Nomex PB993
Grade
PB993 = 993/994
Rigid 1.5–9 mm board for transformer spacers, barriers and end-frame insulation at class 220.
Values for the PB993 condition
Other Nomex grades and fills
Nomex is listed in 8 conditions; see the grade overview at Nomex.
Compare all 8 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
Phenolic-coated aramid honeycomb core, 29 kg/m³ | Lightest common grade for radomes, ducts and non-structural interior panels. | — | 0.85 | — | — |
Phenolic-coated aramid honeycomb core, 48 kg/m³ | Standard aerospace/interior sandwich core: best strength-to-weight with good damage tolerance and FST performance. | — | 2 | — | — |
Phenolic-coated aramid honeycomb core, 144 kg/m³ | High-density core for floor panels, hard points and highly loaded sandwich zones. | — | 10 | — | — |
Uncalendered low-density aramid paper | Soft, porous, highly conformable paper for cushioning/impregnation where varnish penetration matters more than dielectric strength. | — | 20 | 8 | — |
PB993This page 993/994 | Rigid 1.5–9 mm board for transformer spacers, barriers and end-frame insulation at class 220. | — | 45 | 6 | — |
Mica-filled corona-resistant aramid paper | Pick for inverter-fed motors and traction windings where partial-discharge (corona) endurance is required. | — | 55 | 7 | — |
410Default Calendered meta-aramid insulation paper | Standard high-density insulating paper for motor slot liners, phase insulation and transformer windings (class 220). | — | 90 | 12 | — |
Aramid-paper/phenolic laminate sheet | Machinable rigid laminate for lightweight FR structural panels, bushings and electrical insulation parts. | — | 140 | 2 | 100 HRM |
What is Nomex PB993?
Nomex PB993 is Nomex in the PB993 grade — rigid 1.5–9 mm board for transformer spacers, barriers and end-frame insulation at class 220. Nomex PB993 has a tensile strength of 45 MPa (6.53 ksi), weaker than 81% of composite grades. Elongation at break is 6% and the elastic modulus is 2 GPa (0.29 Msi). Nomex PB993 has a density of 0.78 g/cm³ (0.0282 lb/in³), lighter than 82% of composite grades. Its glass-transition temperature is 275°C (527 °F). 410 is the default condition FabDigit quotes; PB993 is available on request or by drawing note.
Advantages
- Ductile — tolerates forming and impact — 6%, better than 88% of composite grades
- Lightweight — 0.78 g/cm³ (0.0282 lb/in³), better than 82% of composite grades
Limitations
- Hard to polish — 10/100, worse than 97% of composite grades
- Absorbs moisture — dry before molding — 4.5%, worse than 95% of composite grades
- Degrades in UV without stabilisers — 25/100, worse than 86% of composite grades
- Low stiffness — 2 GPa (0.29 Msi), worse than 84% of composite grades
- Poor heat conductor — 0.11 W/m·K (0.0636 BTU/hr·ft·°F), worse than 81% of composite grades
Nomex PB993 properties
Typical room-temperature values for Nomex PB993; 15 are specific to this condition. Other listed values are Nomex reference data and may not represent this condition. Bars are the position among composite grades.
Physical4
Nomex PB993 has a density of 0.78 g/cm³ (0.0282 lb/in³), lighter than 82% of composite grades. Its glass-transition temperature is 275°C (527 °F).
Mechanical4
Nomex PB993 has a tensile strength of 45 MPa (6.53 ksi), weaker than 81% of composite grades. Elongation at break is 6% and the elastic modulus is 2 GPa (0.29 Msi).
Thermal8
Nomex PB993 is rated for continuous service to 220°C (428 °F). It conducts heat at 0.11 W/m·K (0.0636 BTU/hr·ft·°F), worse than 81% of composite grades. Thermal expansion is 17 µm/m·K (9.44 µin/in·°F).
Electrical5
Nomex PB993 is an electrical insulator with a dielectric strength of 14 kV/mm (355.6 V/mil) and a resistivity of 1×10¹³ Ω·m.
Chemical & Environmental3
Corrosion resistance is very good (70/100), worse than 64% of composite grades. UV resistance is poor.
Sustainability4
Producing a kilogram of Nomex PB993 takes about 260 MJ of energy and emits 11 kg of CO₂ — more than 57% of composite grades. Typical recycled content is 0%.
Manufacturability2
Nomex PB993's machinability is good (55/100, better than 71% of composite grades).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Nomex PB993
Is Nomex easy to machine?
Paper and pressboard die-cut, laser or waterjet cut cleanly; honeycomb core needs razor/serrated blades, high-speed router with sharp carbide or waterjet plus vacuum fixturing to avoid cell crush and fuzzing.
Can Nomex be welded?
Not weldable or heat-sealable (no melting point) — join by adhesive bonding, resin impregnation, stitching or mechanical clamping.
Can Nomex be formed, bent or molded?
Paper and honeycomb are cold-formable/creped to gentle curvature; core is expanded from an HOBE block and phenolic-dipped, and sandwich panels are co-cured or bonded with 120–180 °C film adhesive.
What surface finishes work on Nomex?
Dry the material before bonding or varnish impregnation (hygroscopic); surfaces accept phenolic/epoxy varnish, corona or plasma treatment improves adhesion; no plating or polishing applies.
Nomex chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| mica filleronly in corona-resistant 418-type paper | 0 – 50 | 0 |
| phenolic resin coatingonly in honeycomb core / laminate forms | 0 – 45 | 0 |
| poly(m-phenylene isophthalamide) (meta-afrom m-phenylenediamine + isophthaloyl chloride; paper grades = floc + binder fibrids | balance | — |
Nomex PB993 — frequently asked
What is Nomex PB993 used for?
Nomex PB993 is typically used for honeycomb sandwich cores, firefighter/protective clothing, electrical insulation paper and filtration media. In short: flame-resistant meta-aramid; standard honeycomb core material; class H electrical insulation.
What is the tensile strength of Nomex PB993?
Nomex PB993 has a typical tensile strength of 45 MPa (6.53 ksi) — weaker than 81% of composite grades. Strength varies by condition: see the 8 listed tempers.
Is Nomex PB993 easy to machine?
Reasonably — machinability is rated good (55/100, better than 71% of composite grades). Paper and pressboard die-cut, laser or waterjet cut cleanly; honeycomb core needs razor/serrated blades, high-speed router with sharp carbide or waterjet plus vacuum fixturing to avoid cell crush and fuzzing.
Can Nomex PB993 be welded?
Not weldable or heat-sealable (no melting point) — join by adhesive bonding, resin impregnation, stitching or mechanical clamping.
What surface finishes work on Nomex PB993?
Dry the material before bonding or varnish impregnation (hygroscopic); surfaces accept phenolic/epoxy varnish, corona or plasma treatment improves adhesion; no plating or polishing applies.
Can Nomex PB993 be formed, bent or molded?
Paper and honeycomb are cold-formable/creped to gentle curvature; core is expanded from an HOBE block and phenolic-dipped, and sandwich panels are co-cured or bonded with 120–180 °C film adhesive.
What is the maximum service temperature of Nomex PB993?
Nomex PB993 is rated for continuous use to about 220°C (428 °F), and briefly to 300°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Nomex 410 / 411 / 418 Technical Data Sheets — DuPont (2022)
- HexWeb HRH-10 Aramid Fibre/Phenolic Honeycomb Product Data — Hexcel (2020)
- Nomex Brand Fiber Technical Guide — DuPont (2021)
- IEC 60216 / IEC 60641 insulation thermal classification (class 220) — IEC (2013)
- ASTM D202 — Testing Insulating Paper — ASTM (2017)
- Engineered Materials Handbook Vol. 2 — Engineering Plastics — ASM International (1988)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.