Glass epoxy is a family of woven-glass-fabric/epoxy-resin thermoset laminates that are among the most widely used electrical insulation materials in industrial and electronic applications. Each grade is defined by NEMA LI-1 and is manufactured by impregnating woven fiberglass cloth with epoxy resin, then curing under heat and pressure into rigid sheet, rod, and tube stock. Ready Plastics stocks the full glass epoxy family — including G-10, FR-4, G-11, and FR-5 — covering a broad range of temperature and flame-performance requirements.
Across grades, glass epoxy laminates are valued for their high strength-to-weight ratio, excellent dimensional stability, low moisture absorption, and strong dielectric performance. Flame-retardant variants (FR-4, FR-5) add UL 94-rated fire safety for applications with regulatory requirements. High-temperature variants (G-11, FR-5) extend continuous service to 180°C (355°F). The fiberglass laminate construction gives all grades good machinability on conventional shop equipment — a key advantage for cut-to-size electrical insulation and precision-machined structural components.
Selecting a grade. G-10 is the standard non-flame-retardant baseline: high compressive strength, 0.11% water absorption, continuous service to 140°C. FR-4 matches G-10's mechanical profile with the addition of a UL 94 V-0 flame rating — making it the default for most electrical insulation applications governed by fire codes. G-11 and FR-5 share nearly identical high-temperature performance at 180°C; the choice between them comes down to whether a flame-retardant designation is required. All are available as industrial laminate sheet and rod stock.
Related families. For applications requiring arc and track resistance, see glass melamine (G-5/G-9). For extreme-temperature service above 180°C, glass silicone Grade G-7 operates continuously to 220°C. Ready Plastics is part of the broader thermoset laminates and phenolics family, which includes cotton phenolic, glass phenolic, paper phenolic, and more.
