Dry-jet wet-spun polyacrylonitrile (PAN) and PAN/carbon nanotubes (CNTs) precursor fibers coated by spin finishes were characterized using the solid-state H-1 nuclear magnetic resonance technique. Series of fiber samples were prepared upon thermal treatment at different temperatures (room temperature to 180 degrees C). Using the Hahn echo sequence, relatively mobile components were identified and the effect of the heat treatment on those components was studied. It was observed that the mobile components are mainly the spin finishes. Heat treatment caused loss of one of the spin finishes (Type B) to a great extent (similar to 80%), whereas the other two spin finishes (Type A and Type C) were more stable. Additional information regarding the change in molecular mobility due to heat treatment was obtained by the spin-lattice relaxation time (T-1) analysis. It was found that the presence of CNT affects the T-1 relaxation time of the polymer in the composite fiber, however, that of relatively mobile components remains unaffected. (C) 2014 Wiley Periodicals, Inc
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