Aqueous polyurethane adhesives are non-toxic, non-flammable and do not pollute the air. However, they have low adhesive strength compared with solvent-based polyurethane adhesives due to the low affinity with the substrate.
In this study, polyurethane adhesive was synthesized from isophorone diisocyanate(IPDI), dimethylol propionic acid (DMPA) as the ionic center in the main chain, triethylamine (TEA) as the neutralization agent, and hydrazine as the chain extender. The polyol was modified by using hydroxyl-terminated polybutadiene(HTPB), hydroxyl-terminated acrylonitrile-butadiene copolymer (HTBN). The effect of the content of HTPB and HTBN on the adhesive strength was investigated. The effect of molecular weight was also investigated. The increase of HTPB and HTBN content led to the increase of the adhesive strength because of the increase of chemical affinity between adhesive and substrate. The adhesive strength increases, as the molecular weight is increased. This is due to the increase of tensile strength and modulus.