Rheological and morphological properties of immiscible blends and microfiber preparation from the blends

One modified poly(ethylene terephthalate) (m-PET) containing 16 mol % of is ophthalic acid content and three kinds of isotactic polypropylene (i-PP) wi th different molecular weights were melt blended in various volume ratios b y a twin screw extruder. The dynamic viscosity of the i-PP/m-PET blend show ed positive deviation at lower volume content of i-PP and negative deviatio n at higher volume content of i-PP. The size of dispersed phase increased w ith an increase of the minor component. Also, the less difference between t he viscosities of two polymers caused the smaller particle size in the blen d and the smaller critical Weber number. After melt spinning of these binar y polymer blends. m-PET and CPP micro staple fiber, whose diameter was abou t 0.13 to 2.75 mum. could be obtained by extracting the continuous phase wi th a proper solvent. The less the minor component in the blend, the better the spinnability of the blended polymers and the physical properties of the fiber. Also, when i-PP was the continuous phase, the spinnability and the physical properties of the fibers were better than the opposite case. Molec ular weight of i-PP and the blend ratio had a marked influence on the diame ter of microfibers. The microfiber obtained from i-PP which has similar vis cosity with m-PET showed the smallest diameter than those obtained from oth er two i-PPs.