Revising the formulization of the Narayanaswamy equation using the Adam-Gibbs theory

Abstract

Hodge's formulization of the Tool-Narayanaswamy-Moynihan (TNM) equation from the Adam-Gibbs (AG) theory was re-evaluated. The non-linearity parameter (x) and the apparent activation energy (∆h*) of the TMN equation were re-derived. Compared with the original derivations, the revised values of x and ∆h* were better correlated with experimental results. Of particular importance, the revised theoretical x correctly predicts the experimental trend of x for the cooling rate of polystyrene, whereas the original derivation predicted an opposite trend. Furthermore, the new derivation establishes a strong relationship between the fragility coefficient (m) and the x of a material. The relationship correlates well with the experimental values for a wide range of

Pressure densification of a simple liquid

“…A factor controlling the non-equilibrium structure is the condition of the liquid upon vitrification. For example, variation of the rate of cooling through Tg can be used to produce glasses with varying departures from equilibrium, and thus varying stability [7,8,9,10]. Another method, employed herein, is the application of pressure to the supercooled liquid.…”

Modeling the Enthalpy Relaxation Kinetics of Glassy Polystyrene Using Different Fictive Temperatures for Different Properties

“…The methods are routinely used by most researchers of polymers and molecular liquids. [20][21][22][23][24] However, the experimental results could not be described properly using one set of model parameters and thermal history dependence of the model parameters was found when different sets of model parameters were used for heat capacity data of sample after different thermal treatments. Even Moynihan himself had pointed out the problems of the TNM model analysis.…”