Polyester composite reinforced with fiber of Mauritia flexuosa treated with alkali: Impact energy, chemical composition and surface topography.

Abstract

Abstract–This work evaluated the influence of the concentration of NaOH (100, 200 and 300 g/L NaOH) in the mercerization process at 25 °C for 1 h, and of the percentage (15, 20 and 25% m/m) of Mauritia flexuosa fibers on impact resistance in a polyester matrix composite. The polyester matrix composite was obtained by the compression molding process, at a constant pressure of 24 MPa. The obtained plates had a dimension of 130 mm long x 80 mm wide x 3.4 mm thick. Specimens for the impact assay were extracted from the obtained plates under the EN ISO 179-1 standard. Likewise, the fiber-reinforced composites without treatment were also evaluated, all the fibers were characterized before and after the NaOH treatment by means of the chemical characterization of the fiber, absorption percentage, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy ( FT-IR). The results showed that with a higher concentration of NaOH, a decrease in extractives, lignin and hemicellulose was obtained, while the cellulose content increased. Additionally, it was shown that the higher the NaOH concentration, the hydrophilic character of the fiber decreases. On the other hand, by means of FT-IR, it was identified that the functional groups related to the fiber composition vary before and after mercerization. While the scanning electron microscopy (SEM) showed morphological changes of the fiber where impurities, waxes and fats were observed for the untreated fiber and a rougher surface and free of impurities for the treated fibers. The highest impact resistance value was obtained by 25% fiber reinforced composites without treatment with an average value of 39.62 kJ/m2, a value that represents an increase of 298.34% with respect to the impact resistance of the polyester matrix. without reinforcement. The results concluded that the weight percentage of fiber increases impact resistance while chemical treatment increases fiber-matrix adhesion and influences the failure mechanism of polyester matrix compounds, however, decreases impact resistance. Thus, the compounds reinforced with 25% fiber and treated with 100, 200 and 300 g/L of NaOH reported average values of impact resistance of 23.02 kJ/m2, 28.01 kJ/m2 and 20.48 kJ/m2 respectively.