Efficient enhancement in polyethylene biodegradation as a consequence of oxidative fragmentation promoted by pro-oxidant/pro-degradant metal stearate

摘要

We report an investigation on the effect of iron and cobalt stearates as pro-degradants and their synergetic effect on the oxidation and subsequently the biodegradation behavior of low density polyethylene (LOPE) film. For this, TAPE films containing different amounts of these additives were prepared and characterized upon exposure to accelerated thermal and photo-oxidation. The analysis shows that the films underwent a significant degradation as monitored by carbonyl index, changes in the crystallinity, in the onset of decomposition temperature and hydrophobicity. The tendency to biodegradation of the oxidized LDPE, with and without pro-oxidant/pro-degradant, was then assessed through the soil burial and the aqueous medium techniques. After an incubation period of 120 days, samples were characterized by means of structural changes and cumulative CO2 emissions. During the incubation in both soil and aqueous medium, the fragmented films with pro-oxidant/pro-degradant showed a significant decrease in oxygenated moieties present initially in the polymer and formed during the accelerated ageing when compared with LDPE without pro-oxidant/pro-degradant, and the biodegradation in the different environment was highly effective following the order LDPE/Co LDPE/Co/Fe LDPE/Fe LDPE and in the range of 13-45% of mineralization after 120 days in aqueous medium and 13-29% in solid medium. These results suggest the role of pro-oxidant/pro-degradant and specially their mixture and the natural environment in oxidation and degradation of LDPE samples and in the mineralization process of oxidized fragments.