Flame-Retardant Glass-Reinforced Epoxy Laminate (NEMA FR-4)
FR-4 glass epoxy provides flame resistance, high mechanical strength, and reliable electrical insulation for printed circuit boards, electrical components, and industrial equipment.
Select a form factor to view real-time inventory, pricing, and custom cut-to-size options.
| Short Description | Color | Diameter | Length | Stock | Price | Add to quote |
|---|---|---|---|---|---|---|
| FR4 - 0.03" dia x 48" Natural Rod | Natural | 0.030″ | 48″ | In stock2 More in 5–7 days | $27.40per rod | |
| FR4 - 0.047" dia x 48" Natural Rod | Natural | 0.047″ | 48″ | In stock182 | $23.46per rod | |
| FR4 - 0.049" dia x 48" Natural Rod | Natural | 0.049″ | 48″ | Out of stock | $6.94per rod | |
| FR4 - 0.062" dia x 48" Natural Rod | Natural | 0.062″ | 48″ | Out of stock | $6.32per rod | |
| FR4 - 0.093" dia x 48" Black Rod | Black | 0.093″ | 48″ | In stock526 | $9.86per rod | |
| FR4 - 0.093" dia x 48" Natural Rod | Natural | 0.093″ | 48″ | In stock431 | $6.46per rod | |
| FR4 - 0.125" dia x 48" Black Rod | Black | 0.125″ | 48″ | In stock42 | $9.79per rod | |
| FR4 - 0.125" dia x 48" Natural Rod | Natural | 0.125″ | 48″ | In stock380 | $8.64per rod | |
| FR4 - 0.156" dia x 48" Black Rod | Black | 0.156″ | 48″ | In stock69 | $9.86per rod | |
| FR4 - 0.156" dia x 48" Natural Rod | Natural | 0.156″ | 48″ | Out of stock | $8.91per rod |
Material Overview
FR4 rod is the solid cylindrical bar form of NEMA FR-4 flame-retardant glass-epoxy laminate — woven fiberglass cloth impregnated with brominated epoxy resin, rolled and cured under heat and pressure into dense, machinable round stock. The FR-4 designation distinguishes this material from G-10 through its certified UL 94 V-0 self-extinguishing behavior, making FR4 rod the preferred choice for turned insulating components in UL-listed electrical equipment and fire-rated industrial assemblies.
FR4 rod exhibits tensile strength of 65,000 psi, flexural strength of 60,000 psi, and compressive strength of 38,000 psi. Rockwell M115 hardness and 21,500 psi shear strength reflect its structural rigidity. Water absorption over 24 hours is 0.10% — essentially moisture-inert — preserving dimensional tolerances in humid service. Maximum continuous operating temperature is 280°F (140°C) with a certified UL 94 V-0 flame rating.
Standards & compliance. FR4 rod conforms to NEMA LI-1 Grade FR-4 and is tested per ASTM D709. The UL 94 V-0 rating is the material's defining compliance attribute for fire-safety applications. Ready Plastics stocks FR4 rod in standard diameters as cut-to-length pieces; contact us for availability.
Sister grades. G-10 glass-epoxy rod is mechanically comparable but rated 94HB rather than 94V-0 — the right choice when flame retardancy is not required. G-11 glass-epoxy rod handles continuous service to 355°F (180°C) for elevated-temperature applications. For extreme thermal environments up to 425°F (220°C), G-7 glass-silicone rod is the step-up grade.
Frequently Asked Questions
FR4 rod is a solid round bar made from NEMA FR-4 flame-retardant glass-epoxy laminate — woven fiberglass cloth impregnated with brominated epoxy resin and cured under heat and pressure. It provides 65,000 psi tensile strength, Rockwell M115 hardness, and a UL 94 V-0 flame rating, making it the preferred glass-epoxy rod for turned insulating components in fire-safety-critical applications.
Ready Plastics stocks FR4 glass-epoxy rod in standard diameters as cut-to-length pieces. Contact us for current size availability and pricing.
FR4 rod is turned and bored using carbide tooling. The woven fiberglass reinforcement is abrasive, so carbide inserts are strongly preferred over high-speed steel. Moderate cutting speeds, positive rake angles, and thorough chip clearance maintain dimensional accuracy and minimize edge chipping. Dust and fiber extraction are essential for operator safety.
FR-4 rod and G-10 rod share essentially identical mechanical properties — both are NEMA glass-epoxy laminates. The key distinction is flame rating: FR-4 is certified UL 94 V-0 (self-extinguishing), while G-10 is rated 94HB. Specify FR-4 wherever UL listing, fire codes, or safety standards require a self-extinguishing material.
FR4 rod is used for insulating bushings, standoffs, spacers, guide pins, and structural supports in UL-listed switchgear, motor controls, relay panels, and electronic assemblies. Its 65,000 psi tensile strength, 0.10% moisture absorption, and UL 94 V-0 rating make it a standard choice wherever both mechanical performance and fire safety are required.
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