Research has moved towards the developments of materials with lower environmental impact both being biodegradable and/or deriving from renewable resources or having lower energic costs of production. Among the so-called “biopolymers”, Nylon 11 (Ny11), a bio-polyamide derived from castor oil, is very interesting for engineering applications. On the other side, nanocomposite materials are very studied: multi-wall Carbon NanoTubes (MWCNT) have been widely used as a reinforcement in engineering materials, due to the increase in mechanical properties given to the polymeric substrate. Their cost is highly influenced by the purification step, therefore making these materials cost-competitive deeply relies on its control and minimization. Our research was therefore focused on the study of thermal and rheological behaviour of Ny11-MWCNT nanocomposites obtained via “in situ” polymerization of aminoundecanoic acid, compared to the one of Nylon 6-MWCNT (Ny6) nanocomposites.
Synthesis were performed in bulk using both raw and purified MWCNT. Results showed that reinforcement with CNT generates a steep increase both in thermal and rheological properties. Comparison between Ny11 and Ny6 showed that, while Ny11 melt viscosity increases when purified CNT are used, in Ny6 the result is opposite. Studies indicate that in Ny11 melt viscosity increase given by purified CNT is due to partial surface oxidation of the nanotube in the purification process, generating acid groups reacting with the monomer in bulk polymerization. Ny6 behaves oppositely because, having a shorter repeating unit, the compatibility with the CNT is significantly lower, generating bundles when increasing nanotube purity.
