Polyamide 6 (PA 6) 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 PA 6/m-iPP conjugated filaments. This study investigated the physical properties of PA 6/m-iPP conjugated filaments with gel permeation chromatography, differential scanning calorimetry, thermogravimetric analysis, potentiometry, rheometry, density-gradient measurements, wide-angle X-ray diffraction, extension stress-strain measurements, and scanning electron microscopy. The flow behavior of PA 6/m-iPP polyblended polymers exhibited negative-deviation blends, and a 50/50 PA 6/m-iPP blend showed the minimum value of the melt viscosity. The experimental results from differential scanning calorimetry indicated that PA 6 and m-iPP molecules formed an immiscible system. The tenacity of the PA 6/m-iPP conjugated filaments decreased initially and then increased as the m-iPP content increased. The crystallinities and densities of the PA 6/m-iPP conjugated filaments had a linear relationship with the blend ratio. Morphological observations revealed that the blends had a dispersed-phase structure. A pore/fiber morphology of a larger size (from 0.5 to 3 mu m in diameter) was observed after a formic acid (PA 6 was moved)/xylene (m-iPP was moved) treatment on the cross section of a PA 6/m-iPP conjugated filament. PA 6 and m-iPP polymers were proved to be an incompatible system. (c) 2006 Wiley Periodicals, Inc.