Analysis of the lamellar structure of semicrystalline polymers by direct model fitting of SAXS patterns.

Small-angle X-ray scattering data of melt-drawn high-density polyethylene (HDPE) have been analyzed by direct model fitting to projections on the drawing direction. On the basis of the assumption of an infinite paracrystalline lattice as proposed by Hosemann and a rectangular density profile, several additional assumptions have been tested. It turned out that to achieve good fits we have to introduce a finiteness of the lattice for the used samples. Transition zones between crystalline and amorphous regions also improve the model but are of less importance. The most suitable model has been tested on data from an annealing and subsequent cooling process. We show that the additional parameters gained in the modeling approach compared to peak analysis or correlation function analysis lead to a better understanding of the structures and processes in the samples.