Effect of recycled glass fibers on mechanical behavior of wood flour polyolefin composites

Wood plastic composites (WPCs) represent a class of relatively new materials which are attracting considerable interest due to their recyclability and sustainability. Their growing industrial acceptance is ascribed to their low moisture absorption, resistance to biological attack, dimensional stability and to a satisfactory combination of high specific stiffness and strength. A possible solution to enhance the mechanical properties of WPCs is represented by the hybridization with inorganic fillers. In this regard, this work aims at investigating the effect of short glass fibers on wood flour polyolefin composites. In particular, glass fibers were obtained from thermoset composites at the end of their service life. This was done aiming at minimizing cost and landfill disposal of thermoset composites, which represents a critical issue for the composite industry. Two different matrices were used, namely low density polyethylene (LDPE) and polypropylene (PP). The composites were manufactured by a two-step process involving a kinetic mixer and a compression molding machine. Several formulations were produced, considering both wood flour and hybrid composites containing recycled and virgin glass fibers. The effect of recycled glass fiber content on water absorption behavior, static mechanical properties (four point flexural strength and modulus, Shore D hardness) and screw withdrawal resistance was assessed. The fracture surfaces of composites were also analyzed by scanning electron microscopy (SEM) in order to assess the failure modes, the extent of filler dispersion and the quality of the interface.