Improvement of adhesive strength of segmented polyurethane on Ti-29Nb-13Ta-4.6Zr alloy through H₂O₂ treatment for biomedical applications

The number of hydroxyl groups on a Ti-29Nb-13Ta-4.6Zr (TNTZ) alloy surface was controlled through H₂O₂ treatment for further improvement of the adhesive strength and durability against water of TNTZ/silane layers (SILs)/segmented polyurethane (SPU) composites. The effect of the terminal functional groups on the adhesive strength of SPU on TNTZ, and the adhesiveness of SPU on TNTZ against water was investigated. Three types of silane-coupling agents were used to bind TNTZ and SPU: methacryloxypropyltrimethoxysilane (γ-MPTS), aminopropyltriethoxysilane (APS), and mercaptopropyltrimethoxysilane (γ-MPS). The adhesive strength of each composite was evaluated by shear bonding tests. The number of hydroxyl groups increases with an increase in treatment time at a H₂O ₂ concentration of 5% (v/v). On the other hand, an increase from 5% (v/v) to 30% (v/v) in H₂O₂ concentration leads to a decrease in the number of hydroxyl groups on the TNTZ surface because at higher H₂O₂ concentrations, the reaction that consumes the hydroxyl groups is dominant. The shear bonding strength is doubled compared with the untreated TNTZ/SIL/SPU interface. Although the shear bonding strength decreases after immersion in water for 30 days when APS and γ-MPS are used, TNTZ/γ-MPTS/SPU composites exhibit good durability to water and maintain an equivalent shear bonding strength before immersion in water.