Surface adhesion of pMDI resin on wood biopolymer model films

Even though polymeric diphenylmethane diisocyanate (pMDI) resin shows strong adhesion in wood bonding, its adhesion to major wood biopolymers is not fully understood. Thus, this study reports the surface adhesion of pMDI resin on wood biopolymer model films, such as cellulose, hemicellulose and lignin. The effects of wood biopolymer chemical structure, surface roughness, and wettability on the adhesion measurement were examined. The results revealed that, in general, pMDI exhibited greater adhesive force toward lignin model films compared with other biopolymer films. This is because lignin has abundant phenolic hydroxyl groups and aromatic rings, smoother surface, and higher surface-free energy than celluloses and hemicelluloses. This result suggests that the surface properties and hydroxyl group content of wood biopolymer provide a significant role in the bonding interaction between pMDI resin and wood biopolymers.