Abstract: Based on polyethylene terephthalate (PET) and cationic dyeable polyester (CDP), one-step PET/CDP composite FDY was obtained by spinning and drafting integrated system. Sound velocity method and different scanning calorimetry (DSC) were used to investigate the properties of the yarns. The experimental results showed that when the speed of GR1 increased, the crystallinity, the breaking strength, the sound velocity oriental factor and modulus decreased, while the breaking elongation of the fibers obviously increased on the same conditions, and the boiling water shrinkage of the fibers increased slightly. According to the difference of the properties between PET and CDP, the process optimization for the spinning and drafting preferably meet the need of the CDP, and PET was also considered at the same time.

Key words: one-step method, PET/ CDP, oriention factor, crystallinity, dyeing property