G-7 glass silicone is a woven-glass-fabric/silicone-resin thermoset laminate defined by NEMA LI-1 Grade G-7. It belongs to the glass silicone family — composites manufactured by impregnating woven glass cloth with silicone resin, then curing under heat and pressure into rigid stock. This g7 laminate earns its specification in extreme-temperature environments: the silicone resin system provides thermal stability far beyond what epoxy or phenolic binders can sustain, combined with outstanding arc resistance and reliable dielectric performance.
G-7 g7 material delivers 45,000 psi tensile strength, 25,000 psi flexural strength, and 17,000 psi shear strength. Water absorption over 24 hours is only 0.20%. Maximum continuous service temperature is 428°F (220°C) — the highest in the glass-reinforced thermoset laminate family at Ready Plastics. Flammability is rated UL 94 V-0. NEMA G7 is specified for transformer insulation barriers, motor end rings and wedges, high-voltage switchgear, furnace jigs, and other components that must perform under prolonged thermal cycling and electrical stress.
Standards. G-7 meets NEMA LI-1 Grade G-7 and carries a UL 94 V-0 flame rating. Test methods follow ASTM D709. The silicone binder's inherent thermal stability and arc resistance are not replicated by epoxy or melamine grades at equivalent temperatures.
Grade comparisons. When 220°C service is not required, G-5/G-9 glass melamine provides arc resistance and UL 94 V-0 performance up to 120°C at lower cost. For high-strength structural insulation up to 180°C, G-11 or FR-5 glass epoxy are appropriate alternatives. See the full glass silicone page at Ready Plastics for stock information and datasheets.
