Acceleration of thermo-oxidative degradation of high-density polyethylene using oxidized polyethylene

In the present study, the thermal oxidation behaviour of high-density polyethylene (HDPE) containing each of two types of oxidized polyethylene (OPE), one prepared using 500 ppm of iron (III) stearate as pro-oxidant and the other without the pro-oxidant, was investigated. Fourier-transform infrared spectroscopy (FTIR) showed that the carbonyl index of the HDPE increased from 1.03 to 6.37 upon the addition of 5.0 wt.% of OPE containing the pro-oxidant after 100 h of thermo-oxidative aging at 90°C. Moreover, it was observed that the rate of changes in retained tensile strength and retained elongation-at-break of the HDPE during the thermal oxidation increased in the presence of 5.0 wt.% of each type of OPE, especially, the one containing iron (III) stearate, which was consistent with the obtained data from gel content measurements. Lastly, the evolution in crystallinity of the film samples was monitored by density measurements as well as differential scanning calorimetry (DSC). It was revealed that the crystallinity of the tested films during thermo-oxidative degradation grows faster in the presence of OPE. Overall, the findings indicated that the utilization of OPE containing trace amounts of iron (III) stearate can accelerate the thermal oxidation of HDPE films and facilitate entering the final biodegradation stage, while resolving the need to use high concentrations of harmful heavy metal salts.