G10 / FR4 Fibre Glass Epoxy Sheet
Woven fibreglass cloth impregnated with epoxy resin, compressed under controlled heat and pressure — this produces a rigid, high-density electrical insulation laminate. Grade G10 delivers peak mechanical strength; Grade FR4 adds UL94 V-0 flame retardancy.
Both grades deliver superior dielectric performance, low moisture absorption and dimensional stability under thermal cycling — mandatory requirements for switchgear panels, power transformers, bus bar insulation and high-voltage control systems.
- Base material: Fiberglass reinforced epoxy resin (GFRP)
- Grades: G10 (NEMA standard) / FR4 (UL94 V-0 rated)
- Thickness: 1mm to 25mm — custom available
- Color: Green (FR4) / Natural / Yellow (customisable)
- Water absorption: <0.1% by weight
- Tensile strength: ~40,000 psi (warp direction)
- Volume resistivity: >1010 MΩ·cm
| Quick Reference Specifications | |
|---|---|
| Material | Fiberglass Reinforced Polymer (FRP / GFRP) |
| Grades | G10, FR4 (NEMA/IEC/UL rated) |
| Thickness | 1mm, 2mm, 3mm, 4mm, 6mm, 8mm, 10mm, 12mm, up to 25mm |
| Sheet Size | Standard 1220×2440mm; custom sizes available |
| Color | Green, Natural, Yellow |
| Surface Treatment | Smooth / Textured (as required) |
| Flame Rating | FR4 — UL94 V-0 compliant |
| Operating Temp | Up to 130°C (standard); 155°C / 180°C (high-temp grades) |
G10 vs FR4 — Which Grade to Choose?
Both grades use identical fibreglass-epoxy construction. Key difference: flame performance.
G10 — General Purpose
Maximum mechanical and dielectric strength. No flame retardant additives. Preferred for applications where flame rating isn't mandated — bus bar supports, jigs, fixtures.
FR4 — Flame Retardant
Identical base properties to G10 plus bromine-based flame retardancy. Mandatory for PCB substrates, MV switchgear, and any panel requiring fire safety compliance.
| Property | G10 | FR4 |
|---|---|---|
| Flame Retardancy | Not rated | UL94 V-0 ✓ |
| Dielectric Strength | ≥50 kV/mm ✓ | ≥50 kV/mm ✓ |
| Tensile Strength | ~40,000 psi ✓ | ~40,000 psi ✓ |
| Water Absorption | <0.10% ✓ | <0.10% ✓ |
| Max Temp (continuous) | 130°C | 130°C |
| Machinability | Excellent ✓ | Excellent ✓ |
| PCB Substrate Use | Not preferred | Standard choice ✓ |
Key Electrical & Mechanical Properties
- High dielectric strength — withstands high-voltage stress without breakdown in transformer and switchgear insulation systems
- Excellent arc resistance — critical for medium-voltage switchgear, MCB and MCCB assembly
- Low water absorption (<0.1%) — stable dielectric performance in humid industrial conditions
- High flexural strength — resists deflection under mechanical load; suitable for structural insulation components
- Dimensional stability — minimal warping or expansion under thermal cycling from −40°C to 130°C
- Chemical resistance — resists transformer oils, cleaning solvents and industrial fluids
- CNC machinable — drills, routes, mills cleanly without delamination
Industry Applications
G10 FR4 fibre glass epoxy sheets serve as structural insulation laminates across high-demand electrical and industrial sectors:
- Switchgear and MV/LV control panel fabrication — arc barriers, phase separators, bus bar supports
- Power and distribution transformer insulation — winding spacers, coil supports, core clamping plates
- PCB and electronics substrates — FR4 standard for multilayer PCB manufacturing
- Renewable energy systems — solar inverter housing insulation, wind turbine generator components
- Railway traction systems — high-voltage insulation for pantograph and traction motor housings
- Automotive and EV — battery pack insulation plates, motor winding separators
- Heavy engineering — precision jigs, fixtures and tooling plates
OEM Supply Note: ACC Insulations supplies cut-to-size G10 FR4 sheets to switchgear manufacturers, transformer OEMs and panel builders across Maharashtra, Gujarat, Tamil Nadu, Telangana and Delhi NCR. Fast dispatch with batch test certificates on request.
Manufacturing Process
Production uses compression moulding — fibreglass cloth layers saturated in epoxy resin, stacked to required thickness, then cured under controlled heat (160–180°C) and pressure (100–200 psi). This ensures:
- Void-free laminate structure with consistent resin distribution
- Tight thickness tolerance (±0.1mm on standard grades)
- Uniform dielectric strength across full sheet surface
- No internal delamination under thermal shock
ACC Manufacturing Capabilities
- CNC routing and precision cutting to exact dimensions
- Custom thickness from 1mm to 25mm — non-standard available on request
- Sheet sizes up to 1220×2440mm; custom panels for OEM drawings
- Batch-level dielectric testing and dimensional QC
- Fast-track dispatch for registered OEM accounts
- Test certificate and material traceability documentation
Why Choose ACC Insulations?
- Direct manufacturer — full production control, no intermediary margin
- Competitive pricing on bulk and OEM orders
- Consistent dielectric strength batch-to-batch
- Custom cut, CNC machined parts available
- Fast PAN-India dispatch with proper packing
- Technical support for material selection — G10 vs FR4 vs other grades
Frequently Asked Questions
Engineering Tools Suite
Calculate dielectric tolerances, thermal endurance limits and exact thickness requirements for G10 FR4 fibre glass epoxy sheets.
