Tensile behavior of irradiated recycled polyolefin plastics

Solid wastes represent a potential source for raw materials in the world. I n Brazil, municipal solid waste (MSW; 2-%) is expected to grow at a rate pe r year higher than the worldwide rate (1%). On the other hand, the consumpt ion of polymer blends increases at a rate more than twice that of all plast ics. Therefore, the recycling of polymeric blends has gained increasing att ention 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 p olyblends, 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 polyeth ylene (LDPE) and high-density polyethylene (HDPE), after exposure to gamma rays in the air, was investigated. Tensile testing, scanning electron micro scopy, infrared and solid-state C-13-nuclear magnetic resonance spectroscop y, as well as gel content were used to study the effect of gamma irradiatio n on the polymer blends. The tensile strength was found to increase with ra diation dose while the elongation at break decreased. Our experimental resu lts indicate that the gamma irradiation degradation process involves crossl inking at lower doses and chain scission at higher doses. (C) 2000 John Wil ey & Sons, Inc.