FR5 Sheet — Thicknesses, Sizes & Stock Forms
FR5 sheet is flat laminate stock produced from NEMA FR-5, a flame-retardant woven glass-fabric/epoxy thermoset rated for continuous service to 180 °C (355 °F). With flexural strength of 75,000 psi, water absorption of only 0.20%, and a UL 94HB flame rating, FR5 sheet is specified for bus bar phase barriers, high-voltage insulation panels, motor winding separators, and structural plates in fire-rated power enclosures — applications where the elevated thermal class of FR5 over FR4 sheet matters and where flame-retardant certification is mandatory.
At a glance:
- Thickness range: 0.020" to 4.0"
- Standard sheet sizes: 36" × 48" and 48" × 96"
- Thickness tolerance: ±10% on thicknesses ≤ 0.062"; ±0.005" on thicker stock
- Material: NEMA FR-5, woven glass-fabric/epoxy flame-retardant thermoset
- Production method: Compression-molded flat laminate
- Color: Natural yellow-green
Standard Thickness Table
FR5 sheet is stocked in the following standard gauges at Ready Plastics:
| Thickness | Sheet Size | Notes |
|---|---|---|
| 0.031" | 36" × 48" | Thin barrier and liner sheet |
| 0.062" | 36" × 48" & 48" × 96" | Gaskets and slot liners |
| 0.093" | 36" × 48" & 48" × 96" | |
| 0.125" | 36" × 48" & 48" × 96" | Standard thickness — broad application |
| 0.250" | 36" × 48" & 48" × 96" | Structural panel and insulation plate |
| 0.500" | 36" × 48" & 48" × 96" | Bus bar barriers, heavier structures |
| 0.750" | 36" × 48" | |
| 1.000" | 36" × 48" | Thermal barrier and fixture plate |
Custom thicknesses and slit widths available on request.
Mechanical & Electrical Properties
| Property | Value |
|---|---|
| Tensile strength | 63,000 psi (430 MPa) |
| Flexural strength (LW, 0.125") | 75,000 psi (515 MPa) |
| Shear strength | 22,000 psi (150 MPa) |
| Bond strength | 2,200 psi (15 MPa) |
| Hardness (Rockwell M) | 112 |
| Izod impact strength (49 °C, LW) | 12.00 ft·lb/in |
| Specific gravity | 1.82 |
| Water absorption (24 hr) | 0.20% |
| Flammability rating | UL 94HB |
| Maximum continuous service temp | 180 °C (355 °F) |
Typical Applications
FR5 sheet is waterjet-cut, CNC-routed, punched, and sheared into flat insulation components for demanding electrical systems:
- Bus bar phase barriers and phase separators — dielectric insulation rated for sustained high-current bus temperatures with flame retardancy
- Motor slot liners and coil separators — thin gauges fit tightly within motor slots; resist winding temperatures
- High-voltage terminal boards and mounting plates — stable dimensions under cyclic thermal loading
- Transformer barrier insulation — low moisture absorption maintains creepage distances over service life
- Flame-rated enclosure panels and partition plates for switchgear and MCC assemblies
- Fixture plates in elevated-temperature test and assembly environments where fire safety is required
Machining FR5 Sheet
FR5 sheet fabricates on the same equipment as G11 and FR4. Waterjet cutting is the preferred method for complex profiles — it produces burr-free edges without heat-affected zones. For straight cuts, a table saw with a carbide-tipped fine-tooth blade works well; feed steadily to prevent chipping on the exit face. Routing with solid carbide spiral bits at moderate speeds produces smooth edge finishes suitable for high-voltage applications. Drilling requires sharp carbide drills with a sacrificial backup board to prevent back-face breakout. Finished surfaces bond well to epoxy structural adhesives for laminated assemblies.
Related
- FR5 Glass Epoxy — Line Card
- FR5 Rod — round bar for machined insulators, standoffs, and bushings
- FR5 Tube — hollow sections for coil forms and conduits
- G11 Sheet — non-flame-retardant counterpart, same thermal class and mechanical properties
- FR4 Sheet — standard-temperature flame-retardant glass-epoxy sheet (130 °C service)