Analysis of X-ray diffraction data from polymers by profile fitting

The profile fitting procedure using the Pearson VII function was used to resolve the X-ray diffraction peaks from polymers. A non-linear least-squares technique based on the Gauss-Newton method was employed to fit the data with several peaks. It was thus possible to resolve overlapping crystal peaks and to attribute the remaining diffraction to an amorphous component. Polyethylene terephthalate, polyethylene and nylon 6 fibres were used to demonstrate the technique. An analysis of the crystallization of nylon 6 molecules was used to show the relationship between processing and structure. The effect of morphology on the diffusion of dye in nylon 6 is also discussed.