| Immiscible blend-spinning is an important method for preparing thermoplastic polymer micro-nanofibers. The microfibrillar structure was obtained through the phase separation, and the dispersed phase was stretched into micro-nanofibers after the matrix phase was removed. Polyethylene (PE) fiber is one of the most versatile fibrous materials today. Carbon nanotubes (CNTs) have special structures and excellent properties, which is considered to be the ideal filling agent for polymer materials. In this paper, the CNTs/PE micro-nanofibers were prepared by immiscible blend-spinning and the structure and properties of composite nanofibers were studied.Firstly, CNTs were embedded into PE matrix with content ranging from 0 to 10wt% via melt blending, and then CNTs/PE extrudates were mixed with cellulose acetate butyrate (CAB) through twin screw extruder. The CNTs/PE micro-nanofibers could be prepared after removal of CAB matrix by acetone. The CAB was employed in immiscible blends as resuable and bio-compatible continuous phase. The morphology development of dispersed phase was studied with samples collected at different zones in a twin screw extruder by using the methods of scanning electron microscopy (SEM), dynamic rheology and capillary rheometer. The morphology evolution of the dispersed phase in the extruder can be explained to go through pellets, sheets with holes, small ribbons, thick fibers to micro-nanofibers. The viscosity ratio (ηd/ηm) of blending system is in the range of 1～3, indicating that good fibrillation can be achieved. The addition of CNTs also affected the morphological deformation and the stability of fibers.The morphology and dispersion of CNTs in composites were observed on a field emission scanning electron microscopy (FESEM) and a transmission electron microscopy (TEM). The CNTs were speculated to disperse into PE fibers and adhere to PE fiber yarns, in the forms of single nanotube, nanotube network or aggregates. The average diameters of CNTs/PE nanofibers increased and the surfaces of fibers appear to be comparative coarse, with increasing the amount of CNTs.In order to obtain the better process conditions during the blending procedure, the morphology of final CNTs/PE nanofibers were studied by SEM to research the relationship of the dispersed phase dimensions with blend ratio, shear rate, draw ratio, respectively.Finally, the effects of CNTs on electrical properties, crystallization and thermal properties of the composite nanofibers were discussed. The volume resistivity measurements indicated that the electrical conductivity of CNTs/PE nanofibers was increased by 10 orders of magnitude (from 10-14 to 10-4 ohm-cm) on addition of 12 wt% CNTs, with a percolation threshold of about 4-5wt%. The thermal degradation of samples were measured using a thermal gravimetric analyzer (TGA), indicating that the composite nanofibers had a better thermal stability contrast to neat PE nanofibers. The crystallinity and melting behavior of samples were investigated on a differential scanning calorimeter (DSC), indicating that the addition of CNTs changed the crystalline structure and decreased the degree of crystallinity. The crystalline structures of composite nanofibers were investigated by a wide angle X-ray diffraction (XRD), showing an obvious (020) bragg reflection at about 2θ=26°with the increase of CNTs.
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