G10 Epoxy Laminate

G10 epoxy laminate (NEMA grade G10 / IEC EPGC 201) is a woven E-glass cloth reinforced thermosetting epoxy resin composite. It is the most widely used general-purpose electrical insulation laminate globally, valued for its combination of high dielectric strength (up to 22 kV/mm), tensile strength above 300 MPa, glass transition temperature of 130°C, low moisture absorption (<0.1%), and outstanding machinability. Common applications include terminal boards, phase barriers, arc chutes, busbar supports, transformer spacers (up to 130°C), motor phase separators, PCB substrate material, cryogenic structural insulation, and precision-machined components for switchgear and control panels.

G10 and FR4 share an almost identical base composition — both are woven E-glass cloth reinforced thermosetting epoxy laminates with very similar mechanical and dielectric properties. The single critical difference is flame retardancy. G10 does not carry a UL 94 flame retardancy rating and uses halogen-free epoxy resin. FR4 incorporates bromine-based flame retardant chemistry and meets UL 94 V-0 (self-extinguishing within 10 seconds). FR4 is the mandatory specification wherever UL 94 V-0 compliance is required — switchgear panels, PCB fabrication, electrical enclosures. G10 is specified where halogen-free materials are mandated, where flame retardancy is explicitly not a regulatory requirement, or where maximum electrical performance and machinability are the priority without brominated additives.

Under IEC 60893, G10 is designated EPGC 201 — where EP = epoxy resin, GC = glass cloth reinforcement, and 201 is the property class number. Under Indian Standard IS 13529, the same material is referenced as EPGC 201. Under German DIN/VDE standards it is HGW 2372. Under US military specification MIL-I-24768, the equivalent is MIL-I-24768/2. All four designations refer to the same general-purpose glass cloth epoxy laminate composition with the same property requirements. If your engineering drawing specifies EPGC 201, NEMA G10, or HGW 2372, ACC Insulations supplies the correct material.

G10 has a glass transition temperature (Tg) of approximately 130°C and is rated for continuous service at up to 130°C (IEC Thermal Class B/F). Below 130°C, G10 maintains its full mechanical and dielectric performance. Above the Tg, the epoxy resin begins to soften and mechanical strength — particularly flexural and compressive strength — drops significantly. This is not a sudden failure but a gradual property degradation that can cause dimensional change and loss of structural integrity under load. For applications requiring sustained operating temperatures above 130°C — such as transformer spacers in Class F insulation systems at 155°C or motor slot wedges in Class H motors — G11 epoxy laminate must be specified instead.

ACC Insulations supplies G10 epoxy laminate from 0.5 mm to 100 mm thickness as flat sheets in standard sizes of 1020 × 1220 mm and 1220 × 2440 mm, with custom sizes available on request. We also produce precision CNC-machined G10 components — phase barriers, terminal boards, busbar saddles, arc chute plates, spacers, and any custom-profiled parts — from flat sheet stock to customer drawings with tolerances to ±0.05 mm. Both flat sheet supply and machined component orders are handled without minimum order restrictions.

Yes — G10 is one of the best-machining electrical insulation materials available. It can be CNC routed, milled, drilled, and turned with carbide-tipped tooling to produce clean edges, burr-free holes, and complex profiles without delamination. ACC Insulations operates CNC machining centres in Nashik producing custom G10 components to ±0.05 mm tolerance from customer DXF or DWG drawings. We produce phase barriers, terminal boards, slot wedges, busbar saddles, arc chute plates, transformer spacers, cryogenic support components, tooling plates, and any custom profiled insulation part. Please provide your engineering drawing or DXF file for a quotation.

G10 epoxy laminate achieves a dielectric strength of up to 22 kV/mm measured perpendicular to the laminate layers (tested in oil per IEC 60243). Parallel to the laminate layers (along the surface), the breakdown voltage typically exceeds 60 kV for standard thickness sheets. Volume resistivity exceeds 10¹² Ω·cm. These properties make G10 suitable for medium-voltage electrical insulation in switchgear, transformer components, and motor insulation at system voltages up to approximately 33 kV. For exact dielectric strength values at your specific thickness and test conditions, we can provide material test certificates on request.

Use G10 when: (1) your continuous operating temperature is below 130°C — G10 is ideal and more cost-effective than G11 in this range; (2) you need halogen-free materials — G10 uses halogen-free epoxy while FR4 contains bromine; (3) UL 94 V-0 flame retardancy is not a compliance requirement — if flame retardancy is needed, specify FR4 instead; and (4) cryogenic applications — G10 is the preferred glass epoxy grade for structural insulation at cryogenic temperatures. Upgrade to FR4 when UL 94 V-0 is required. Upgrade to G11 when operating temperature exceeds 130°C continuous or the application demands retained mechanical strength above 130°C (transformer spacers, motor slot wedges, Class F/H rated assemblies).