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

G5/G9 glass melamine is a woven-glass-fabric/melamine-resin thermoset laminate classified under NEMA LI-1 Grade G-9. It belongs to the glass melamine family — composites manufactured by impregnating woven glass cloth with melamine resin and curing under heat and pressure into rigid phenolic sheet, rod, and tube stock. The melamine resin system gives G5/G9 outstanding arc and track resistance, distinguishing it from epoxy-based grades and making it particularly effective in high-voltage switchgear and motor insulation applications where surface tracking is a concern.

G5/G9 delivers 70,000 psi tensile strength, 55,000 psi flexural strength, and 39,000 psi compressive strength with a Rockwell M115 hardness. The material is rated UL 94 V-0 — self-extinguishing under vertical flame exposure — with water absorption of only 0.60% over 24 hours. Maximum continuous service temperature is 248°F (120°C). These properties make G5/G9 a dependable choice for motor slot liners, bus bar insulation, switchgear panels, and other high-voltage components where both arc resistance and flame retardance are required.

Standards. G5/G9 meets NEMA LI-1 Grade G-9 and carries a UL 94 V-0 flammability classification. ASTM D709 governs test methods for this laminated thermosetting material. The melamine resin's inherent arc and tracking resistance is a core performance differentiator versus epoxy grades.

Related materials. For applications requiring higher service temperatures, glass epoxy grades G-11 and FR-5 operate up to 180°C. Where extreme heat resistance is paramount, glass silicone Grade G-7 extends continuous service to 220°C. For applications where melamine's arc resistance is the primary requirement but at this temperature range, G5/G9 from Ready Plastics provides a proven, purpose-built solution. See the glass melamine family page for the full offering.