Evaluation of Crystallinity in Polyethylene Terephthalate Fibre by X-Ray Diffraction

Abstract

<span style="font-size:11.0pt;line-height:115%; font-family:" calibri","sans-serif";mso-ascii-theme-font:minor-latin;mso-fareast-font-family:="" "times="" new="" roman";mso-fareast-theme-font:minor-fareast;mso-hansi-theme-font:="" minor-latin;mso-bidi-font-family:"times="" roman";mso-ansi-language:en-us;="" mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">Five techniques of determining the crystallinity of polyethylene terephthalate (PET) fibres (due to Farrow and Preston, Hermans and Weidinger, Statton, Bosley, and Dumbleton and Bowles), all based on diffraction study, are evaluated. For this purpose, a large number of samples were prepared from commercial PET yarn by heat-setting and texturized under different conditions. These samples had high crystallite orientation, but widely different structures and morphologies. The crystallinity of these samples was computed using the five procedures. It has been concluded that the absolute crystallinity of a particular sample, as determined by these procedures, may show considerable variations, but a comparison of the relative values of crystallinity for samples belonging to a particular set shows broadly similar trend within the set irrespective of the procedure adopted. This observation highlights the caution necessary in interpreting data on crystallinity of textile fibres as determined by the X-ray diffraction method. Another important conclusion is that the procedures which make use of the total scattering curve appear to result in a parameter which is more closely related to crystallinity than those which are based on intensity at one or two points on the intensity curve.</span>