Melt-electrospinning of poly(ether ether ketone) fibers to avoid sulfonation

We have successfully electrospun un-sulfonated fibers of poly(ether ether ketone), PEEK, from the molten state at 350 °C. Unlike solution electrospinning of PEEK, which produces sulfonated fibers with reduced thermal stability, melt electrospinning produces chemically unaltered PEEK fibers. These fibers are smooth, defect-free, and round in cross-section. Most fiber diameters range from 1.5 μm to 8.5 μm. A large interstitial fiber with diameter reaching up to 100 μm is occasionally deposited at the end of the spin. As-spun oriented amorphous fibers, having diameters less than 10 μm, were selected for fast scanning calorimetric studies of the glass transition and melting behavior. Dynamic fragilities of melt electrospun oriented amorphous PEEK fibers and amorphous PEEK quenched from the molten state, were evaluated according to Moynihan's method of cooling at variable rates then reheating at a fixed rate and were found to be 200 ± 5 and 150 ± 5, respectively. These results suggest that orientation in the amorphous state of electrospun fibers plays a role in the dynamics of glass formation.