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UNI’s Bio Binders Score Well in Casting Trials
McWane-Clow Valve tested bio-urethane nobake (BUNB) cores on a 4-in. valve body (shown left during shakeout) and a 16-in. valve body (shown right with a 250-lb. BUNB core).
The Center for Advanced Bio-Based
Binders (CABB), a project funded by the U.S. Department of Energy and conducted by the Univ. of Northern Iowa (UNI) Metal Casting Center, Cedar Falls, Iowa, have developed two new metalcasting bio-urethane binders, with bio-renewable materials replacing the phenol- and formaldehyde-based part 1 resin of phenolic urethane binders. One new bio-urethane uses the sac-
charides of corn syrup, which is low in cost, readily available and environmen- tally-friendly. The second bio-urethane is based on the humic acids of lignite, which is readily available and mined in all areas of the world. Both binders are compatible with reactive solvents that are low in hazard- ous air pollutants (HAPs) and volatile organic compounds (VOCs). Traditional phenolic ure-
thane binders tend to soften with increasing temperature and by 392F (200C) have lost more than half of their strength at room temperature. The bio- urethane binders have shown a lack of thermal softening and result in less core distor- tion. The lignite binder retains strength properties longer than phenolic urethane for improved
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dimensional accuracy, followed by a quick degradation period at 482F (250C), which aids in shakeout. The saccharide binder also experiences a quick degradation period but retains additional strength after the casting has been poured. The base materials of the bio-ure-
thane binders are less dependent on petrochemicals and show less market price fluctuation. When compared to a traditional phenolic urethane nobake mold, both bio-urethanes generate more than 50% fewer overall HAP emissions during pouring, cooling and shakeout and 80% fewer phenol and formaldehyde emissions.
UNI’s bio-urethanes serve as a di-
rect replacement of phenolic urethane and can be used with current molding equipment in both nobake and coldbox processes. They have been successfully used in casting aluminum, copper-base alloys, gray and ductile iron, and steel. In a casting trial at McWane-Clow Valve, Oskaloosa, Iowa, a 4-in. ductile iron valve body with a 35-lb. bio-urethane nobake core and a 16-in. gray iron valve body with a 250-lb. core were cast. Both castings showed improved casting qual- ity with no shakeout required. A lignite-based bio-urethane coldbox
Progress Castings successfully cast aluminum ATV engine heads using these BUNB cores.
core was tested at Progress Castings, New Hampton, Iowa, for an aluminum all-terrain vehicle engine head. Successful castings were poured 15 minutes after the cores were produced. The cores did not show the core stain usually associated with conventional urethane cores. At John Deere Waterloo Foundry, Waterloo, Iowa, a gray iron axle housing, har- vester discharge elbow and 4,000-lb. gray iron slag pot were cast. The trials exhibited shakeout and surface finish comparable to conventional urethane binders, without the use of a core coating.
MODERN CASTING / June 2010
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