Interaction of vinyl chloride with poly(vinyl chloride) by inverse gas chromatography: effect of monomer concentration, plasticizer content and temperature.

The interaction of vinyl chloride (VC) with poly(vinyl)chloride) (PVC) has been studied by inverse gas chromatography (IGC). The present work focusses on the effect of monomer concentration, temperature and plasticizer content. Values for thermodynamic parameters such as free energy (delta GS), excess free energy (delta GSXS), enthalphy (delta HS), entropy (delta SS) and activity coefficient (gamma S) corresponding to sorption of the monomer (VCM) by the polymer, have been calculated using chromatographic data. It was found that retention of VC by PVC is favored at lower monomer concentrations. Increase in temperature resulted in increase of delta GS, delta GSXS, and gamma S values corresponding to a less spontaneous process or a weaker interaction between VC and PVC. An increase in plasticizer content of the polymer resulted in an increase of degree of binding of the monomer. Data support the hypothesis that at significantly low concentrations of residual monomer, low storage temperatures and high concentrations of plasticizer, in the polymer, the probability of migration of VC from a plastics packaging material into a food contacting phase is markedly reduced.