Should I use FKM rubber or silicone rubber for products? If you’re still struggling with this question, please read this article to learn about these two similar yet different synthetic rubbers in various aspects so that you can make a wiser decision.
What Is FKM Rubber
FKM rubber, FPM, Viton, and Fluoropolymer actually all refer to the fluoroelastomer. It is a high-performance specialty synthetic rubber that is widely used in aerospace and fuel transportation systems.
Core Advantages
● Good chemical compatibility and corrosion resistance
● Ability to work in extreme environments
● High temperature resistance
What Is Silicone Rubber
Silicone rubber is actually a form of silicone. It is processed from quartz sand and finally cured into this soft, durable elastomer. Silicone rubber has long been used to make all kinds of products, from household items to industrial parts, to medical devices, it’s everywhere in life.
Core Advantages
● Soft
● Good biocompatibility
● Very wide temperature range
● Electrical insulation
Similarities Between FKM Rubber and Silicone Rubber
Even though these are two different rubber materials, FKM rubber and silicone rubber share some similar properties.
Weatherability
Both FKM rubber and silicone rubber are adaptable to various environments. Whether it’s indoors in high temperatures or outdoors in changing conditions, they can handle it with ease. You may know that many plastics and rubbers deteriorate easily when exposed to sunlight, but FKM rubber and silicone rubber are both highly resistant to UV. Ozone and mold, which are the two main tests for materials used outdoors, are also hard to affect them.
Good stamping resistance
FKM rubber and silicone rubber both perform well in the face of great pressure and do not crack or wrinkle easily. After the pressure has disappeared, they can easily revert to their initial shape.
In short, they are materials that are durable and can be used outdoors. Apart from these two aspects, FKM rubber and silicone rubber have a lot of differences in terms of physical properties, chemical properties, safety, and commodity properties.
FKM rubber vs. silicone rubber: Physical properties
Temperature tolerance range
FKM rubber: Performs well at high temperatures
FKM rubber can withstand temperatures from -15°F to 500°F, and it can also withstand temperatures of nearly 600°F for a short time. It is particularly resistant to high temperatures and maintains good performance at high temperatures. When temperatures far exceed the upper limit of FKM rubber’s temperature tolerance, FKM produces toxic hydrogen fluoride.
Its shortcoming is also obvious: it can’t tolerate too low temperatures. Exposure to low temperatures for a long time causes the internal physical structure to change, making it harder, more brittle, and more easily damaged.
Silicone rubber: wider temperature range and greater resistance to low temperatures
The maximum temperature that general silicone rubber can withstand is 480°F. High-temperature silicone rubber with special additives has a higher upper limit of 572°F, but it ages faster at higher temperatures than FKM rubber.
Silicone rubber can withstand temperatures as low as -58° F. For phenyl silicone rubber (PVMQ), this temperature can even be lowered to -148° F. Therefore, in some low-temperature production environments, a still-soft silicone rubber would be a better choice.
If your product needs to work at relatively high temperatures, it is better to choose FKM rubber. But if you need to face unconventional low-temperature environments, silicone rubber or the more specialized phenyl silicone rubber is up to the task.
Abrasion resistance
Because of the lower coefficient of friction, FKM rubber is able to tolerate more outside friction, and after a long period of use, it will have less physical damage than the same silicone rubber. This allows it to be used in dynamic sealing applications, providing a longer-term sealing effect. In contrast, silicone rubber, which has poor abrasion resistance, is more suitable for static sealing applications.
Hardness and tensile properties
FKM rubber: Harder and more durable
The hardness of FKM rubber is generally between 60 Shore A and 90 Shore A. It is flexible and strong. It has a tensile strength of roughly 10 MPa, which means it is much less likely to crack or break under tension.
Silicone rubber: more flexible and elastic
Silicone rubber has a much lower hardness than FKM rubber, ranging between 30 and 70 Shore A. Flexible is a better description for it than hard. Although silicone rubber is more likely to break under tension, with a tensile strength of only 5 MPa, it can be stretched to seven times its original length, which FKM rubber cannot do.
Permeability
FKM rubber is not easily permeated by external gases and liquids, which makes it perform better than silicone rubber when used for barrier and protection. Silicone rubber has good breathability because of the intermolecular spaces that can easily be passed through
That’s why Silicone rubber can be a raw material for wound dressings.
Insulation properties
Both FKM rubber and silicone rubber have good electrical insulation properties, and they are effective in preventing current from passing through them and being conducted to surrounding parts. But if you’re looking for better dielectric properties, silicone is better. FKM rubber is recommended for more extreme insulation needs, such as fuel pump seals that require both corrosion resistance and insulation.
FKM rubber vs. silicone rubber: Chemical properties
For chemical compatibility, FKM rubber is very different from silicone rubber. The most important feature of FKM is its excellent corrosion resistance. Usually, silicone rubber is enough, and the use of FKM rubber results in excess performance.
But if you have a sufficient budget, use industrial raw materials or manufacture pharmaceuticals that are more corrosive, and are looking for materials for machines that come into contact with fuel, FKM would be a wise choice.
Corrosion resistance of FKM rubber
Because of the presence of trifluoropropyl in the molecular structure, FKM rubber is very resistant to corrosion. In addition to common substances such as aqueous solutions, it can also tolerate acids, alkalis, strong oxidizers, and a wide range of organic substances.
This includes many oils, fuels, ethanol, and most solvents that begin to swell when rubber is exposed to them for a long period of time, so it is a special countermeasure when faced with these industrial materials.
But even FKM rubber, which is extremely resistant to corrosion, has chemicals that are difficult to deal with. If your production line or machine involves any of these substances, it is recommended that you do not use FKM rubber:
- Solvents in paints
- Oxygenated solvents
- Ketones
- Esters
- Amines
- Organic acids
Corrosion resistance of silicone rubber
Silicone is also chemically inert, which makes it non-reactive in the presence of most substances found in food and medicine. Silicone rubber can be used in machines or products that come into contact with these substances:
- Water
- Oils and fats
- Alcohol, Glycerin
- Hydraulic fluids
- Brake fluids
- Ozone
- Weak bases and weak acids
And in industrial applications, it’s not a good idea to expose silicone rubber to these substances for long periods of time:
- Fuels
- Ketones and esters
- Aromatic hydrocarbons
- Trichloroethylene
- Some solvents, such as benzene
- Strong acids and bases
- Steam at excessively high temperatures
FKM rubber vs. silicone rubber: Safety
Although there are special medical FKM rubbers designed to resist corrosion, FKM rubber is more commonly used in industrial production. The industrial-grade material is not manufactured with consideration of whether it is harmful to the body or not, so it is not a healthy material in most cases.
Silicone is a well-known material in the food and medical fields, and its safety is guaranteed. The FDA and others specify the specifications that food-grade and medical-grade silicone need to comply with. Medical silicone also has more stringent standards, such as ISO 10993, that further limit the materials that can be used to ensure that it is not toxic to the cells and tissues of the human body.
If your machine is going to be used for food, pharmaceutical, or medical purposes, and there is no need for corrosion resistance, silicone rubber is your best partner.
FKM rubber vs. silicone rubber: Product Attributes
Cost
Because of the price of raw materials and specialized production processes, FKM rubber tends to be much more expensive than silicone rubber. So when there is no special need, such as high chemical resistance, buying silicone rubber is an affordable option.
As a special-purpose rubber, if FKM rubber is used in the right way, the reduction in maintenance and replacement times will undoubtedly save more time and financial costs.
Style and appearance
The color of FKM rubber is generally less, mostly black or brown, but after special treatment, it can bring a sense of high class. For example, FKM straps have a matte appearance.
Silicone rubber can be processed into a variety of vibrant colors, and high-quality silicone rubber can even have a highly transparent appearance. If you are looking for a wider variety of product styles, silicone rubber can better meet your needs.
FKM Rubber and Silicone Rubber: How to Choose
Medical field
Silicone rubber is a widely used material in the medical field. Because of its good biocompatibility, it can be transplanted into the body as a prosthesis over time, minimizing possible discomfort and inflammatory reactions. It can also be made into catheters for insertion into the body and diaphragms for medical devices. It is also an excellent dressing material because of its good breathability.
Medical-grade FKM rubber can be used for instruments or components that need to work under harsh conditions or be resistant to cleaning with aggressive detergents. Biochemistry analyzers can work more reliably with O-rings made of FKM rubber.
Food and pharmaceuticals
In addition to the medical field, silicone rubber is a veteran player in the food sector. Oven door gaskets and brewery washout seals made with silicone rubber are resistant to high temperatures while maintaining sealing and food safety.
Even in healthcare applications such as mother and baby products and pharmaceuticals, where safety requirements are stringent, silicone rubber ensures that it is non-toxic to the human body. If you’re looking for materials for baby pacifiers, gaskets, O-rings, and pharmaceutical equipment, silicone rubber is a safe and reliable choice.
Because of its resistance to various chemicals and oils, FKM rubber is used in packaging for food or medicine.
Industrial sector
FKM rubber performs well in prolonged contact with oils, solvents, fuels, corrosive substances, etc, making it ideal for machines that come into contact with these chemicals. Industrial pipe joints and oil handling machine components made with FKM rubber are durable and cost-effective.
If you’re looking for a sealing material that is insulating and also resistant to high and low temperatures, silicone rubber has you covered. It can be used as seals for electronic components and cable glands.
In addition to electrical-related applications, it is also made into molds, O-rings, and gaskets, which are common parts in industrial production.
Aerospace and automotive
If you are looking for the right sealing material for your aviation or automotive engine, FKM rubber is the specialist. It effectively stops gases and fuels from escaping, allowing your car to run safely and stably.
So whether it’s in a jet fuel system, an automotive fuel emission control system, or any other corrosive specialty fuel system, FKM rubber does the job.
Although not in direct contact with fuel like FKM rubber, silicone rubber is also widely used in automotive and aerospace applications. Pipes and seals working in cooling systems need to take into account the minimum operating ambient temperature, so components in them must be able to function in fairly cold environments, and there is no doubt that silicone rubber would be a more appropriate choice.
In new energy vehicles, silicone rubber will also be used to make battery pack gaskets, providing a long-term and reliable seal.
Consumer goods
FKM rubber, because of its price constraints, may be used for high-end goods that require long-term use, such as watch bands and high-end hairdryer parts.
Silicone rubber is much more widely used in consumer goods because it’s cheaper. Insulation cups and lid seals are made of soft and safe silicone rubber. Silicone rubber is also used to make cell phone cases, protective films, and non-slip pads for furniture – it’s all part of life!
FAQ
What are the different types of FKM rubber?
Depending on the fluorine content, fluoroelastomers can be categorized as highly fluorinated rubbers and perfluoroelastomers. Perfluoroelastomers have a fluorine content of 67 to 70%, and they have excellent corrosion resistance.
As the fluorine content increases, the corrosion resistance of the fluoroelastomer becomes stronger. Perfluoroelastomers with a fluorine content of more than 70% are able to resist erosion even in the face of strong acids and bases.
What are the different types of silicone rubber?
Common types of silicone rubber include high-temperature vulcanized silicone rubber (HTV/HCR), room-temperature cured silicone rubber (RTV), liquid silicone rubber (LSR) with high flexibility, the most widely used methyl vinyl silicone rubber (MVQ), and low-temperature resistant phenyl silicone rubber (PVMQ).
If you want to learn more, please click on A Simple Guide to Silicone Rubber Types and Applications.
Does FKM rubber contain PFAS?
Some poor-quality or industrial-grade FKM rubbers do contain the harmful substance PFAS. But good quality FKM rubber, because it has no additional coatings and is vulcanized with safer chemicals, such as perfluorohexanoic acid, ensures that it does not contain PFAS.
Are FKM Rubber and Silicone Rubber Environmentally Friendly?
Compared to materials such as plastics, FKM rubber and silicone rubber are undoubtedly environmentally friendly.
FKM rubber and silicone rubber are both very durable materials, and although more resources and energy are used to synthesize them at first, after repeated use, using both actually saves a lot of resources. They can also be recycled through specialized rubber recycling chains after they have reached their maximum useful life.
FKM Rubber vs. Silicone Rubber vs. Nitrile Rubber
The major differences between these three types of rubber are their cost, mechanical strength, oil resistance, and the range of temperatures they can withstand.
Nitrile rubber is a kind of rubber that can withstand a narrow range of temperatures but has excellent mechanical strength. Since it is also resistant to oil and fuel, it is a more cost-effective option for oil-resistant silicone.
Silicone rubber can withstand the widest range of temperatures, but is not oil-resistant.
FKM rubber is the most expensive, but it has excellent oil and corrosion resistance.
If you want to learn more, please click on Silicone vs Nitrile: Which is Better.
Would it be better to choose FKM rubber or silicone rubber as the strap material?
If you want an affordable strap that is colorful and can appeal to customers in terms of fashionability, or is more comfortable to wear and less likely to cause allergic reactions, a silicone rubber strap would be a better choice.
But if durability is more important to you, FKM rubber will do a better job. It’s more water and sweat-resistant, and better able to withstand the elements, so it lasts longer.
Final Thoughts
Overall, FKM rubber is suitable for extreme environments and where greater corrosion resistance is required. Silicone rubber has a wider temperature tolerance range, better biocompatibility, and is generally a more cost-effective choice. If you still want to know more details, click Legensilico now!
