Avaliação das propriedades mecânicas e de barreira de filmes de EVA/Argila

Abstract

Polymer films based on ethylene vinyl acetate (EVA) were produced in this work, as well as nanocomposites of EVA and Cloisite 20A clay. These films and nanocomposites were produced with two different solvent types, chloroform and tetrahydrofuran by the solvent evaporation technique. Compositions 3% and 5% clay by weight with respect to the polymer weight were used for the production of nanocomposites, both using chloroform as solvent, such as tetrahydrofuran. To evaluate the influence of the type of solvent and the addition of clay in the polymer matrix on the properties of the films the techniques of x - ray diffraction, Fourier transform infrared, contact angle, water vapor transmission rate, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy and tensile strength were used. The x-ray diffraction showed a dispersion of the clay in the films. The Fourier transform infrared showed that the addition of clay as well as the use of the different solvents did not modify the characteristic bands of the film. From the results obtained by the water vapor transmission test an increase of the barrier properties of the films with the addition of clay and a greater homogeneity in the results obtained using tetrahydrofuran as solvent can be verified. The contact angle characterization showed that the addition of clay in the polymer matrix caused a change in the hydrophobicity of the films. The thermogravimetric analysis evidenced an increase in the temperature for beginning of degradation with the addition of clay. The exploratory difference calorimeter analysis showed a decrease of the crystallinity with addition of the clay. However, the melting temperatures did not change significantly. Microscopy analysis revealed dense structures of the films. The addition of clay promoted an increased stiffness of the films. In general, the addition of clay to the polymer matrix improved the mechanical and barrier properties of the films.