Volume 1 Issue 5
|The Missouri S&T Coatings Institute on April 23, 2004 awarded Dr. James O. Stoffer the “Missouri S&T Coatings Institute Distinguished Scientist Award¿?. This award is given to distinguished scientists who have benefited the coatings field through outstanding research, educational efforts and service. Dr. Stoffer is the third recipient of this award. It was presented by Michael R. Van De Mark, Director of the Missouri S&T Coatings Institute at the annual Chemistry Department awards banquet. |
Dr. James O. Stoffer was born on October 16, 1935 in Homeworth, Ohio. He received his B.S. in Chemistry from Mount Union College in 1957 and his Ph.D. from Purdue University in 1961. He did a post doctoral study at Cornell University from 1961-63. In 1963 he entered the Missouri School of Mines as an assistant professor. He was granted tenure and promoted to Associate Professor in 1966 and Full Professor in 1982. In 1985 he became a Senior Investigator with the Materials Research Center. He directed the Missouri S&T Paint Short Course Program from 1985-87. He became the Director of the Materials Research Center in 1992 through 2001. He became Professor Emeritus in 2000. He was hired back by the University part time to continue his research activities with his four graduate and three post doctorate students. Most of his efforts are now directed toward finding a replacement for chrome in air craft coatings. Some success has been made and a non-chrome primer has been developed, licensed by Deft and is now commercially available for use by the Air Force that performs as good as the present chromate primers.
Dr. Stoffer’s accomplishments are extensive including:
He has published over 117 papers and given numerous presentations. He also holds several patents. He has been a very highly regarded grantsman averaging over $250,000 per year for the past five years.
Technical Insights on Coatings Science
Zeta Potential: Does Zeta have potential in coatings?
Zeta potential is zero when the surface charge is zero. This potential is a measure of the potential drop in the diffuse double layer. For pigments, the pH at which the zeta potential is zero is critical to the dispersion of pigments. In general, if the pH of the water in the coating is above the pH of zero charge, the pigment will usually bear a negative charge. If all the particles in the paint bear a negative charge they will repel each other and the system will be more stable, less likely to flocculate. A general rule of thumb is to try to have the pH at least 0.5 pH units above the point of zero charge. Many pigment manufacturers will give this value for their pigments. It may be necessary for you to ask the pigment manufacturer for the value. In coatings, we stabilize our dispersions by either steric or ionic stabilization. If our pigments can be made to be ionic just by pH, we will not require as much dispersant to help stabilize our pigments. Most dispersants are oligomeric materials with anionic groups on the chain. When they adsorb on the pigments they create a negative charge to the particle analogous to the effect we described at pHs above the zeta potential.
The analytical methods depend upon the type of chemistry you are following. Many reactions can be followed by infrared spectroscopy. In this method the loss or formation of an absorption band would be followed as a function of time. Reflectance, UV or even transmission can be used. We have utilized quartz disks coated with a clear reaction cure coating and followed the chemistry of cure via transmission. When using these techniques, care must be taken to insure that a quantitative method is employed and that all the variables such as thickness are controlled. Ultrasonic transmission can be used to follow the curing process since the speed of sound and the interfacially reflected signal both have a matrix dependency. Thus this technique can be used. The ultrasonic method should use a transducer of 100 MHz or higher frequency in either a pitch and catch or transmission mode. We have successfully watched paint dry by this technique. If the film can be removed through the use of a release coating, free standing films can be analyzed by other methods. The curing of the “dry¿? film can be followed by solid state NMR, but the film should be solvent free since no solvent evaporation will occur in the NMR. Through the use of NMR, many resin curing chemistries can be followed. In addition to the above, hardness, solvent resistance (MEK double rubs) and even calorimetric measurements can be used to gain insight as to the curing of a coating.
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|September 13-17/04 Basic Composition of Coatings This course provides an overview of the components of paint and how they work. Participants are also introduced to methods for testing and manufacture of paint.|
|September 27-October 1/04 Introduction to Paint Formulation This course provides techniques used in|
formulating paint from raw materials. It involves formulating and making paint in the laboratory, "Hand on!"
|Coatings for Engineers available on-line anytime This course is designed to educate engineers in coatings science. Coatings systems will be covered from cleaning and surface prep to pretreatment, priming and topcoats. Specification and testing sections will aid all engineers who are charged with these tasks.|
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