| Volume 2 Issue 6 What’s Happening at Missouri S&T: Missouri S&T Chemist Earns EPA Award for "Green" Latex Paint Additive US Representative Jo Ann Emerson Congratulates Missouri S&T Chemist Dr. Michael Van De Mark
Van De Mark's invention reduces harmful VOCs in latex paint. Latex paint makes up approximately 65 percent of all paint used in the U.S. and it contains two sources of volatile organic components. One component is a glycol that is used as an antifreeze and for wet edge retention; the other is a coalescing agent. Van De Mark’s invention, a vegetable-oil derivative, replaces the volatile coalescent with one that doesn’t leave the film. “It doesn’t continuously plasticize the paint forever,¿? Van De Mark explains. “It air oxydizes and oligomerizes the additive, linking several coalescent aid molecules together to form a low-molecular weight polymer, and you get part of the hardness back. It softens the paint right away, but over a period of weeks, it regains most of its hardness.¿? Latex resins are solid particles of plastic approximately one-tenth of a micron in diameter. Without a coalescent aid in the paint mixture to allow the drying particles to flow together to form a film, a hard-type resin will crack as it dries. “With the coalescent aid, those little hard particles are softened and flow together, forming a film,¿? Van De Mark explains. “Without the coalescent aid, you can’t form a film.¿? Traditional coalescing agents soften the paint, then evaporate away to return the paint’s hardness, releasing the solvent into the air, which adds to air pollution. To create the derivative, Van De Mark took a simple glycol and reacted it with the unsaturated fat, the vegetable oil, which then formed a new coalescent aid. Unlike traditional chemicals like IBT filmer (a trade name of Dow), Texanol (a trade name of Eastman) and butoxy ethanol, Van De Mark’s product stays in the paint. Van De Mark’s invention was licensed by Archer Daniels Midland and is currently marketed under the trademark Archer RC. The process works with any unsaturated oil derivative, but ADM chose to use sunflower oil. Van De Mark first invented the additive 10 years ago while trying to find a use for Missouri plant-based oils, originally studying soybean oil derivatives with funding from the Missouri Soybean Merchandising Council. The Presidential Green Chemistry Challenge was established in 1995 as part of the Reinventing Environmental Regulations Initiative to promote pollution prevention and industrial ecology through a new EPA Design for the Environment partnership with the chemical industry. EPA’s Office of Pollution Prevention and Toxics leads this voluntary partnership program. In addition to Van De Mark, the award is shared by Dr. Paul Bloom and Dr. George Poppe from ADM; and Jeff Nelson of Stepan Co., who were responsible for implementing the Missouri S&T technology. Fall Short Courses This fall we will be offering “Basic Composition of Coatings¿? on September 12-16, 2005 and “Introduction to Paint Formulation¿? on October 10-15, 2005. The Basic Composition course is intended for new personnel in the coatings profession. It targets the components of coatings (resin, pigments, extenders, solvents and additives), testing and specifications, general formulation and manufacturing methods. Basic Composition is primarily a lecture course with several laboratory demonstrations. The Introduction to Formulation course is intended to give the person a fundamental knowledge of how to approach a starting formulation and troubleshoot it. This course involves both lecture and laboratory work For more information see our web site at http://coatings.mst.edu/ and to register contact Michael Van De Mark at coatings@mst.edu or call 573-341-4419. Spring Short Courses We will also be offering "Basic Composition of Coatings" on March 14-18, 2006 and "Introduction to Paint Formulation" on May 16-20, 2006. Summer Interns Remember to contact us early if you are planning to hire a summer intern next year. We will make sure that our students are informed of the opportunity. Technical Insights on Coatings Science What Causes "Mud Cracking" In Some Formulations? Mud cracking is a condition in which the film dries with shrinkage. As the solvent, or water, is lost from the film, the net volume of the paint film decreases. If the surface undergoes a more rapid volume loss than the material beneath, but both are virtually solid, stress develops. As the stress increases, a fault develops and a crack forms. This condition is very prevalent in highly pigmented systems such as low cost flat latex and inorganic zinc rich primers. Both of these systems are formulated with high pigment loading. In the case of the zinc rich primer, the high zinc content is to give conductivity between the zinc particles which offer galvanic protection. The low cost flat paints are usually formulated with high extender pigment loadings which reduce the coating’s cost. The mud cracking condition generally implies the coating has been formulated close to the CPVC (critical pigment volume concentration). To avoid cracking of this type, keep the applied single coat film thickness low. This allows the stress to be minimized and thus fewer and finer cracks. If thicker films are required, the customer will need to apply multiple coats to avoid mud cracking. The End User Side Bonding in Wood Products The condition known as side bonding is generally applied to floor coatings or in multiple board structures. When a coating such as a urethane varnish is applied to a wood floor, the coating not only coats the top of the board but penetrates between the boards. When dry, the coating between the boards bonds the boards together. This is called side bonding. Wood exhibits unique properties when compared to steel, aluminum or concrete. Wood not only changes dimension with temperature as do the others but exhibits a more substantial dimensional change due to humidity changes. The increase in humidity will cause the wood to expand and conversely contract as the humidity drops. These changes in a small board are measurable. When a large floor such as a gym is coated, the expansion and contraction of the floor could easily be several inches. If all the boards are side bonded and one bond is weak all the expansion or contraction will occur at that weak site causing a large crack to form on contraction or the floor to buckle when it expands. If the side bonding is relatively weak, the boards can break where stress is formed to relieve it locally, forming very small cracks. Another way to think of this is to assume a shrinkage of 0.01 inch per board width. If the floor is 1000 boards wide, a total of 10 inches of shrinkage would be possible. If the cracks between the boards were 0.01 inch it would not be noticeable, but if in the middle of the floor there was a 10 inch crack, the floor would be unusable. Thus, testing of the side bonding strength is very important in these types of finishes including finishes for hard wood paneling and many cabinetry applications. The ASTM D6958-03 method is typically used to quantitatively evaluate this property. It reports the tensile strength of the bond between two blocks of wood bonded by the coating after the appropriate cure and at set humidity and temperature conditions. Controlling the side bonding strength is a significant problem for both the formulator and the coater. Any error could result in major floor or wall paneling cracks. Is there a topic you would like discussed? Contact us by e-mail at coatings@mst.edu. |
| September 12-16, 2005; March 14-18, 2006 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. |
| October 10-15, 2005; May 16-20, 2006 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!" |
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