Compósitos de polipropileno/biofibras de sisal para partes leves de automóveis

Abstract

Composites based on virgin and recycled polypropylene (PP and rPP) and sisal fabric, with and without alkali treatment, were prepared by compression molding technique in a mat with a three-layers sandwich structure. The sisal was characterized by Fourier infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The composites were characterized according to physical and mechanical properties. Also, the factorial experimental design was used to statistically evaluate the behavior of the composition of the composite on mechanical properties. The FTIR spectrum and X-Ray diffraction indicated the partial removal of amorphous materials from the sisal surface after alkali treatment. The composites density results ranged from 0.892 to 0.927 g.cm-3, which is important for lightweight automotive component design. A slight decrease in the hardness of the rPP and rPP composites, compared to the PP, was observed. The water absorption was higher in rPP composites, regardless of the chemical treatment. Moreover, the impact resistance of PP and their composites were higher than the values for rPP. Statistical analysis showed that the alkali treatment represents a significant factor for the hardness of the rPP and PP composites and the addition of the sisal layer was relevant to improve the impact resistance of the composites. Because of these results, the composites obtained with virgin matrix were submitted to a statistical analysis, which showed that the alkaline treatment was a significant factor for the hardness of the composites and that the addition of the sisal layer was relevant to improve the impact resistance. Ultimately, an economic feasibility study was carried out, comparing the sisal composites with composites possibly obtained with glass blanket, a material traditionally used. Regardless of the formulations of composites reinforced with sisal present a higher cost than those formulated with glass blankets, environmentally thinking, the use of sisal fiber is justified.