Abstract
When polycarbonate (PC) is irradiated by high-energy radiation, it generates some free radicals and changes the chemical structure of PC. We used two kinds of PC sample. One is PC irradiated by Gamma-ray and the other is PC without gamma-ray irradiation. As annealing time increases, the transmittances of these two kinds of samples recovers gradually and reaches a steady state. We use FTIR to study the chemical structure. We found that the band of 3100-3500 cm-1 and the peaks of 3620, 2330cm-1 have lower intensity for high dose than for small dose. The peaks at 3620 cm-1 is assigned to the free OH (non-associated) and the peaks at 2330cm-1 is assigned to CO2. We also found that the band of 3100-3500 cm-1 and the peaks of 3620 cm-1 of non-irradiated PC changed, but not as much as PC irradiated by Gamma-ray, the peaks at 3620 cm-1 is assigned to the free OH (non-associated), just like irradiated samples. In order to know the difference between irradiated and non-irradiated samples, we analyze these two FTIR spectra and found that the peaks of 3350, 3575, 2330cm-1 changed with time at a given temperature. The peaks at 3350cm-1 and 3575cm-1 are due to its association (hydrogen bonding) with other functional groups in the material, including with neighboring OH group and C=O and C-O in the polymer. This process follows a second-order kinetic process and the activation energies are obtained. Electron spin resonance spectroscopy (ESR) has been used to study the free radicals of polycarbonate irradiated by Co60 Gamma-ray. When PC is irradiated by Gamma-ray, it generates three kinds of radicals Ra, Rb and Rc in PC. Ra, Rb and Rc correspond to –C(CH3)2-C6H4-O．, –C(CH3)2-C6H4．, and -O-C6H4-Ċ(CH3)2, respectively. Analyze all spectra using WINEPR SimFornia and WinSim; and the numbers of radicals were calculated by comparing with DPPH. As annealing time increases, all radicals of Ra, Rb and Rc decay. Rb decays faster than the other two radicals. It seems that they follow a second-order annihilation process.