It can get overwhelming when trying to comprehend synthetic elastomers. For one, many types exist as well as diverse properties and suitable applications. Without a doubt, this brings about confusion. Fortunately, this article highlights fluorosilicone as one of these synthetic rubbers to help you understand it better.
What is Fluorosilicone?
To understand fluorosilicone, you need to learn about elastomers. The basic definition of elastomer is a material that has elastic properties. In technical terms, it is a polymer with a dense network of cross-linked molecules. These molecules are primarily what determine an elastomer’s chemical and mechanical properties.
An elastomer can be either a synthesized or natural material. Natural elastomers include natural rubber and can be found in the latex sap of certain trees. On the other hand, synthetic elastomers are fabricated in a laboratory using various techniques.
Fluorosilicone rubber is an example of an artificially made elastomer. This material is synthesized by combining fluorocarbon compounds with silicone polymers. Through a controlled reaction, selected monomers of fluorocarbon and silicone are mixed over catalysts, curing agents, and other conditions for bonding to occur.
The polymerization techniques and conditions can be tailored to produce fluorosilicone with distinct properties, based on your needs. Essentially, the manufacturer ends up with fluorosilicone by the end of these reactions. This material is then prepared for milling fluorosilicone-based products.
Properties and Characteristics of Fluorosilicone Rubber
Properties are the particular qualities that fluorosilicone possesses and make it a favorable material. On the flip side, characteristics are the innate features that come as a result of their qualities. In any case, both are intertwined. Let us explore some of them.
High shrinkage rate
Shrinkage means size contraction. In this case, it means fluorosilicone reduces in size at a huge than expected rate. This is a characteristic that results from tight bonds caused by the polymerization and cross-linking processes.
A high shrinkage rate restricts the manufacturing of fluorosilicone. In other words, there is a limited range of products that can be produced from this material. On the bright side, fluorosilicone was invented for the manufacture of specific groups of products that can are not affected by this shrinking.
Low tear strength
Tear strength is expressed as the force required to rip apart a material. Low strength implies that the force needed is low and vice versa. Therefore, it means fluorosilicone requires low strength to tear it apart. This is a mechanical property of fluorosilicone. Clearly, it shows that fluorosilicone does a poor job of maintaining tensile force.
Friction is the resistance experienced when one surface is rubbing against another. It is also known as abrasion. In more technical terms, it is a force that opposes the movement of bodies that come into contact.
Conveying that fluorosilicone rubber has low friction means that its resistance when in contact with other substances or surfaces is limited. While this might look like a negative thing, low friction is quite helpful in certain applications.
High resistance to mineral oils and fuels
Chemical resistance is a desirable property. Mineral oils and fuels are made of organic and inorganic chemicals that can affect various materials. Fluorosilicone is one of the elastomers that resist the diminishing effects of these compounds. It makes fluorosilicone suitable for making products used in conditions bearing these chemicals.
The environment consists of many types of solvents whether natural or synthetic that can corrode, age, or halt the performance of elastomers. Fluorosilicone is among the few that resist different solvents. These include both polar and non-polar solvents.
Most solvents, especially inorganic, contain corrosive chemicals. The fluoride atoms in fluorosilicone make this material inert to the effects of the chemicals. This is a desirable property, especially for marine environment applications.
Extreme temperature resistance
Fluorosilicone is among the top synthetic rubbers with the highest thermal stability you can find today. Thermal stability refers to the ability to tolerate extremely high temperatures for extended periods. This material can sustain temperatures within the range of 100 – 250oC.
This property can be defined as the overall ability to last long in harsh environmental conditions. This capability makes it a superior material to its counterparts. The repeated wear and tear that is expected in various conditions are averted because of this mechanical property.
Grades of Fluorosilicone Rubber
Grading fluorosilicone is pertinent because it helps identify and categorize it based on its inherent properties. This process involves the identification of levels of resistance and the identification of unique characteristics.
It is also worth mentioning that different manufacturers have different grading systems they use to assign these categories. Regardless, they all follow the international standards stipulated by ASTM, FDA, and other organizations. Generally, the grading standards can fall on any of the following grades.
Grading fluorosilicone based on tolerance to temperature is critical because it helps you identify which grade is suitable for your application. For instance, the American Military Standard (AMS) requires fluorosilicone rubber to attain extremely high temperatures for it to be applicable. Most manufacturers can produce high–temperature grades.
You will also realize that most grades are bundled together. In other words, some grading systems set standards that go hand in hand. For instance, high-temperature grades might be categorized alongside dense, and UV resistant to form a class.
Low-temperature environments such as polar regions and cryogenics also need products made from fluorosilicone. As such, this is a much-needed grade of fluorosilicone. Most of these grades have durometers ranging from 30 – 80. That implies this grade can be used to make both soft and hard fluorosilicone products.
The Food and drugs administration (FDA) is a body that regulates the manufacture of products that are used with foods. One of the core mandates is to ensure these products are safe. Therefore, if you intend to make anything out of fluorosilicone rubber, you must use the approved food-grade fluorosilicone.
Generally, fluorosilicone rubber is a good insulator. This means it is a poor conductor of electric currents. This property is desired for applications where electrical energy is inevitable.
However, the level of insulation varies. Therefore, manufacturers perform tests to ascertain the insulation degrees and assign grades to materials. If you need either low or high insulation, you will get the right fluorosilicone rubber.
How to cure Fluorosilicone Rubber
Curing an elastomer is otherwise known as vulcanization. The curing of fluorosilicone involves a chemical reaction that transforms the material from its semi-liquid state to a hardened material that is ready for milling. Note that some grades of fluorosilicone rubber undergo a post-curing to further enhance its properties.
Fluorosilicone curing techniques
The general-grade fluorosilicone is cured using one of two systems. Let us discuss them and what they entail;
Peroxide curing system
During the vulcanization process of rubber, there are catalysts used to initiate and speed up the process. In the peroxide curing system, peroxide compounds are used to perform these functions.
There is no need to bog you down with the intricate details of the chemical reactions that take place. What you should know is that peroxide curing enhances the cross-linking of fluorosilicone rubber and gives it high heat and chemical resistance.
Platinum-based curing system
As with the peroxide system, the platinum-based uses platinum as the catalyst in the vulcanization process. The platinum salts or complexes used serve to initiate and speed up the reaction to form an elastomer with strong bonds and desirable properties.
This curing system is particularly reliable since it requires relatively less heat. In most cases, room temperatures can be used as the source of heat. However, this requires a secondary curing process to promote the enhancement of fluorosilicone properties.
Trends in Fluorosilicone Manufacturing
According to reports, fluorosilicone was invented in the 1950s. Since then, many rubber manufacturers have made efforts to enhance this material, primarily by improving its properties. This has led to new synthesis mechanisms and manufacturing standards for fluorosilicone.
A significant advancement seen is the increase in heat tolerance of this material. Before, fluorosilicone was meant to sustain up to 220°C when in use. Recently, advancement in its synthesis has seen it being able to sustain up to 250°C. This tolerance makes fluorosilicone the ideal material for applications that require extreme thermal stability.
Improvement of properties such as durability, chemical, and mechanical properties has also been noted with emerging grades of fluorosilicone rubber. What all this means is that fluorosilicone is quintessentially the best rubber for extreme applications.
Advantages of Fluorosilicone over Regular Silicone
Comparing fluorosilicone to regular silicone can help you understand why this material is held in such high regard. During the synthesis of fluorosilicone rubber, silicone is one of the polymers used. Therefore, technically, you would expect the resulting product to be superior to regular silicone.
While regular silicone rubber has its strengths but it is no match for what the capabilities of fluorosilicone rubber. If anything, the addition of silicone to fluorosilicone’s composition means fluorosilicone has double the properties of regular silicone. The following are some of the benefits fluorosilicone has over regular silicone.
- Superior compression set resistance: While fluorosilicone is known to have a high shrinkage rate, it has one of the best compression set resistance. This means it can retain its shape and elastic properties for ages. This is unlike silicone rubber which is highly prone to deformation.
- Excellent gas impermeability: Essentially, products made from fluorosilicone can resist the absorption of gases to a huge extent compared to regular silicone-based ones.
- Extreme thermal and chemical resistance: Most silicone elastomers have the ability to resist the degrading effects of chemicals and heat. Fluorosilicone rubber takes the extra mile to brave the conditions. That means it can perform optimally in these conditions for extended times.
These benefits, coupled with the properties discussed earlier position fluorosilicone rubber on top of the list of reliable synthetic elastomers. It might seem as if they are few, but keep in mind that most applications of this material consider them critical.
Disadvantages of Fluorosilicone Rubber
Flurosilicone rubber is not without a flaw. It has its fair share of setbacks. The positive thing is that these disadvantages are not fully tied to the inadequacies of the material. In other words, they are more of external factors. Some of these drawbacks include;
- Fluorosilicone is expensive: This should not come as a shocker. As a premium material, its price would be expected to be high. It is an expensive material also due to its intricate and specialized synthesis. This means the production cost will be high and so will the purchase price.
- Material availability can be limited: There are not a lot of manufacturers of fluorosilicone. As such, it can be in low supply in some regions.
- Few color options: Contrary to most synthetic elastomers, fluorosilicone does not come in a lot of colors. This can be a challenge if you are looking for a specific color for your project.
As you can see, most of these setbacks are not quite a deal breaker. In other words, if you decide to look at the strengths of this material, you will realize the drawbacks will not affect your decision to choose it.
Applications of Fluorosilicone Rubber
The properties and characteristics of fluorosilicone rubber make it useful in very specific situations. These are situations where the conditions are mostly too harsh for regular rubber. Some of the common use cases include;
Aviation fuel seals
Aviation is among the industries that rely on fluorosilicone rubber for the manufacture of certain parts. Most aviation equipment has a lot of parts that generate extreme heat or come into contact with fluids.
Specifically, engine parts are made from fluorosilicone since they can sustain heat and corrosive fluids. Mostly, they are used to make fuel seals, grommets, o-rings, and control diaphragms.
The automotive engine produces a lot of thermal energy that can be damaging to some materials. As such, materials with high resistance to heat like fluorosilicone are used to manufacture parts that come into direct contact with heat.
Such parts include gaskets and o-rings. Moreover, gaskets used for cushioning bolts and screws are used for their high compression set. In other words, they are able to withstand high pressure without deforming.
Chemical equipment sealants
Sealants, especially for chemicals, are also made from fluorosilicone. As earlier noted, this material can tolerate a wide range of chemicals. Equipment used for storing, transferring, or gathering chemicals requires tight, durable, and compatible seals to avoid accidents when handling them.
Construction equipment rubber seals
Construction is another industry that fully relies on heavy-duty materials. In that case, fluorosilicone rubber fits the description. This material is used to manufacture products such as seals for pumps. The mechanical properties of fluorosilicone rubber in particular come in handy in this application.
Electrical equipment coatings
Coatings used for electric cables are supposed to have high insulation. Therefore, in an attempt to achieve the best insulation, manufacturers look for materials such as fluorosilicone for the best results.
The uses of fluorosilicone are not tied to specific industries. It all depends on what application or need you are looking to solve with a high-end rubber material. At the end of the day, your rubber miller will be able to advise you on which material is best suited for your specific application.
Fluorosilicone has benefitted a lot from continuous R&D. Manufacturers spend a lot to make the best possible material to ensure your demanding applications are future-proof and adapted to the environment. As you have seen, this material is capable of withstanding the harshest of environments due to its properties. If interested to learn more, visit our website.
Frequently Asked Questions (FAQs)
Here are some commonly asked questions to help you learn more about fluorosilicone.
Why fluorosilicone is known as FVMQ?
FVMQ is an internationally used abbreviation for fluorosilicone. In full, it stands for Fluorosilicone Vinyl Methyl Quality. In some cases, fluorosilicone can be categorized as silicone, then FVMQ could be used to single out this type of silicone.
What is the difference between regular silicone and Fluorosilicone?
The main difference between these two is in their synthesis and also properties. Regular silicone (PDMS) involves hydrolysis and a condensation reaction. On the other hand, fluorosilicone involves more complex reactions depending on the desired properties and characteristics.
Why is fluorosilicone blue in color?
While most fluorosilicone is formulated in blue color, it does not mean that it is their characteristic color. The color of this material can be anything depending on the specific additives and synthesis processes used.