Sometimes the answers to long-standing questions are right under our noses, even if they are not recognized as such. And some solutions to problems come from unexpected sources. Who would have expected that experts at Oregon State University's College of Forestry would propose a solution to the problem of noxious fumes emitted by binder chemicals used by sand casting foundries to form molds and cores? Or, that their recommendation would be such a simple one?
Sand binders currently available are generally effective, but containing or eliminating the fumes they emit is an ongoing problem, and a cost factor. In the U.S., phenol-formaldehyde resins are widely used, and can emit toxic air pollutants. In China and elsewhere, the emissions may be even worse because the binder chemicals in use are often furan resins and combinations of furan resins and urea-formaldehyde resins.
Kaichang Li, a professor of wood science and engineering at OSU, and other researchers there, have applied for a patent on a new use for an "environmentally benign" compound that works well to bond sand. It also would be much less expensive than the range of commercially available formulations. It's sugar.
"We were surprised that simple sugar could bind sand together so strongly," said Li, who noted that sugar and other carbohydrates are "abundant, inexpensive, food-grade materials. The binder systems we've developed should be much less expensive than existing sand binders, and not have toxicity concerns," he said.
Sugar is highly water-soluble, of course, and the OSU team discovered a novel way to use it to make strong and moisture-resistant sand molds. An inaccurate reading of temperature in a baking oven helped lead to their discovery, they said.
Li and OSU faculty research assistant Jian Huang identified combinations of sugar, soy flour, and hydrolyzed starch, or even sugar alone, bind sand very effectively for molds used to solidify molten metal. The molds set up rapidly and retain their bonded strength in high humidity, which is critical to their effectiveness.
Sugar or the other agricultural products used for this purpose should have no environmental drawbacks, because all or most of the residuals will decompose into carbon dioxide and water.