Grafting of bentonite with a functional silane via different reaction strategies

OLLIER, ROMINA; D'AMICO DAVID ALBERTO; A. VÁZQUEZ; CYRAS VIVIANA; ALVAREZ VERA

Rio de Janeiro

Conferencia; XV International Clay Conference; 2013

Bentonites are important due to their chemical and physical properties; this type of clay is characterized by a moderate cation exchange capacity, CEC, which is a measure of the quantity of the exchangeable cations neutralizing the negative charge of the clay (usually expressed in meq/100 g). In addition, there are several mines of bentonite in Argentina, mainly in San Juan (Allo and Murray, 2004), Mendoza and Neuquén but it is not utilized in the industry in an efficient way. There are different methods of increasing the matrix/clay compatibility. The most popular one is based in the conversion of these hydrophilic layered silicates in organophilic ones via an ionic exchange reaction (Xi et al., 2004). The activation of clay minerals includes a wide range of chemical treatments (Pinnavia, 1983), the acid activation of smectites or bentonites are used before cation exchange reactions. The treatment with mineral acid is also known to impart surface acidity of the clay, which improves its catalytic properties. Newly, the possibility of grafting some silane molecules on the surface of the clay mineral layers has been studied (Park et al., 2004). The main objective of the present work was to study the effect of chemical modifications (cation exchange, grafting and activation) of bentonite (Bent) in order to improve the compatibility with polymeric matrices for the future development of nanocomposites with optimized final properties for several applications. The clay employed in this work was a bentonite supplied by Minarmco S.A. (Neuquén, Argentina). The organic modifiers were dimethyloctadecylchlorosilane (DMOCS) and tributylhexadecylphosphonium bromide (TBHP). One single step and multi-step modifications were performed: cation exchange (E), activation (A) and grafting (G) and the effect of each treatment was analyzed. All modified bentonites were characterized by means of X-rays diffraction analysis (XRD), Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) and water absorption tests. This work was performed under the project FSNano004: “Development of modified nanoclays and innovative products from national clays”.