Glass Silicone Laminates — Sheet & Rod

Glass silicone is a family of woven-glass-fabric/silicone-resin thermoset laminates defined by NEMA LI-1. These composites are manufactured by impregnating woven glass cloth with silicone resin and curing under heat and pressure into rigid stock. The silicone resin binder provides thermal stability that fundamentally outperforms epoxy, phenolic, and melamine alternatives at elevated temperatures — making glass silicone the material of choice when electrical insulation must remain dimensionally stable, electrically reliable, and structurally sound under sustained extreme heat. Ready Plastics stocks glass silicone Grade G-7, the NEMA standard designation for this family.

Glass silicone offers excellent dielectric strength, strong arc resistance, low moisture absorption, and a maximum continuous service temperature of 220°C (428°F) — the highest thermal rating of any glass-reinforced thermoset laminate in the Ready Plastics lineup. It carries a UL 94 V-0 flame classification. These properties make glass silicone an indispensable material for transformer insulation barriers, high-temperature motor and generator components, furnace fixtures, and high-energy electrical switchgear where other laminates would degrade. The glass silicone grade also handles thermal cycling reliably, reducing the risk of cracking or delamination under repeated heat-and-cool stress.

Standards and performance context. Glass silicone Grade G-7 meets NEMA LI-1 Grade G-7 and is tested per ASTM D709. While mechanical strength is lower than glass epoxy grades, the exceptional thermal and arc resistance of silicone resin more than compensates in high-temperature applications. For applications below 180°C requiring higher mechanical strength, glass epoxy grades G-11 or FR-5 are more appropriate. For arc-resistant insulation below 120°C, glass melamine G-9 is a cost-effective alternative.

Related families. Ready Plastics carries the complete thermoset laminate family, including glass epoxy (G-10, FR-4, G-11, FR-5), glass melamine (G-9), and glass phenolic (G-3), all within the broader thermoset laminates and phenolics lineup.