Layer structure formation in oriented poly(ethylene terephthalate) relating to micromechanical properties

Glassy poly(ethylene terephthalate), uniaxially drawn at 25 °C (cold drawing) and at 90 °C (hot drawing), was crystallized in a taut state without shrinkage at 100 °C, 150 °C, 200 °C and 250 °C. The nanostructure and the mechanical properties were surveyed by X-ray diffraction and microhardness. Small-angle X-ray diffraction diagrams reveal typical 4-point patterns characteristic of the cold-drawn samples, whereas 2-point patterns are observed for the hot-drawn ones. Comparison of the molecular and the nanolayer inclinations in both drawings suggests that a mutual supplementary relationship holds between the c-axis tilting and the lamellar inclination. The layer structure formation is discussed in the light of these results. In addition, a correlation between the nanostructure formation and the micromechanical properties is offered, highlighting the differences found between the hot- and the cold-drawn materials.