Influence of temperature on the thermo-oxidative degradation of polyamide 6 films

The thermo-oxidative degradation of polyamide 6 (PA6) was studied at relative high temperatures (between 120 and 170 C) using oxygen uptake and hydroperoxide determination methods, chemiluminescence, FT-IR and UV VIS spectroscopy as well as solution viscosity and tensile property measurements. The relation between the results of the different analytical techniques and influence of temperature on these relations was determined. Arrhenius plots of the degradation determined with the different methods are linear; however the activation energies determined from these plots depend on the analytical method used. For oxygen uptake measurements and changes in UV absorbance (at 280 nm) and solution viscosity an activation energy of about 120 kJ/mol was calculated, for the increase in carbonyl index of about 80 kJ/mol and for the decrease in elongation at break of about 150 kJ/mol. The changes in oxygen uptake UV absorbance and solution viscosity are probably due to the same chemical process. The lower activation energy from changes in the carbonyl index is attributed to the formation of gaseous products, which play a larger role at higher temperatures. The higher activation energy from the elongation at break measurements was ascribed to the contribution of physical changes that play the largest role at the highest temperatures. (C) 2010 Elsevier Ltd. All rights reserved.