Complete decomposition of polymers by means of thermally generated holes at high temperatures in titanium dioxide and its decomposition mechanism

Thermoplastic as well as thermosetting polymers are found to be completely decomposed in the presence of titanium dioxide due to thermally excited holes at high temperatures. The decomposition mechanism has therefore been investigated in terms of thermal analysis, electron-spin resonance, and infrared spectra, using polycarbonate (PC) as the model substance. The initial stage of the decomposition is the electron capture from PC by means of thermally generated holes at the TiO2∕PC interface to create radicals in PC. Then, the radicals propagate throughout the PC chains to rupture the chemical bond between monomer units, leading to the remarkable reduction in molecular weight. Finally, the decomposition within the monomer unit takes place at the CH3 site to give small fragments. These fragments end up with complete combustion in the presence of oxygen to give H2O and CO2.