Nonequilibrium aging state

Nonequilibrium Aging State (NEAS). The system is initially prepared in a nonequilibrium state and put in contact with the sources. The system is then allowed to evolve alone but fails to reach thermal equilibrium in observable or laboratory time scales. In this case the system is in a nonstationary slowly relaxing nonequilibrium state called aging state and is characterized by a very small entropy production of the sources. In the aging state two-times correlations decay slower as the system becomes older. Two-time correlation functions depend on both times and not just on their difference. 

The nonequilibrium aging state (NBAS, see Section III.A) is a nonstationary state characterized by slow relaxation and a very low rate of energy dissipation to the surroundings. Aging systems fail to reach equilibrium unless one waits an exceedingly large amount of time. For this reason, the NEAS is very different from either the nonequilibrium transient state (NETS) or the nonequilibrium steady state (NESS). 

The nonequilibrium glassy state, 5(t) = f(t) -f, is determined by solving the kinetic equations which describe the local motion of holes in response to molecular fluctuations during vitrification and physical aging. The solution is (11)... 

In the next sections I briefly discuss some of the theoretical concepts important to understanding the glass state and nonequilibrium aging dynamics. 

The relaxation process that takes place in plastics after fabrication. Upon cooling a melt, the molecular mobility decreases, and when the relaxation time exceeds the experimental time scale, the melt becomes a glass in nonequilibrium thermodynamic state (density, enthalpy, etc.). Thus, the value of the thermodynamic parameters continues to change toward an equilibrium state. The process may lead to development of cracks and crazes that initiate critical failure. See also Aging, Accelerated aging, Artificial aging, and Chemical aging. ... 

Figure 3.1. Schematic illustration of temperature dependences of the specific volumes of amorphous materials. This figure also illustrates the effects of the nonequilibrium nature of glass structure, which results from kinetic factors. Glass 1 and Glass 2 are specimens of the same polymer, but subjected to different thermal histories. For example, Glass 1 may have been quenched from the melt very rapidly, while Glass 2 may either have been cooled slowly or subjected to volumetric relaxation via annealing ( physical aging ) in the glassy state.

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