Nitrile Selection Guide
Nitrite 0-rings are used with gasoline, crude oiL power steering fluId, hexane, toluene, u’aret; water-based hyd raulic fluids, and dtiute bases such as sodium hydroxide a! tern peratuivs betu,ei -65(111(1285°F More than 50% of sealing ticeds can be met by using nitrite seaLs. Parco most popular inateriaijbr 0-rings is nifrile compound 4200-70. It is used for service to 1500 psi between -3.5 and 250 °E Selected specia fry nitrites u’ith wider ten iperature ranges or special characteristics an’ (IlS() (IeSL711)ed in this guide.
Nitrile compounds are the most widely used industrial seal materials. Parco nitrile seals offer excellent service in diverse fluids, inch iding hydrocarbon fuels and (luids, many solvents, water, and water-based solutions. Parco mediumhardness (60 to 75 Shore A durorneter) nitrite seals have a long history of reliable service from -65 to +285°F at pressures to 1500 psi. Because of the excellent economy of nitrite seals, follow Parco’s general rule consider nitrite seals first. Nitrile compounds are copolymers of acrvlonitrile and butadiene. Acrylonitrile provides resistance to petroleum-based Iluids such as oils and fuels, while butadiene contributes low-temperature flexibility. Different nitrite compounds are forinulated by adjusting acrylonitrile levels to achieve the needed balance of petroleum -based fluid resistance and flexibility at the anticipated service temperature.
Standard nitrile is also known as Buna N Rubber or by the ASTM D1418 designation NBR. Parco offers many nitrite compounds tailored to a broad range of operating conditions. Acrylonitrile content, curing system, and type and quantity of plasticizers are hut a lew of the compounding tactors that can be varied to match the seal material to the end-user’s requirements.
Parco also produces special types of nitriles for applications that are too demanding for standard nitriles. Hydrogenated nitrile, designated I-INBR,is used with automotive lubricants and sour crude oil containing amine-based corrosion inhibitors. HNBR is also used for exposure to ozone and higher temperatures. Carboxylated nitrite, designated XNBR, provides improved abrasion resistance and superior extrusion resistance at high pressures.
if you are unfamiliar with the different types of elastomeric seal materials currently in use, consult the Parco Elasroiner Selectioii Guide before reading this guide. There you will find guidelines for selecting among the major elastomers.
When you have determined that a nitrile compound may be appropriate for your application, use this guide to narrow your choice. Contact your local Parco distributor to discuss your selection or to obtain additional product information about specific nitrile compounds.
Nitrile compound characteristics
A brief review of the characteristics of nitrile compounds can remove much of the guesswork from the selection process. Consider the following five factors when selecting a nitrile seal compound:
(iii and low-tent peralure resistance — The relative proportions of acrylonirrile aiid btitadiene determine the oil resistance and low-temperature performance of nitrile seals. High acrylonitrile content improves oil resistance at the expense of low-temperature perfortnance (Figure 2). The acrylonitrile content of commercial nitriles typically ranges from about 20 to 50%.
coin pression set resistance — Nitrile compotmds incorporate either sulfur or peroxide curative. Sulfur- cured seals, such as those made from Parco’s most Popular nitrile compound 4200-70, are generally more economical as they require shorter molding times. Sulfur curing produces resilient compounds with good resistance to compression set and good extrusion resistance and ultimate elongation. Sulfur-cured compounds are often used to mold rubber- to-metal bonded parts.
By contrast, peroxide-cured compounds generally have better compression set resistance, higher extrusion resistance and lower elongation. They also tend to have better heat resistance hut may be more expensive due to the longer molding times required.
Low-tempera lure resistance — Plasticizers typically improve low-temperature flexibility and resistance to vol ii me swell. However, n itrile seals containing ester plasticizers frequently cause surface crazing when used in contact with some plastics. Parco manufactures several types of nitrile seals containing non-ester plasticizers specifically developed for use with plastics.
Mechanical properties —All Parco nitriles contain filler materials that reinforce the compound and generally improve the mechanical properties of the seal. Carbon black, the most commonly used filler, improves the tensile strength, extrusion resistance and abrasion resistance of the compound. When non-black seals are required for identification, mineral fillers are used instead of carbon black. Compounds with mineral fillers generally have somewhat lower compression set resistance and resilience than compounds with carbon black fillers.
Price — NJitriIe seals are the most economical of the popular seals available and, due to their outstanding service capabilities, offer excellent value (Figure 3). Of popular seal materials, only neoprene can routinely match the low price offered by nitrile.
Selecting medium-hardness nitrile compounds
Figure 4 provides a selection diagram for the twelve most popular Parco nitrile compounds. The eleven specialty nitriles have been formulated specifically for applications with service requirements outside the performance range of Parco 4200-70 general-purpose nitrile seals.
Parco’s most popular nitrile compounds*
Nitrile 045 760** — Low acrylonitrile (ACN) and high plasticizer content provide excellent flexibility at temperatures as low as -65°F; moderate volume swell in jet fuel; listed in MIL-P-5315 Qualified Product List (QPL) for use with aviation fuel systems.
Mtriie 4024-65 — Formulated expressly for use in low-temperature aviation ftiel systems; low ACN content provides minimum service temperatures a full 30°F lower than general-purpose compound 4200—70; meets requirements of Aerospace Materials Specification (AMS) 7271.
Nitrile 0209-70— High ACN content with low plasticizer level provides excellent resistance to petroleum oils, automatic transmission fluid (ArF), and crude oil; formulated as a transfer-moldable
variant of Parco general-purpose nitrile 4200-70 for producing thick cross-section custom molded parts; used extensively in oil tool seals and packing elements for pressures to 1500 psi.
Nitrile 0228-70— SpecifIcally formulated for continuous service in automobile fuels; UL listed for conventional gasolines, kerosene, liquid petroleum gas (1.P gas), and hydrocarbon fuels; compatible with diester synthetic lubricants; meets SAL 120B1 Class H (fuel) requirements.
Nitrile 22 76-70 — Originally developed for adj iistable- beam flashlights, 2276-70 seals are suited for dynamic applications requiring low friction materials; very high ACN content and low plasticizer level provide oil resistance: incorporates an organic internal lubricant.
Nitrite 2295-70— Resists fuels rich in alcohol better than 4200-70 general-purpose nitrile seals; UL-listed for gasoline, diesel fuel, kerosene, naphtha and gasoline- alcohol blends with a full range of ethanol and methanol concentrations as well as 100% methanol; high ACN content for very low swell in fuels; compound not recommended for hot air or ATE
Nitrite 4067-70 —Widely used for M IL-H -5606 petroleum - based “red oil” aircraft hydraulic fluid; low ACN formulation for flexibility at very low temperatures; broad service range from -65 to +275°F, extending 30°F lower and 25°F higher than general-purpose corn - pound 4200-70; TR- 10 below -50°F: meets Mll-P-25732 QPL for aircraft hydraulic fluid service.
Nitrite 4200-70— General- Prnoe nitrile seals for service between -35 and 250°F at pressures to 1500 psi. Principal uses include dilute bases, many solvents, petroleum-based hydraulic oiIs fuel oil, diesel oil and hydrocarbons. LJL listed for diesel oil, fuel oil, kerosene, naphtha, LP gas, MPS gas, natural gas1 and fire extinguishers (dry chemical, CO2 and water). 4200-70 seals are also FDA conforming.
Nitrile 4249-70 — Ideal for the extreme service demands of heavy equipment; high ACN content withstands hydrocarbon fluids; peroxide cure provides best compression set resistance at elevated temperatures among Parco’s most popular nitrile coin pounds.
Nitrile 4367-70—Low ACN content extends low-end temperature range; TR-l0 below -50°F; peroxide cure enhances heat and compression set resistance; greater high-end durability than 4067-70 seals; meets MIL-R-83461 QPL for petroleum- based aircraft hydraulic fluid.
Nitrite 4456-70— Containing no ester plasticizers, compound 4456-70 provides superior compatibility with ABS, polvcarbonates and other stress- sensitive plastics; meets SAE 120R1 Class I (oil) and AMS 7270 requirements; used in injection-molded automotive power steering seals.
Nitrite 4262-75 — Excellent compatibility with drilling muds and petroleum oils: withstands service demands of heavy equipment hydraulic systems; Parco’s lowest compression-set, sulfur-cure nitrile.
Turn to Parco for nitrile seals
For more than fifty years, major industrial users have relied on Parco for quality, delivery and sealing excellence. Today, Parco research has extended the capabilities of nitrile seals far beyond their former limits.
Contact your local Parco distributor to learn how you can benefit from the latest developments in nitrile seal technology.
Parco medium-hardness nitrile seals offer:
• Excellent service in a wide variety of industrial, automotive and aircraft fluids, including hydrocarbon fuels and fluids (such as gasolines crude oil (old power sleering fluid) hydrocarbon soiven rs (such as hexane and ioiuene,J water aiid water-based solutions (such as certain hydraulic fluids and dilute bases like sodium hydroxide) • Temperature ratings from -65 to +285°F — TR-l0 -60°F
• Pressure ratings to 150() psi — higher-durornerer seals also available for pressures over 1500 psi
• UL listed — selected compounds listed for gasoline, kerosene, LP gas these! fuels, fIre exiinguishers
• MIL spec compliance — selected compounds meet M!L-P -5315, MJL-R-25 732, M1L-J?-83461, etc.
• Colored compounds for identification — available in oilier compounds no listed belou’
• Exceptional compounding versatility — acrylonurile content variable from under 20 to over 50%
• Unsurpassed economy — most econwnical high—performance seal material available