Every material has a high or low-temperature limit that, once it is reached, the material will fail. Governed by the coefficient of thermal expansion (CTE), contraction or expansion of material occurs as the material cools or warms. Stresses that occur at low temperatures may not happen at higher temperatures and vice versa. To prevent failure, gaskets, o-rings and other elastomeric sealing material must have specific compounds added to make sure its mechanical properties can withstand the necessary temperature. It’s important to know a seal’s temperature limit before application to avoid component failure.
Low-temperature applications for seals are critical to a number of industries. Pharmaceutical, medical, aerospace, petrochemical, oil, and gas, food and dairy all rely on sealants that must perform in low-temperature environments. When a seal reaches its low-temperature limit it will harden, become stiffer, begins to lose its elastic properties and flexibility, and crack. As the temperature lowers, at some point it will undergo a glass transition phase and become glassy and brittle. If a state of glass transition occurs, though some elasticity may be present, the seal will no longer function. Once a leak path has formed in a seal, even after temperatures return to “normal,” the leak path will remain.
High-temperature applications for seals, such as in engines, also require the right material to prevent leakage and failure. Environmental conditions or excessive and extreme heat will gradually degrade elastomeric materials and the performance level will deteriorate. The fact is an elastomer ability to resist thermal degradation plays a significant role in its ability to function effectively as a seal over time. To ensure thermal stability, the material selected for a high-temperature sealant application should be tested through heat aging.
Obviously, design engineers are well aware that temperature fluctuations can alter the mechanical properties of elastomers. In today’s market, elastomers are tested to meet temperature performance requirements. Gaskets, o-rings, and other seals are designed for specific work environments. However, it is the consumer’s responsibility to know or be aware that not just “any” elastomeric material will suffice as a sealant. To avoid complications and leakage in sealing applications, and that your rubber seal will perform at its fullest potential, consult with your vendor and let them guide you through the process.