Algae fiber polypropylene composites: Modeling of the degradation by solid state kinetics

Knowledge of the mechanisms of degradation in natural fiber composites (NFCs) has great importance for the life cycle assessment of the automotive components based on NFCs. The purpose of this study was to evaluate the solid state kinetic models available to describe the degradation process of algae fiber/grafted polypropylene (AFPPg) composites processed by extrusion compression molding (ECM). Samples of the 0.14 volume fraction (upsilon(f)) AFPPg composite, algae fiber, and grafted PP were evaluated before and after 576 hours of accelerated UV light weatherization. The weight loss of the specimens was determined by thermogravimetric analysis (TGA) at six isothermal temperatures, and weight loss data were transformed into the conversion fraction alpha. Curves of the factor alpha and time were linearized using MATLAB software to find the parameters of the degradation. The best statistical fit to model the degradation was given by the Avrami-Erofe'ev model. The kinetic parameters of PP grafted after UV exposure were frequency factor (A) of 6.26 min(-1) and activation energy E-0 of 24 kJ/mol. The effect of degradation was characterized by Fourier transformed infrared spectroscopy (FTIR). The characteristic bands of the main products of degradation in the composite were identified as pentane and propane. (C) 2016 Wiley Periodicals, Inc.