Bio-Based Composites for Light Automotive Parts: Statistical Analysis of Mechanical Properties; Effect of Matrix and Alkali Treatment in Sisal Fibers

Composites based on virgin and recycled polypropylene (PP and rPP) reinforced with 15 wt% sisal fibers, with and without alkali treatment, were prepared by compression molding in a mat composed of a three-layer sandwich structure. The sisal was characterized by Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The composites were characterized according to physical and mechanical properties. Additionally, a factorial experimental design was used to statistically evaluate the mechanical properties of the composite. The FTIR and XRD indicated the partial removal of amorphous materials from the surface of the sisal after alkali treatment. The composites' density results varied from 0.892 to 0.927 g center dot cm(-3), which was in the desirable range for producing lightweight automotive components. A slight decrease in the hardness of the pure rPP and rPP composites in relation 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 its composites was higher than the values for rPP. Statistical analysis showed that the alkali treatment was a significant factor for the hardness of the rPP and PP composites, and that the addition of the sisal layer was relevant to improve the impact resistance of the composites.

Automated summary

Composites based on virgin and recycled polypropylene (PP and rPP) reinforced with sisal fibers were prepared by compression molding. The alkali treatment of sisal removed some amorphous materials from the surface. The density of the composites was suitable for lightweight automotive components. The hardness of rPP composites decreased slightly, while water absorption increased compared to PP. PP composites showed higher impact resistance than rPP. Alkali treatment significantly influenced the hardness of rPP and PP composites, and the addition of sisal improved the impact resistance of the composites.