A hybrid recycled polypropylene/dimension stone waste/coconut fiber composite

Hybrid composites were prepared using recycled polypropylene (rPP), dimension stone waste (Bege Bahia, BB) and coconut fiber (CF). Post-consumer PP was processed in a twin-screw extruder to obtain a more homogeneous material in the form of pellets (rPP) to be used as matrix for the hybrid composites. The formulations of rPP/BB/CF and virgin PP, were processed in a Haake mixer. The films were characterized according to density, water absorption behavior, morphology (scanning electron microscopy, SEM), and impact resistance. Density variations were associated with differences in particle packing and particle wall roughness. The impact resistance of rPP/BB/CF was slightly higher in the 70/10/20 wt% composite, attributed to the equilibrium between chain scission and self-reinforcement mechanisms. Moreover, the impact resistance of rPP/BB/CF (70/10/20 wt%) was the closest to that of the virgin PP. SEM micrographs of the ternary composite rPP/BB/CF (70/20/10 wt%) showed stronger traces of decohesion, allowing higher water absorption and reducing impact resistance. The ternary composite rPP/BB/CF (70/10/20) was best for replacement of virgin PP. (author)