Relationship between Draw Ratio and Strain-Induced Crystallinity in Uniaxially Hot-Drawn PET MXD6 Films

The evolutions of the strain-induced crystalline phase of poly(ethylene terephthalate) (PET), poly(m-xylene adipamide) (MXD6), and PET–MXD6–ionomer blend films are investigated by differential scanning calorimetry, X-ray diffraction, and birefringence measurements. Initially wholly amorphous, the films are uniaxially hot-drawn above the glass transition temperature T g . During drawing and depending on the draw ratio, an induced crystalline phase appears in the three materials. The comparison of the degree of crystallinity shows that the maximum degree of crystallinity is close to 40% for the three materials and the DSC analysis shows a similar thermal behavior between PET, MXD6, and blend samples. The critical draw ratios for the crystalline phase appearance are equal to 2, 3, and 3 for PET, MXD6, and blend, respectively.