On interconversion of various material functions of PMMA

The interconversion between various linear viscoelastic functions for Poly (methyl) methacrylate (PMMA) is explored. With the availability of four tim e or frequency-dependent material functions (shear, bulk, uniaxial and Pois son) on the same material, various material functions are computed using th e correspondence principle of the linearized theory of viscoelasticity thro ugh the use of standard relations. Computed material functions are evaluate d against the directly measured properties and the limitations imposed on s uccessful interconversion due to the experimental errors in the underlying physical data are explored. It is observed that the differences between the computed and measured functions were larger than suggested by experimental error. The results intimates the need to thoroughly re-examine the applica bility of time-temperature superposition principle often employed to develo p 'master curves' for viscoelastic functions, especially with respect to th e glassy domain.