The following is taken from a publishers accounting of my accomplishments in an attempt to promote a handbook: "Charles M. Hansen began his work with solvents in 1962, and almost immediately began producing new and groundbreaking results. Since then his Hansen solubility (or cohesion) parameters have been extensively used and proven valuable to a variety of industries and in research. They allow correlations and systematic comparisons previously not possible, such as polymer solubility, swelling, permeation, surface wetting and dewetting, solubility of organic salts, and many biological applications, including such materials as drugs, skin, proteins, cholesterol, etc. (see the second edition of the my handbook on Hansen solubility parameters."

For my own part, among the most important accomplishments, seen with my own perspective of some 45 years in active research include:

Showing that solvent retention in coatings is a matter of slow diffusion to and through the coating just at the air surface, and not a matter of hydrogen bonding as thought at that time.

The development of Hansen solubility parameters in an attempt to determine the importance of hydrogen bonding for solvent retention. It was not hydrogen bonding that caused solvent retention. These parameters are now applied to gases, liquids, solids, polymers, biological materials, etc. etc. and have been confirmed by a statistical thermodynamic approach by Prof. Panayiotou (See Chapter 3 in the second edition of the handbook). The agreement for a large number of liquids and polymers is amazing and certainly very satisfying.

An emphasis on the size and shape of diffusing molecules as being of major importance in absorption, diffusion, and permeation in polymers.

The conclusive proof that the concentration dependent diffusion follows an exponential relation. This was confirmed by solving the diffusion equation many times and comparing solutions with experimental data. These comparisons for both absorption and desorption that give the same diffusion coefficients over a very wide concentration range conclusively support this approach.

The recognition that surface resistance can be significant in absorption into polymers. Combining surface resistance with the exponential diffusion equation accounts for what has erroneously been called non-Fickian diffusion. The usual diffusion equation is quite valid without add-ons, just so one includes both the verifiable concentration dependent diffusion coefficients together with a verifiable surface resistance.

There is still need for much work on surfactants, drugs, biological applications, and the like. See suggestions in the second edition of the handbook for more details. Remember that almost any gas, liquid, surface, or other item that behaves differently when contacted with different solvents will presumably lend itself to a Hansen solubility parameter characterization.