Polyurethane adhesive system from biomaterial-based polyol for bonding wood

Polyester polyols for use in the preparation of polyurethane (PU) adhesives were synthesized from potato starch and natural oils by a transesterification reaction. These polyester polyols were combined with an aromatic adduct based on toluene 2,4-diisocyanate to form a PU adhesive. Both the polyols and the PU adhesives were characterized by means of FTIR spectroscopy. The adhesive performance of the PU adhesives in bonding wood was evaluated by lap shear tests. The effect on adhesion of variation of NCO/OH ratio and hydroxyl value were studied. The change in lap shear strength before and after exposure to cold water, hot water, acid, and alkali were evaluated. Development of bond strength to wood was determined by means of tests at regular intervals, and also curing time required for different adhesive formulations were determined. The PU adhesive derived from natural products was found superior to the commercially available adhesive.