INFLUENCE OF A MONOMERIC PLASTICIZER ON THE WATER-SORPTION BEHAVIOR OF FOOD-GRADE PLASTICS PACKAGING MATERIALS

The interaction of water with poly(vinylchloride) and poly(vinylidene chloride-vinylchloride) (p(VdC-VC)) plasticized with different amounts of a monomeric plasticizer (dioctylphthalate) has been studied using inverse gas chromatography. The present work was focused on the effect of temperature and plasticizer content on the water sorption behaviou r of these plastics packaging materials. Values for thermodynamic para meters such as Gibb's free energy (DELTAG(s)), enthalpy (DELTAH(s)), e ntropy (DELTAS(s)) and activity coefficient (gamma) corresponding to s orption of water by the polymers have been calculated using chromatogr aphic retention data. It was found that the sorption of water vapours increases with increasing the amount of plasticizer and decreases with increasing temperature. The Van Deemter equation was found to be appl icable to these systems and was used to determine diffusion coefficien ts and activation energies for diffusion. Diffusion coefficient values increase with increasing amounts of plasticizer and they also increas e with increasing temperature; this latter increase is accompanied by a decrease in the activation energy for diffusion. Present results wer e also compared to our own previous data, using a polymeric plasticize r.