Creep, often referred to as "viscous flow" or "permanent deformation over time," is the tendency of a material to progressively deform when subjected to a constant load over a prolonged period.
It is not a sudden failure, but a slow and continuous phenomenon: the material, while apparently intact, changes its geometry under stress.
In the case of a Tri-Clamp gasket, this means that, after initial tightening, the gasket over time:
is further compressed under the applied load
gradually loses thickness
reduces the contact pressure between the mating surfaces
The system does not "fail," but the compressive force gradually relaxes.
The practical result is clear: a decrease in sealing force, possible micro-leakage, the need for periodic retightening or, in the most critical cases, gasket replacement.
In PTFE, creep is an intrinsic behavior.
It is a viscoelastic material: it combines an immediate elastic response with a viscous component that develops over time under load. This is well known to those who work with fluoropolymeric materials.
For this reason, modified and structured PTFE formulations are used, with an internal matrix designed to improve dimensional stability and increase resistance to long-term deformation. The goal is to reduce stress relaxation and maintain a more constant contact pressure.
Sichem Seal is designed and manufactured specifically to reduce this phenomenon and ensure a more stable seal over time.
Sichem Seal is a Carrara product.