A kinetic analysis of the gauche‐trans isomerization in semicrystalline poly(ethylene terephthalate)

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Abstract
A series of kinetic measurements using FT‐IR have been carried out in order to clarify the mechanism of the gauche‐trans isomerization process and the time‐temperature‐transformation relationships in poly(ethylene terephthalate). Two‐stage isomerization isotherms are distinguished on the logarithmic scale of annealing time: a primary transformation stage with an activation energy of 40 kcal/mol characterized by a sigmoidal curve, followed by a linear secondary process. The activation energies of the secondary transformation obey an equation of the Arrhenius type InaT = B(1/T − 1/Tm) where 160 < T < 260°C ≈ Tm and can be used to describe the effects of annealing time and temperature on the isomerization process of PET in the secondary transformation region. On the basis of these analyses, the morphology and microstructure of PET in these temperature regimes of the isomerization process are proposed.