Use of UV-visible spectroscopy to monitor nitrocellulose degradation in thin films

Activation energies for nitrocellulose (NC) degradation have been determined from Arrhenius plots constructed using first-order rate constants measured at 40, 50 and 60 °C. The rate constants were obtained by monitoring the absorbance (A) at a wavelength in the visible region of an anthraquinone dye dispersed in NC thin films. The dye acts as a stabilizer and is slowly depleted as a result of its reaction with NOx from the breakdown of the nitrate ester groups on NC. The data produced two linear regions in the first-order plots of ln(A0/At) vs aging time. The first-region is attributed to the reaction of the dye with NOx desorbed from the NC surface. The activation energy (∼73.5 kJ mol−1) is in line with that found for NOx surface desorption processes. The second linear region is thought to be due to the reaction of NOx from the breakdown of the nitrate ester groups on the NC molecule. The activation energy (∼104.0 kJ mol−1) is consistent with that for nitrate ester hydrolysis. The use of UV-visible spectroscopy has in this way made it possible to monitor the degradation of NC non-destructively without the need for stabilizer extraction and analysis.