Meaning
Time-dependent deformation of polymer-based materials under a constant applied stress measures the material’s capacity to yield and flow over extended periods. This property, known as viscoelastic compliance, defines the ratio of time-dependent strain to the applied stress under static load conditions. The measurement governs the selection of structural adhesives and sealants in building construction and automotive assembly.
Material Behavior
Continuous exposure to mechanical stress causes the internal polymer chains to slide past each other, resulting in permanent deformation. Under conditions of high viscoelastic compliance, the material deforms significantly over time, even if the applied stress is well below its short-term yield strength. This behavior is highly sensitive to temperature changes, with higher temperatures accelerating the rate of deformation.
Engineers must select sealants with low compliance to prevent joint failures in structural applications.
Technical Validation
Laboratory testing of polymer materials involves applying a constant load and measuring the resulting strain over several days or weeks. To determine the viscoelastic compliance, technicians use precision creep testing equipment under controlled temperature and humidity conditions. This testing produces compliance curves that show how the material will behave over its expected service life.
These curves are used to verify that the sealant meets the performance requirements specified in industry standards.
Warranty Clause
Commercial supply agreements for industrial adhesives include specific performance warranties that are based on the material’s long-term behavior. The supplier must guarantee that the viscoelastic compliance of the adhesive will not exceed a specified limit under normal operating conditions. If the material deforms excessively and causes a structural failure within the warranty period, the supplier is liable for the cost of replacement and any associated damages.
To protect themselves, suppliers include clauses that limit their liability if the adhesive is subjected to loads or temperatures that exceed the specified design limits. This ensures that the risk is shared appropriately between the material supplier and the construction contractor.
