Effects of Adhesive Application Methods on Performance of a Soy‐based Adhesive in Oriented Strandboard

A wet method and dry method of applying a soy flour (SF)–curing agent (CA) adhesive onto wood flakes were evaluated for making randomly oriented strandboard (R‐OSB) and OSB. The wet method involved the thorough mixing of SF and CA prior to spraying the SF–CA mixture onto wood flakes. SF:CA weight ratio, adhesive add‐on rate, hot‐press conditions were optimized for enhancing internal bond strength (IB), modulus of rupture (MOR), and modulus of elasticity(MOE) of the resulting R‐OSB. The highest IB, MOR and MOE were obtained at the 1:1 SF:CA weight ratio. IB, MOR and MOE of R‐OSB exceeded the minimum industrial requirements at a ≥7% adhesive add‐on rate, a hot‐press temperature in the 170–220 °C range, and a ≥4 min hot‐press time. The dry method involved spraying aqueous CA solution onto a mixture of SF and wood flakes. The dry method allowed the strengths of the resulting R‐OSB to exceed the minimum industrial requirements at a higher SF:CA ratio (up to 7:1). The dry method was superior to the wet method because a higher SF:CA ratio meant a lower adhesive cost. OSBs made with the SF–CA adhesive had strengths higher than or comparable to commercial OSBs.