Effect Of Surface Modification On Adhesion Improvement Between The Silicon Rubber Substrate And Antibacterial Composite Coationgs

In recent years, polymer materials have been widely used in the medical field. However, implant-associated infection occurs easily in clinical applications and leads to increased pain and medical cost. Therefore, antibacterial medical materials become one of the most important research focuses. Silver (Ag) is a broad-spectrum antibacterial agent and has superior heat resistance, safety and non-talerance, so it is widely used in the field of antibacterial. Antibacterial coatings on medical polymer surface is approved an effect way to solve the problem. In addition, electrolss plating method is chosen to prepare the antibacterial coatings. Electroless plating need only simple equipment, applicable to both conductive and non-conductive substrates, and cost is lower comparing to other methods. But adhesion between the polymer matrix and the metal-based coatings is very weak, and the coating is readily to be peeled off, leading to limited clinical applications. In this study, surface modification is employed with the purpose to improve surface activity and reactivity, and the as-prepared antibacterial coatings bond chemically onto modified substrates and the adhesion is enhanced remarkably.Ultraviolet radiation (UV) and plasma are used to generate active groups on the inert silicon rubber surface, and the followed grafting of silane coupling agent forms self-assembly monolayer (SAM) and active the substrates surface. Effect of different modification method, processing time and coupling agents on adhesion improvement is studied to obtain optimal technological conditions. X-ray photoelectron spectroscopy (XPS) is used to analyze surface composition, scanning electron microscopy (SEM) is employed to observe the morphology, energy dispersive X-ray spectroscopy (EDS), mapping are applied to analyze the elements distribution. ASTM D3359(Standard Test Methods for Measuring Adhesion by Tape Test) and anticorrosion test are used to test the adhesion between the coatings and the substrate. The antibacterial performance was tested by inhibition zone test and flask shaking method. The results show that:(1) Ultraviolet radiation (UV) and plasma technology can both induce reactive groups onto the substrate surface, which is in favor of the reaction between coupling agents (y-aminopropyl triethoxysilane and y-mercaptopropyl trimethoxysilane) and silicon rubber substrates and form self-assembled monolayer (SAM). N and S was detected illustrating the grafting of coupling agent on the substrate surface. (2) N or S in silane coupling agent (y-aminopropyl triethoxysilane and y-mercaptopropyl trimethoxysilane) has lone electron pair and they anchor Ag+during electroless plating and so the Ag antibacterial coatings are bonded onto matrix surface covalently, leading to enhanced adhesion. It is proved that plasma treatment and3-mercaptopropyltrimethoxysilane (KH590) grafting give the optimal adhesion. According to ASTM, the adhesion is classified5B.(3) The as-resulted antimicrobial coatings are completed, uniform and crack free with components distribute uniformly. The coatings possess superior antibacterial performance.(4) The established modification strategy employed in this paper is convenient, reliable and repeatable, and the coatings have satisfied adhesion and superior antibacterial performance. This method can be extended for commercial applications.