Investigation of sorption for the vapours of organic species in polyethylene on the basis of the Orr equation

Abstract

The experimental isotherms were interpreted as for the sorption (at 293 K) for a range of organic vapours. Materials of various structure and polarity were sorbed in low-density polyethylene (LDPE). The Orr isotherm equation was used with the modification that an additional term was introduced taking into account the elastic properties of the material. The calculation of sorption obeying the Orr equation is given together with the theoretical evaluation of the parameters of the equation. This allows the derivation of data comparable with the experimental ones and the evaluation of the role of the cluster formation during the sorption of low-molecular weight-species in the polymeric matrix. The formation of the sorbate clusters in the polymeric matrix can be predicted from the anisotropy of intermolecular interactions in the respective liquids; it is a consequence of the non-spherical shape of the molecules and of the effects of polar and specific interactions. It was shown that carbon tetrachloride and cyclohexane are sorbed mainly as monomers while hexane, methylene chloride, ethyl acetate and acetone are sorbed as clusters of various structures.