Magnetic Resonance Imaging as a Tool for Studying Soy-Based Adhesives in Plywood

Magnetic resonance imaging (MRI) is a well-established technique used in medical applications and bio-based research. It has also been used to study wood and composite materials of various types. Soy-based adhesives used in hardwood plywood applications are not very moisture-resistant. We have employed MRI to study water-soaked plywood composites made with soy adhesives in an attempt to gain insight into how water interacts and affects the soy adhesive bondlines. Various MRI data acquisition sequences were used to show how water interacts and migrates within the soy adhesives and to quantify the presence of water at the bondline of the plywood samples. The data from MRI was combined with cyclic testing data of plywood to help understand how soy adhesives can be modified to reduce their moisture sensitivity. MRI of plywood bondlines made with chemically modified soy adhesives shows that moisture ingress can be reduced dramatically. Cyclic water soak/drying testing of plywood made with chemically modified soy adhesives shows that the reduction in moisture sensitivity results in dramatic improvements in bondline durability, as measured by the ANSI/HPVA EF 2020 cyclic testing protocol for hardwood plywood.