Thermal properties and mechanical characteristics of cationic dyeable poly(trimethylene terephthalate)/metallocene isotactic polypropylene conjugated filaments

Cationic dyeable poly(trimethylene terephthalate) (CD-PTT) and metallocene isotactic polypropylene (m-iPP) polymers were extruded (in proportions of 75/25, 50/50, and 25/75) from two melt twin-screw extruders to prepare three CD-PTT/m-iPP conjugated filaments of the island–sea type. This study investigated the thermal properties and mechanical characteristics of the CD-PTT/m-iPP conjugated filaments with gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, potentiometry, rheometry, density gradients, wide-angle X-ray diffraction, extension stress–strain measurements, and scanning electron microscopy. The rheological behavior of the CD-PTT/m-iPP polyblended polymers exhibited negative-deviation blends, and the 50/50 CD-PTT/m-iPP blend showed a minimum value of the melt viscosity. The experimental results from differential scanning calorimetry indicated that CD-PTT and m-iPP molecules formed an immiscible system. The tenacity of the CD-PTT/m-iPP conjugated filaments decreased initially and then increased as the m-iPP content increased. Morphological observations revealed that the blends were in a dispersed phase structure. A pore/filament morphology of a larger size (0.5–3 μm in diameter) was observed after a 1,1,1,3,3,3-hexafluoro-2-propanol (CD-PTT was removed)/decalin (m-iPP was removed) treatment in the cross section of a CD-PTT/m-iPP conjugated filament. The CD-PTT and m-iPP polymers were identified as an immiscible system. Blends with 10 wt % compatibilizer exhibited the maximum improvement in the tenacity. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2387–2394, 2007