Study of Antioxidant Effectiveness of Kraft Lignin in HDPE

Polymers are subject to oxidative degradation during all steps of their useful cycle. This degradative process is prevented using stabilizers like antioxidant of the type sterically hindered phenols or amines. Lignin, due to the presence of phenolic groups in their structure, can present characteristic as antioxidant agent, in a similar way to the additives used in polymers. Therefore, in this work, the antioxidant capacity of the lignin in a sample of polyethylene is studied. For this reason, in this paper, a method based on nonisothermal differential scanning calorimetry (DSC) to evaluate this property is used. The samples studied were subjected to heat treatment at different scan rates and in presence of oxygen to promote thermooxidation of the material. The antioxidant capacity of different formulations of lignin and additives in the polymer resin was determined from the temperature of onset of oxidation (Ti) at different heating rates and adjusting Arrhenius model prediction. The results indicate that the procedure can predict the antioxidant capacity of antioxidant additives in HDPE with good reproducibility and accuracy, according to the Arrhenius model prediction