Meaning
Ratio of the reversible strain to the applied stress provides a quantitative measure of the elasticity of a polymer melt. Recoverable compliance is particularly sensitive to the high molecular weight tail and long chain branching of a resin. Unlike viscosity, which describes the energy lost as heat, this value describes the energy that the material can use to return to its original shape.
Creep Response
Measuring the strain after a constant stress is removed allows for the calculation of the elastic portion of the deformation. In a creep test, the recoverable compliance is the value reached once the material has finished its time-dependent return.
Structural Sensitivity
Small changes in the architecture of the polymer chains lead to large shifts in this rheological parameter. Because recoverable compliance is more sensitive to long chain branching than the storage modulus, it is an excellent tool for characterizing metallocene-based polyolefins. It helps engineers identify differences between materials that appear identical in standard viscosity tests.
Processing Guide
Moulders use this information to predict the behavior of the melt in processes where elastic recovery is a dominant factor. High values of recoverable compliance correlate with increased die swell and better parison stability in blow molding. By monitoring this property, a facility can avoid the surface defects and dimensional instability associated with excessive melt elasticity.
