resumo
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.
palavras-chave
WALLED CARBON NANOTUBES; TRANSFER RADICAL POLYMERIZATION; MECHANICAL-PROPERTIES; SURFACE MODIFICATION; CRYSTALLIZATION BEHAVIOR; NANOCOMPOSITES; DISPERSION; FIBERS; OXIDATION; PLASMA
categoria
Materials Science
autores
Ghislandi, M; Prado, LASD; Schulte, K; Barros-Timmons, A
nossos autores
Ana Margarida Madeira Viegas de Barros Timmons
Professor associadoagradecimentos
Marcos Ghislandi acknowledges the European Commission for his Erasmus Mundus Scholarship (via EMMS - Joint European Masters in Materials Science) and CNPq in Brazil. Dr. Jean Carlos Lorenzzi's technical support in the preparation of CNF-Perox samples is appreciated. CICECO acknowledges FCT for Pest-C/CTM/LA0011/2011 project.