Flow and thermal characteristics of cationic dyeable nylon 6/cationic dyeable poly(ethylene terephthalate) polyblended polymers and filaments

Cationic dyeable nylon 6 (CD‐N6) and cationic dyeable poly(ethylene terephthalate) (CD‐PET) polymers were extruded (in the proportions of 75/25, 50/50, 25/75) from one melt twin‐screw extruders to prepare three CD‐N6/CD‐PET polyblended polymers and then spin filaments. The molar ratio of 5‐sodium sulfonate dimethyl isophthalate (5‐SSDMI) for CD‐N6 and CD‐PET polymers were 2.01% and 2.04%, respectively. This study investigated the flow and thermal characteristics of CD‐N6/CD‐PET polyblended polymers and filaments using gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), potentiometer, a rheometer, the density gradient, wide‐angle X‐ray diffraction (WAXD), and extension stress–strain measurement. Flow behavior of CD‐N6/CD‐PET polyblended polymers exhibited negative‐deviation blends (NDB), and the 50/50 blend of CD‐N6/CD‐PET showed a minimum value of the melt viscosity. Experimental results of the DSC indicated CD‐N6 and CD‐PET molecules formed an immiscible system. Particularly, a double endothermic peak was observed from CD‐N6, CD‐PET and their polyblended filaments. The tenacity of CD‐N6/CD‐PET polyblended filaments decreased initially and then increased as the CD‐PET content increased. Crystallinities and densities of CD‐N6/CD‐PET polyblended filaments were the linear relation with the blend ratio. The miscibility parameter μ values of CD‐N6/CD‐PET all samples were less than zero. It indicated the electrostatic repulsion was evident between CD‐N6 and CD‐PET molecules. From the experimental data, the CD‐N6 and CD‐PET polymers were identified to be immiscible. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2049–2056, 2007