Determination of lamella thickness distributions in isotactic polypropylene by X-ray line profile analysis

X-ray line profile analysis was used to determine the size distribution of the crystalline lamellae in isotactic polypropylene (iPP) assuming a log-normal size distribution. A comparison with the size distribution as determined by differential scanning calorimetry (DSC) yields an excellent agreement of both methods. It is noted that the agreement depends strongly on whether linear lattice defects, particularly dislocations are taken into account in the X-ray analysis. This is especially true for deformed iPP with a high number of deformation induced dislocations. It was also found that for a multimodal distribution of lamella thickness in the DSC experiment as induced by the introduction of titanium dioxide nanoparticles as filler material the lamella thickness distribution from X-ray profile analysis is still in good agreement with DSC although the model used was only monomodal.