R. Chaos-Morán

The mechanical response of epoxy resins filled without treated carbon nanofibers and carboxylated ones has been evaluated through tensile tests. The elastic properties did not improve compared to the neat epoxy resin regardless of filler content or functionalization treatment, while the tensile strength and the elongation at break were reduced for the highest filler content (1 wt%). Fractographic analysis showed that composites reinforced with carboxylated nanofibers showed better filler dispersion than those without treatment. However, in both cases, the fibers tended to agglomerate and the formation of porosity was favored. The size of bundles of nanofibers rose with the content of nanofiller and for the same addition of carbon nanofibers, the size and distribution was respectively bigger and wider for the untreated carbon nanofibers‐reinforced composites than for the carboxylated carbon nanofiber‐reinforced composites. These defects degraded the mechanical response. The dilute suspension of clusters model was applied to estimate the elastic properties, showing agreement with the experimental results. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

A functionalization technique for carbon nanofibers (CNFs) via acid is described. The integrity and chemical nature of the CNFs during the different stages of the applied treatment (oxidation, activation, and functionalization) were examined using different microscopic, chemical, and thermal analysis techniques. The treatment effect on the dispersion ability of the nanofibers in different solvents (tetrahydrofuran, chloroform, and acetone) was also evaluated. Results show that chloroform is the best medium to reach good dispersions and stability of the CNFs in a wide range of concentrations. Using this medium, the functionalization process using 4,4′-diaminodiphenylmethane (DDM) was adopted for the fabrication of reactive CNFs with linker molecules on their surface capable of binding covalently to thermosetting polymers, such as epoxy. The DDM surface derivatized CNFs have been used as reinforcement in epoxy matrix nanocomposites with improved thermomechanical properties in relation to non-treated carbon nanofibers.