Aspects of solubility, surfaces and diffusion in polymers

Eleven different plots are discussed. These relate to each other since diffusion, surfaces, and solubility in polymers are involved in some way in each of them. These plots and the understanding associated with them are summarized as follows: 1. To explain that polymer film formation by solvent evaporation takes place in two stages, using amount of solvent retained versus a dimensionless time as axes. 2. To correctly measure diffusion coefficients of challenge chemicals in polymers over the entire concentration range. Required corrections for surface resistance and concentration dependence were found from appropriate solutions to the diffusion equation. 3. To confirm that solutions to the diffusion equation with significant surface resistance combined with concentration diffusion coefficients yields absorption rates of the type normally called anomalous (Case II, Super Case H). 4. To report concentration profiles for anomalous diffusion (Case II, Super Case II, etc.) using a plot of weight gain versus distance into a polymer film for different elapsed times. To do this the diffusion equation was solved with significant surface resistance combined with concentration dependent diffusion coefficients. 5. To correct for surface or cup resistance in permeation measurements using a plot of the inverse of the apparent transport coefficient versus the inverse of the film thickness. 6. To explain that the formation of water blisters in polymers first occurs at the water saturation point using a plot of weight gain versus the square root of time with water temperature cycling. 7. To characterize physical affinities such as solubility, chemical resistance, permeability, adsorption behavior, etc. for various materials using individual Hansen solubility parameters as axes, two or three at a time. 8. To characterize surface wetting behavior using contact angle/spontaneous spreading/wetting tension data for selected test liquids with individual Hansen solubility (cohesion) parameters as axes. 9. To correlate the solubility of a material in a large number of solvents using a plot of the RED affinity number. 10. To correlate the breakthrough behavior of chemical protective clothing using the molar volume of the challenge chemical versus the RED affinity number as axes. 11. To correlate environmental stress cracking of plastics using the RED affinity number versus the molar volume of the challenge chemicals as axes. (C) 2004 Elsevier B.V. All rights reserved.