Nanocomposites based on Biodegradable Polymer

A. VÁZQUEZ; V. ALVAREZ; V. CYRAS; L. LUDUEÑA; J. MORÁN

Buenos Aires

Congreso; 15th Internacional Symposium on Metastable, Amorphous and Nanostructured Materials ISMANAM 2008; 2008

Universidad Nacional de Buenos Aires

One of the most available biodegradable polymers is the starch. The thermoplastic starch or plasticized starch has some limitations: it is mostly water-soluble and has poor resistance and low strength. Blends of thermoplastic starch with biodegradable polymers have been proof of one solution to the problem (1-2). MaterBi-Z is biodegradable blend of poly--caprolactone (PCL) and starch, is actually used as packaging material (4) due to their low cost. It is possible to improve the mechanical properties of these polymers by the addition of nanopartiles. These composites could be use in packaging where good barrier and thermal properties are required (1-2). Montmorillonite is among the most commonly used layered silicates because it is available in large quantities with relatively low cost. The increment on the mechanical properties in nanocomposites greatly depends on the dispersion of clay platelets into the polymer; which is related with the compatibility between the two components and with the processing technique (3). The relationship between the mechanical properties and processing methods were carried out. The processing technique was analyzed by using casting and intensive mixing. Mechanical properties were higher for the second one due to a free defects morphology and higher clay dispersion degree produced by shear forces during processing. For both techniques nanocomposites showed a mixed structure: intercalated and exfoliated, and the highest mechanical properties were displayed for nanocomposites with 5 wt. % clay. An effective filler parameters model was used to predict the dispersion of clay within the nanocomposites considering the experimental values of stiffness. The nanocomposites were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Tensile Test and water-uptake behavior. X-Ray Diffraction (XRD) results showed that the most of the clays are intercalated and partially exfoliated within the polymeric chains. An increment of the Young’s modulus and tensile strength for different clays as a function of clay content for different nanocomposites was verified. The highest increment was obtained with the lowest matrix modulus. The used micromechanical models based on the effective filler parameters, also permit to demonstrate that the best dispersion agreed with the highest effective stacked clay value.