Structural recovery nonexponential

The decrease in volume during physical aging is specifically known as volume recovery or volume relaxation. Volume recovery experiments include down-jump, up-jump, and memory experiments. The results of these experiments, which are shown and discussed later, demonstrate that structural recovery is both nonlinear, nonexponential and path-dependent. 

Models of structural recovery include the Kovacs-Aklonis-Hutchinson-Ramos (KAHR) model (119), Moynihan s model (120), and Ngai s coupling model (121). These models are based on work done originally by Narayanaswamy (122), incorporating the ideas of Tool (13). The models of stnictiual recovery reflect the nonlinear and nonexponential effects observed experimentally. The historical development of these equations has been detailed (7,8) only a brief description follows. The KAHR formulation (119), which is written in terms of a departure from equilibrium S rather than in terms of Tf, is conceptually easier to use when the full three-dimensional PVT surface is considered ... 

The nonexponentiality of the structural recovery process is described by the nonexponentiality parameter in equation (15) the history dependence is accounted for by the integral of the reduced time (dt/r) and the nonlinearity is incorporated into the model by allowing the characteristic relaxation time r... 

The nonexponentiality of the structural recovery process is described by the nonexponentiality parameter p in equation (15) the history dependence is... 

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