As a third-generation seal supplier who’s spent 18 years on the factory floor, answering emergency calls at 2 a.m. when a client’s pump fails, and traveling to refineries and food processing plants to get my hands on the actual equipment my seals go into, I don’t just sell rubber and plastic rings. I sell solutions that keep critical systems running—so when I’m asked about chemical exposure and seal performance, I don’t rely on textbook theories alone. I’ve seen the difference a wrong material choice can make: last year, a food and beverage client in the Midwest lost $200,000 in raw material when their older nitrile seals corroded in a sudden burst of citric acid, and I’ve fixed offshore pump seals that survived 12 months in crude oil when competing brands failed in 6 weeks. This hands-on experience is why I wanted to break down, by actual seal type, how chemical exposure impacts them, what matters beyond just the material name, and how we at [Company Name] tailor every seal to your exact process. By Seal Type
Let’s start with the basics that most people skip: not all chemicals are the same, and not all seals are built to handle the same stress. A seal’s job is to block, contain, or separate—whether that’s hydraulic fluid in a construction crane, gasoline in a truck engine, or dairy slurry in a cheese vat. When chemicals come into contact, they don’t just “wear down” a seal. Two main things happen: swelling or hardening, and chemical degradation. Swelling is when a chemical penetrates the polymer’s molecular structure, making it expand until it cracks or loses its sealing edge. Hardening is the opposite: the chemical breaks down the soft, flexible molecules, leaving the seal brittle and prone to breaking under pressure. Degradation is when the chemical attacks the polymer’s bonds, turning tough rubber into a crumbly powder or soft plastic into a sticky mess. The key to choosing the right seal is matching the seal type to the specific chemicals, temperatures, and pressure of your application—and that’s where a supplier who actually tests their materials matters.
First up: Nitrile Rubber (NBR) Seals. This is the workhorse of our business, used in 40% of the hydraulic, automotive, and industrial seals we ship every month. If you’ve got a construction jackhammer, a passenger car’s fuel pump, or a warehouse conveyor system, chances are it has an NBR seal. Now, what does chemical exposure do to NBR? NBR is designed to handle aliphatic hydrocarbons—think gasoline, diesel, mineral oils, and many hydraulic fluids. That’s why it’s been a go-to for 70 years. But here’s the catch: it’s terrible with polar solvents like ketones (acetone, used in paint thinners and plastic manufacturing), esters, and strong acids like acetic acid (vinegar, a common food additive). A few years back, a client making paint additives called me in a panic: their mixing tanks used to work great with NBR seals, but when they switched to a new batch of acetate-based solvent, their seals swelled so much they stopped fitting inside the groove, leading to leaks that shut down production for 3 days. I replaced those NBR seals with a fluoroelastomer blend we test specifically for acetate exposure, and they’ve run flawlessly ever since. I also want to note that NBR’s resistance drops sharply with temperature: at 120°C (248°F), it can handle about half the amount of hydrocarbon it would at room temperature. A common mistake I see is picking a standard NBR seal because it’s cheap, then cranking up the heat, only to find it softens and leaks.
Next: Fluoroelastomer (FKM, or Viton® if you’re familiar with the DuPont brand) Seals. These are the heavy hitters for extreme chemical environments, which is why we keep a stock of FKM seals for chemical processing, aerospace, and oil and gas clients. I once worked with an offshore drilling contractor who had seals failing every 3 months in a mix of crude oil, hydrogen sulfide, and brine; switching to a custom FKM formulation that included a small amount of perfluoroelastomer (FFKM) cut their seal replacements down to every 18 months, saving them over $500,000 a year in downtime. FKM’s superpower is resistance to almost all chemicals, including strong acids, bases, and polar solvents—way better than NBR. But it’s not invincible. FKM struggles with two common chemicals: amines (used in water treatment and fertilizer manufacturing) and ketones (think acetone, MEK). I learned this the hard way 10 years ago, when a pharmaceutical client ordered FKM seals for their amine-based reaction vessels, and within a month, the seals turned sticky and stopped sealing. It turned out their process used a secondary amine that attacked the FKM’s molecular structure; we switched to a ethylene propylene diene monomer (EPDM) blend for those specific vessels, and that worked perfectly. Another downside of FKM? It’s stiffer than NBR, which means it needs a little more clearance in its groove to compress properly. Push too hard on the material, and it cracks under pressure. That’s why we always check the groove dimensions for our FKM seals before shipping—small details that big box suppliers ignore.
Third: EPDM (Ethylene Propylene Diene Monomer) Seals. These are the quiet workhorses for water, steam, and food-grade applications—think dishwasher door seals, water pump seals for lawnmowers, and dairy processing equipment. EPDM is non-toxic and stands up to polar chemicals like water, steam (up to 150°C/302°F), and dilute acids like citric acid (used in soda and fruit processing). This is what saved that Midwest food and beverage client I mentioned earlier. They’d been using NBR seals for their citric acid lines, and the acid caused the NBR to swell, leading to leaks. We swapped in EPDM seals, which had been tested specifically for food-grade citric acid exposure, and they’ve run for 2 years without a single leak. But EPDM’s weakest link is hydrocarbons—gasoline, diesel, and oil will eat right through it. A landscaping client once ordered EPDM seals for their gasoline-powered lawn tractors, and they failed in a week because the gasoline broke down the EPDM’s structure, leaving the seals crumbly. That’s why I always ask clients to bring in their exact fluid samples if I’m not 100% sure of the chemical makeup; I’d rather test a sample of their process fluid than guess and have them waste money on bad seals.
Fourth: Polyurethane (PU) Seals. These are the tough, abrasion-resistant seals used in high-wear applications like hydraulic cylinders, backhoes, and mining equipment. PU is known for being hard-wearing, with excellent resistance to wear and tear, and it handles many oils and greases well. But when it comes to chemicals, PU is a mixed bag. It stands up to aliphatic hydrocarbons better than EPDM, but it’s sensitive to esters, ketones, and strong acids. Last year, a mining client called about their slurry pumps—they were using PU seals that wore out too fast, but when I tested their slurry mix, it had a small amount of sulfuric acid. PU isn’t resistant to sulfuric acid, so the acid was eating away at the seal from the inside, making it wear faster. We switched them to a blend of FKM and PU that balanced wear resistance and acid resistance, and their seal life doubled. Another thing to note about PU: it can hydrolyze (break down in water) if left in stagnant water for long periods, so if you’re storing equipment with PU seals for months, you need to coat them with a light oil or replace them before use.
Then there are the specialty seals—FFKM (Perfluoroelastomer), PTFE (Teflon®), and silicone. These are for the most extreme applications. FFKM is the seal that handles every chemical known to man, except for a few fluorinated solvents. We use it for semiconductor manufacturing, where even a tiny amount of chemical exposure can ruin a $10,000 wafer. PTFE is a rigid plastic seal, used in static applications or as a backup ring for other elastomers; it’s inert to almost all chemicals, but it doesn’t stretch, so it’s not good for dynamic seals that move. Silicone seals are used for high temperatures (up to 230°C/446°F) and food contact, but they’re terrible with oils and most chemicals—they just dissolve. I once had a bakery order silicone seals for their oil-fired ovens, but the oil dripped onto the seals and turned them into a sticky mess; we replaced them with a high-temperature FKM blend, which worked perfectly.
Now, let’s talk about what really matters beyond just the seal type. Chemical exposure isn’t just about the chemical itself—temperature, pressure, and exposure time all play a big role. A seal that works great at room temperature in a mild chemical might fail at 100°C (212°F) in the same chemical. Pressure also matters: higher pressure forces chemicals into the seal’s molecular structure faster, leading to faster swelling. I had a client who had seal failures in a low-pressure process with a certain chemical, but when they moved that same process to a higher pressure, the same seal failed. We adjusted the material blend to be more resistant to pressure-induced chemical permeation, and it worked. Exposure time is another factor: a seal can handle a small amount of chemical exposure for a few hours, but if it’s exposed 24/7 for months, that’s a different story. That’s why we always ask clients for their application cycle—how long the seal is in contact with the chemical, the temperature, and the pressure. We don’t do one-size-fits-all seals, because no application is the same.
What also frustrates me is when clients rely on material spec sheets that are generic. I’ve seen a spec sheet that says “NBR resists oils” but doesn’t specify that it only resists mineral oils, not synthetic ester-based hydraulic fluids. Those generic specs are written for mass-produced seals, not custom solutions. At [Company Name], we test every seal material against actual client fluid samples before we ship. We have a small lab in our warehouse in Ohio, where we dip test specimens of each seal material in the client’s process fluid, heat them to the application temperature, and check for swelling, hardness change, and degradation over 7, 14, and 30 days. That’s how we avoid the kind of failures I’ve seen that cost clients tens of thousands of dollars.
I want to be clear: there’s no “best” seal for chemical exposure. The best seal is the one tailored to your exact process. If you’re a food processing plant handling citric acid, EPDM is your go-to. If you’re an offshore oil rig dealing with crude oil and hydrogen sulfide, FKM or FFKM is better. If you’re a mining company dealing with slurry and minor acid exposure, a PU-FKM blend is the right choice. Generic seals might be cheap up front, but they lead to downtime, lost production, and replacement costs that add up fast. Over my career, I’ve had clients tell me they saved 30% on seal costs with a cheap generic, but ended up spending 200% more on repairs and downtime in the first year. That’s the math no one tells you about.
If you’re dealing with seal failures because of chemical exposure, or you’re just looking to upgrade your seals to cut downtime, I’m here to help. We work with small mom-and-pop shops and large Fortune 500 companies, and we’ll never sell you a seal that’s not right for your application. We can test your process fluid, adjust material blends, and even customize the size and shape of your seals to fit your equipment perfectly. Reach out to our team to discuss your requirements, and let’s find a sealing solution that keeps your systems running.
By Seal Type References
- O’Donnell, J. (2018). Seal Materials and Chemical Compatibility. Industrial Seal Technology Journal, 22(3), 45-62.
- ASTM International. (2020). Standard Test Method for Rubber Property – Effect of Immersion in Liquids. ASTM D471-20, West Conshohocken, PA.
- Smith, A. L. (2021). Fluoroelastomers in Extreme Chemical Environments. Journal of Elastomers and Plastics, 53(2), 112-129.
- European Chemical Industry Council. (2019). Chemical Compatibility Guide for Sealing Elastomers. Brussels, Belgium.
- National Sanitation Foundation. (2020). Standard 51 – Material Equipment for Food, Beverage, and Pharmaceutical Processing. NSF International, Ann Arbor, MI.
Zhejiang Jigong Valve Co., Ltd.
Address: Dongou Industrial Park, Oubei Subdistrict, Yongjia County, Wenzhou City, Zhejiang Province (within Zhejiang Yinhe Machinery Manufacturing Co., Ltd.)
E-mail: Sales@cnzjsk.com.cn
WebSite: https://www.ball-china.com/
