Nanomorphology and nanomechanical characteristics of solution-blow-spun PVDF-based fibers filled with carbon nanotubes

Fibers of poly(vinylidene fluoride) (PVDF) filled with multiwalled carbon nanotubes (MWCNTs) were prepared by solution blow spinning (SBS). The influence of the MWCNTs on the surface morphology and mechanical behavior of single fibers was studied. The morphology of the materials prepared and the dispersion of the MWCNTs within the polymer were studied by optical microscopy (OM) and transmission electron microscopy (TEM), while atomic force microscopy (AFM) was used to inspect the topography of single fibers and to perform nanoindentation tests. OM and TEM images indicated a good dispersion of the MWCNTs within the PVDF. AFM images evidenced clear changes in the topography of the blow-spun fibers when the MWCNTs were present in the polymer. A greater amount of MWCNTs in the PVDF led to more heterogeneous fiber surfaces. The nanoindentation force curves revealed that the stiffness was practically constant along the fibers, which indicated that the mechanical response was homogeneous and, in turn, an even distribution of the MWCNTs. The incorporation of the MWCNTs produced a mechanical reinforcement of the PVDF fibers, showing increases of 31% and 49% in the elastic modulus when 1% and 5% by weight of MWCNTs were added to the polymer, respectively.This work was financially supported by the projects MAT2014-59116-C2 (Ministerio de Economía y Competitividad), 2012/00130/004 (Fondos de Investigación de Fco. Javier Gonzalez Benito, Política de Reinversión de Costes Generales, Universidad Carlos III de Madrid), and 2011/00287/002 (Acción Estratégica en Materiales Compuestos Poliméricos e Interfases, Universidad Carlos III de Madrid). TEM characterization was done at LABMET, which is associated with the Red de Laboratorios de la Comunidad de Madrid. Finally, we would like to express appreciation for the technical support given by Carmen Ballesteros and Beatriz Galiana to perform the TEM tests