Improvement of the thermal and thermo-oxidative stability of high-density polyethylene by free radical trapping of rare earth compound

A kind of rare earth compound, ytterbium trifluoromethanesulfonate (Yb(OTf) 3 ), was introduced into high-density polyethylene (HDPE) by melt compounding to investigate the effect of Yb(OTf) 3 on the thermal and thermo-oxidative stability of HDPE. The results of thermogravimetric (TG) and differential scanning calorimetry (DSC) showed that the addition of Yb(OTf) 3 made the thermal degradation temperatures dramatically increased, the oxidative induction time (OIT) extended, and the enthalpy (Δ H d ) reduced. Very low Yb(OTf) 3 loading (0.5   wt%) in HDPE could increase the onset degradation temperature in air from 334 to 407   °C, delay the OIT from 11.0 to 24.3   min, and decrease the Δ H d from 61.0 to 13.0   J/g remarkably. Electron spin resonance spectra (ESR), thermogravimetric analysis coupled to Fourier transform infrared spectroscopy (TGA-FTIR), rheological investigation and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) indicated that the free radicals-trapping ability of Yb(OTf) 3 was responsible for the improved thermal and thermo-oxidative stability.