Effect of High-Shear Mixing on Alignment of Carbon Nanofiber/Epoxy Nanocomposites

Abstract

Abstract

One of the major technological issues limiting widespread use of epoxy polymer nanocomposites containing carbon nanofibers is processability, where the dispersion or alignment of the nanofibers is crucial to performance of the composite. Poor dispersion of the nanofibers can lead to deterioration in properties, while aligning them affords the opportunity to maximize properties in a given direction. The authors have recently investigated the effect of high-shear mixing as a potential method for dispersing and aligning carbon nanofibers in an epoxy resin matrix. Carbon nanofiber/epoxy polymer nanocomposites were produced by dispersing surface-modified and unmodified carbon nanofibers into the epoxy resin using two shearing techniques (mechanical mixing and high-shear mixing). The viscoelastic behavior of the resulting composites was investigated using a dynamic mechanical analyzer. The dimensional stability of the carbon nanofiber/epoxy polymer nanocomposites was determined using a thermomechanical analyzer. An improvement in the dimensional stability, as denoted by decreases in coefficients of thermal expansion, was observed for the 1.0 and 0.1% modified high-shear specimens. In addition, the coefficients of thermal expansion exhibited a directional dependence, with lower values exhibited in the direction of the carbon nanofiber alignment. The 1.0% high-shear specimen exhibited a noticeable T_g enhancement.

Keywords: Nanofibers, nanocomposites, alignment, shear