XNBR FR (Flame-retardant XNBR)
Flame-retardant grade
Mining conveyor belt covers, cable jackets and rail interiors requiring self-extinguishing behaviour; heavy mineral loading reduces tensile and tear.
Values for the FR condition
Other XNBR grades and fills
XNBR is listed in 10 conditions; see the grade overview at XNBR.
Compare all 10 grades and fillsHide
| Grade · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness |
|---|---|---|---|---|---|
FRThis page Flame-retardant XNBR | Mining conveyor belt covers, cable jackets and rail interiors requiring self-extinguishing behaviour; heavy mineral loading reduces tensile and tear. | — | 14 | 320 | 25 Shore D |
Shore A 50 | Soft, high-elongation grade for low-pressure gaskets, diaphragms and flexible boots where sealing on rough flanges matters more than extrusion resistance. | — | 16 | 570 | 8 Shore D |
ozone- and weather-resistant compound | Use where the part sees outdoor ozone, sunlight or fuel-hose duty; PVC gives weathering and flame resistance but raises low-temperature stiffness and compression set. | — | 20 | 400 | 22 Shore D |
Shore A 60 | General gasket and O-ring hardness with a good balance of sealing conformability and abrasion life. | — | 21 | 500 | 13 Shore D |
Low-ACN (≈18–26 % acrylonitrile) low-temperature XNBR | For cold-climate seals and belts needing flexibility to about −40 °C, at the cost of higher oil swell. | — | 22 | 500 | 16 Shore D |
A70Default Shore A 70 | Default industrial hardness: highest-volume XNBR compound for oil seals, rod wipers, hydraulic packings and abrasion-resistant rubber goods. | — | 25 | 450 | 20 Shore D |
Carboxylated nitrile latex | Aqueous XNBR latex dipped into thin films: the standard powder-free examination/industrial glove material, protein-free versus natural latex. | — | 25 | 550 | 10 Shore D |
High-ACN (≈33–40 % acrylonitrile) fuel/oil-resistant XNBR | Pick when swell in aromatic fuels, gear oils or aggressive additives must be minimised; accept a much colder brittle point penalty. | — | 27 | 400 | 20 Shore D |
Shore A 80 | Choose for high-pressure hydraulic seals, packer elements and backup rings where gap extrusion is the failure mode. | — | 28 | 340 | 30 Shore D |
Shore A 90 | For roll covers, wear liners and anti-extrusion components; near-maximum abrasion resistance but low elongation and poor sealing conformability. | — | 30 | 240 | 38 Shore D |
What is XNBR FR?
XNBR FR is XNBR in the FR grade — mining conveyor belt covers, cable jackets and rail interiors requiring self-extinguishing behaviour; heavy mineral loading reduces tensile and tear. XNBR FR has a tensile strength of 14 MPa (2.03 ksi), weaker than 75% of polymer grades. Elongation at break is 320% and the elastic modulus is 0.01 GPa (0.0016 Msi). XNBR FR has a density of 1.45 g/cm³ (0.0524 lb/in³), heavier than 86% of polymer grades. Its glass-transition temperature is -24°C (-11 °F). A70 is the default condition FabDigit quotes; FR is available on request or by drawing note.
Advantages
- Conducts heat well — 0.36 W/m·K (0.208 BTU/hr·ft·°F), better than 92% of polymer grades
- Ductile — tolerates forming and impact — 320%, better than 82% of polymer grades
Limitations
- Absorbs moisture — dry before molding — 1.5%, worse than 91% of polymer grades
- Difficult to machine — 28/100, worse than 90% of polymer grades
- Heavy — 1.45 g/cm³ (0.0524 lb/in³), worse than 86% of polymer grades
- Needs corrosion protection — 68/100, worse than 85% of polymer grades
- Difficult to weld — 10/100, worse than 82% of polymer grades
XNBR FR properties
Typical room-temperature values for XNBR FR; 19 are specific to this condition. Other listed values are XNBR reference data and may not represent this condition. Bars are the position among polymer grades.
Physical4
XNBR FR has a density of 1.45 g/cm³ (0.0524 lb/in³), heavier than 86% of polymer grades. Its glass-transition temperature is -24°C (-11 °F).
Mechanical9
XNBR FR has a tensile strength of 14 MPa (2.03 ksi), weaker than 75% of polymer grades. Elongation at break is 320% and the elastic modulus is 0.01 GPa (0.0016 Msi).
Thermal8
XNBR FR is rated for continuous service to 100°C (212 °F). It conducts heat at 0.36 W/m·K (0.208 BTU/hr·ft·°F), better than 92% of polymer grades. Thermal expansion is 220 µm/m·K (122.2 µin/in·°F).
Electrical5
XNBR FR is an electrical insulator with a dielectric strength of 16 kV/mm (406.4 V/mil) and a resistivity of 1×10⁹ Ω·m.
Chemical & Environmental3
Corrosion resistance is good (68/100), worse than 85% of polymer grades. UV resistance is poor.
Sustainability4
Producing a kilogram of XNBR FR takes about 110 MJ of energy and emits 4.2 kg of CO₂ — more than 64% of polymer grades. Typical recycled content is 3%.
Manufacturability6
XNBR FR's machinability is poor (28/100, worse than 90% of polymer grades); weldability not recommended (10/100); formability very good (78/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with XNBR FR
Is XNBR easy to machine?
Machine only in the cured state — cryogenic deflashing, water-jet or die cutting, and wet grinding with sharp tooling; the tacky, high-friction surface tears with dull blades.
Can XNBR be welded?
Not weldable; join by hot vulcanized splice, uncured tie-gum bonding to metal (chemlok primers), or cyanoacrylate/polyurethane adhesive on abraded surfaces.
Can XNBR be formed, bent or molded?
Compression, transfer or injection mold at 150–190 °C; carboxyl groups raise Mooney viscosity and scorch risk, so keep barrel and mill stock below ~100 °C and use stearate/ZnO dispersion control.
What surface finishes work on XNBR?
Surfaces are as-molded or ground; use post-cure (2–4 h at 100–150 °C) to cut compression set, and chlorination or silicone/PU topcoat to lower tack on gloves and rolls.
XNBR 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 |
|---|---|---|
| acrylonitrile (ACN)governs oil resistance and Tg | 18 – 40 | 28 |
| carboxylic acid monomer (acrylic/methacrsites for ZnO ionic crosslinking; source of abrasion/tear gain | 1 – 8 | 4 |
| carbon black (N330/N550)phr in the vulcanizate, not wt% of polymer | 20 – 70 | 45 |
| zinc oxidephr; ionic cure activator/crosslinker | ≈ 5 | 5 |
| sulfur or peroxide cure system + plasticphr, compound dependent | ≈ 10 | 10 |
| butadienebalance of polymer backbone | balance | — |
XNBR FR — frequently asked
What is XNBR FR used for?
XNBR FR is typically used for conveyor belt covers, printing rollers, golf ball cores and wear-resistant gaskets. In short: most abrasion-resistant nitrile; tear-resistant NBR upgrade; roller and belt grade.
What is the tensile strength of XNBR FR?
XNBR FR has a typical tensile strength of 14 MPa (2.03 ksi) — weaker than 75% of polymer grades. Strength varies by condition: see the 10 listed tempers.
Is XNBR FR easy to machine?
Not especially — machinability is rated poor (28/100, worse than 90% of polymer grades). Machine only in the cured state — cryogenic deflashing, water-jet or die cutting, and wet grinding with sharp tooling; the tacky, high-friction surface tears with dull blades.
Can XNBR FR be welded?
Not readily — weldability is rated not recommended (10/100). Not weldable; join by hot vulcanized splice, uncured tie-gum bonding to metal (chemlok primers), or cyanoacrylate/polyurethane adhesive on abraded surfaces.
What surface finishes work on XNBR FR?
Surfaces are as-molded or ground; use post-cure (2–4 h at 100–150 °C) to cut compression set, and chlorination or silicone/PU topcoat to lower tack on gloves and rolls.
Can XNBR FR be formed, bent or molded?
Compression, transfer or injection mold at 150–190 °C; carboxyl groups raise Mooney viscosity and scorch risk, so keep barrel and mill stock below ~100 °C and use stearate/ZnO dispersion control.
What is the maximum service temperature of XNBR FR?
XNBR FR is rated for continuous use to about 100°C (212 °F), and briefly to 125°C. Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
Sources
- Krynac X carboxylated nitrile rubber grade data — ARLANXEO / Lanxess (2022)
- Nipol NX series carboxylated NBR technical data — Zeon Corporation (2021)
- Engineered Materials Handbook Vol. 2 — Engineering Plastics & Elastomers — ASM International (1988)
- Rubber Technology: Compounding and Testing for Performance — Hanser (2009)
- ASTM D2000 — Classification System for Rubber Products in Automotive Applications — ASTM (2020)
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.