine laminate — a hard, arc-resistant thermoset composite produced by impregnating woven fiberglass cloth with melamine resin and laminating under heat and pressure into rigid flat stock. G-5 emphasizes mechanical strength and G-9 emphasizes electrical and arc-resistance performance; both grades deliver outstanding arc and tracking resistance, high surface hardness, and inherent flame retardance, making G5/G9 sheet the standard choice for arc-chute walls, barrier panels, and switchgear insulation.
G5/G9 sheet delivers tensile strength of 35,000 psi, flexural strength of 55,000 psi, and compressive strength of 55,000 psi. Rockwell hardness exceeds M115, shear strength is approximately 18,000 psi, and water absorption over 24 hours is approximately 1.2%. Arc resistance typically exceeds 180 seconds per ASTM D495 — far better than glass-epoxy grades. The material is self-extinguishing and operates continuously up to 311°F (155°C). These properties make G5/G9 sheet ideal for arc-chute walls, switchgear barrier panels, contact mounting plates, and high-voltage insulators in heavy power equipment.
Standards & compliance. G5/G9 sheet conforms to NEMA LI-1 Grades G-5 and G-9 with test methods per ASTM D709 and arc resistance per ASTM D495. Ready Plastics stocks G5/G9 sheet in a range of thicknesses; custom cuts are available through our cut-to-size service or contact us for sizing.
Sister grades. For higher mechanical strength without melamine’s arc resistance, G-10 glass-epoxy sheet is the standard choice. For UL 94 V-0 flame retardance, see FR-4 glass-epoxy sheet. For arc resistance combined with high-temperature service, G-7 glass-silicone sheet is preferred.
Technical Specifications
Typical values at 23°C / 50% RH. Values are nominal and not guaranteed; refer to lot-specific certificates of conformance for production parts.
Frequently Asked Questions
G5/G9 is a NEMA LI-1 Grade G-9 glass-fiber-reinforced melamine thermoset laminate. Made from woven glass cloth bonded with melamine resin, it is rated UL 94 V-0 and is known for exceptional arc and track resistance. It is used in high-voltage switchgear, motor slot insulation, bus bar supports, and other applications where surface tracking could cause failure.
G5/G9 uses a melamine resin system, giving it superior arc and track resistance and a UL 94 V-0 flame rating. G-10 uses epoxy resin and offers lower water absorption (0.11% vs. 0.60%) and higher compressive strength. Choose G5/G9 when arc resistance and flame retardance are the primary requirements; choose G-10 when maximum moisture resistance and compressive strength matter most.
Ready Plastics stocks G5/G9 glass melamine in sheet form. Contact Ready Plastics for current inventory, available thicknesses, and cut-to-size options.
Yes. G5/G9 glass melamine can be drilled, milled, sawed, and punched on standard machine shop equipment. Carbide tooling is recommended due to the abrasive glass reinforcement. Dust extraction is advised.
No. G5/G9 is a glass melamine laminate with a 120°C (248°F) maximum service temperature. G-7 is a glass silicone laminate capable of continuous service at 220°C (428°F). Both offer arc resistance and UL 94 V-0 ratings, but G-7 is chosen for extreme-temperature applications where G5/G9 would be insufficient.
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