Assisted permeation through surface fluorinated polymers

The permeation rates of constituent components of toluene and methanol mixtures through surface fluorinated, fluoroxidized and unmodified HDPE was measured using a new flow through chamber, GC-based technique. The polymer systems demonstrated assisted permeation wherein the presence of one component increased the permeation rate of a second minor component. The presence of 1000 ppm of methanol in the solvent mixture increased the permeation rate through the fluoroxidized composite by over an order of magnitude. For the unmodified HDPE, the activity adjusted toluene permeability (Ptoluene) remained virtually constant, independent of the methanol concentration. Swelling due to the presence of toluene in the plastic for the unmodified HDPE case increased the methanol permeability by three orders of magnitude. The Ptoluene for the surface fluoroxidized composite was determined to be 1.5±0.4×10−7 cm2 s−1 (cm Hg)−1 and the Ptoluene for the surface fluoroxidized layer was found to be 1.1±0.4×10−9 cm2 s−1 (cm Hg)−1, an 850-fold decrease in permeability relative to the untreated HDPE. The long term Ptoluene for the fluorinated composite was found to be 0.6±0.3×10−7 cm2 s−1 (cm Hg)−1.