S. Commereuc et al., IN-SITU DETECTION OF HINDERED AMINE STABILIZER CONSUMPTION IN POLYMERTHROUGH OXIDATION BY INDIRECT ELECTRON-SPIN-RESONANCE, Journal of applied polymer science, 69(6), 1998, pp. 1107-1114
The stabilization mechanisms of hindered amine stabilizers (HAS) invol
ve various oxidation products oft;he piperidine structure. Thus, we pr
opose a novel method, based on electron spin resonance (ESR) spectrosc
opy, to check in situ the consumption of the total piperidyl species (
intact HAS and all of its byproducts) in polypropylene (PP) films thro
ugh photooxidation. First, the concentration of nitroxyl radicals prod
uced upon irradiation in stabilized PP has been measured by direct ESR
analysis. Then, the changes of concentration of the overall stabilizi
ng species have been detected by indirect ESR, after conversion of the
overall HAS derivatives into nitroxyl-free radicals by exposure of ph
otooxidized PP to peracetic acid vapor at room temperature. Results we
re compared with those obtained by the conventional Fourier transform
infrared method in the particular case of [2,2,6,6-tetramethyl piperid
inyl] sebacate, and the reliability of both techniques was discussed.
Thus, we assume that indirect ESR experiments consist of a easy, accur
ate, and very sensitive method to monitor the time evolution of a low-
molecular weight HAS-NH concentration in PP upon photooxidation. (C) 1
998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1107-1114, 1998.