O-17 NMR investigation of radiolytic hydrolysis in polysiloxane composites

The gamma -irradiated hydrolysis of polysiloxane composites was investigate d as a function of gamma -irradiation dose using O-17 nuclear magnetic reso nance (NMR) spectroscopy. It is demonstrated that by using O-17 labeled wat er during the high humidity exposure of the siloxane copolymer, details abo ut the radiolytic hydrolysis degradation mechanism can be obtained directly from analysis of the O-17 NMR spectra. The formation of O-17 labeled silan ols and Si-O-Si linkages occurs during the radiolytic hydrolysis, with the silanol species being the dominant non-volatile degradation product observe d. For the polysiloxane composite investigated the distribution of hydrolys is species shows little variation at high total irradiation doses. In addit ion, the silica filler does have an effect on the distribution of the hydro lysis species within the copolymer at lower gamma -irradiation doses. The a bility of O-17 NMR to isolate the hydrolysis species from other degradation processes within the polysiloxane composites demonstrates the applicabilit y of this technique to address hydrolytic aging in other materials. (C) 200 1 Elsevier Science Ltd. All rights reserved.