A method for modeling polymer viscoelastic data and the temperature shift function

Dynamic viscoelastic polymer data is traditionally time-temperature shifted to obtain a temperature shift function (TSF) and then fitted to various analytical models. The process of obtaining the TSF can introduce considerable procedural or operator bias. Nevertheless the Havriliak and Negami (HN) model using the TSF methodology can generally describe polymers that are rheologically simple. In this paper the “wicket” plot is utilized as an important tool in analyzing data, as it is completely independent of time-temperature shifting (TTS). Using the wicket plot the data is fit to the HN equation to determine the four material HN constants independent of TTS. Having obtained the complete spectra of dynamic properties the specific relaxation time (frequency) at each temperature is obtained by matching the HN curve to the experimental data at that temperature thus determining the TSF. The procedure is illustrated by analyzing computer-generated data with random error in modulus and loss and finally real data...