CONICET | Buscador de Institutos y Recursos Humanos

Unsaturated polyester (UP) composites have been widely used in industrial applications such as marine, automotive and building industries due to its low cost, high chemical resistance and good processability (Xu and Lee, 2004). UP is an economical thermoset material that is widely used due to its excellent process ability and good crooslinking tendency as well as mechanical properties when cured (Mortaigne et al., 1999). In the last years, a new strategy has been developed for increasing the performance UP resins: the incorporation of nano-reinforcements such as clays. Clay particles, which are about 1 nanometer thick, have a perfect crystalline structure and have been successfully used in thermosetting polymer matrices for improving mechanical properties (Liu et al, 2005), reducing water absorption (Abu-Jdayil y col, 2002) and improving other properties like thermal conductivity and chemical stability (Liu y col, 2008). But one of the main problems that arise when adding nanoclays to polymers is the dispersion of the particles. A totally exfoliated structure (this means that the silicate layers are completely and uniformly dispersed in a continuous polymeric matrix) is necessary to maximize the mechanical properties, but the tendency of the particles to agglomerate is, in general, difficult to overcome. Therefore, it is necessary to make a previous treatment to the clay or to the polymer so as to make them more compatible. One of the most reliable methods for increasing compatibility consists in converting the hydrophilic silicates into organophilic ones. The hydratated cations that are in the galleries are replaced by positively charged surfactants like alkyl or hydroxyl ammonium cations. Which are the most convenient chemical modifications for the different thermosetting polymers is a question that has not been solved yet in the literature. In this work, dynamic-mechanical properties of UP/bentonite nanocomposites are studied in order to evaluate the effect of different chemical modifications of bentonites on the final performance of these materials.