FFKM seals are not in demand because there are no alternative compounds. Their high initial costs are balanced by their cost-effectiveness in the long run. This is attractive to customers.
In this article, we’ll explore six reasons why customers consistently choose FFKM O-rings and seals. We’ll examine the chemistry of this compound, how it affects its properties, and why the high initial costs of FFKM O-rings and seals are easily offset during their service life.
The Chemistry Behind FFKM
FFKM materials are fluorinated elastomers with over 71% fluorine content by weight. This gives them excellent thermal performance and chemical resistance.
Chemical Structure of FFKMs
The main bonds in FFKMs are carbon-fluorine bonds, considered some of the strongest bonds in chemistry. These bonds give both FKMs and FFKMs better heat and chemical resistance than other elastomers.
However, FFKMs stand out from FKMs because their backbones are fully-fluorinated. They don’t have any carbon-hydrogen bonds that would weaken their heat and chemical resistance.
Crosslinking Systems for FFKMs
The carbon-fluorine bonds are not the only things affecting FFKMs’ heat and chemical resistance. The crosslinking system used will also give different levels of chemical and temperature resistance.
Cross-linking using organic peroxide creates the broadest chemical resistance. Bisphenol crosslinking gives better levels of thermal stability.
Different applications require thermal stability at different temperatures and resistance to different combinations of chemicals in the same product. To achieve this, different grades of FFKMs are developed for different operating conditions.
Reasons for Choosing FFKM O-Rings and Seals
There are many good reasons to choose FFKM o-rings and seals. The six reasons below are the most important in many industries.
1. Unparalleled Chemical Resistance
FFKMs’ carbon-fluorine bonds are extremely hard to break using other chemicals. As a result, FFKMs have the highest chemical resistance of any elastomer today. They are often described as having nearly universal chemical compatibility.
Some of the best grades of FFKMs can withstand exposure to over 1,800 chemicals. FFKMs can also withstand the increased aggressiveness of chemicals at higher concentrations and temperatures.
In modern industries, seals and o-rings are exposed to harsh chemicals that degrade elastomers. These can be the medium being sealed, cleaning agents, or lubricants.
FFKMs excellent chemical resistance means it may be the only elastomer that can withstand the different combinations of chemicals the seal or o-ring will be exposed to.
Some FFKMs have also been developed to resist hydrolysis. They can be reliably used in applications with hot water or steam exposure.
2. Extreme Temperature Stability
Extreme temperatures are the norm in many industries. Applications such as space exploration, geothermal drilling, oil and gas extraction, and chemical processing will expose seals to very high or very low temperatures. Some will expose a seal to both.
Extremely high or low temperatures change the properties of elastomers making them rigid. This affects their sealing ability and in some cases, this change is permanent.
The operating temperature range of FFKM is better than that of other elastomers. Some FFKM seals and o-rings can operate at consistent temperatures as high as 335°C and occasional exposure to even higher temperatures. Other FFKM materials are rated for temperatures as low as -55°C.
This broad temperature range makes FFKM seals the best option for many applications. It should be noted that these thermal properties depend on compounding and other factors. Different FFKM grades have different levels of thermal stability.
3. Exceptional Compression Set Resistance
Compression set is a measure of how much deformation is left over once a deforming force is removed. This is an important parameter in elastomers used for seals and o-rings because it determines whether they are durable and reusable.
Elastomers are used for sealing because they deform and fill the gaps between meshing faces. However, depending on the force and the temperature, the elastomeric material may not regain its original dimensions.
FFKM has a low compression set and the permanent deformation left after a force is removed is low. Therefore, the seal or o-ring will still deform enough to create a good seal when reused.
Their low compression set makes FFKM seals durable and able to withstand multiple loading cycles before they must be replaced. This quality is important because the seals are more reliable and cost less in the long run because they are replaced less often.
4. Low Contamination Potential
When subjected to different forces or operating conditions, elastomers can release contaminants into their surroundings. These can be particles of the material, substances added during compounding, or gases trapped or formed within the material (outgassing).
This is a major problem in applications involving food and potable water. It’s also a problem in semiconductor production where any contaminants can interfere with product quality.
Some grades of FFKMs have been specially formulated to limit outgassing and release of other contaminants which can happen when the seal material breaks down.
Seals and O-rings used in semiconductor production must also be plasma-resistant because plasma can break down the elastomer, leading to the release of contaminants.
5. Broad Range of Applications
FFKMs are used for sealing applications across various industries. When considering a sealing solution, the limiting factor for FFKM is typically cost or availability, not function.
FFKMs can be formulated to withstand many chemicals used in industries. The material can also be formulated for thermal stability in extremely low or high temperatures. Therefore, its application potential is broader than that of other elastomers.
The few instances where FFKM can’t be used involve exposure to the few chemicals that rapidly degrade it or where operating temperatures exceed its limits. This may also mean no other elastomer can be used in such applications.
To ensure compatibility, FFKM materials must be made with the specific conditions of the application in mind. The specific chemicals and temperatures to which the seal will be exposed should be considered.
6. Meeting Industry Standards
FFKMs’ superior qualities make it easy for these materials to meet the stringent standards set in place by bodies such as the Food and Drug Administration (FDA) and the Norwegian Oil and Gas Association (NORSOK).
O-rings and seals used in many industries require approval by regulatory bodies. In the US, o-rings and other seals used in food production must meet FDA contamination prevention standards.
Similarly, o-rings used in oil and gas applications must meet standards set by bodies such as NORSOK to prevent failures due to issues like rapid gas decompression. The chemistry of FFKM materials makes it easy for these seals to meet the standards set in different industries.
Cost-Benefit Analysis of FFKM O-Rings
Cost is an important factor in seal and o-ring selection. Seals and o-rings may cost hundreds of dollars each and need to be replaced from time to time Companies prefer to avoid expensive seals that must be replaced regularly.
FFKM seals have the highest upfront cost due to many factors. However, in their chosen applications, they tend to last significantly longer than any alternatives including FKM seals.
FFKM seals may be expensive, but companies save more money in the long run because:
- Fewer replacement seals will be needed due to the longer lifespan of FFKM
- Fewer man-hours will be spent inspecting seals for damage or replacing worn seals
Another factor to consider is that less expensive and less reliable seal materials are more likely to fail suddenly. This can cost companies more in terms of damage to products and equipment and puts workers at risk. The long downtimes can also be expensive.
These factors mean that despite the high initial costs of FFKM seals and O-rings, they are often very cost-effective in many applications.
However, there are other applications where FFKMs’ extreme properties are unnecessary. These are applications where a cheaper material like FKM (Viton) will still serve reliably. In such cases, the cost-benefit of FFKM o-rings will be negative.
Conclusion
FFKM materials offer unmatched chemical and thermal resistance. Where elastomeric seals are needed, you are unlikely to find an alternative that will perform better. This material also has great compression set resistance and can serve longer than most other seals.
FFKM is the default option for many applications with strict standards including semiconductor manufacturing, food manufacturing, and oil and gas extraction. Despite their higher upfront costs, choosing FFKM seals and o-rings pays off in the long run.
