Volume 2 Issue 4
What’s Happening at Missouri S&T:
Coatings Industry Summer Interns
The Missouri S&T Coatings Institute would like to invite any companies who have interest in coatings to consider sponsoring a Missouri S&T student for a summer intern position. Most students have established their choices for this summer but we are now planning for next year, yes next year. We would like to promote the opportunities to students at Missouri S&T and to students considering a career in chemistry or science. Most students need to find summer support to be able to afford college. Working at a burger joint or in a department store may help pay the bills but will not give the student experience in their field. If you are interested in having a student, please send your contact information to Michael Van De Mark and we will include it in mailings to our students and on promotional material used to attract students from high schools to enter this exciting field.
Technical Insights on Coatings Science
How is Mica typically used in coatings?
Mica is often used in exterior architectural coatings as well as many industrial maintenance paints. Mica is considered a barrier pigment which is used to improve the weather resistance of a coating. The pigment has a large aspect ratio, like a sheet of paper, so it lays flat in a coating parallel to the surface. Oxygen and moisture must travel around the pigment to get to the substrate. The amount of mica used in a coating is typically 25-35 lbs/100 gallons. If this amount is exceeded, the pigment will not lay flat. The result is an increase in permeability rather than a decrease. The mica sheets can have a flattening effect on gloss due to the fact that other pigments may sit on top of the mica particle and stick out of the coating. Mica, in general, is not a pure white pigment and therefore it will add a dirtying of the color of a paint. A close relative to mica is micatious iron oxide. This pigment is extensively used in Europe for coatings of bridges and other steel structures. Its advantage is analogous in that it acts as a barrier pigment. This pigment is gaining popularity here in the US as well. Many of the micatious iron oxide containing systems for bridges are either epoxy or moisture cure urethane coatings.
What factors control the drying of a coating?
The drying of a paint is very complicated in that several things must happen at the same time. The major factor is the evaporation of the solvent or volatile components. During this process, the surface is cooled due to the removal of heat caused by the vaporization of the solvent, i.e. heat of vaporization. The evaporation process creates concentration gradients within the coating which can result in coatings defects such as Bernard Cells, floating or flooding. As the temperature drops, the coating can pick up water from the atmosphere especially if the coating temperature drops below the dew point. Most resins are not water soluble and thus if the coating picks up water it may cause precipitation of the resin or aggregation of the pigment.
Is there a topic you would like discussed? Contact us by e-mail at firstname.lastname@example.org.
|September 12-16, 2005 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.|
|May 16-20, 2005 Introduction to Paint Formulation This course provides techniques used in|
formulating paint from raw materials. It involves formulating and making paint in the laboratory, "Hands 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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