ABSTRACT
The diffusion coefficients of the untreated natural rubber film, as determined by diffusion time lag measurements, were 1.04 106 cm2/s for nitrogen and 1.15 106 cm2/s for oxygen. The nitrogen diffusion coefficient decreased to 2.8 107 cm2/s and the oxygen diffusion coefficient decreased to 3.2 107 cm2/s for the 240-min argon plasma-treated film. This indicates that the increase of oxygen permeability coefficients (to sustain O2 permeability of untreated film) is due to an increase in the solubility of oxygen in the Ar plasma-treated natural rubber film. A plausible reason for the increased oxygen solubility is the formation of polar groups on the Ar plasma-treated natural rubber surface due to the introduction of polar groups caused by the post-plasma reactions of dangling bonds with ambient oxygen, which makes the top surface more specifically interact with oxygen.
