Effect of filler functionalization on thermo-mechanical properties of polyamide-12/carbon nanofibers composites: a study of filler-matrix molecular interactions

The effect of carbon nanofiber (CNF) functionalization on the thermo-mechanical properties of polyamide-12/CNF nanocomposites was investigated. Three main different surface treatments were performed to obtain CNF-OH (OH rich), CNF-Silane (C6H5Si-O-), and CNF-peroxide. CNF modified with poly-(tert-butyl acrylate) chains grown from the surface via ATRP (atom transfer radical polymerization) were also prepared and tested. The modified CNFs and neat CNFs were used as fillers in polyamide-12 nanocomposites and the properties of the ensuing materials were characterized and compared. Universal tensile tests demonstrated a substantial increase (up to 20 %) of the yield strength, without reduction of the final elongation, for all functionalized samples tested within 1 wt% filler content. Further evidences of mechanical properties improvement were given by dynamic mechanical thermal analyses. CNFs functionalized with poly-(tert-butyl acrylate) and silane exhibited the best performance with stiffening and strengthening at low (a parts per thousand currency sign1 wt%) filler loadings, via a partial decrease of the intensity of beta-transitions attributed to favorable interactions between the functional groups on the surface of functionalized CNFs and polyamide-12. CNFs treated with peroxide proved to be the most simple preparation technique and the ensuing nanocomposites exhibited the highest storage modulus at high (5 wt%) filler content. Theoretical simulations using the micro-mechanics model were used to predict the Young modulus of the composites and compare them with experimental data. The results obtained suggest a synergistic effect between the matrix and the filler enhanced by surface functionalization

In situ small angle X-ray scattering investigation of the thermal expansion and related structural information of carbon nanotube composites

In-situ thermal expansion tests on a series of carbon nanotube bucky-paper composites were performed with direct heating within a synchrotron SAXS source. The impact of the samples density and morphology as well as the chemistry and degree of decoration of the carbon nanotubes on the scattering patterns were investigated and correlated to the materials macro-properties. The results demonstrate that simple densification techniques, such as acetone dipping or gold electroless deposition, could reduce greatly the displacements of the carbon nanotubes within the structure and lead to more thermally stable materia