CONICET | Buscador de Institutos y Recursos Humanos

Nanocomposites are a new class of composites, for which at least one dimension of the dispersedparticles is in the nanometer range. In the case of polymer-clay nanocomposites, they have unique propertieswhich are attributed to their nanometer size features and the extraordinarily high surface area of thedispersed clay [1].Nowadays, poly (vinyl alcohol) (PVA) has received great attention in different areas and due to itsexcellent properties such as: non-toxicity, water-solubility, biodegradability and biocompatibility properties.PVA is characterized by strong hydrophilic and hydrogen bonding character [2]. It has excellent film andhydrogel forming abilities; thermal stability; chemical resistance, transparency and flexibility, and because ofthose, it is widely used in several applications such as paper coating, textile sizing, packaging, biomedicaldevices and membrane preparation [3-4]. However, some applications are still restricted because of its highdegree of swelling and solubility in water, and its limited mechanical properties [5]. Some of these drawbackscan be improved by the incorporation of reinforcement like claysor layered silicates, which are popular fillersfor various polymeric materials. Their crystalline net consists of bidimensional layers where a centraloctahedral layer of either alumina or magnesia is joined to two external tetrahedrons of silica in such a waythat the oxygen ions of the octahedral layer also belong to the tetrahedral layers [6-7]. Among these clays,the use of bentonite is interesting because, added to their environmental and economic importance; theirnatural abundance and mechanical and chemical resistances make them very useful as polymeric materialreinforcements.PVA/clay nanocomposites can be easily obtained because, as both of them are hydrophilic, the claycan be incorporated into the PVA without pre-treatments by simply dispersing the two components in water[3]. In this work, two different kind of PVA/clay nanocomposites were prepared: films (by casting) andhydrogels (by freezing-thawing). In the case of hydrogels, 3 and 7.5 wt.% of bentonite were used, whereas inthe case of the films only 5 wt.% was used. The aim of this work was to determine the chemical, mechanical,barrier and thermal properties of the obtained nanocomposites in order to analyze the effect of clayincorporation on the general behavior of PVA matrices.In all cases, bentonite was correctly dispersed in PVA matrix. Moreover, clay incorporation caused anincrement on the thermal stability of PVA films and reduced the degree of crystalinity as well as the waterabsorptionof the neat matrix, which make them suitable for packaging. On the other hand, the PVA/bentonitehydrogels exhibit the water vapor permeation and swelling characteristics suitable for use as wound dressingand they displayed high antimicrobial behavior.