FR5 material is a high-temperature, flame-retardant glass-reinforced epoxy laminate defined by NEMA LI-1 Grade FR-5. Like its sibling grades, it belongs to the glass epoxy family — thermoset composites made from woven fiberglass cloth impregnated with epoxy resin and cured into rigid stock. FR5 extends the performance envelope of standard glass epoxy laminates, delivering elevated thermal endurance while maintaining strong mechanical and dielectric properties.
FR5 delivers 63,000 psi tensile strength and 75,000 psi flexural strength — the highest flexural value in the FR/G glass epoxy lineup. Shear strength reaches 22,000 psi, and water absorption over 24 hours is only 0.20%. Maximum continuous service temperature is 355°F (180°C), making this fr5 laminate well-suited for motor insulation, transformer coil forms, high-heat switchgear components, and any structural electrical part that must retain integrity at elevated temperatures.
Standards. FR5 meets NEMA LI-1 Grade FR-5 and carries a UL 94HB flammability classification. Test methods follow ASTM D709 for laminated thermosetting materials. The elevated glass transition temperature distinguishes FR5 from lower-rated grades.
Grade comparisons. Step down to FR-4 when continuous service stays below 140°C and a V-0 flame rating is needed. For applications that require the same high-temperature capability without flame-retardant additives, G-11 is the non-FR counterpart to FR5 and offers a virtually identical mechanical profile. All grades are available from Ready Plastics; see the parent glass epoxy page for the full family.
