Production of Natural Fibers Reinforced Composites: Macro and Nano Scales

Abstract

Natural fibers, namely taboa (typha), sisal, coir and curaua, have strong social importance in tropical countries, specially generating jobs in the rural areas and in economically deprived areas. However, the main challenge to use these fibers is the development of an interface fiber/matrix with good mechanical characteristics. After technological development, these fibers are light, resistant, non-abrasive, renewable, biodegradable and recyclable. These characteristics enable them to compete with other man-made materials that show environmental or availability problems. Besides composites developed with natural fibers, there is also the nanocomposites as a new class of materials that has attracted great interest among the researchers due to their unique properties as well as unique applications in commercial sectors. This class of materials can exhibit better properties at very low filler content and at least one dimension of the dispersive particles is in the nanometer scale (less than 100nm). For this reason they will present mechanical, thermal, optical and physico-chemical properties improved when compared to the pure polymers or conventional composites. Usually, they will present increase in the Young´s Modulus, storage modulus, thermal stability, gas barrier properties and good flame retardancy. In addition, they can also present higher value to the heat distortion temperature -HDT (up to 100ºC), and at this way make viable the use of the nanocomposites at higher temperature environments.Then, the mains goals of this project are:* To increase de tensile modulus and flexural modulus of the composites based on natural fibers;* To increase the natural filler content to 80% (weight), in the composites (macro scale) without significant loss in the physico-mechanical properties;* To use natural fibers with high aspect ratio;* To develop industrial applications to the natural fibers;* To improve the matrix properties through the addition of nanoparticles;For the development of the nanocomposites, cellulose nanofibers and cellulose whiskers obtained from natural fibers (taboa and sisal) will be used as nanoparticles. The nanocomposites will be obtained through the melting compounding in a twin screw extruder, using additives and screw profile that optimize the distribution and dispersion of the nanofibers in the polymeric matrix. Since particles agglomeration is a problem during the processing for the composites materials, chemically modified fibers will be used to prepare the nanocomposites. The nanofibers will be obtained combining chemical and mechanical process, and by this way, several components (hemicellulose, lignin) will be dissolved. It will be also made a comparison between the composites (macro scale versus nanoscale) to establish the increase in the mechanical properties through the introduction of the nanofibers.