Synthesis and Morphological Characterization of Sodium and Calcium Clay Nanostructured Poly(η-Caprolactam) [Nylon 6] Hybrids

Abstract

The synthesis and morphological characterization of Nylon 6 hybrids using the most common montmorillonite types, sodium and calcium, are reported. Two local nanoclays and a commercial, cation exchanged, reference were used in order to obtain the hybrid products. The local sodium and calcium nanoclays were first homoionized and then ion ex- changed with surfactants, being the main purpose to obtain similar reaction precursors as the commercial clay. Both local clay precursors and commercial clay showed similar crystallographic structure and layer-to-layer spacing after all phys- icochemical treatments. The best reaction conditions were first determined and then a simple infra-red based technique was implemented with the purpose to obtain the molecular weight of the hybrid products. It was determined that, sodium, calcium, and commercial nanoclays render relatively similar molecular weights of nanoclay hybrids using identical syn- thesis conditions. Thermal analyses indicated the formation of two and three melting endotherms in all cases depending on the isothermal crystallization temperature. X-ray diffraction patterns displayed crystal plane truncation which is usually observed in nanoclay hybrids. Plane truncation depended on the nanoclays nature, although the highest truncation was ob- served with commercial and sodium nanoclays. X-rays dispersion results allowed to infer the partial formation of non- hybrid polymer depending on the type of clay, sodium nanoclay showing the lesser proportion, and as a consequence the highest hybridization. Transmission electron microscopy results corroborated the relative degree of exfoliation and nano- clay dispersion of the hybrid products.