Effect of cobalt carboxylates on the photo-oxidative degradation of low-density polyethylene. Part-I

The effect of three cobalt carboxylates of increasing chain length, namely cobalt laurate, cobalt palmitate and cobalt stearate on the photooxidative degradation of low-density polyethylene (LDPE) films has been investigated. LDPE films containing cobalt carboxylates were irradiated with UV-B light at 30 degrees C for extended time periods. FTIR spectroscopy, mechanical testing, morphological studies, molecular weight, density and MFI measurements were performed to monitor the degradation behaviour. The results of these studies were analysed to explain the structural and chemical modifications taking place in the polyethylene matrix due to UV-B exposure. FTIR studies indicate that the degradation is dominated by formation of carbonyl and vinyl species. The studies on mechanical properties reveal that samples-containing cobalt carboxylates, become mechanically fragile after UV exposure for 400 h, while neat LDPE exhibits insignificant changes-during this period. The degradation was found to increase proportionally with increasing chain length and follows the order CoSt(3) > CoPal(3) > CoLau(3). Migration studies were performed on food simulant systems to investigate the applicability of these films for food packaging. (c) 2006 Elsevier Ltd. All rights reserved.