Characterisation of thermal and chemical properties of photo-oxidized reinforced Mater-Bi KE/natural fibres biocomposites degraded in soil

Abstract

Reinforced biocomposites of natural fibres (cotton and kenaf fibres) with a commercial biodegradable material (Mater-Bi KE03B1) were subjected to an accelerated soil burial test. A set of samples was previously photo-oxidized in order to evaluate the effects of solar radiation on the degradation in soil process of these biocomposites. Thermal and chemical measurements were performed to study the degradation in soil, photo-degradation and their synergetic effects on the biodegradable polymeric matrix and its reinforced biocomposites. Thermogravimetry Analysis (TGA) was used to investigate the thermal behavior of the samples during the proposed different experimental degradation tests. In addition, the kinetics of each sample was analyzed using three different mathematical models: Kissinger method was used for calculating the Ea whereas Criado and Coats-Redfern methods were applied to analyze the thermal degradation kinetic model of each thermal decomposition process. In addition, the effects that take place as a consequence of the degradation in soil and the photo-degradation of materials were studied by Fourier Transform Infrared Spectroscopy (FTIR). These studies were completed with morphological analysis by means of Scanning Electron Microscopy (SEM). Photo-oxidation induces an increase in the thermal stability and in the Ea related to the starch component of pure Mater-Bi KE together with an increase in the C-O-C band associated with the glycosidic bond of the starch component. Whereas, the effects of photo-oxidation on the reinforced biocomposites were related to the natural fibre used. When the polymeric matrix were submitted to soil burial test the starch was found to be the most susceptible polymeric matrix component in soil. However, the presence of natural fibres modified the degradation rate of both matrix components; the degradation rate of the synthetic component was enhanced, whereas the biodegradation of the starch was slowed down as a function of the soil exposure time. The photo-oxidation of the pure Mater-Bi KE, Mater-Bi KE/cotton and Mater-Bi KE/kenaf achieved to enhance the degradation rate of all materials, being the Mater-Bi KE/kenaf the affected in major extent by the synergetic effects of both photo-oxidation and soil burial test.