Crystalline behaviors and phase transition during the manufacture of fine denier PA6 fibers

Recently we have successfully produced fine denier PA6 fibers by using additives containing lanthanide compounds. Meanwhile, crystallization and phase transition of PA6 fibers during spinning and drawing processes were investigated. During the spinning process, β phase crystal could be obtained in as-spun PA6 fibers which were produced with relatively high melt draw ratio, while γ phase crystal predominated when the melt draw ratio was relatively low. β phase crystal, whose behaviors are similar with those of γ phase by FT-IR and XRD characterization, could be transformed to α form easily when PA6 fibers are immersed in boiling water. However, γ phase crystal of PA6 remains unchanged in boiling water. Thus, β and γ phase crystals of PA6 can be differentiated by the crystalline behaviors of PA6 fibers after treatment in boiling water. Further experiments demonstrate that the β phase can also be produced during a drawing process where a phase transformation from γ to α occurs. In other words, β phase may act as an intermediate state during the phase transformation.