Gamma-irradiated recycled polyethylene filled with Tectona grandis (teak) leaf powder: a method for upcycling of polyethylene

Recycling process in general reduces the strength and stiffness of plastics, which limits the application of recycled products. To find a solution, composites of recycled low-density polyethylene (rLDPE) filled with Tectona grandis (teak) leaf powder were formed by extrusion and injection molding techniques. The composites, fabricated with teak leaves content of 10–30%, were irradiated by max 125 kGy of gamma dose. The experimentation was performed in accordance with full factorial design (3 × 3) and the mechanical properties were analyzed by “response surface methodology”. Desirability index method was implemented to find the composite with the best mechanical properties and the same was found for the composite with 30% of teak leaves content and 125 kGy gamma dose. At this composition, the ultimate tensile strength, tensile modulus, flexural strength and flexural modulus values were obtained as: 11.03, 49.13, 56.57 and 578.72 MPa, respectively. All the above values are higher when compared with those of rLDPE. The performance indices, i.e., ratio of mechanical properties to density, for the optimized composite were better than those of the recycled polymer. The cross-linking effect of gamma irradiation was studied by FTIR, SEM and XRD analyses, to explain the improved mechanical properties. Composites are thermally stable at 444 °C and the stability is sustained even after gamma irradiation. Graphical abstract