Synthesis of nanoparticles for biopolymer reinforcement: strategies and examples

ROBERTO CANDAL

Buenos Aires

Workshop; BioPoli 2015; II WorkshopPolímeros Biodegradables y Biocompuestos; 2015

INTRODUCTIONDifferent kind of Nano Particles (NP) have been used during the last decade for the production of polymeric composites. The incorporation of this novel materials to a polymeric matrix may improve mechanical properties, hardness, conductivity, resistence to microbial degradation, between others. Typicaly a notable effect is obtained with a low porcentaje of NP with respecto to the matrix leading to light materials. The shape and size of the nanoparticles is as important as the material from which they are made. The aspect ratio of the particles has a notable role in mechanical properties and gas/vapor permeability of the composite, which are very important for packaging, protecting films, etc. The adherence and homogeneous distribution of the NP into the matrix are other characteristics that should be considered for the succesfull preparation of nanocomposites [1]. Several strategies have been adopted by researchers all around the world to synthesize NP with the needed aspect ratio and easily dispersable in the polymer matrix. In what follow some examples will be discussed with the aim to show different aproaches to obtained the desidered characteristics EXAMPLES AND DISCUSSIONCarbon-Nanotubes/Hercynite hybrid: Carbon nanotubes (CNT) are considered very promisory for the preparation of reinforced plastics. However its dispersability in most matrixes is poor due to the strong tendency to form aggregates, which is consequence of van der Waals forces between the CNTs. The problem is worst in the case of water soluble polyemrs (as starch) where CNTs are poorly dispersed. Recently, a highly water dispersable CNT/Hercynite (FeAl2O4) hybrid was prepared byChemical Vapor Deposition using C2H2 as carbon source and Fe-Al2O3 as catalyst. This new material was succesfuly used in the preparation of Starch/CNT/Hercynite composite with improved mechanical and vapor barrier properties. The high dispersability was key to incorporate as much as 4% of the hybrid in the starch matrix. The presence of the hercynite NP attached to the CNT decrease van der Waals forces hindering aggregation ZnO nanorods: ZnO NP modify the mechanical properties of biopolymers and its resistance to microbial degradation. Nanorods may display better barrier effect to vapor difussion. The synthesis of nanorods involve the preparation of seeds in a medium that direct the growing in the [100] direction. The presence of quaternary alkyl ammonium cations helps to obtaine the desidered shape.