Crystalline structures of poly(ethylene terephthalate) fibers

A graphic multiple peak resolution method by wide angle X‐ray scattering (WAXS) pattern was described and used to estimate the interplanar spacings, crystallinities, and crystalline sizes of eight poly(ethylene terephthalate) (PET) fibers. The values for interplanar spacings of Dacron 54 suggested that the unit cell model by Daubeny et al. was appropriate for Dacron fibers. In general, crystallinities of the eight PET fibers ranged from 44.7% for Dacron 54 to 62% for Dacron 56 with the copolymers in between. Crystallinity by density measurements was determined and compared to that by WAXS in both fabric and ground fiber forms. Crystallinity values for each fiber derived by these three methods were different. For each fiber, crystallinity was lowest by WAXS in the ground fiber form, followed by the density measurement and WAXS in the fabric form.