Desarrollo de nuevos nanocompuestos biodegradables basados en mezclas de ácido poliláctico y caucho natural

Resumen

Recently, the possibility of replacing petroleum-derived synthetic polymers by natural, abundant and biodegradable products has gained much interest in both academic and industrial fields.1, 2 The production of plastics in Europe reached 57 million tons in 2010, mostly divided between polyethylene, polypropylene, poly(vinyl chloride), polystyrene and poly(ethylene terephthalate).3 These fossil fuel-based plastics were consumed and discarded into the environment, generating 10.4 million tons of plastic wastes ending up in landfills. Therefore, the development of ¿environmentally-friendly¿ materials will result in a huge benefit to the environment and will also contribute to a reduced dependence on fossil fuels. Polymers produced from alternative resources, non-toxic to the environment, biodegradable and with low energy consumption are a crucial issue especially for short-life range applications, as they can be easily degraded by micro-organisms.4 Moreover, a wide number of biomacromolecules exists in Nature and can be involved in the preparation of these green materials. Nevertheless, the properties of these biomaterials are often behind those of common thermoplastics and some improvements are needed in order to make them fully operative for their industrial use. On another hand, polymer nanocomposite materials have aroused a great interest in the area of polymer and material science. A polymer nanocomposite is a hybrid material consisting of a polymer matrix reinforced with fibres, platelets, or spherical particles presenting at least one dimension at the nanometre scale. The ideal design of a nanocomposite involves individual nanofillers homogeneously dispersed in the polymeric matrix. In this case, an ultra-large interfacial area per unit of volume between constituents is obtained, resulting in markedly improved properties for low levels of nanofiller incorporation (< 5 wt.-%) when compared to traditional composites. Especially, significant improvements of mechanical properties, thermal stability, flame retardancy, heat distortion temperatures and gas barrier properties together with weight reduction have been demonstrated. Bionanocomposites can be considered as a subset of polymer nanocomposites where the nanofillers, the matrix or both come from bio-based, renewable resources. Therefore, adding nanofillers into biopolymers presents a practical way to improve the properties of these bioplastics, making them competitive with petroleum-derived materials. One of the most promising biopolymers for its production at an industrial scale is the poly(lactic acid) (PLA). PLA is a biodegradable thermoplastic polyester derived from biomass such as sugar, corn, and beet, which possesses interesting properties combined with biocompatibility and biodegradability properties. Due to its initial production costs, the starting applications of PLA have been focused on high value products such as medical devices. However, its price has been falling as the production increases and new methods for the production of high molecular weight PLA are developed. PLA¿s potential for consumer products such as packaging is very high due to its transparency, low toxicity and environmentally benign characteristics. Nevertheless, there are some drawbacks, such as its high brittleness, poor crystallisation behaviour and low gas barrier properties that limit its current use.