Effect of metal oxides on the pyrolysis residues of poly(ethylene terephthalate): Formation of carbonaceous submicron, nano-scale filaments and mesoporous compounds

Thermal decomposition of mixture of poly(ethylene terephthalate) (PET) and metal oxide has been investigated. Morphology of pyrolysis residues has been observed by using scanning electron microscopy. Among various oxides examined the addition of zinc oxide or trivalent rare earth oxide (Ln2O3) resulted in the formation of porous fibre-like structures with the diameter of ∼1 μm for ZnO and ∼100 nm (or thinner) for Ln2O3. The formation process as well as thermal decomposition behaviour has been studied by various analytical methods. The thermal decomposition of PET on single crystal ZnO indicated that the unique morphology was due to the oxygen-terminated surface of the metal oxide. Furthermore, pore structures of the carbonaceous compounds from various PET-metal oxide mixtures have been determined by nitrogen adsorption isotherm at −196 °C. It was found that the carbonaceous compounds obtained from PET-Fe2O3 and PET-Ln2O3 had large mesopore volumes. This was confirmed also by the adsorption study of large molecules such as humic acid (HA).