Sticking To It: Early Adhesive Studies Waited Years for Results

Without a good adhesive, plywood is useless, which is true of any glued-laminated product. The following photographs from the 1930’s show that adhesives have been studied for decades at the Forest Products Laboratory, as well as illustrate the point that patience is a necessary virtue when studying durability.

This test fence was constructed to expose plywood samples to the elements to determine the durability of new glues. The test samples were made of the same woods and thickness combinations, but glued with different adhesives. The fence was assembled and then nature was allowed to take its course…for three years!

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As an example of how varied the results were, here is a section of panels glued with phenol-formaldehyde adhesive after three years of braving Wisconsin weather.

plywood3Next, have a look at these panels which endured the same weather but were glued with casein adhesive.

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Yikes.

Not surprisingly, phenol-formaldehyde adhesives became a popular and effective glue for laminated wood products. Decades later, however, it was discovered these adhesives negatively affect indoor air quality, leading FPL researchers to explore alternatives, such as soy-based adhesives.

Today, adhesives research takes place within the Forest Biopolymer Science and Engineering work unit, and while technology has brought us a long way, FPL still has an outdoor test site where researchers can rely on mother nature to put their products to the test — if they have the patience to wait for her.