‘What temperatures can silicone rubber withstand?’ is a question the team at Viking Extrusions are commonly asked by designers and engineers looking to assess the material’s suitability for their application.
Interestingly, there isn’t a default answer our silicone experts can offer without asking further questions about the environment in which the silicone will be operating.
Unlike most other types of rubber, silicone can withstand extreme temperatures from as low as -60°C to +200°C while maintaining its properties. Once critical factor which determines the operating temperatures silicone can really withstand is the length of time of exposure, which has a key impact on performance and lifespan.
For most applications where parts are exposed to continuous temperatures over 150°C will require the use of silicone rubber to ensure performance and longer life span.
Silicone does not melt due to temperature alone!
Most plastics begin to melt at high temperatures. Silicone, however, exhibits unique behaviour at elevated temperatures. Silicone does not have a melting point but instead remains solid until combustion occurs. At high temperatures (above 200°C) silicone will begin to slowly lose its mechanical properties becoming harder and more brittle. At temperatures above 300°C this process is accelerated. There is no set temperature for silicone auto ignition which can depend on may factors such as the hardness of the silicone, type of curing catalyst used, and any additives or pigments However, auto ignition generally occurs around 450°C.
Silicone also displays unique behaviour during the combustion process. Once autoignition temperature has been reached, the material will briefly smoke before it cracks and begins to combust. At this stage the silicone will expand in volume and volatiles are released, before brittle combusted material breaks away from the sample and disintegrates into a fine powder.
Silicone is made from a silicon-oxygen-silicon backbone with carbon-containing methyl and vinyl groups. During combustion, silicone dioxides and carbon dioxides are produced. The carbon monoxides and carbon dioxides are released into the atmosphere. The silicon dioxide creates a layer of white powder on the sample. This layer of silicone dioxide cannot combust any further, it acts as an insulating layer which helps to slow down or prevent further combustion of the silicone.
General purpose grades of silicone are suitable for continuous exposure of temperatures up to 180°C and intermittent exposure up to 200°C.
Heat stabilised silicones contain additives that increase their maximum operating temperature to 260°C.
High temperature grades of silicone contain additive that make them suitable for applications up to 300°C for intermittent periods. If the part is to be exposed to continuous temperatures over 300°C then the silicone’s properties would degrade with time.
Flame retardant grades of can withstand intermittent temperatures up to 220°C (depending on the specific grade). These materials contain additives which enhance silicones self-extinguishing properties. A variety of flame retardant grades are available specifically formulated to meet standards such as:
For detailed information on all of the silicone grades we offer, visit our technical datasheets page.
Silicone is a synthetic polymer made of the chemical element silicon.
To clarify the difference between silicon and silicone, silicon is the raw chemical element and silicone is a rubber primarily derived from it. In its pure form, silicon is very brittle and hard. It forms as a crystalline solid with a grey/blue metallic sheen. Despite being the eighth most common element in the universe, it very rarely forms as a solid in the earth’s crust. Silicon is most often found as silica, an oxide of silicon and also the main constituent part of sand.
Silicone is primarily made of silicon but also includes oxygen, hydrogen and carbon. It is a man-made material and has viscoelasticity, meaning that it is both viscous and elastic. Materials that display viscoelasticity are known generally as rubbers. Silicone rubber is categorised as a synthetic elastomer because silicone polymer is both man-made and displays elastic properties. Silicones are compounds made up of repeating units of siloxane. Siloxane is an alternating chain of silicon-oxygen atoms, which are combined with hydrogen and carbon.
To make silicone, the silicon atoms must be isolated from the silicon dioxide compound silica. This is done by heating large volumes of quartz sand to extremely high temperatures, up to 1800°C. From here, there are several processes where silicon is combined with methyl chloride and heated. It is then distilled into a polymerised siloxane known as polydimethylsiloxane. The polydimethylsiloxane can then be polymerised. This is done using a variety of techniques depending on the use of the final product.
The production of silicone rubber base compounds can be done on a mass scale at relatively low costs. As a result, silicone has become one of the most popular elastomers for both commercial and industrial usage.
At Viking Extrusions all our grades of silicone are mixed using our in-house milling facilities. We take the raw silicone compound, add pigments and additives as required then blend with catalyst ready to be extruded and cured by High Temperature Vulcanisation (HTV). The use of in-house facilities means everything we produce is fully traceable to its original batch. This way we can ensure the highest standard of quality management throughout the entire process from raw compound to finished product. As such, we produce large quantities of both food grade silicone and medical grade silicone.
There are two main types of rubber, synthetic man-made rubbers and natural rubber. Natural rubber, commonly known as latex, is harvested from the rubber tree. Latex is a sticky material drawn from the tree by making incisions in the bark and collecting the fluid that drains out in a process known as “tapping”. The first uses of rubber were by the indigenous cultures of Mesoamerica who used the material to waterproof textiles and to make rubber balls and containers. Mesoamericans even produced different grades of stabilised rubber by combining different proportions of raw latex with juice from the morning glory vine. This was 3000 years before Charles Goodyear stabilised it in the 1800s!
Any rubber-like material which is not formed from natural rubber is known as a synthetic rubber. Materials are mixed together to form what is called a synthetic polymer. An elastomer is a polymer that displays both viscosity and elasticity.
Silicone rubber is used across a diverse range of industries due to its many useful properties such as:
These uses mean that silicone products have become part of our everyday routine. We encounter silicone rubber every day and make use of silicone in many industries. From its use in the process of generating the energy that powers our home, to the silicone caulk sealant around our bathtub. For example, food-grade silicone is used to make a huge variety of products such as dishwasher safe muffin trays and other bakeware, pot holders, oven mitts, cookware such as spoons and whisks as well as extrusions for ovens, freezers and refrigerators. Medical grade silicone is used in both medical applications and as a common ingredient in personal care products.
At Viking Extrusions, we produce silicone rubber extrusions for application in a wide range of industries.
To learn more about the properties and applications of silicone rubber please contact one of our technical advisors who will be happy to answer any queries.
Viking extrusions have been working with the rail and mass transit industry for over 25 years, helping keep thousands of passengers safe every day across the country, and the world!
We’ve worked on several major rail projects around the world including:
Trains have changed a lot over the time we’ve been working with them- adapting with the availability of new materials and advancements in aerodynamic design. In this infographic we go back even further into their development, looking at major milestones in the development of railways and the materials that made them possible.
The rail and mass transit industries require high performance materials that can meet the health and safety standards required to ensure passenger welfare, whilst also operating in demanding environments where they will be exposed to extreme temperatures and weathering. This was not always the case- trains were originally made from wood and then cast iron, leading to dangerous dilapidation!
Train design has required the development of new materials to meet the high performance standards required, and in turn developments in material technology have spurred train design. With advancements in both silicone and steel zinc alloys, trains are faster, safer and more efficient than ever before.
Read through the infographic below to see how they have developed through time.
General purpose grades of silicone are used across a wide range of industries due to their versatile properties. They can operate across a wide temperature range from -60°C to +200°C. They are naturally translucent and can be easily pigmented and matched to any required colour. Viking Extrusions can manufacture products in general purpose silicone from 20° Shore A up to 80° Shore A. All grades of general purpose silicone are FDA compliant and USP class VI certified.
Heat Stabilised grades of silicone contain an additive enabling them to operate at temperatures up to 260°C. These are available from 30° Shore A to 80° Shore A.
High temperature grades of silicone are available from 40° Shore A to 80° Shore A and contain special an additive enabling them to withstand even higher temperatures, up to 300°C. The additives give these grades a natural cream/off-white colour and pigmentation is more limited.
High tear strength grades of silicone are FDA approved and are available from 50° Shore A to 70° Shore A. They are naturally translucent and can be pigmented to any colour.
VINF60 is a specialised grade of silicone developed by Viking Extrusions specifically for the manufacture of inflatable seals. It has a high tear strength, is FDA approved and can be pigmented into any colour.
Viking Extrusions provides specialist grades of material to meet specific aerospace and rail requirements.
VFR(2) is a flame retardant grade of silicone developed for rail applications. It is available in 68° Shore A, pigmentation is limited to shades of grey. This material meets the following rail spec:
Learn more about rail applications of silicone rubber.
This flame-retardant grade of material is specified for use in aerospace applications and is available from 20° shore A to 80° shore A. Its natural colour is off-white and pigmentation is limited to shades of grey and some other colours. This material meets the following FAR/JAR specifications:
Learn more about silicone rubber in aerospace.
Platinum cured silicone is crosslinked using a platinum catalyst rather than a peroxide catalyst used for other silicone grades. This material does not require post curing, is more optically translucent and has a high tear strength.
Find out the differences between platinum cured silicone and peroxide cured silicone
Silicone sponge is available in a range of densities and colours. Specialised food safe and flame-retardant grades are available.
Learn more about silicone sponge products from Viking Extrusions.
Metal detectable grades of silicone contain metal filings in them and are widely used in the food industry. These filings allow for easy detection if material breaks away from the seal. Metal detectable grades are available from 45° Shore A to 75° Shore A in blue.
This is a high-quality compound that has been developed specifically to resist high pressure steam applications. It has an operating temperature from -60°C to +260°C and is available in 60° shore A.
Semi-conductive silicone has a low volume resistivity after high temperature exposure and is available in black 75° Shore A.
For more information on any of our available compounds please contact one of our technical advisors.
Curing is the process by which an elastomer becomes cross linked. In a peroxide cured silicone, high temperatures break down the peroxide which creates the chemical which crosslinks the polymers in the chain. Addition curing, platinum is added to the silicone as a catalyst. This causes the polymer chain to cross link with itself. Most of the silicone processed by Viking Extrusions is heat cured rubber (HCR) which uses the peroxide curing system to convert the silicone from compound to rubber.
The different curing systems give silicone rubber different properties. Below are the pros and cons of each method of curing silicone:
Learn more about the solutions Viking Extrusions provide to the Food & Dairy and Pharmaceutical industries.
Viking Extrusions Supply both peroxide and platinum cured grades of silicone. If you are unsure about which grade you require for your application, please contact one of our experienced technical advisors who will be happy to assist you.
UL94 is a plastics flammability standard released by Underwriters Laboratories in the United States. The standard determines whether a material will extinguish or spread a flame once it has been ignited. V-0 is a classification of this standard outlined as:
V-0: Burning stops within 10 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.
The test is conducted on five specimens of the material which measure 13mm x 125mm x 13mm thick (maximum thickness). Each material specimen is then clamped in a vertical position. A Bunsen burner with a flame height of 20mm is then positioned so that the top of the burner is 10mm lower than the material specimen. The flame is then applied to the material for 10 seconds. The Bunsen burner can be moved to ensure that the flame remains directly below the material. After 10 seconds the flame is removed, the time that the specimen continues to burn for is recorded. Once the flame is extinguished the burner is applied for another 10 seconds and the process is repeated.
UL standards are used as a safety rating for a range of produces when there are concerns about the product burning. From LED lighting to electronics and ovens.
In automotive, rail and aerospace industries where safety is of critical importance UL94 V-0 and other tests such as EN45545 and FAR/JAR 25.823 are essential safety standards. In the event of a fire, the silicone rubber would help resist the flames and prevent the spread of fire.
Find out more about the applications of silicone rubber in automotive, rail and aerospace industries.
The aerospace industry is a challenging and complex area. Keeping aircraft flying and ensuring passenger safety leaves no room for error. Every component on an aircraft is critical to its operation and high-performance materials are required. Silicone rubber’s outstanding sealing properties and ability to operate across an extreme temperature range make it a widely used material within the Aerospace Industry.
Properties of Silicone Rubber
During operation, aircraft go through large temperature fluctuations from freezing temperatures when flying at full altitude to high temperatures when on the ground in hot countries. Materials used on aircraft need to withstand such temperature changes while fully maintaining performance.
Viking Extrusion’s specially developed aerospace grades of silicone are stable from -70°C to + 230°C, these grades can be used in the construction of gaskets for windows and cabin doors. Silicone rubber can be moulded with tight tolerances ensuring gaskets form airtight seals both on the ground and in the air.
Silicone Rubber in Aircraft Engines
Silicone Rubbers ability to withstand high temperatures enables it to be used for gaskets in aircraft’s engines where it will outlast other types of rubber. This resistance to heat corrosion both improves aircraft safety and reduces maintenance costs.
In the Cockpit and Electrical Components
In the cockpit silicone acts to seal instrument panels and other electrical systems, protecting printed circuit boards from the risks of extreme altitude such as moisture and extreme low temperature. Silicone can be used as a sheath to protect wires and electrical components from any dust or ice that may creep into a plane’s inner workings.
The nature of air travel results in lots of noise and vibration, powerful engines, landings and high speeds all need to be considered to ensure passenger comfort and safe operation of the aircraft. Silicone rubber has exceptional noise reduction and anti-vibration properties. It can be formed into small components and fitted into small gaps ensuring all equipment can be protected from unwanted vibration such as: overhead lockers, vent ducts, hatches, entertainment system seals, and LED lighting systems.
Learn more about the products manufactured by Viking Extrusions.
In the aviation industry, passenger safety is of critical importance. It is therefore important that all materials used on aircraft are flame retardant. Silicone rubber has natural flame-retardant properties. Viking extrusions have developed specialist grades of silicone that have been certified to demonstrate self-extinguishing properties. Moreover, if there were an outbreak of fire, aircraft grades of silicone give off low smoke and toxic gas, preventing passenger harm.
To learn more about the use of silicone rubber on aircraft visit our dedicated page.
What is our Minimum Order Quantity?
At Viking Extrusions Ltd, we pride ourselves in offering a bespoke service to customers seeking MOQ’s for new prototype orders. We make sure to give the best value and turnaround time at every step of the way. We manufacture everything to order, when required, and offer the best services regardless of whether the order is for a few metres or a few thousand metres. But the number 1 question we get asked when new customers are seeking a prototype partner is, “What’s your MOQ?”
To elaborate on this question, let’s look at the process we follow in each instance:
Every new order requires enough silicone material to fill our extruders and to set and test the new die design. This is usually at least 5kgs, maybe more depending on the complexity of the new profile. We extrude a few metres of material, check the tolerance against the customer’s profile drawing requirements and adjust accordingly- usually needing to remove and machine the profile slightly to help create a more even flow of material through it and, in turn, a more consistent profile for the customer.
This process can take several attempts, often requiring tool machining each time. As silicone has a variety of shore hardnesses from 10 shore A (our softest silicone) up to our hardest 80 shore A, this must be considered when designing and machining our customer’s tool. Each type of silicone material reacts differently when being extruded with the softer material swelling more when extruded compared to harder material which extrudes truer to the tool being used. Simply speaking, if we were to extrude 20 shore A compound through a die that was designed to be used with 80 shore A material, the final product would be larger due to the swell created. To add to this, the speed of extrusion, the temperature of the curing box and, in some extreme cases, the ambient temperature can all affect the end result of the product.
All of these variables must be taken into account when quoting for MOQ’s and as such, if a customer wants 2metres compared to 25metres, the price will most likely remain the same as the setup cost is the main expense involved.
Our most common material used is White VGP60 grade silicone rubber and if you’re only requiring a few metres, we should be able to accommodate you. Otherwise, our MOQ for most orders is 25 Metres which offers the customer the best price/metre and covers our costs.
Give us a call now to find out how best we can assist you or look at our 6000+ current designs to see if we already have what you’re looking for.
At Viking Extrusions Ltd, we offer a wide variety of silicone compounds that are available in various hardnesses to suit a multitude of applications. A common question our customers ask is, “What shore hardness should I get for use with ……?” To elaborate on the right answer to that question, we would like to give our customers a better understanding of how a shore hardness is measured, how it affects the final product, and how best to make the most educated decision to choose the correct option.
What is a shore hardness and how is it measured?
Simply speaking, shore hardness is a measure of the rigidity of a given material and how resistant it will be to permanent indentation. It is measured by the depth of indentation that is created on the material with a specified force. Albert Ferdinand Shore, defined a durometer scale at which this could be measured against. In the 1920s, he developed a device (also commonly known as a durometer) to measure Shore Hardness. There are several scales of hardnesses, all ranging from 0 to 100 with higher values indicating a harder material. Viking Extrusions uses the Shore A scale which is a common scale for softer plastics and polymers.
We offer a range of silicones available in as soft as 10° Shore A up to 80° Shore A in increments of 5° Shore A.
Because our 10° Shore A material is so soft, as it is extruded, the material tends to catch slightly through the die design which causes a minor ‘snake skin’ affect. Whilst this doesn’t affect the quality of the product, the rougher skin can affect it visually and if your product is to be used in a location that it is visible, we would recommend you choose a slightly harder option to prevent this.
20° Shore A can easily be compared to the hardness of a rubber band. The material extrudes smoothly and is a great option for soft, visible applications. It is one of our lesser used compounds but may be a good option for your requirements.
40° Shore A is similar to the hardness of a pencil eraser. This is flexible and a good option for a variety of seals and applications.
Our most common option is 60° Shore A which is applicable to many tubes, profiles and gaskets. It is the material we use for our inflatable seals as we have found that the material expands more evenly compared to softer materials which tend to create ‘bulbs’ in the profiles during inflation and harder materials which tend not to be as malleable.
70° Shore A can be compared to that of a tire tread. Whilst still malleable, this material works well for applications where a harder seal is needed.
The hardest material we currently offer is 80° Shore A which is as hard as an average shoe heel. This is a great product if you’re seeking a rigid product to replace a plastic component. Whilst it’s not as hard as plastic, it is a great alternative.
Whilst it can be difficult to make the right decision, you can give us a call and request a few samples to display each shore hardness we can offer. Silicone Rubber is an incredibly versatile polymer and offers a resilient, affordable option to a variety of applications in a multitude of industries from simple edging strips for use in engineering, to complex hatch profiles for use in automotive production, to inflatable seals for use in pharmaceutical, marine, nuclear, aeronautics, packaging and many more. Tooling needed to produce a new prototype extrusion is affordable and costs of scaling up to larger production orders are manageable. In many cases, we’re able to turn over orders in a matter of days so if you’re in a rush, we will make every effort to accommodate you.
What we need to know to effectively quote you
Silicone rubber is an extremely versatile elastomer that is capable of being used in a wide variety of industries, from automotive through to household, nuclear, marine, agriculture, aeronautical and many more. There are several different grades of silicone that are designed specifically for certain applications and each of these have their own properties. For a more effective quotation, we would like to know a few details.
What is the application that our profile/seals will be used in?
Are these seals used in an industrial oven (and require metal detectable grade silicone) or will they be used in rail applications (requiring flame retardant grade silicone). Any information you may be able to supply here will help us pinpoint the right type of silicone for you.
Will the product be used in any heat sensitive environment?
Our standard General Purpose silicone (VGP) will work efficiently in operating temperatures of -70°C to +200°C. We also have Heat Stabilised Silicone (VGP-HST) capable of operating between -70°C to +260°C. There is also a High Temperature Silicone (VTHT) which is efficient between -70°C to +300°C. If -70°C isn’t sufficient, we can provide a Low Temperature Silicone (VLTD) which operates between -116°C to +200°C
Apart from our VTHT and VLTD grade compounds, we are still able to offer colour matching to meet your requirements. Give us a call to find out more about this.
Will the product come into contact with any chemical or oil?
Whilst silicone rubber can be used in varied applications, certain chemicals and oils can degrade the compound causing premature failure of the seals. If you believe the seal may have contact with any chemical products during its use or for cleaning it, make us aware so that we can assist you.
What shore hardness do you need?
We operate to shore A grade hardness silicones from 10°sh A to 80°sh A. Each grade of silicone acts differently during extrusion and we will need to effectively adjust the dies and curing environment accordingly to match the required tolerances for your orders. Let us know what you need and we will help you make the right choice.
What grade of silicone is required?
Viking Extrusions Ltd has a wide variety of silicone grades to choose from. Whether it’s extremely low temperature or flame retardant you require, we have a grade that will work.
VGP– this is our general purpose grade silicone. The compound is a translucent base polymer which is FDA approved and available from 10° Sh A to 80° Sh A and is effective for most applications.
VTHT– High temperature grade silicone available from 20° Sh A to 80° Sh A and is a cream/ off white base. The pigmentation options are limited in this grade.
VHTS– High tear strength grade silicone. Available from 50° Sh A to 70° Sh A. If you require extra rigidity, this grade is worth a look.
VFR– Flame Retardant silicone available in a range of shore hardness’s. We have certain grades of this specialised and tested for use in aviation and rail applications. If you’re unsure of exactly what you need, let us assist you.
VPLT– Platinum Cured silicone available in 10°Sh A to 80° Sh A. This differs to our other grades which are hydrogen peroxide cured and require an overnight post cure whereas platinum cured silicone will cure during extrusion. Due to the lack of peroxide residue, the VPLT range will not bloom during long term storage.
VGD– Silicone Sponge grade available in a range of densities. Call us with your requirements and we can assist you.
VCL– Carbon Loaded silicone. This is a semi conductive compound and available in 75° Sh A
VMD– Metal Detectable silicone for use mainly in the food industry. Available in 45°Sh A to 75° Sh A. This is also an X-ray detectable silicone compound should you require this for your application.
We are always increasing our material variety and if you require a certain compound to meet your requirements, give us a call as we may be able to help.
Are there any particular tolerances that are to be adhered to?
Viking Extrusions Ltd currently operates to ISO 3302-1: 2014 standards. Tubes are run to Class E1 tolerances, strips and cords to class E2, and profiles to class E3. All values below are in Millimetres
|Nominal Dimension||Class E1||Class E2||Class E3|
|Above||up to and including||+/-||+/-||+/-|
With regards to cutting, we operate to a Class L3.
|Nominal Dimension||Class E3|
|Above||up to and including||+/-|
While these are house margins, if you require tighter tolerances, just let us know and we will make every effort to meet your needs.
Whilst this isn’t an exhaustive list of requirements, we can quote you efficiently and get you the right product for your particular needs.