Structural studies of binary blend fibers of nylon 6 and nylon 66 by means of WAXD, SAXS, and DSC

Abstract

Measurements of wide-angle X-ray diffraction (WAXD), small-angle X-ray scattering (SAXS), and differential scanning calorimetry (DSC) were performed on binary blend fibers of nylon 6 and nylon 66 prepared by drawing and annealing of melt-spun blend fibers. To detect coexisting crystalline phases of both nylon components, we developed a procedure to distinguish α-form crystals of nylon 6 and nylon 66 in their mixtures by utilizing higher-order diffraction spots of WAXD for the α-form crystals, and applied it to nylon 6/nylon 66 blend fibers over the whole range of composition. Nylons 6 and 66 thus crystallize separately and form individual crystallites of their respective α-form crystal structures. By analyzing data of DSC diagram, the appreciable depression of the total degree of crystallinity of both components observed in the intermediate range of composition for unoriented mixture samples reported previously, is almost recovered for drawn and annealed samples treated in this work. The development of crystalline state in the blend fibers brought about by drawing and annealing was confirmed by changes of profiles of SAXS diagram. This tendency is more prominent in nylon 6 rather than nylon 66. The cause for this is discussed.