The enthalpic relaxation of amorphous poly(aryl ether ketone)s

The development of physical aging in four amorphous poly(aryl ether ketone)s at temperatures below the glass transition temperature, T-g, was studied using differential scanning calorimetry (DSC). The change in enthalpy lost on aging, determined by scanning through T-g, was used to determine the kinetics of the aging process through fitting to the Cowie-Ferguson model. The kinetics of aging were found to depend on the ketone-ether ratio as well as the substitution pattern of the polymers. The maximum enthalpy lost at equilibrium, Delta H-proportional to, was found to be a linear function of the change in heat capacity at T-g, Delta C-p(Tg), and the degree of supercooling, Delta T. A composite curve incorporating T-g values from physical aging and dynamic mechanical studies, covering 15 decades, could be fined to the Volger-Fulcher equation and demonstrated that physical aging is an extension of the glass forming process.