Influence of Temperature and Dose Rate of E-Beam Modification on Electron-Induced Changes in Polyacrylonitrile Fibers

The present study investigates the influence of modification temperature and the dose rate of electron modification on the progress of these and the three important thermal induced reactions namely: cyclization, dehydrogenation, and oxidation. Since electron induced chemical reactions strongly depend on the polymer chain segment mobility, temperatures below the glass transition temperature (T-g) and above T-g are tested. Electron paramagnetic resonance (EPR) spectroscopy measurements show the presence of alkyl-, peroxy-, and polyimineradicals alongside each other. Gel measurements identified a temperature dependent crosslinking behavior at doses <= 150 kGy, but no dose rate depending on crosslinking. Changes in chemical structure are investigated using Fourier transform infrared spectroscopy (FT-IR), showing a dependency of stabilization behavior depending on dose and temperate more than on dose rate. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements complete the analyses by describing the behavior during further thermal treatments and measuring the residual mass at 800 degrees C.