{"id":1201,"date":"2026-10-29T09:30:32","date_gmt":"2026-10-29T09:30:32","guid":{"rendered":"https:\/\/www.marcorubber.com\/blog\/?p=1201"},"modified":"2026-10-27T20:46:41","modified_gmt":"2026-10-27T20:46:41","slug":"buna-o-rings-nbr-properties-uses-and-limitations","status":"publish","type":"post","link":"https:\/\/www.marcorubber.com\/blog\/?p=1201","title":{"rendered":"Buna O-Rings (NBR): Properties, Uses, and Limitations"},"content":{"rendered":"<p><span style=\"font-weight: 400;\"><a href=\"https:\/\/www.marcorubber.com\/buna-n-o-rings.htm\" target=\"_blank\" rel=\"noopener\">Buna O-rings<\/a> are one of the most widely used seals in industry. They are also called nitrile or NBR O-rings. Engineers specify them for hydraulic systems, fuel handling, and general industrial equipment. Procurement teams like them too, because they cost little and are easy to find.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">However, Buna O-rings are not the right fit for every environment. The wrong fluid, temperature, or exposure can cause swelling, cracking, or leaks. Therefore, it pays to understand the material before you specify it.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">This guide walks through:<\/span><\/p>\n<ul>\n<li>Key properties and Marco&#8217;s Buna compounds<\/li>\n<li>Temperature range and chemical compatibility<\/li>\n<li>Advantages, limitations, and common applications<\/li>\n<li>How Buna compares to EPDM, FKM, silicone, and FFKM<\/li>\n<li>Common failure modes and how to prevent them<\/li>\n<\/ul>\n<h3>Quick Reference: Buna O-Rings at a Glance<\/h3>\n<table style=\"width: 100%; border-collapse: collapse; font-size: 15px; margin: 20px 0;\">\n<thead>\n<tr style=\"background-color: #004588; color: #ffffff; text-align: left;\">\n<th style=\"padding: 10px; border: 1px solid #d0d7de;\" scope=\"col\">Property<\/th>\n<th style=\"padding: 10px; border: 1px solid #d0d7de;\" scope=\"col\">Typical Value<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Material<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Acrylonitrile-butadiene rubber (NBR)<\/td>\n<\/tr>\n<tr style=\"background-color: #f2f4f7;\">\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Standard temperature range<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-30 \u00b0F to +250 \u00b0F (-34 \u00b0C to +121 \u00b0C)<\/td>\n<\/tr>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Specialty grade range<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-65 \u00b0F to +275 \u00b0F (-54 \u00b0C to +135 \u00b0C)<\/td>\n<\/tr>\n<tr style=\"background-color: #f2f4f7;\">\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Common hardness<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">70 and 90 Shore A<\/td>\n<\/tr>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Best with<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Petroleum oils, fuels, hydraulic fluids, water<\/td>\n<\/tr>\n<tr style=\"background-color: #f2f4f7;\">\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Avoid<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Ketones, brake fluids, strong acids, ozone, UV<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><span style=\"font-weight: 400;\">Use this table as a starting point. Then confirm the details below for your specific application.<\/span><\/p>\n<h2><strong>What Are Buna O-Rings?<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Buna is a synthetic rubber called acrylonitrile-butadiene rubber (NBR). You will also see it listed as Buna-N, nitrile, or NBR.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">It is one of the &#8220;big four&#8221; elastomer sealing materials. The other three are EPDM, <a href=\"https:\/\/www.marcorubber.com\/fkm-o-rings.htm\/\" target=\"_blank\" rel=\"noopener\">FKM (Viton\u00ae)<\/a>, and silicone. Buna stands out for its balance of performance and cost. As a result, it is one of the most widely stocked O-ring materials in the industry.<\/span><\/p>\n<h2><strong>Key Properties of Buna O-Rings<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Buna O-rings offer well-rounded mechanical properties:<\/span><\/p>\n<ul>\n<li><strong>Good wear resistance:<\/strong> suitable for dynamic applications<\/li>\n<li><strong>Strong compression set resistance:<\/strong> holds sealing force over time<\/li>\n<li><strong>Good resilience:<\/strong> recovers its shape after deformation<\/li>\n<li><strong>Low permeability:<\/strong> seals gases and fluids well<\/li>\n<li><strong>High tensile strength:<\/strong> stands up to mechanical stress<\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">Most standard Buna O-rings come in 70 or 90 durometer. The 70 durometer grade is the standard, more flexible choice. In contrast, 90 durometer is harder and better for high pressure.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Buna O-rings are usually black, though other colors are available. They also come in standard <a href=\"https:\/\/www.marcorubber.com\/o-rings.htm\/\" target=\"_blank\" rel=\"noopener\">AS568 and metric sizes<\/a>, making them easy to source and replace.<\/span><\/p>\n<h3><strong>Marco&#8217;s Buna O-Ring Compounds<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Marco stocks a full range of <a href=\"https:\/\/www.marcorubber.com\/buna-n-o-rings.htm\/\" target=\"_blank\" rel=\"noopener\">Buna-N compounds<\/a>. Each one is built for a specific need:<\/span><\/p>\n<table style=\"width: 100%; border-collapse: collapse; font-size: 15px; margin: 20px 0;\">\n<thead>\n<tr style=\"background-color: #004588; color: #ffffff; text-align: left;\">\n<th style=\"padding: 10px; border: 1px solid #d0d7de;\" scope=\"col\">Compound<\/th>\n<th style=\"padding: 10px; border: 1px solid #d0d7de;\" scope=\"col\">Durometer (Shore A)<\/th>\n<th style=\"padding: 10px; border: 1px solid #d0d7de;\" scope=\"col\">Temperature Range<\/th>\n<th style=\"padding: 10px; border: 1px solid #d0d7de;\" scope=\"col\">Key Feature \/ Specification<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1000\" target=\"_blank\" rel=\"noopener\">B1000<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">70<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-31 \u00b0F to +250 \u00b0F (-35 \u00b0C to +121 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Lowest-cost general-purpose NBR<\/td>\n<\/tr>\n<tr style=\"background-color: #f2f4f7;\">\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1001\" target=\"_blank\" rel=\"noopener\">B1001<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">90<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-31 \u00b0F to +250 \u00b0F (-35 \u00b0C to +121 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">General purpose, higher pressure<\/td>\n<\/tr>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1002\" target=\"_blank\" rel=\"noopener\">B1002<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">70<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-31 \u00b0F to +250 \u00b0F (-35 \u00b0C to +121 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">FDA compliant (21 CFR 177.2600)<\/td>\n<\/tr>\n<tr style=\"background-color: #f2f4f7;\">\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1011\" target=\"_blank\" rel=\"noopener\">B1011<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">70<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-31 \u00b0F to +230 \u00b0F (-35 \u00b0C to +110 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Internally lubricated with PTFE<\/td>\n<\/tr>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1058\" target=\"_blank\" rel=\"noopener\">B1058<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">70<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-31 \u00b0F to +250 \u00b0F (-35 \u00b0C to +121 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">NSF 61 certified (drinking water)<\/td>\n<\/tr>\n<tr style=\"background-color: #f2f4f7;\">\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1083\" target=\"_blank\" rel=\"noopener\">B1083<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">70<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-65 \u00b0F to +275 \u00b0F (-54 \u00b0C to +135 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Improved low- and high-temperature resistance<\/td>\n<\/tr>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1105\" target=\"_blank\" rel=\"noopener\">B1105<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">70<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-31 \u00b0F to +250 \u00b0F (-35 \u00b0C to +121 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Metal detectable; FDA compliant<\/td>\n<\/tr>\n<tr style=\"background-color: #f2f4f7;\">\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1122\" target=\"_blank\" rel=\"noopener\">B1122<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">70<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-31 \u00b0F to +250 \u00b0F (-35 \u00b0C to +121 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">NSF 51 certified (food contact)<\/td>\n<\/tr>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1000\" target=\"_blank\" rel=\"noopener\">M1000<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">70<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-65 \u00b0F to +275 \u00b0F (-54 \u00b0C to +135 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">MIL-P-25732 \/ AMS-P-25732, MS28775<\/td>\n<\/tr>\n<tr style=\"background-color: #f2f4f7;\">\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1001\" target=\"_blank\" rel=\"noopener\">M1001<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">75<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-65 \u00b0F to +275 \u00b0F (-54 \u00b0C to +135 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">AMS-P-83461; improved hydraulic fluid resistance<\/td>\n<\/tr>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1002\" target=\"_blank\" rel=\"noopener\">M1002<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">65<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-65 \u00b0F to +250 \u00b0F (-54 \u00b0C to +121 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">AMS-P-5315, MS29513, MS29512<\/td>\n<\/tr>\n<tr style=\"background-color: #f2f4f7;\">\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1004\" target=\"_blank\" rel=\"noopener\">M1004<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">90<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-65 \u00b0F to +275 \u00b0F (-54 \u00b0C to +135 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">AMS-P-5510, MS28778<\/td>\n<\/tr>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\"><a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1005\" target=\"_blank\" rel=\"noopener\">M1005<\/a><\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">65<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-70 \u00b0F to +200 \u00b0F (-57 \u00b0C to +93 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">AMS7271, AS3578<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><span style=\"font-weight: 400;\">Temperature ranges are approximations for dry air service only. Do not use them as design specifications.<\/span><\/p>\n<h2><strong>Temperature Range of Buna O-Rings<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Temperature is one of the most important factors in O-ring selection. Standard Buna O-rings typically work from -30 \u00b0F to +250 \u00b0F (-34 \u00b0C to +121 \u00b0C). Specialty grades reach further. For example, <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1000\" target=\"_blank\" rel=\"noopener\">M1000<\/a> and <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1083\" target=\"_blank\" rel=\"noopener\">B1083<\/a> are rated from -65 \u00b0F to +275 \u00b0F (-54 \u00b0C to +135 \u00b0C).<\/span><\/p>\n<p><span style=\"font-weight: 400;\">That range covers most industrial environments. Still, Buna struggles at the extremes:<\/span><\/p>\n<ul>\n<li><strong>At low temperatures,<\/strong> Buna stiffens and loses elasticity.<\/li>\n<li><strong>At high temperatures,<\/strong> it can degrade and lose sealing performance over time.<\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">For colder service, consider silicone or a low-temperature Buna grade. For hotter service, <a href=\"https:\/\/www.marcorubber.com\/fkm-o-rings.htm\/\" target=\"_blank\" rel=\"noopener\">FKM O-rings<\/a> are often the better choice.<\/span><\/p>\n<h2><strong>Chemical Compatibility of Buna O-Rings<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Buna is popular mainly because it resists petroleum-based fluids. For this reason, it is a top choice in automotive, oil and gas, and hydraulic systems.<\/span><\/p>\n<h3><strong>Where Buna O-Rings Perform Well<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Buna works well in contact with:<\/span><\/p>\n<ul>\n<li>Petroleum oils, fuels, and greases<\/li>\n<li>Mineral and vegetable oils<\/li>\n<li>Hydraulic fluids, including HFA, HFB, and HFC water-based fluids<\/li>\n<li>Water<\/li>\n<li>Silicone oils and greases<\/li>\n<li>Ethylene glycol fluids<\/li>\n<li>Air and inert gases<\/li>\n<\/ul>\n<h3><strong>Where Buna O-Rings Fall Short<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Despite its versatility, Buna is not compatible with everything. Buna O-rings are not recommended for:<\/span><\/p>\n<ul>\n<li>Ketones, such as acetone and MEK<\/li>\n<li>Halogenated and chlorinated hydrocarbons<\/li>\n<li>Strong acids<\/li>\n<li>Automotive and aircraft brake fluids<\/li>\n<li>Highly aromatic fuels and hydrocarbons<\/li>\n<li>Polar solvents<\/li>\n<\/ul>\n<p><span style=\"font-weight: 400;\">In addition, Buna resists environmental exposure poorly. Ozone, direct sunlight, and weathering all break it down over time. For outdoor or ozone-heavy environments, <a href=\"https:\/\/www.marcorubber.com\/epdm-o-rings.htm\" target=\"_blank\" rel=\"noopener\">EPDM<\/a> or <a href=\"https:\/\/www.marcorubber.com\/viton-o-rings.htm\" target=\"_blank\" rel=\"noopener\">FKM<\/a> are usually better alternatives.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">Before you specify a material, check <a href=\"https:\/\/www.marcorubber.com\/o-ring-chemical-compatibility-chart.htm\/\" target=\"_blank\" rel=\"noopener\">Marco&#8217;s O-ring chemical compatibility guide<\/a>.<\/span><\/p>\n<h2><strong>Advantages of Buna O-Rings<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">There are good reasons Buna remains one of the most common sealing materials.<\/span><\/p>\n<h3><strong>1. Cost-Effectiveness<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Buna O-rings are among the least expensive elastomer options. As a result, they suit high-volume and cost-sensitive projects.<\/span><\/p>\n<h3><strong>2. Wide Availability<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Buna comes in standard sizes and durometers. This shortens lead times and simplifies maintenance.<\/span><\/p>\n<h3><strong>3. Versatility<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Buna is compatible with many oils, fuels, and industrial fluids. Therefore, it fits a wide range of applications.<\/span><\/p>\n<h3><strong>4. Good Mechanical Performance<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Buna combines durability, flexibility, and sealing strength. It also performs well in both static and dynamic service.<\/span><\/p>\n<h2><strong>Limitations of Buna O-Rings<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Buna is a reliable general-purpose material. However, it has clear limits you should weigh:<\/span><\/p>\n<ul>\n<li><span style=\"font-weight: 400;\"><strong>Limited temperature range:<\/strong> It does not suit extreme heat or deep cryogenic conditions.<\/span><\/li>\n<li><span style=\"font-weight: 400;\"><strong>Poor ozone and UV resistance:<\/strong> It degrades in outdoor environments over time.<\/span><\/li>\n<li><span style=\"font-weight: 400;\"><strong>Chemical restrictions:<\/strong> It is incompatible with several aggressive chemicals and fluids.<\/span><\/li>\n<li><span style=\"font-weight: 400;\"><strong>Aging and hardening:<\/strong> In harsh environments, it can harden and lose elasticity, which reduces sealing performance.<\/span><\/li>\n<\/ul>\n<h2><strong>Common Applications for Buna O-Rings<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Thanks to its balance of performance and cost, Buna is used across many industries.<\/span><\/p>\n<h3><strong>Hydraulic Systems<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Buna O-rings are a natural fit for hydraulic oils and fluids. You&#8217;ll find them in cylinders, valves, and pumps.<\/span><\/p>\n<h3><strong>Aerospace and MIL-SPEC Applications<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Military and aerospace hydraulic systems usually call out a specific material spec. For example, <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1000\" target=\"_blank\" rel=\"noopener\">M1000<\/a> is made to MIL-P-25732, and <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1001\" target=\"_blank\" rel=\"noopener\">M1001<\/a> is made to AMS-P-83461. See <a href=\"https:\/\/www.marcorubber.com\/o-ring-mil-specs-chart.htm\" target=\"_blank\" rel=\"noopener\">Marco&#8217;s O-ring Mil-Spec chart<\/a> for the full list.<\/span><\/p>\n<h3><strong>Fuel Handling Systems<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Because Buna resists petroleum fuels, it is a staple in automotive fuel systems. For aerospace fuel service, <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1002\" target=\"_blank\" rel=\"noopener\">M1002<\/a> is made to AMS-P-5315.<\/span><\/p>\n<h3><strong>Food, Beverage, and Drinking Water<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">FDA-compliant and NSF-certified Buna grades are available. Learn more about <a href=\"https:\/\/www.marcorubber.com\/fda-o-rings-food-grade.htm\/\" target=\"_blank\" rel=\"noopener\">Marco&#8217;s food-grade O-rings<\/a>.<\/span><\/p>\n<h3><strong>Pneumatic and General Industrial Equipment<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Buna also works well in air systems, including compressors and actuators. In fact, it is used wherever a dependable, economical seal is needed.<\/span><\/p>\n<h2><strong>How to Choose the Right Buna O-Ring<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Choosing a Buna O-ring involves more than the material itself. Consider these factors:<\/span><\/p>\n<ul>\n<li><strong>Durometer:<\/strong> 70 vs. 90, based on pressure and motion<\/li>\n<li><strong>Temperature range:<\/strong> match the grade to your operating conditions<\/li>\n<li><strong>Media exposure:<\/strong> confirm chemical compatibility<\/li>\n<li><strong>Application type:<\/strong> static vs. dynamic sealing<\/li>\n<li><strong>Size standard:<\/strong> AS568 vs. metric<\/li>\n<li><strong>Certifications:<\/strong> MIL-SPEC, FDA, NSF, or UL requirements<\/li>\n<\/ul>\n<h2><strong>Buna O-Rings vs. Other O-Ring Materials<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Comparing Buna with other elastomers can guide your material selection:<\/span><\/p>\n<table style=\"width: 100%; border-collapse: collapse; font-size: 15px; margin: 20px 0;\">\n<thead>\n<tr style=\"background-color: #004588; color: #ffffff; text-align: left;\">\n<th style=\"padding: 10px; border: 1px solid #d0d7de;\" scope=\"col\">Material<\/th>\n<th style=\"padding: 10px; border: 1px solid #d0d7de;\" scope=\"col\">Typical Temperature Range<\/th>\n<th style=\"padding: 10px; border: 1px solid #d0d7de;\" scope=\"col\">Strengths<\/th>\n<th style=\"padding: 10px; border: 1px solid #d0d7de;\" scope=\"col\">Weaknesses<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Buna (NBR)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-30 \u00b0F to +250 \u00b0F (-34 \u00b0C to +121 \u00b0C); specialty grades -65 \u00b0F to +275 \u00b0F<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Cost-effective; excellent petroleum oil and fuel resistance<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Poor UV, ozone, and weather resistance<\/td>\n<\/tr>\n<tr style=\"background-color: #f2f4f7;\">\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">EPDM<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-65 \u00b0F to +300 \u00b0F (-54 \u00b0C to +149 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Excellent weather, ozone, water, and steam resistance<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Poor with petroleum oils and fuels<\/td>\n<\/tr>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">FKM (Viton\u00ae)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-15 \u00b0F to +437 \u00b0F (-26 \u00b0C to +225 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">High temperature and broad chemical resistance<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Higher cost; limited low-temperature flexibility<\/td>\n<\/tr>\n<tr style=\"background-color: #f2f4f7;\">\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Silicone (VMQ)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">-65 \u00b0F to +400 \u00b0F (-54 \u00b0C to +204 \u00b0C)<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Excellent low-temperature flexibility and heat resistance<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Lower tear strength and abrasion resistance<\/td>\n<\/tr>\n<tr>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">FFKM<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">+5 \u00b0F to +550 \u00b0F (-15 \u00b0C to +288 \u00b0C); specialty grades to +650 \u00b0F<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Near-universal chemical resistance; highest temperature capability<\/td>\n<td style=\"padding: 10px; border: 1px solid #d0d7de;\">Highest cost<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p><span style=\"font-weight: 400;\">Each material has its place. For oil-based systems at moderate temperatures, however, Buna is often the most practical choice. For a deeper comparison, see <a href=\"https:\/\/www.marcorubber.com\/o-ring-material-selection-comparison.htm\/\" target=\"_blank\" rel=\"noopener\">Marco&#8217;s O-ring material selection guide<\/a>.<\/span><\/p>\n<h2><strong>Buna O-Ring Failure Modes and Troubleshooting<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Even with the right material, Buna O-rings can fail when design factors are overlooked. Knowing the common failure modes helps extend seal life.<\/span><\/p>\n<h3><strong>1. Compression Set<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Compression set is one of the most common issues. The material deforms permanently and can no longer rebound. It usually comes from three causes:<\/span><\/p>\n<p><span style=\"font-weight: 400;\"><strong>High temperatures:<\/strong> Prolonged heat speeds up permanent deformation.<br \/>\n<strong>Excessive squeeze:<\/strong> Over-compression in the gland stresses the material.<br \/>\n<strong>Long-term static service:<\/strong> Constant load over time sets the seal.<\/span><\/p>\n<p><span style=\"font-weight: 400;\"><strong>Solution:<\/strong> Select the correct durometer. In addition, follow <a href=\"https:\/\/www.marcorubber.com\/o-ring-groove-design-directory.htm\" target=\"_blank\" rel=\"noopener\">proper groove design<\/a> to avoid over-compression.<\/span><\/p>\n<h3><strong>2. Swelling and Chemical Degradation<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Incompatible chemicals can cause Buna to swell, soften, or break down. Common culprits include strong acids, solvents, ketones, and brake fluids.<\/span><\/p>\n<p><span style=\"font-weight: 400;\"><strong>Solution:<\/strong> Always verify chemical compatibility first. If you can&#8217;t avoid exposure, consider an alternative such as FKM.<\/span><\/p>\n<h3><strong>3. Abrasion, Wear, and Extrusion<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">In dynamic applications, Buna O-rings can suffer surface wear or extrusion damage. Causes include high friction, poor lubrication, rough sealing surfaces, and high pressure without back-up rings.<\/span><\/p>\n<p><span style=\"font-weight: 400;\"><strong>Solution:<\/strong> Use proper lubrication. For high-pressure systems, also consider a 90 durometer grade and <a href=\"https:\/\/www.marcorubber.com\/o-ring-backup-rings.htm\" target=\"_blank\" rel=\"noopener\">back-up rings<\/a>.<\/span><\/p>\n<h3><strong>4. Ozone and UV Cracking<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Buna is especially vulnerable to outdoor exposure and ozone-rich environments, such as areas near electrical equipment. Over time, this leads to cracking and seal failure.<\/span><\/p>\n<p><span style=\"font-weight: 400;\"><strong>Solution:<\/strong> Switch to EPDM or FKM O-rings for outdoor or ozone-exposed service.<\/span><\/p>\n<h3><strong>5. Installation Damage<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Sharp groove edges, improper tools, or overstretching can nick or cut an O-ring. As a result, the seal is compromised before it enters service.<\/span><\/p>\n<p><span style=\"font-weight: 400;\"><strong>Solution:<\/strong> Follow installation best practices and use the proper tools and lubrication.<\/span><\/p>\n<h2><strong>Sourcing Buna O-Rings Through Marco<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Marco Sealing Solutions stocks Buna O-rings in AS568 and metric sizes across general-purpose, MIL-SPEC, FDA, and NSF grades. Marco is also an approved Freudenberg-NOK distributor. Read more about what <a href=\"https:\/\/www.marcorubber.com\/blog\/?p=875\" target=\"_blank\" rel=\"noopener\">Freudenberg-NOK Approved Distributor Status Means for You<\/a>.<\/span><\/p>\n<p><span style=\"font-weight: 400;\">With Marco, you get:<\/span><\/p>\n<ul>\n<li>Stocked Buna O-rings in standard sizes, such as <a href=\"https:\/\/www.marcorubber.com\/product\/B1000-011\" target=\"_blank\" rel=\"noopener\">B1000-011<\/a> and <a href=\"https:\/\/www.marcorubber.com\/product\/M1000-206\" target=\"_blank\" rel=\"noopener\">M1000-206<\/a><\/li>\n<li>MIL-SPEC, FDA, NSF, and UL-listed nitrile compounds in one place<\/li>\n<li>Access to 3,600+ materials when Buna isn&#8217;t the right fit<\/li>\n<li>Application engineering and failure analysis support<\/li>\n<\/ul>\n<h2><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-1053\" src=\"https:\/\/blog.marcorubber.com\/wp-content\/uploads\/2026\/08\/CTA-Engineer-connect-slim.jpg\" alt=\"Contact an engineer\" width=\"1024\" height=\"280\" srcset=\"https:\/\/blog.marcorubber.com\/wp-content\/uploads\/2026\/08\/CTA-Engineer-connect-slim.jpg 1024w, https:\/\/blog.marcorubber.com\/wp-content\/uploads\/2026\/08\/CTA-Engineer-connect-slim-300x82.jpg 300w, https:\/\/blog.marcorubber.com\/wp-content\/uploads\/2026\/08\/CTA-Engineer-connect-slim-768x210.jpg 768w\" sizes=\"auto, (max-width: 1024px) 100vw, 1024px\" \/><\/h2>\n<h2><strong>Frequently Asked Questions About Buna O-Rings<\/strong><\/h2>\n<h3>What are the temperature limits of common o-ring materials: NBR, FKM, EPDM, Silicone, FFKM?<\/h3>\n<p><span style=\"font-weight: 400;\">Standard NBR (Buna) runs about -30 \u00b0F to +250 \u00b0F, with specialty grades reaching -65 \u00b0F to +275 \u00b0F. EPDM runs about -65 \u00b0F to +300 \u00b0F, and FKM about -15 \u00b0F to +437 \u00b0F. Silicone covers about -65 \u00b0F to +400 \u00b0F. Finally, FFKM reaches +550 \u00b0F, with specialty grades to +650 \u00b0F. These ranges are approximate and apply to dry air service only.<\/span><\/p>\n<h3>What sealing solutions meet MIL-SPEC requirements for aerospace hydraulic systems?<\/h3>\n<p><span style=\"font-weight: 400;\">For Buna, Marco offers <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1000\" target=\"_blank\" rel=\"noopener\">M1000<\/a> (MIL-P-25732), <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1001\" target=\"_blank\" rel=\"noopener\">M1001<\/a> (AMS-P-83461), and <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1004\" target=\"_blank\" rel=\"noopener\">M1004<\/a> (AMS-P-5510). For higher temperatures, FKM compounds such as <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/v1002\" target=\"_blank\" rel=\"noopener\">V1002<\/a> are also available. See the <a href=\"https:\/\/www.marcorubber.com\/o-ring-mil-specs-chart.htm\" target=\"_blank\" rel=\"noopener\">Mil-Spec chart<\/a> for details.<\/span><\/p>\n<h3>Which rubber compounds are rated for jet fuel and aviation hydraulic fluid exposure?<\/h3>\n<p><span style=\"font-weight: 400;\">For petroleum-based aviation hydraulic fluid, consider nitrile compounds <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1000\" target=\"_blank\" rel=\"noopener\">M1000<\/a> and <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/m1001\" target=\"_blank\" rel=\"noopener\">M1001<\/a>. For jet fuel, fluorosilicones such as <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/f1001\" target=\"_blank\" rel=\"noopener\">F1001<\/a> are a common choice. However, Buna is not recommended for aircraft brake fluids.<\/span><\/p>\n<h3>Which O-ring materials are approved for direct food-contact applications?<\/h3>\n<p><span style=\"font-weight: 400;\">Several Buna grades qualify. <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1002\" target=\"_blank\" rel=\"noopener\">B1002<\/a> and <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1105\" target=\"_blank\" rel=\"noopener\">B1105<\/a> comply with FDA 21 CFR 177.2600. In addition, <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1122\" target=\"_blank\" rel=\"noopener\">B1122<\/a> is NSF 51 certified for food contact. <a href=\"https:\/\/www.marcorubber.com\/store\/compound\/b1105\" target=\"_blank\" rel=\"noopener\">B1105<\/a> is also\u00a0<\/span><span style=\"font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 1rem;\">metal-detectable.<\/span><\/p>\n<h3>What sealing materials can withstand H2S and sour gas environments?<\/h3>\n<p><span style=\"font-weight: 400;\">Standard Buna is generally not the best choice for sour gas. Alternatives include <a href=\"https:\/\/www.marcorubber.com\/aflas-o-rings.htm\" target=\"_blank\" rel=\"noopener\">Aflas\u00ae (FEPM)<\/a> and base-resistant FKM. For the harshest conditions, FFKM compounds such as <a href=\"https:\/\/www.marcorubber.com\/markez-o-rings.htm\" target=\"_blank\" rel=\"noopener\">Markez\u00ae<\/a> are often used. See our guide <\/span><a href=\"https:\/\/www.marcorubber.com\/blog\/?p=1163\" target=\"_blank\" rel=\"noopener\">Elastomer Seal Materials for Oil &amp; Gas: Subsea, Sour Gas, and Refinery Service<\/a> for recommended compounds.<\/p>\n<h3>Can Buna O-rings be used outdoors?<\/h3>\n<p><span style=\"font-weight: 400;\">Usually not for long-term service. Ozone and UV exposure cause Buna to crack over time. Instead, choose EPDM or FKM for outdoor applications.<\/span><\/p>\n<h2><strong>Need Help Choosing the Right Buna O-Ring?<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">Buna O-rings remain a reliable, economical choice for oil, fuel, and hydraulic service. Still, they are not a one-size-fits-all solution. Fortunately, you don&#8217;t have to sort through the options alone.<\/span><\/p>\n<p><span style=\"font-weight: 400;\"><a href=\"https:\/\/www.marcorubber.com\/inquiry-quote.htm\" target=\"_blank\" rel=\"noopener\">Request a quote<\/a> or <a href=\"https:\/\/www.marcorubber.com\/inquiry-general.htm\" target=\"_blank\" rel=\"noopener\">contact Marco&#8217;s engineering team<\/a> to find the right Buna O-rings for your application.<\/span><\/p>\n<p><a href=\"https:\/\/www.marcorubber.com\/inquiry-quote.htm\" target=\"_blank\" rel=\"noopener\"><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-905\" src=\"https:\/\/blog.marcorubber.com\/wp-content\/uploads\/2026\/04\/Request-Quote-CTA.png\" alt=\"Request a quote for FFKM with tight lead times.\" width=\"1028\" height=\"280\" srcset=\"https:\/\/blog.marcorubber.com\/wp-content\/uploads\/2026\/04\/Request-Quote-CTA.png 1028w, https:\/\/blog.marcorubber.com\/wp-content\/uploads\/2026\/04\/Request-Quote-CTA-300x82.png 300w, https:\/\/blog.marcorubber.com\/wp-content\/uploads\/2026\/04\/Request-Quote-CTA-1024x279.png 1024w, https:\/\/blog.marcorubber.com\/wp-content\/uploads\/2026\/04\/Request-Quote-CTA-768x209.png 768w\" sizes=\"auto, (max-width: 1028px) 100vw, 1028px\" \/><\/a><\/p>\n<p><em><span style=\"color: #999999;\">The information contained herein is to the best of our knowledge accurate and reliable. However, Marco Sealing Solutions makes no warranty, expressed or implied, that parts manufactured from these materials will perform satisfactorily in the customer&#8217;s application. It&#8217;s the customer&#8217;s responsibility to evaluate parts prior to use.&#8221;<\/span><\/em><\/p>\n<hr \/>\n<h3>Related Reading<\/h3>\n<p><span style=\"font-weight: 400;\"><a href=\"https:\/\/www.marcorubber.com\/buna-n-o-rings.htm\/\" target=\"_blank\" rel=\"noopener\">Buna-N O-Rings Selection Guide<\/a><br \/>\n<a href=\"https:\/\/www.marcorubber.com\/o-ring-chemical-compatibility-chart.htm\/\" target=\"_blank\" rel=\"noopener\">O-Ring Chemical Compatibility Guide<\/a><br \/>\n<a href=\"https:\/\/www.marcorubber.com\/o-ring-mil-specs-chart.htm\" target=\"_blank\" rel=\"noopener\">MIL Spec Compounds<\/a><br \/>\n<a href=\"https:\/\/www.marcorubber.com\/o-ring-groove-design-directory.htm\" target=\"_blank\" rel=\"noopener\">Groove Design Guide Directory<\/a><br \/>\n<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Buna O-rings are one of the most widely used seals in industry. They are also called nitrile or NBR O-rings. Engineers specify them for hydraulic systems, fuel handling, and general industrial equipment. Procurement teams like them too, because they cost little and are easy to find. However, Buna O-rings are not the right fit for [&hellip;]<\/p>\n","protected":false},"author":9,"featured_media":1205,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-1201","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-general"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.7 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>Buna O-Rings (NBR): Properties, Uses &amp; Limitations<\/title>\n<meta name=\"description\" content=\"Learn about Buna O-rings (NBR): temperature range, chemical compatibility, MIL-SPEC and FDA grades, and when to choose another material.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.marcorubber.com\/blog\/?p=1201\" \/>\n<meta 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