ELASTOMER MATERIAL / NBR
NBR is commonly screened for contact with mineral oils and greases and for wear-resistant seals and mouldings. Acrylonitrile content, formulation and cure system control the trade-off between oil resistance, low-temperature flexibility and processing.
Upload a drawingNBR is a sensible family to screen for seals, diaphragms, boots, mouldings and protective parts exposed to many mineral-based oils and greases. Abrasion resistance and broad commercial availability also make it relevant in machinery and fluid handling. The abbreviation does not define compatibility. Oil chemistry, additives, temperature, pressure, motion, ozone exposure and required life must be documented before a supplier selects a compound.
Trelleborg gives standard NBR an initial operating range of approximately −30 °C to +100 °C and short exposure up to +120 °C; suitably formulated low-temperature grades may reach about −50 °C. Parker lists individual NBR O-ring compounds with different limits. That variation is the point: no one range applies to every NBR component. Limits may also differ in oil, air and water. Use the offered compound data and validate against the real combined temperature and fluid duty.
Acrylonitrile, or ACN, content is a central design lever in NBR. Trelleborg describes a typical 18–50% range, while Zeon lists commercial polymer grades across that spectrum. Higher ACN generally improves resistance to many oils and fuels but can reduce low-temperature flexibility. “NBR” is therefore incomplete without the fluid, swelling limit and low-temperature requirement. Ask the supplier to identify the polymer basis and provide relevant test data for the proposed formulation.
NBR is frequently assessed with mineral oils, lubricating greases, hydraulic oils and selected fuels. Water compatibility is compound- and temperature-dependent. Standard NBR is more vulnerable to ozone, weather and ultraviolet exposure than EPDM, while polar solvents, glycol-based brake fluids and strongly oxidising media demand caution. A compatibility statement is meaningful only for a named fluid, concentration and temperature. Additive packages and mixed fluids can change swelling and ageing significantly.
NBR mouldings are available across the normal Shore A range, but there is no universal default hardness. Hardness affects assembly, deformation, extrusion resistance and contact stress. State the nominal value, tolerance and test method such as ISO 48-4. For static seals, compression set tested to ISO 815-1 can matter more than hardness alone. Suppliers must use the same temperature, time, compression and recovery conditions for results to be comparable.
ISO 3302-1 is a common basis for solid NBR mouldings. Classes M1 to M4 represent different precision and cost levels, and the actual tolerance depends on nominal dimension and how the mould controls it. Very tight tolerances can require tool iteration, sorting or specialised measurement. Specify sealing interfaces, fits and functional dimensions deliberately; give non-critical dimensions an economical general tolerance. Define flatness, coaxiality and other geometry separately, where appropriate using ISO 3302-2.
NBR is normally screened first for mineral oil and grease, while EPDM is normally screened first for weathering, ozone, water and hot water. Real parts may see oil mist, outside air, cleaning fluid and temperature cycles at the same time. Compare candidates against one duty profile: volume and hardness change after immersion, low-temperature behaviour, compression set, ozone exposure and functional testing. A coating does not automatically correct a poor base-material choice.
HNBR is often assessed when oil resistance must be combined with higher heat, ozone or mechanical performance. It is not an automatic upgrade: low-temperature behaviour, fluid compatibility, cost, availability and approvals remain compound-specific. Do not mix NBR and HNBR as interchangeable quotation lines. Set one clear baseline and request any alternative separately with a data sheet, deviation list and price effect.
Geometry, cavity count, part size, parting line, flash limit, demoulding, inserts, compound flow and inspection concept determine tooling and cycle time. Compression moulding may suit some low or complex demands; injection moulding may help stable higher volumes. A universal break-even quantity would be unreliable. Give every supplier the same annual and batch demand and require separate figures for tooling, samples, unit price, minimum quantity, scrap assumption, packaging and freight.
Provide the drawing and revision, part function, exact fluid designation, temperature and pressure profile, motion, mating surface, lubrication, target hardness, permitted swelling, critical dimensions, annual and batch demand, and inspection and documentation needs. For a replacement part, include the existing material, known failures and installation conditions. State whether alternative compounds are allowed and which data must be approved before tooling.
NBR is a common first choice for technical seals and mouldings in contact with mineral oils and greases. Its usable temperature and fluid range depends strongly on ACN content and compound, and standard NBR is weaker against ozone and weather than EPDM. Comparable quotations require one drawing revision, one fluid definition, identical test conditions, an ISO tolerance basis, common quantities and separated tooling cost.
The ranges and properties support initial screening. The offered compound, complete specification and customer approval remain decisive.
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