Integrating Multi-Scale Studies of Adhesive Penetration into Wood

The development of new and improved wood adhesives is hindered by an incomplete mechanistic understanding of what makes a wood-adhesive bond able to withstand changes in moisture levels. Although common methods are established to test and report the bulk level properties of bondlines, such as bondline shear strength and wood failure analysis, the development of experimental tools to study wood-adhesive bondlines and the effects of moisture at the nm- to mm-length scales remains an active area of research. Here we introduce and briefly review four recently developed tools that, when combined, we have found capable to facilitate the study of bondlines and the effects of moisture across these length scales. The tools are X-ray computed tomography (XCT), X-ray fluorescence microscopy (XFM), nanoindentation, and small angle neutron scattering (SANS). Their combined utility has been demonstrated by studying model bondline systems made using loblolly pine and phenol formaldehyde adhesives. The results led to a n...