Physical Aging of Amorphous PEN: Isothermal, Isochronal and Isostructural Results
M L. Cerrada, G B. McKenna
The viscoelastic and physical aging responses have been analyzed for an amorphous poly(ethylene naphthalate) (PEN) using uniaxial tension stress relaxation experiments. It is known that PEN exhibits a strong β relaxation that overlaps the α relaxation in the experimental time and temperature ranges studied. In prior work, we had shown that both amorphous and semi-crystalline PEN exhibit thermo-rheologically complex behaviors in that neither time-temperature nor time-aging time superposition apply to the materials. Here we compare results of aging experiments in which the material is aged into an isostructural state, i.e., constant fictive temperature. We find, for samples annealed at 100 degrees C, that the amorphous PEN shows time-temperature superposition behavior for constant fictive temperature. However, when the responses are compared isothermally for different fictive temperatures, as found previously, thermo-rheological simplicity breaks down. Possible reasons for this behavior are discussed.
and McKenna, G.
Physical Aging of Amorphous PEN: Isothermal, Isochronal and Isostructural Results, Macromolecules, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851586
(Accessed June 2, 2023)