Study of the polyvinyl chloride polymer structure in relation to migration of residual vinyl chloride monomer by inverse gas chromatography

The polyvinyl chloride (PVC) polymer structure was studied using inverse gas chromatography (IGC). The specific retention volume (Vg°) of a vinyl chloride monomer (VCM) probe, as well as the thermodynamic parameters of the interaction between PVC and VCM were calculated. Changes in Vg°, free energy(ΔG°s), enthalpy (ΔH°s) and entropy (ΔS°s) observed as the temperature and the amount of VCM decreased, clearly indicate that the PVC—VCM interaction was both concentration and temperature dependent. The Vg° and thermodynamic parameters also varied with changes in polymer structure. Data were interpreted in terms of the active site hypothesis. Active sites in the PVC matrix strongly bind VCM at low enough concentrations and temperatures. Inferably, migration of VCM from PVC packaging materials containing very low concentrations of residual monomer should be for all practical purposes, essentially zero, particularly at low temperatures.