The performance of rubber materials in low temperature environments is a critical factor when evaluating their application in seals, such as O-rings. As temperatures drop, rubber becomes harder and loses elasticity, which can compromise its sealing capability. Therefore, assessing the physical properties of rubber at low temperatures, especially its sealing performance, is essential to ensure product reliability. Normally we could evluate the rubber low temperature performance by parameters as below:
1. Low-Temperature Elasticity (TR10)
A key parameter for evaluating the low-temperature performance of rubber is TR10, which refers to the temperature at which the material’s rebound rate drops to 10%. This parameter reflects the rubber’s ability to recover elasticity at low temperatures. The test method to determine TR10 is outlined in ASTM D1329, which measures the temperature at which rubber exhibits 10% elastic recovery after being stretched. Generally, the lower the TR10 value, the better the rubber maintains its elasticity at low temperatures, making it suitable for use in colder environments.
For example, if an O-ring needs to operate at -40°C, selecting a rubber material with a TR10 value close to or below -40°C is crucial. This ensures that the rubber retains sufficient elasticity at low temperatures, adapting to the contraction and expansion caused by temperature changes, thereby maintaining its sealing effectiveness.
2. Glass Transition Temperature (Tg)
The glass transition temperature (Tg) is another important parameter for low-temperature performance. It represents the temperature at which the rubber material transitions from a flexible rubbery state to a hard, brittle glassy state. This transition is typically evaluated using ASTM D3418, a standard test method for determining Tg via differential scanning calorimetry (DSC). When the temperature falls below Tg, the rubber loses its softness and elasticity, significantly reducing its sealing performance. To ensure good sealing at low temperatures, it is essential to choose a rubber material with a Tg lower than the operating temperature.
3. Low-Temperature Brittleness (Low-Temperature Impact Test)
Low-temperature brittleness is another crucial test to assess whether rubber becomes brittle at low temperatures. This is typically measured through the ASTM D2137 test method, which evaluates how the material cracks or breaks under force in cold conditions. If the rubber becomes too brittle at low temperatures, it may fail when subjected to mechanical stress or compression, leading to seal failure. Therefore, ensuring low brittleness in rubber is key to maintaining sealing performance in cold environments.
Rubber Formulation Selection
Choosing the right rubber material for low-temperature sealing applications is crucial. Common rubber materials suitable for low-temperature seals include silicone rubber, fluorosilicone rubber (FVMQ), EPDM, and low-temperature FKM. These materials generally have lower TR10 values and Tg, allowing them to maintain good elasticity and sealing performance at extremely low temperatures.
- Silicone Rubber (Silicone): It has a low Tg and excellent low-temperature elasticity, making it suitable for seals in very cold environments.
- Fluorosilicone Rubber (FVMQ): It offers both chemical resistance and low-temperature elasticity, making it ideal for harsher chemical and cold environments.
- EPDM: Affordable and offering good low-temperature performance and resistance to aging, making it suitable for certain low-temperature sealing applications.
- Low-Temperature FKM: For applications that require both chemical resistance and low-temperature performance, low-temperature FKM is an optimal choice, especially when -30°C to -40°C operating temperatures are required.
Low-Temperature FKM
FKM (fluorocarbon rubber) is generally known for its excellent heat and chemical resistance but is often less effective in low-temperature applications. However, specific low-temperature FKM grades have been developed to improve this performance. OBT Rubber Seal can offer TR10 values in the range of -30°C to -35°C, making them suitable for certain low-temperature environments.
Low-temperature FKM grades typically have slightly different formulations and may use specialized cure systems, such as peroxide curing, to enhance their flexibility and sealing performance in cold environments. Standard tests like ASTM D1329 can be used to evaluate the low-temperature recovery of these FKM materials.
Please contact us, OBT Rubber Seal, for better understanding your technical requirement and our proposal.
