Study of the morphology of semicrystalline poly(ethylene terephthalate) by hydrolysis etching

Semicrystalline poly(ethylene terephthalate) was hydrolysed in water at 180°C under elevated pressure and subsequently treated with ethanol, following the etching process first developed by Miyagi and Wunderlich. The weight loss, the wide-angle X-ray scattering and the molecular weight were measured as a function of etching time. It was found that even at the end of the etching process not all the amorphous material could be removed by the hydrolysis treatment. By comparing the obtained results with those derived from an elaborate small-angle X-ray scattering study and with wide-angle X-ray scattering measurements, it was concluded that only those amorphous regions lying outside of the lamellar stacks were removed. Subsequently, the lamellar stacks themselves were attacked. It was also found that at the very beginning of the hydrolysis process additional crystals were formed in the material.