Fig. 4.
From: Quantifying the fragmentation of polypropylene upon exposure to accelerated weathering
13C CP MAS NMR spectra of A PP with stabilizer and B without stabilizer for different weathering times. Upon irradiation, the generation of new signals assigned as signals I (ketone), II (carboxylic acid), III (peroxide) and IV (alcohol) is observed [56, 57]. No refinement of vinylidenes was performed between 100–150 ppm, since the resonances of the decomposition products of Irgafos® 168 superimpose with the vinylidene resonances. The spectra are normalized to the intensity of the methyl sidechain carbon signal (at approx. 24 ppm). Individual spectra are shifted vertically for better comparability. Exemplarily, the individual fits for the peaks in the spectrum of the 3200 h weathered particles are shown as black lines; Derived proportions (SI Eq. 2 - Eq. 6) of alcohols, peroxides, carboxylic acids and ketones, as functions of the exposure time, for PP particles C with and D without stabilizer. Trend curves with exponential build-up and an induction period (PP with stabilizer) are included as guide for the eye