Interaction of antioxidants with carbon black in polyethylene using oxidative induction time methods: Fid-Bau Portal

Interaction of antioxidants with carbon black in polyethylene using oxidative induction time methods

Wong, Wai-Kuen / Hsuan, Y. Grace

Abstract Carbon black (CB) is added to the geosynthetics for ultraviolet protection. However, CB can interact with antioxidant (AO) in the geosynthetics, and their interaction has been documented to be synergistic and/or antagonistic towards the oxidation reaction. In this paper, two oxidative induction time (OIT) methods, a standard (Std) OIT test and a high pressure (HP) OIT test, were used to evaluate the interaction of CB with two types of antioxidants during the oven aging. Test samples made from high density polyethylene (HDPE) blended with different amounts of Irganox^®1010 (I-1010) and Irgafos^®168 (I-168) together with 0 or 2.5wt.% of carbon black were studied. The sample were incubated in a forced air oven at 85 °C to accelerate the oxidation reactions. After 1000 days, Std-OIT values of samples with 500 ppm and 1000 ppm I-1010 exhibited only 10% drop from their initial values from 19.42 min and 34.01 min to 17.53 and 31.0 min respectively. In comparison, a continuous decrease of Std-OIT value was observed for samples contained both I-1010 and I-168; a 40% drop was measured after 1000 days, corresponding to 16.4 and 26.8 min reduction. For samples contained 2.5% CB and I-1010, an exponentially decrease of Std-OIT and HP-OIT with aging time was obtained. However, adding I-168 to those samples did not change the OIT decreasing trends, indicating that the interaction of CB with I-168 is negligible. The test data further verify that the effectiveness of the OIT test is strongly correlated to the functional temperature range of the AO. The Std-OIT test with testing temperature of 200 °C can detect both I-1010 and I-168, while the 150 °C testing temperature of the HP-OIT test can only detect the I-1010.