Performance of layered birnessite-type manganese oxide in the thermal-catalytic degradation of polyamide 6

Breaking of the hydrogen bonds between PA6 chains after BMO addition. [Display omitted] ► Synthesis, characterization, and catalytic properties of LMO were discussed. ► The LMO presented an excellent catalytic property to decomposition of PA6. ► A marked reduction in the degradation temperature in the presence of LMO. ► The thermal-catalytic degradation efficiency increased with increasing the amount of LMO. ► The thermal oxidation mechanisms were investigated by IR, XRD and TA techniques. The nature and the extent of degradation of polyamide 6 (PA6) in the presence of layered birnessite-type manganese oxide (LMO) were analysed by thermogravimetric analysis under static air atmosphere at several heating rates between 5°C/min and 20°C/min. The samples were characterized using infrared (IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 gas adsorption–desorption and thermal analysis (TA) techniques. XRD and DTA results for LMO showed that the oxidative transformation of MnO2 was occured on heating from 300°C to 500°C. The IR spectra of Mn–O band proved the covalent character of oxygen bonding to the metal ions of the surface. The addition of LMO caused the change in the crystalline phase of PA6 from predominantly α to largely γ phase. The activation energy for degradation estimated by Kissinger method for PA6 and 10wt.% LMO/PA6 composite were found to be 213 and 118kJ/mol in static air atmosphere, respectively. The experimental results revealed that the addition of 10wt.% LMO decreased the thermal stability in static air of PA6 by about 80°C.