Reprocessing and restabilization of greenhouse films

From the ecological and economical points of view, reprocessing of polyethylene greenhouse films is a promising solution to reduce discarded materials and to produce useful, or potentially useful, objects for service. Films exposed outdoors, however, show inferior mechanical properties and the melt processing worsens these properties. The addition of stabilizers and antioxidants to recycled plastic products prevents inherent thermal instabilities from occurring within the time frame of proper processing. In this study, we attempt to explore ways for improving product performance by the addition of four different additives when the recycled films undergo intensive shear processing. The process is evaluated by measuring the changes in chemical structure (carbonyl evolution) as well as rheological and mechanical characteristics (tensile properties). The effectiveness of the various additives was estimated and the one with the best antioxidant ability was identified. The analysis of processing conditions allowed us to find that the best results are emphasized by the continuous addition of the stabilizer at each step of reprocessing. (C) 2002 Elsevier Science Ltd. All rights reserved