Understanding the heat resistance of silicone can help you better select the appropriate silicone products for your industrial production line. Next, based on the comparison of the heat resistance performance and applications of different types of silicone, we will provide you with a detailed guide.
Heat Resistant Characteristics: Why Silicone Won’t Melt?
Molecular Structure Advantage
As is well known, silicone is a thermosetting material. And all types of silicone are polymers composed of siloxanes. Siloxanes are chain-like structures composed of alternating silicon and oxygen atoms, and their side chains typically contain carbon or hydrogen.
It is precisely because of the extremely stable chemical structure of silicone that it has excellent heat resistance and can prevent the silicone from decomposing in high-temperature environments. Due to its outstanding features, you can apply it to a wide range of uses.
Side Groups and Modification
By introducing different side groups, you can further enhance the thermal stability of the silicone material. And you can customize the thermal and chemical properties of the silicone based on your different application requirements. Now we will introduce to you the different applications of the various side groups:
The methyl group, as the basic side group, provides the basic thermal stability for general applications. Adding a bulky phenyl group can significantly increase the thermal decomposition temperature, making it highly suitable for use in high-temperature special silicone products.
Furthermore, fluorosilicone materials with fluorine-containing groups (such as trifluoropropyl) combine excellent heat resistance with outstanding oil resistance and solvent resistance.
So, unlike other organic rubbers, silicone rubber does not melt when heated; instead, it gradually loses its elasticity and hardens. You can use the above knowledge about the heat resistance of silicone to distinguish between thermosetting materials and thermoplastic materials.
A Comparison of High-Temperature Silicone Grades
If you purchase different types of silicone, due to their varying qualities, their heat resistance will also differ. Moreover, the heat resistance performance of silicone cannot be simply described by a single number. Usually, two indicators, namely continuous service temperature and intermittent peak temperature, are used to evaluate it.
Continuous Service Temperature: This refers to the upper temperature limit for your silicone material, which remains stable in performance even when used continuously for a long period of time.
Intermittent Peak Temperature: It refers to the maximum temperature that your silicone material can withstand within a short period of time, but it is not suitable for repeated or prolonged use at this temperature.
Due to the fact that the heat resistance of silicone is closely related to the vulcanization method, we have listed in the following table the heat resistance comparison of silicone for three different vulcanization methods:
| Type | Curing Method | Temperature Resistance | Key Notes |
| HTV (High Temperature Vulcanizing Silicone / HCR) | Heat curing (100–250℃) | Continuous: -60℃ – 230℃; intermittent peak up to above 270℃ | High mechanical strength and good chemical resistance, suitable for high-performance molded and extruded parts |
| LSR (Liquid Silicone Rubber) | Platinum-catalyzed two-component injection molding | Continuous: -40℃ – 180–230℃; peak: 230–250℃ | High precision, fast curing, excellent biocompatibility; slightly inferior low-temperature performance |
| RTV (Room Temperature Vulcanizing Silicone) | Room temperature curing | Varies by formulation, up to 230–280℃ (special grades) | Used in sealants, adhesives and coatings; heat-curable types offer higher temperature resistance |
Heat Resistance Requirements for Silicone in Different Industries
Automotive and EV Applications
If you are in the automotive and electric vehicle industry, you will find that silicone is used for engine compartment sealing, turbocharger hoses and the intake system. And these parts will be exposed to extremely high temperatures and temperature fluctuations for a long time.
If you are planning to use it in the engine compartment, you need to consider that this part requires the silicone to operate continuously at temperatures ranging from 150℃ to 175℃, while the peak temperature at the turbine end can reach 200℃ to 230℃.
In this application, in addition to paying attention to the high-temperature environment, you also need to prevent the silicone from being eroded by the high-temperature engine oil or fuel vapor. Ordinary silicone will swell and lose its effectiveness when exposed to oil, so we recommend that you use FVMQ or special silicone resistant to oil.
Unlike gasoline vehicles, the gasket of the battery pack in electric vehicles needs to be flame-retardant, and it has to work continuously in an environment of 60-80℃. If you are in this industry, you should pay extra attention to the low compression set data of the silicone used, in order to prevent moisture from entering.
Food and Beverage Processing
Silicone is the ideal choice for you as it meets the requirements of being odorless, non-toxic and easy to clean.
If you are involved in food production or beverage manufacturing, especially in the use of ovens and coffee machines, the silicone you choose must perform reliably under high temperatures. It also needs to comply with food contact safety regulations.
When you are in the dairy industry, the silicone used in the pipes needs to function in systems that undergo high-temperature cleaning (such as clean-in-place (CIP) system) and in refrigeration systems. The operating temperature of the oven is usually between 220℃ and 250℃.
The silicone used in these applications should ideally meet the LFGB/FDA standards to ensure that there is low volatile migration at high temperatures, thereby guaranteeing food safety.
Medical Device Sterilization
A safe and sterile environment is of vital importance for your pharmaceutical and medical production industries. This requires that the silicone remain intact and undamaged throughout the repeated high-pressure steam sterilization process at temperatures ranging from 121℃ to 134℃, without decomposing or contaminating the liquid.
The failure of silicone rubber does not manifest as melting, but rather as hardening, embrittlement, higher compression set and loss of elasticity. Therefore, we recommend using Medical-Grade LSR or HCR, because this type of silicone has excellent high tear strength and hydrolysis resistance.
Industrial Sealing and Gasketing
If you are involved in the industrial machinery industry, silicone is commonly used in heating rollers, ovens, HVAC systems, and other equipment that requires maintaining the material’s functionality during the heat cycle process.
Because silicone works under pressure for a long time, when placing a large order for silicone materials, you should ask the supplier to provide the test data on the compression set.
For outdoor use and in situations where it is exposed to harsh environments, it is required that the silicone seals and the casing can function properly even in extremely cold winters or under intense sunlight, without cracking, fading or becoming brittle.
We recommend that you use HTV, as it is more resistant to outdoor high temperatures, ultraviolet rays and ozone, and thus has more advantages over EPDM.
How to Choose High-Quality Heat-Resistant Silicone?
Compression Set at Elevated Temperatures
When you are choosing high-quality heat-resistant silicone, you may not know which aspect to focus on first. In that case, start by looking at the core indicator of the compression set.
It is specifically designed to measure how much a silicone product can return to its original shape after being compressed, heated, and then released. This directly reflects the material’s ability to maintain elasticity under high-temperature conditions, and it also represents the sealing capability of the silicone products you are using.
If the value is lower, it indicates that the silicone rubber has a better recovery ability after being subjected to high temperature compression and provides a more durable seal.
For applications with high-temperature sealing requirements, you must prioritize the use of silicone materials with a low permanent deformation rate. Only in this way can you ensure that the product remains leak-proof, non-leaking and has stable sealing performance during long-term use.
Heat Aging Hardness Change
High-quality silicone must have a good thermal aging performance. When the products you produce achieve high cost-effectiveness due to the long lifespan of the silicone components, it not only increases your sales volume but also enhances the reputation of your enterprise.
The key feature is that the silicone will gradually harden at high temperatures, and once it hardens, it will lose its elasticity and completely lose its sealing effect. So the key to judging the quality of the material lies not in whether it will eventually become hard, but in the rate at which it hardens and fails under high temperatures and pressure.
Third-Party Test Reports
If you want your product to smoothly pass through customs and enter the market, you cannot rely on verbal promises. What really works is the test report issued by an authoritative third-party institution.
When selecting materials, you should verify all the relevant test certificates to ensure that the silicone complies with the safety, environmental protection, heat resistance and flame retardancy standards of the corresponding countries and industries. Below is the detailed list of certifications that we have compiled:
| Certification Type | Specific Regulation / Standard No. | Application and Procurement Significance |
| High-Temp Electrical Insulation | UL 746B RTI | Relative Temperature Index (RTI Elec/Str/Imp), serving as a core selection criterion for electronic sealing components. |
| Flammability Rating | UL 94 V-0 | Mandatory requirement for EV battery packs and internal parts of household appliances. |
| US Food Grade | FDA 21 CFR 177.2600 | Compliance for food-contact rubber products intended for repeated use. |
| EU Food Grade | LFGB (German Food Code) | Stricter sensory testing than FDA (taste and odor migration). |
| Environmental Compliance | REACH / SVHC | Mandatory environmental registration for imports into the European Union. |
| Medical Biocompatibility | ISO 10993-5, -10 | Tests for cytotoxicity and skin irritation. |
FAQ
What Is the Maximum Continuous Service Temperature of Standard Industrial Silicone?
The maximum continuous service temperature for standard industrial silicone is usually between 200℃ and 230℃. However, please refer to the test report of the silicone you purchased for the exact temperature.
We suggest that you use it at a temperature 10℃ to 20℃ below the specified maximum continuous service temperature to ensure the lifespan of the silicone.
Why Is Post-Curing Important for High-Temperature Silicone Applications?
It can enhance the heat resistance of the silicone and improve its quality. You can stabilize the internal cross-linked network through post-curing treatment, or remove volatile chemical substances to make the silicone odorless and tasteless.
Why Does Silicone Fail Prematurely in High-Temperature Industrial Applications?
There are many possible reasons for such a situation to occur. If you fail to properly solidify or do not adjust the proportion correctly, it will reduce the heat resistance of the silicone, leading to failure.
It could also be that you didn’t use the silicone within the appropriate range. For instance, its maximum heat resistance is 190℃, but you were using it in an environment with a temperature of 200℃ for a long time.
Certainly, the repeated expansion and contraction of the silicone due to long-term thermal cycles can cause tiny cracks to form, accelerating the aging process.
Final Thoughts
Legensilico, as a professional silicone manufacturer in China, possesses extensive experience and knowledge in silicone. If you would like to know more or wish to cooperate with us, please contact us as soon as possible. Our staff are available to serve you at any time.
