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

Abstract

Kinetics of polystyrene (PS) around the glass transition are revisited using relaxation model upon two fictive temperature approach by assuming different contributions of the component to average fictive temperature representing different properties of entropy (or volume) and enthalpy. The different contributions are described using Kohlrausch distribution functions with different 𝜷. The fitting quality improves significantly for both normalized heat capacity and limit fictive temperature data of PS obtained after being cooled at different rates when the kinetic model upon two fictive temperature approach is used, no matter the relaxation time is calculated using the Adam-Gibbs-Vogel (AGV) model or free-volume (FV) equation. This result indicates that the relaxation kinetic of polymer around the glass transition can be described more accurately by using models upon two fictive temperature approach instead of the conventional models upon one fictive temperature approach.

Viscosity and heat capacity of As2Se3 connected via Adam–Gibbs model

“…This model and its modifications have been mainly used to describe structural relaxation processes and to solve changes related to this important feature observed in amorphous materials. Over the decades, many researchers have approved 17–23 but also disproved 24,25 the AG model and its application. There are many interesting papers discussing the applicability of the AG model for different systems, from room‐temperature ionic liquids to evolving magmas 25–32 .…”