General considerations

The measurement of residual content requires the complete extraction of the target substance from the polymer.

This can be achieved by headspace or by dissolving the polymer with a strong effective solvent and re-precipitating the polymer with a solvent that would not risk entrapping again the substance.

It is widely accepted that the solvent used should both dissolve the target compound well and also swell or dissolve the polymer matrix. Polymer swelling data are readily available in the literature, but the solubilities of the selected substances in potential extraction solvents are not always available and sometimes have to be estimated as a function of the analyte and of the extraction solvent. Several combinations solvent/analyte/polymer have been used. Tetra-hydrofuran (THF) has been used to dissolve PVC, as well, other extraction procedures are Soxhlet and reflux. The polymeric material is extracted with a solvent, for example it can be isooctane for 4 h at 60°C (conventional conditions for tests — Directive 82/711/EEC) [57].

The sample preparation involves usually pre-cutting the polymer or materials in small pieces or grinding to facilitate the extraction process.

0 0

Post a comment