Non-equilibrium features of glassy polymers and physical ageing

3 NON-EQUILIBRIUM FEATURES OF GLASSY POLYMERS AND PHYSICAL AGEING 

The glass transition obeys second-order characteristics, i.e. volume and enthalpy are continuous functions through the transition temperature. However, their temperature derivatives, the thermal expansion coefficient and the specific heat, change in a discontinuous manner at the glass temperature. 

The experiment illustrated in Fig. 5.13 and conducted by many researchers shows the non- 

The term recovery is often used instead of relaxation to indicate that the process leads to the establishment (recovery) of equilibrium. We may replace specific volume by enthalpy and obtain a curve similar to that shown in Fig. 5.13. The curvature on 

The volume recovery curves of amorphous atactic polystyrene previously equilibrated at different temperatures above and below a new equilibration temperature (95.46 C) are shown in Fig. 5.15. The initially excessive and deficient volume states approach the same equilibrium volume in a nonlinear way. Also worthy of note is the asymmetrical character of the expansion and contraction curves, which is further demonstrated in Fig. 5.16. The contracting specimen is always closer to the equilibrium than the expanding specimen. The 

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Non-equilibrium features of glassy polymers and physical ageing S3... 

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