Considerations for Raman spectroscopic determination of polyene length distribution in degraded poly(vinyl chloride)

Abstract

Practical complications in the quantitative Raman spectroscopic determination of the polyene sequence length distribution in degraded poly(vinyl chloride) samples were found. If samples are measured directly, i.e. without dissolving them, the distribution of polyenes changes during the Raman experiment if power densities above 20 W/mm2 are used. Lower power densities or short exposure times (<1 min) must be used to avoid these effects. The direct method turned out to be an appropriate method for the quantitative determination of the polyene length distribution in lightly degraded poly(vinyl chloride) samples (<0.05 % HC1 loss). If the samples are dissolved in tetrahydrofuran, the influence of laser power is negligible. However, in that case other problems are encountered; solutions must be stored in a cooled state and in the dark in order to avoid disappearance of the polyenes. Moreover, the solution process results in an altered polyene sequence distribution. The tetrahydrofuran method turned out to be a quick and convenient way to obtain information about the polyene sequence distribution for samples with relatively high degradation levels (>0.05% HC1 loss).

Use of a rapid scanning stigmatic Raman imaging spectrograph in the industrial environment

“…These have included in situ electrochemical experiments4 and the study of dynamic reacting systems at elevated temperatures or press~res.~ Other investigations have included corrosion studies,6 the study of polymer morphology' and polymer degradation. 8 In 1966, the first paper demonstrating the practical application of Raman spectroscopy using a researchgrade near-infrared Fourier transform (FT) spectrometer was published.' This was quickly followed in a subsequent paper by the demonstration of FT-Raman spectroscopy on an inexpensive bench-top interferometer.…”

Selective elimination in dialkoxy-PPV precursors yielding polymers with isolated tetraalkoxy-stilbene units

“…Although this preference cannot be concluded from Fig. 2(a), there is experimental evidence available from the elimination of HC1 from PVC [14]. In the base-catalysed elimination of the sulfonium group and HCI, however, no carbenium ion intermediate is expected (E2-mechanism).…”

PVC Morphology

“…Kip et al 31 argued that the polyene sequence distribution might not be the same for the skin and core of the PVC grains. Braun et al 121 believe that sample morphology may affect dehydrochlorination rate.…”