The Mechanical Properties of Recycled Polyethylene-Polyethylene Terephthalate Composites

Polyethylene terephthalate (PET)، one of the thermoplastic polymers، is encountered with arduous problems in its recycling. After recycling، its mechanical properties drop dramatically and therefore it cannot be used to produce the products as virgin PET does. Polyethylene is a thermoplastic polymer which can be easily recycled using the conventional recycling processes. The decreased mechanical properties of virgin polyethylene due to the environmental factors can be improved by reinforcing fillers. In this paper، we studied the effects of adding recycled polyethylene terephthalate (rPET) as a filler، in various amounts with different sizes، on the physical and mechanical properties of recycled polyethylene. Composite samples were prepared using an internal mixer at temperature 185°C، well below rPET melting point (250°C)، and characterized by their mechanical properties. To improve the compatibility between different components، PE grafted with maleic anhydride was added as a coupling agent in all the compositions under study. The mechanical properties of the prepared samples were performed using the tensile strength، impact strength، surface hardness and melt flow index (MFI) tests. To check the dispersity of the polyethylene terephthalate powder in the polyethylene matrix، light microscopy was used. The results showed that the addition of rPET improved the tensile energy، tensile modulus and surface hardness of the composites while reduced the melt flow index، elongation-at-yield، tensile strength and fracture energy of impact test. We could conclude that with increasing rPET percentage in the recycled polyethylene matrix، the composite became brittle، in other words it decreased the plastic behavior of recycled polyethylene. Decreasing particle size led to higher surface contacts، increased the mechanical properties and made the composite more brittle. The light microscopy micrographs of the samples showed a good distribution of small rPET particles in the polyethylene matrix.