Rate Theory and Polyethylene Relaxations

Polyethylene relaxation results are shown to be described very well by the rate theory associated with the name of Eyring. In agreement with this theory the oa, B, and ϒ relaxations have constant AH and AS values as long as the results are plotted properly, i. e. as log(ω/T) vs 1/T. Since AS values are far from being negligible this means that the energy parameter typical of a given relaxation is the Gibbs free energy change ΔG. It is shown that the ΔG values of the α relaxation are linearly related with crystallinity and not with crystallite thickness. In agreement with our theoretical model, the activation enthalpy and entropy of each relaxation are linearly related - the compensation law. It is concluded that important information on polymer relaxations can be gained from the ΔS-ΔH plots.