How to not come unglued: A wood adhesive story

It all started with a broken (tanbur) neck

A traditional Persian tanbour. Photo credit: nasehpour.com

While playing the tanbur in his native country of Iran, tonight’s guest Yahya Mousavi found the wooden instruments are sensitive to the moisture and it cannot produce high quality sounds in humid conditions. The tanbur, a traditional Persian string instrument, is the ancient ancestor of the guitar with a pear-shaped body composed of wood, a long neck, and many strings. In his third year of undergraduate studies, Yahya begin to develop a suitable substitute for wood in making musical instruments. He shared his idea with his professor. The professor was excited about the idea and allowed Yahya to pursue the research, which resulted in many publications, such as [1-3], both in English and Persians, as well as the manufacturing a tanbur, a setar, and a tar (the names of some Persian musical instruments) from polymeric composites, rather than wood.

Hunting for safe adhesive alternatives

Wood Science & Engineering PhD Student, Yahya Mousavi

It seems that wood science has always piqued Yahya’s interest, but now instead of focusing on instruments, he is focusing on an issue with a much broader impact – developing a safe, sustainable adhesive for wood composite production. Wood-composites such as particleboard and plywood wood are mainly used to construct buildings, make furniture, cabinetry, etc.; however, in order to make these wood composite panels, an adhesives have to be used to hold all the layers together. The problem is, the adhesive that has been used historically and is currently in use contains the toxic chemical formaldehyde, which is known to cause different cancers and mental disorders. The California Air Resources Board (CARB) passed a regulation on limiting formaldehyde emission from wood-based products used and sold in California in April 2007. A national regulation of limiting formaldehyde emission, ‘‘formaldehyde standards for composite wood products act,’’ was signed into law on July 7, 2010.

This has been the focus of Yahya’s PhD research for the past three years in Dr. Kaichang Li’s lab in the Department of Wood Science and Engineering in Oregon State University’s College of Forestry. The first goal of the research was to find a safe replacement for formaldehyde-based adhesives. Currently, isocyanates is being used as a replacement, but poses similar health risks. Secondly, the Li Lab was seeking to find something renewable. Yahya set out to find if he could fulfill both of these goals with soybean-based adhesives. In order to do so, he would need to find a way to make an adhesive that could pass all the standard requirements for use, which requires various water soaking tests. The main issue with soy-based adhesives was that they are not water resistant.

Close-up view of plywood board. Photo credit: apawood.org

Success for soy-based adhesives

In his research, Yahya was able to crosslink the functional groups of soybean flour using a polymer named poly (glycidyl methacrylate-co-styrene) (PGS). To do this, poly (glycidyl methacrylate-co-styrene) (PGS) emulsions were synthesized through a free radical initiated emulsion polymerization of glycidyl methacrylate (GMA) and styrene. The PGS was characterized with FTIR, and investigated as a curing agent for soybean flour (SF)-based wood adhesives. Seven-ply plywood panels were prepared with the SF-PGS adhesives and were evaluated for their water resistance through a three-cycle water-soaking test. Effects of the PGS/SF weight ratios, hot press temperature, hot press time, and usage of NaOH on the water resistance of the resulting plywood panels were investigated. Plywood panels made with the SF-PGS adhesives met the industrial requirement for interior plywood. More information about this research can be found in [4].

In another study, Yahya was able to develop a cold-set wood adhesive based on soy protein isolate. This adhesive was able to pass all the standard requirements for exterior plywood such as the two-cycle boil test, dry shear test, and cyclic-boil shear test. Now, Yahya is working to modify this cold-set adhesive for manufacturing of cross-laminated timber (CLT) panels, which are a novel wood product recently introduced to the construction industry and it is expected to grow very fast.

While Yahya is not personally involved in the translation of his research into industry practices, the ultimate goal would be for these soy-based adhesives to be widely used by the wood composite industry reducing widespread exposure to toxic chemicals.

Following passion with purpose

Yahya enjoying one of Oregon’s many waterfalls at Silver Falls State Park.

Yahya is an engineer by trade and began his career in polymer engineering when obtaining his Bachelor of Science and Master of Science at the Islamic Azad University (IAU)in Tehran, Iran. (Fun fact: IAU is the fifth largest university in the world based on an enrollment of over 1.5 million students!?) Yahya hopes to one-day have a faculty position where he can continue conducting polymer research on meaningful projects.

Join us on Sunday, October 14 at 7 PM on KBVR Corvallis 88.7 FM or stream live to learn more about Yahya’s quest to find a safe, sustainable wood adhesive alternative and his journey to graduate school at Oregon State.

[1] Jalili MM, Pirayeshfar AS, Mousavi SY (2012) A comparative study on viscoelastic properties of polymeric composites measured by a longitudinal free vibration non-destructive test and dynamic mechanical thermal analysis. Iran Polym J 21:651–659. DOI: 1

[2] Jalili MM, Mousavi SY, Pirayeshfar AS (2014) Investigating the acoustical properties of carbon fiber-, glass fiber- and hemp fiber-reinforced polyester composites. Polym Compos DOI: 10.1002/pc.22872.

[3] Jalili MM, Mousavi SY, Pirayeshfar AS (2014) Flexural free vibration as a non-destructive test for evaluation of viscoelastic properties of polymeric composites in bending direction. Iran Polym J (2014) 23: 327. DOI: 10.1007/s13726-014-0227-x.

[4] Mousavi SY, Huang J, Li K (2018) Investigation of poly (glycidyl methacrylate-co-styrene) as a curing agent for soy-based wood adhesives. Int. J. Adhes. Adhes 82: 67-71, DOI: 10.1016/j.ijadhadh.2017.12.017.

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