Micro‐voids that evolve during mechanical deformation in polypropylene have been characterized by small‐angle X‐ray scattering. Such voids can be modelled as randomly distributed cylinders which are oriented along the stretching direction, showing a log‐normal size distribution. The model and simulation results are presented here. Advantages and disadvantages of the approach, the validity of the model, and important considerations for data evaluation are discussed. Data analysis of two‐dimensional scattering images has been performed using a fully automated MATLAB routine by direct model fitting to scattering images.

We present a method for the evaluation of SAXS data of highly oriented semicrystalline polymers, allowing us to determine up to seven structural parameters from the measurements. The utilized samples were polypropylenes with varied distributions of the molecular weight, which were spun with different take-up velocities to alter the spinline stress, thus influencing the structural properties. We were able to determine the degree of orientation, lamella radius, long spacing, lattice distortion, and lamella height simultaneously. The microscopic orientation was compared with the crystalline orientation evaluated by Herman's orientation function from WAXS.

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