NMR imaging-A promising new adhesive evaluation technique

Nuclear magnetic resonance imaging (NMRI) has been used to study the nature of the adhesive bond formed by using a water based poly(vinyl acetate) (PVAc) adhesive to glue together Finnish pine wood blocks. Using NMRI, it is possible, in a non-invasive way, to follow the curing of the adhesive in the joints and to observe flaws and voids in the resulting bond structures. The spatial resolution of the NMR image at 300 MHz is < 100 μm. As the drying occurred, voids were observed to form in the adhesive layer as a consequence of the loss of water and the shrinkage of the adhesive. The results indicate that NMRI will find many applications in adhesive studies, since one can view the action of the adhesive system in the form of images which are easily interpreted.