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

G5/G9 rod is the solid round-bar form of NEMA G-5 / G-9 glass-melamine laminate — a thermoset composite produced by impregnating woven fiberglass cloth with melamine resin and curing the layup under heat and pressure into a hard, dense, arc-resistant cylindrical stock. The grade is best known for its outstanding arc and tracking resistance, exceptional surface hardness, and inherent flame retardance, making G5/G9 rod the specified material for arc-chute components, switchgear contacts, and high-voltage standoffs in heavy power equipment.

G5/G9 rod delivers tensile strength of 30,000 psi, flexural strength of 50,000 psi, and compressive strength of 55,000 psi. Rockwell hardness exceeds M115 — among the highest of any thermoset laminate — and shear strength is approximately 17,000 psi. Water absorption over 24 hours is approximately 1.2%. The material is self-extinguishing (UL 94HB or better) and operates continuously up to 311°F (155°C). The arc resistance of G5/G9 (typically >180 seconds per ASTM D495) is far superior to glass-epoxy grades. These properties make G5/G9 rod the right choice for arc-chute pins, switchgear standoffs, and contact-mount hardware.

Standards & compliance. G5/G9 rod conforms to NEMA LI-1 Grades G-5 and G-9 and is tested per ASTM D709 with arc resistance per ASTM D495. The two grades are closely related: G-5 emphasizes mechanical strength while G-9 offers improved electrical and arc-resistance performance. Ready Plastics stocks G5/G9 rod in standard diameters; request a custom cut or contact us for availability.

Sister grades. For higher mechanical strength at lower cost, G-10 glass-epoxy rod outperforms melamine on flexural strength but lacks the arc resistance. For flame-retardant electrical service, FR-4 glass-epoxy rod offers UL 94 V-0 performance. For high-temperature arc resistance specifically, see G-7 glass-silicone rod.