G-5 / G-9 Arc-Resistant Glass Melamine — Sheet

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.