Gas Chromatographic Determination of Sorption Isotherms of Vinylidene Chloride on Vinylidene Chloride Copolymers

A simple procedure for obtaining sorption isotherms from chromatographic peak shapes was applied to poly(vinylidene chloride-vinylch-loride 80:20) and poly (vinylidene chloride-actylonitrile 80:20) surfaces using vinylidene chloride as sorbate. Absolute values of the isosteric heat of adsorption (at constant uptake) increased with decrease in the amount of vinylidene chloride adsorbed, indicating a stronger monomer-polymer interaction at lower monomer concentrations. Absolute values of Gibb's free energy of adsorption increased with decrease in monomer concentration and temperature, indicating a more favorable monomer-polymer interaction at low temperatures and monomer concentrations. Data under present experimental conditions correspond to a strong thermodynamic polymer/monomer interaction leading to a substantially limited migration of monomer from a polymeric package into a food contacting medium.