Cinética de cura do sistema Epóxi (DGEBA) - Anidrido (MTHPA) / Casca de ovo e sua membrana: uso sustentável de um catalisador biológico.

Abstract

This work sought evaluating by thermal, chemical and kinetic models the influence of natural catalysts on epoxy resin cure; properties changes were quantified through mechanical and morphological tests. To this task, DGEBA/MTHPA/DEH 35 based epoxy compositions were produced by magnetic stirring. In order to observe the efficiency in replacing the DEH 35 catalyst during the curing reaction, the chicken eggshell (ES) and its membrane (M) were added to the epoxy compounds. Compounds’ thermal stability, physical and chemical parameters, mechanical properties and fracture surface morphology were investigated by Thermogravimetry (TGA), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Mechanical Properties (tensile) and Scanning Electron Microscopy (SEM). In general, ES and M addition subtly decreased thermal stability with the decomposition degree parameter at 5% (T0.05) lower than synthetic compounds. The rate cure and degree of conversion were higher for lower heating rates, while the best results were collected after membrane addition (M). Among the kinetic models analyzed, the ones that presented the best fit were Friedman Model - Based and Málek, they were able to render better fits as the activation energy in this investigated process not being constant. Through chemical analysis the degree of crosslinking was measured where membrane composition (M10) was equally crosslinked compared to the synthetic one (S5). Mechanical properties were improved with ES as well as with M, with Young's Modulus 18%, Tensile Strength 50% and Deformation 35% higher compared to synthetic compounds. In SEM micrographs, the synthetic compounds presented a smooth fracture surface, while in compounds with ES and M multiplane rough one was verified suggesting fracture with higher energy absorption. Summing up, better performing epoxy/Mx biocompositions have been produced and effective tools are offered to control and obtain even better, eco-friendly properties.