Casca de cupuaçu (Theobroma Grandiflorum) como estabilizante térmico para poliestireno cristal: uma investigação experimental

Abstract

The Amazon Region offers a high diversity of lignocellulosic biomasses that can be reused as vegetal fillers for polymers, in order to improve their properties. In this context, we can mention cupuaçu husk (Theobroma grandiflorum), an agro-industrial residue that has already shown potential as a thermal stabilizer, due to its antioxidant properties. Therefore, the present work used this residue as a vegetal filler in crystal polystyrene to evaluate the influence of its incorporation on the polymer’s properties. The chemical characterization of the residue was performed using FTIR and FRX. Furthermore, the mass percentages of its major constituents (such as cellulose, lignin and extractives) were determined, as well as its antioxidant activity and total phenolics content. The thermal behavior was investigated by TG/DSC. The surface morphology was observed by SEM. Particle size distribution was evaluated by Laser Light Scattering (LLS). The polymer was processed in its pure form and with vegetal filler through extrusion and injection. The residue was incorporated into the polymeric matrix at different mass proportions (1%, 2% and 3%). Additionally, samples were submitted to thermal aging in a oven (with durations ranging from 15, 30, 45 to 60 days), to evaluate the influence of the additive incorporation on the thermo-oxidative degradation of the polymer during the test. The samples were characterized mechanically (tensile test), thermally (TGA/DSC), and chemically (FTIR). Furthermore, the fracture regions of the samples were evaluated by SEM. The residues exhibited a high lignin content and substantial cellulose content, as well as good antioxidant activity. Results demonstrated that the incorporation of the additive influenced the mechanical behavior of the polymer. Additionally, thermal stability increased with the presence of vegetal filler. The fracture region of the sample with vegetal filler showed homogeneous dispersion of the particle in the polymer matrix. According to the thermal aging, samples with only pure polymer showed lower performance in terms of mechanical and thermal properties. Moreover, the fracture region of these samples exhibited more surface damage compared to the other types of samples, implying that the presence of vegetal filler may influence the degradation process of the samples.