Wood–thermoplastic adhesive interface—method of characterization and results

The mechanical interlocking of a thermoplastic adhesive and wood substrate is studied with scanning electron microscopy. A thermoplastic/glass composite is bonded to oak (Quercus) using a polypropylene based adhesive. The wood is etched away using a combination of chromic, nitric, and sulfuric acids, leaving the morphology of the adhesive interface intact. The revealed surface is examined with environmental scanning electron microscopy. We have shown for the first time that a thermoplastic adhesive conforms to features of the wood as small as 1 μm across. The adhesive penetrates the vascular tissues of the wood for more than 150 μm through openings 15 μm across, and invades hundreds of microns through larger channels.