Accelerated aging of LDPE films containing cobalt complexes as prooxidants

This paper deals with the synthesis and characterization of two cobalt complexes, namely cobalt styrene maleate copolymer (CSMA) and cobalt stearate (CS) and studying the effect of these complexes on the degradation behavior of Low Density Polyethylene (LDPE) films. Seventy micron films containing these additives were prepared by sheeting process and were subsequently exposed to two different degradative environments, i.e. UV-B irradiation and heat. The degradation was monitored by measuring the changes in tensile strength, elongation at break, Carbonyl Index (0), Melt Flow Index (MFI) and density. It was observed that although both the additives contained the same metal and similar type of bonding, CSMA was incapable of initiating thermal/photodegradation of LDPE while the analogous CS at the same concentration range significantly accelerated degradation. Films were also subjected to soil burial tests for a period of I year and the degradation was monitored by weight loss measurements. Multiple extrusions of LDPE were performed in the presence of the two additives to investigate their practicability for reprocessing. Overall migration of constituents from these films was determined in food simulants to evaluate the application of these films as food packaging material. (c) 2005 Elsevier Ltd. All rights reserved.