Tensile behavior of irradiated recycled polyolefin plastics

Solid wastes represent a potential source for raw materials in the world. In Brazil, municipal solid waste (MSW; 2-%) is expected to grow at a rate per year higher than the worldwide rate (1%). On the other hand, the consumption of polymer blends increases at a rate more than twice that of all plastics. Therefore, the recycling of polymeric blends has gained increasing attention in the world due to economic and environmental considerations. A two-step process, developed at the Institute (IMA/UFRJ), allows one to recover plastic residues and permits the production of materials with controllable composition and homogeneous characteristics. The compression behavior of polyblends, composed of typical polymers that appear in domestic wastes-low and high polyethylenes-can be improved by gamma irradiation. In the present work, the tensile behavior of recycled 75/25 blends of low-density polyethylene (LDPE) and high-density polyethylene (HDPE), after exposure to gamma rays in the air, was investigated. Tensile testing, scanning electron microscopy, infrared and solid-state C-13-nuclear magnetic resonance spectroscopy, as well as gel content were used to study the effect of gamma irradiation on the polymer blends. The tensile strength was found to increase with radiation dose while the elongation at break decreased. Our experimental results indicate that the gamma irradiation degradation process involves crosslinking at lower doses and chain scission at higher doses. (C) 2000 John Wiley & Sons, Inc.