Amorphous orientation in polymers determined using two-dimensional x-ray diffraction data and its significance

Amorphous orientation in polymers is described in terms of the fraction of the amorphous chain segments which are oriented, and the degree of alignment of the amorphous chain segments. The method for evaluating these two features using two-dimensional x-ray diffraction data is described. Whereas the unoriented amorphous component contributes to an isotropic amorphous halo, the oriented component gives rise to enhanced scattering near the equator. The method is illustrated using the data from PET and nylon 6. The role of amorphous orientation in determining dimensional stability, diffusion behavior and glass transition temperature is discussed.