The application of certain memory functions to the description of linear viscoelasticity of solid polymers

The work presents the applicability of the exponential-type functions to the description of linear viscoelasticity in polymers. These functions can be treated as memory functions and are applied to the constitutive equations which consist of the Volterra integrals. The equations are included in the theory of viscoelasticity which is mathematically coherent. This enables the evaluation of all functions neccesary to describe a viscoelastic body such as spectra, components of complex modulus and compliance, etc. A new memory function competitive to the ones previously used is introduced in this work.

The suggested description is verified with the help of complex rheological tests. The numerical values of the parameters in the constitutive equations are calculated based on a simple creep test. To verify, these values, another type of rheological test is applied and the obtained, experimental curves are compared with numerical simulation based on the formerly calculated parameters.

Apart from the purely phenomenological verification, a comparison is made between the molecular weight distribution curves and the curves calculated from the newly introduced memory function. A good convergence of the curves which simulate the rheological processes as well as the spectral curves with the experimental results confirms the proper structure of the function.