Synergistic Regulation Mechanism of Inorganic Thermal Oxidation Coating and Poly (Vinylphosphonic Acid) (PVPA) Coating for High Load Bearing Superlubricity

Abstract

A low friction coefficient and high bearing capacity can improve the service life of implants in the human body. In this study, we firstly investigate the mechanical properties of inorganic thermal oxide coatings on titanium alloy (Ti6Al4V). Tribological experiments were performed for different tribo-pairs under uniform conditions. The inorganic thermal oxide coating on Ti6Al4V formed at 300℃ was found to have excellent tribological properties and can effectively improve the bearing capacity of Ti6Al4V. The organic poly (vinylphosphonic acid) (PVPA) on Ti6Al4V has excellent anti-friction properties, which can help achieve superlubricity. An inorganic thermal oxide/organic PVPA composite coating was fabricated on Ti6Al4V to obtain a surface with low friction and high bearing capacity. It is found that the presence of the thermal oxide doubled the bearing capacity of the composite coating compared to that of the PVPA coating alone. This study can serve as a guide for the modification of artificial joints.

Regulation Mechanism of Special Functional Groups Contained in Polymer Molecular Chains on the Tribological Properties of Modified Ti6Al4V

“…Klein et al found that the polyethylene-glycol-modified surface can exhibit ultra-low friction in an aqueous solution due to the hydroxyl groups on its side chain, which can produce hydration and osmotic pressure effects [14,15]. Poly(vinylphosphonic acid) (PVPA) was found to be an excellent hydrophilic polymer in our previous studies [16,17]. A large number of phosphate groups contained in PVPA molecular chains can not only promote the formation of a stable three-dimensional skeleton structure of the PVPA coating, but also interact with hydrated salt ions and water molecules in the salt solutions to achieve ultra-low friction [10,18].…”

“…PVS, PAA and PVPA coatings were all prepared on Ti6Al4V substrates based on the method of horizontal evaporative self-assembly [17]. First, the Ti6Al4V foils were heated in an oven in air at 140 • C for 8 h to obtain an oxide layer.…”

“…The mold was then heated at the temperature of 50 • C to accelerate the physical adsorption of polymer molecules on Ti6Al4V. PAA and PVS coatings were formed on Ti6Al4V after heating the samples at 120 • C for 24 h [19], while the PVPA coatings were formed on Ti6Al4V after heating the samples at 260 • C for 6 h [17].…”

“…Combined with the stability of the PAA coating in the NaCl solution, carboxyl groups contained in PAA molecular chains can be considered to form stable chemical bonds with the Ti-OH on the Ti6Al4V surface during the modification process, as shown in Figure5c. Previous studies have showed that PVPA molecules can be connected to the Ti6Al4V substrate through P-O-Ti covalent bonds, as shown in Figure5d, ensuring the stability of the entire PVPA coating on Ti6Al4V[17].…”

Superlubricity of Materials: Progress, Potential, and Challenges

“…Researchers have explored the use of self-lubricating materials, such as hydrogels and polymer composites, to achieve superlubric conditions in orthopedic applications. These materials can provide lubrication and reduce friction, thereby reducing wear debris and the potential for inflammation or implant failure [ 74 , 75 , 76 ].…”