Effect of low content reed (Phragmite australis) fibers on the mechanical properties of recycled HDPE composites

This paper discusses the influence of low content red fibers on the mechanical characteristics of recycled HDPE composites. Composites of High Density Polyethylene (HDPE) and common reed (Phragmite australis) natural fibers were prepared by successive single screw extrusion blending. The mechanical and thermal properties of these composites which have low concentrations of fibers were investigated. It was found that the number of extrusions had no effect on the thermal stability of composites, even if the presence of fibers may be accelerating the degradation of the polymer matrix. Moreover, rheological measurements showed a decrease in the viscosity of the neat matrix, while the opposite was observed in composites for which the highest viscosity is obtained after five cycles of extrusion. These results suggest a decrease in the molecular weight of the HDPE during reprocessing. For composites, however, a good dispersion of the RF matrix was obtained, which increased as the number of extrusions grew larger. As for the mechanical properties, a substantial enhancement in ductility was observed, as compared to that of neat recycled matrices, when small RF concentrations were added. Thus, for 2.6% RF the best enhancement of ductility was obtained with the conservation of the fiber length and a good dispersion of fibers. These findings show that incorporating low contents of reed fibers can be an interesting solution when trying to improve the mechanical behavior of recycled polyethylene.