Nuclear magnetic resonance and principal component analysis for investigating the degradation of poly[chlorotrifluoroethylene-co-(vinylidene fluoride)] by ionizing radiation

Reported here is the application of multivariate statistical analysis to nuclear magnetic resonance (NMR) data for the understanding of irradiative degradation in Kel-F 800: poly[chlorotrifluoroethylene-co-(vinylidene fluoride)]. 19F NMR has been employed to characterize changes in the chain structure as a function of radiation dosage. Multivariate statistical analysis of the NMR data elucidates significant variance from comparatively minor changes in the collected NMR spectra, extracting meaningful information on subtle degradation mechanisms from the spectroscopic data. It is shown that the combination of NMR and principal component analysis reveals that PCTFE units are particularly susceptible to the effects of γ-irradiation and that scissioning and cross-linking occur simultaneously. The results of the statistical analysis are supported by gel permeation chromatography and dynamic scanning calorimetric analyses. The combination of statistical analysis with 19F NMR offers a non-destructive means of studying degradation in fluoropolymeric materials.