If you're the person who gets handed a worn-out gasket and told 'just get me another one of these,' this article is for you. After five years of managing maintenance and facilities purchases for a 200-person manufacturing plant, I've learned to start every rubber-related order with one question: What is this thing actually touching?
Because there's no single best silicone gasket material or all-purpose rubber. It depends on temperature, fluids, pressure, and a handful of things you only discover after something starts leaking. I'll walk through the three scenarios I run into most often: silicone, fluoroelastomer rubber (FKM), and hydrogenated nitrile-butadiene rubber (HNBR).
The 30-second scenario split
Here's how I sort requests in my head:
- General sealing, air, water, weak chemicals: silicone, often a Dow Corning silicone product.
- Oil, fuel, solvents, high heat: fluoroelastomer rubber (FKM).
- Hydrocarbon gas or oil with heat, but not extreme: HNBR.
That's not a replacement for a compatibility chart, but it gets you 80% of the way there. Now the long version.
Scenario A: Silicone gasket material and Dow Corning sealants
If you're sealing air, water, steam, or just trying to keep weather out, silicone is usually the right answer. It handles temperature swings way better than natural rubber—depending on formulation, roughly -50°C to 200°C—and it stays flexible longer than many organic rubber gasket materials. Plus, it's easy to find in sheet, roll, and custom-cut gasket forms. I order silicone gasket material for everything from oven doors to weatherproofing panels.
When someone asks for 'dow corning silicone white' around our facility, there are two common meanings. One is Dow Corning 732 sealant in white, a general-purpose sealant that works for formed-in-place gaskets and seam sealing. Another is the white silicone compound we keep for lubricating O-rings and valve stems. I should add: that white silicone compound is not a gasket maker. It's a lubricant and sealant for rubber parts, and it's saved us a ton of time on low-pressure valves.
For structural glass and exterior joints, Dow Corning 795 silicone is the product. It's a structural glazing sealant designed to bond glass to metal and handle UV exposure. I've used it on office window projects and it's held up fine. (Should mention: for a real structural glass application, follow the spec. 795 is strong, but not every sealant can do that job, and this isn't the same as a rubber gasket.)
The big limitation of silicone? Petroleum. Motor oil, hydraulic fluid, and diesel will make many silicone gaskets swell, soften, or fail fast. So if your part will see oil, move to Scenario B.
Scenario B: Fluoroelastomer rubber (FKM)
Fluoroelastomer rubber—usually called FKM—is what you order when silicone won't survive. FKM is rated for continuous service around 200-230°C in many formulations, and it resists oils, fuels, solvents, and aggressive chemicals that destroy silicone. It costs more, but it's cheaper than a leak.
In my experience, FKM is the material for hydraulic seals, fuel-line O-rings, and anything that touches hot oil. The first time I ordered a silicone O-ring for a hydraulic fitting that was seeing oil at 180°F, it failed in about three weeks. Looking back, I should have checked the material compatibility chart before ordering. At the time, I figured silicone was tough—it's used in ovens, right? Ovens don't have hydrocarbon exposure. That was a humbling $400 mistake.
If I remember correctly, the replacement FKM O-rings cost about $1.80 each versus $0.40 for silicone, but don't quote me on that exact number. The key point is the FKM ones are still in service two years later.
One caution: FKM has different chemistries and curing systems, and not all grades handle hot water or steam equally. If steam is part of the application, ask the supplier to verify the grade. But for hot, oily, chemical-filled environments, FKM is usually the right call.
Scenario C: What is hydrogenated nitrile-butadiene rubber?
This is the acronym that confuses a lot of people: HNBR. What is hydrogenated nitrile-butadiene rubber? It's nitrile rubber (NBR) that has been chemically modified by hydrogenation, which saturates most of the double bonds in the polymer chain. That change gives HNBR much better heat resistance and ozone resistance than standard nitrile, while keeping its oil and fuel resistance. It also handles hydrogen sulfide, which is why it shows up in oilfield and refrigeration seals.
HNBR can't take sustained 250°C heat as comfortably as FKM, but it's usually stronger mechanically and more affordable. For shafts, belts, and seals that see oil and moderate heat—say 130°C to 160°C—HNBR can be a smarter pick. I've seen it on compressor seals in our plant, and the maintenance team said it lasted much longer than the standard nitrile seals we were using before.
I can only speak to the purchasing side; the engineering team chose HNBR after a fluid compatibility review. But if you're deciding between 'fluoroelastomer or HNBR?' and the fluid is hydrocarbon-based without extreme temperatures, don't overlook HNBR.
How to decide which scenario you're in
Here's the checklist I use when the datasheet isn't clear:
- Temperature. Under 150°C? Silicone or HNBR may work. Above 200°C? Look at FKM.
- Fluids. Oils or solvents? Avoid plain silicone. Hydrocarbons? HNBR or FKM. Water or steam? Check compatibility; even FKM grades vary.
- Physical demands. If the part needs abrasion resistance or high tear strength, HNBR and FKM are usually tougher than silicone.
- Chemical exposure. Acids, bases, cleaners? Get a compatibility chart. There's no shortcut.
- Regulatory or special requirements. Food contact, potable water, or low-smoke needs require specific grades. Tell the supplier the full application.
If you're still torn, ask for sample sheets or data from two or three suppliers. I'd rather spend 10 minutes explaining your application than deal with mismatched expectations later. An informed customer asks better questions and makes faster decisions—and that saves everyone money.
Bottom line: Dow Corning silicone white sealant and 795 have their place. Silicone gasket material covers a lot of everyday sealing jobs. But for hot, oily, chemical-heavy situations, fluoroelastomer rubber or HNBR are the specialized tools that won't let you down. This worked for us, but our facility is climate-controlled and not a drilling rig. If your environment is harsher, the calculus might be different. Start with the scenario, check the compatibility chart, and you'll avoid the mistake I made: ordering on price and hoping for the best.