Sub-Tg relaxations and physical ageing in hydrated glassy polysaccharides

Among the different models accounting for the physical ageing and more gene rally for the dynamics of glassy materials, the Quasi Point Defect model, ( Perez, J. 1988, 1993), based on a solid state description, was chosen for t he physical significance of its parameters. It was applied to simulate the effects of enthalpy relaxation on DSC traces of glassy polysaccharides. Die lectric spectroscopy in the domain of sub-Tg relaxations was used to determ ine the characteristic times and activation energies of the beta-relaxation , needed for the simulation procedure. DSC thermograms obtained after agein g at different ageing times and temperatures were both collected and simula ted on glassy polysaccharides at various water contents.