Viton® is a trading name given to polymers in low-melting solids (below 423 °C), used primarily in the chemical, petroleum, and rubber industries.
There are two types: Viton® A, which has a monomer structure that polymerizes on heating to form a rigid crystalline structure with high tensile strength; and B, which is made from rosin monomers that polymerize on heating to create a flexible material with lower density than A.
You can try these if you’re looking to acquire quality-standard Viton® FKM Gaskets.
So, What’s the Difference?
The main difference between Viton® A and B is the chemical structure and its corresponding physical structure.
The chemical structure is related to the polymerization mechanism, while the physical structure refers to a material’s general property.
Chemical Structure
Both Viton® A and B are produced by radically initiated polymerization of alkenes, often using hydroperoxide or peroxides as initiators.
The chemical structure in Viton® A is linear, while that in B is branched. In Viton® A, each atom is in a regular arrangement, and the length of the chain is almost equal to a single bond.
Physical Structure
Viton® A has a rigid crystalline structure meaning it has limited mobility and a high modulus.
On the other hand, Viton® B has a soft amorphous structure, meaning that it has less elasticity and lower modulus than Viton® A.
The high tensile strength and modulus make it ideal for seals in vacuums, liquids, and gases in general.
Viton® A
Viton® A is known for its outstanding thermal resistance and chemical stability.
It can withstand the attack of oxygen, ozone, strong acids (except for hydrofluoric acid), strong bases (except for molten alkali metals), weak alkalis, weak oxidizing agents (except for strong oxidizers), organic compounds, and many solvents.
However, as its molecular weight increases, it loses its mechanical properties and becomes erratic in solvents.
Therefore, for Viton® A to retain its high properties, chemical and thermal treatments must be performed before the rubber is processed.
Viton® B
As for Viton® B, some sources say that it is flexible when unheated but becomes rigid at higher temperatures.
Others say that it becomes flexible upon heating.
The rigidity of Viton® B is mainly attributed to the structure of its monomers, which are more rigid than those used in rubber and can form strong hydrogen bonds.
Therefore, Viton® B has a higher modulus and tensile strength than rubber.
It is highly resistant to most chemicals but sensitive to acids, bases, and oxidizers.
Viton® A and B have excellent resistance to abrasion, ozone attack, weathering, insect attack, and good electrical insulation properties.
In addition, both have a low compression set and high heat resistance.
Unfortunately, there are currently no comprehensive standards for Viton®.
However, several standards relate to either Viton®’s properties or specific applications in the industry.
For example, ASTM D2000 is the latest standard of synthetic rubber and certain natural rubbers for general industrial use.
It prescribes the test methods used to determine several elastomers’ physical, mechanical, and chemical properties, including Viton® A.
Why use Viton®?
The long history and extensive range of applications for Viton® elastomers have made them the material of choice for many sealing applications.
In addition, Viton® A and B are both FDA-approved for food contact applications.
They meet the strict regulations of the Toxic Substances Control Act and US Food Code.
Viton® A
Viton® A (FKM) is an increasingly popular material for food-grade packaging.
Especially where chemical exposure is a concern, it provides excellent barrier properties to protect products from moisture, oxygen, and other contaminants.
This can be crucial in pharmaceutical applications, where low contamination levels can result in product failure and even death.
Furthermore, the increased use of Viton® in pharmaceutical applications has triggered specialized grades that offer good aging characteristics under exposure to ozone/oxygen mixtures or UV light.
Viton® A is also used for its excellent resistance to high temperatures.
In addition, the fluorine-free versions of Viton® are now extensively used in the semiconductor industry because of their good heat-sealing properties, especially at elevated temperatures.
Viton B
Viton® B (FKPB) is widely used for food packaging applications due to its enhanced barrier properties over Viton® A, resulting from higher carbonyl groups on the polymer chains.
The precursors for Viton® B are the organo-modified polymers of tetrafluoroethylene (TFE) and hexafluoropropylene (HFP).
The most common precursor is an ethylene-tetrafluoroethylene copolymer, with ethylene units making up 30 to 40 wt % of the polymer.
TFE and HFP have very high glass transition temperatures (Tg), and the polymer chains become mobile at temperatures above the Tg.
These mobile polymeric chains can migrate through a curing agent, resulting in improved seal strength.
Although Viton® A has higher thermal stability than Viton® B, it is typically used in applications where high surface pressures or low temperatures are present.
The fundamental properties of Viton® are a low compression set, good electrical properties, and good resistance to abrasion, ozone attack, weathering, and insect attack.
These factors make it suitable for a wide range of industrial uses.
For many common applications in the industry, including motor oils and hydraulic fluids, Viton® is the material of choice.
It is considered to have the best combination of performance and cost.
In addition, the high degree of freedom makes it ideal for seal rims.
As well as being used in the automotive industry where it has a role as both seal and gasket material, Viton® is also commonly used in non-sealing applications due to its relatively low cost.
Applications
The main application for rubber seals today is in energy-saving and environmental protection applications.
For example, recent studies have shown that the combination of rubber seals and frictional seals in a compressor can reduce electricity consumption by as much as 50–70%.
These seals are also ideal for air conditioning applications as they provide substantial energy savings and low operating costs.
Viton® elastomers are applied to fulfill various applications where resistance to wear, impact, chemical exposure, and heat and pressure are required.
For instance, nitrile rubber is currently being researched for injection molded parts used in the automotive industry.
High purity rubber compounds are available in extruded sheets, continuous cast extrusions, or pellets.
They may be made by curing the polymer at elevated temperatures or vulcanizing it to a crosslinked polymer network.
Porous films are also commercially available for these products. Typical applications include tires, hoses, gaskets, elastomers, and agricultural implements.
Take Note
Although rubber and FKM are more costly than other elastomers, they offer a better balance of seal properties combined with chemical resistance.
They also require low maintenance and can be used for years.
Because of their excellent resistance to chemicals, high-quality Viton® seals are widely used in pharmaceutical applications where low contamination levels can result in product failure and even death.
It is important to note that Viton® A has higher thermal stability than FKM, although it is typically used in applications where high surface pressures or low temperatures are present.
It is also important to note that different grades of Viton® can have several end-use applications due to the difference in formulation grades.
Get in touch with us at Gorilla Gaskets for high-end Viton® FKM Gaskets in the market.