The Study on Tribological Performance of UHMWPE and PMMA Reinforced by GO
|Keywords||Graphene oxide UHMWPE PMMA Friction and wear properties|
Ultra-high Molecular Weight Polyethylene (UHMWPE) is widely used as a kind of artificial joint acetabulum material. However, many clinical studies had demonstrated that the polyethylene wear particles could be produced during the application process owing to its poor wear resistance, which could cause to the bone loss, the aseptic loosening, leading to the failure of joint replacement implant. In addition, as another kind of the medical macromolecule polymer material, the denture base materials made by polymethyl methacrylate (PMMA) exhibits a good appearance and function features. However, some obvious disadvantages restrict its clinical application, such as its low hardness and poor wear resistance. Therefore, it is very necessary to improve the properties of these medical polymer materials for the practical applications. As a new two dimensional nanoscale carbon material composed and tightly connected by the sp" carbon atoms, Grapheme nano-sheet (GNS) has a unique cellular structure and excellent mechanical, electrical, thermal and chemical properties. Graphene oxide (GO) derivatived functionalization from GNS contain a large number of organic hydroxyl groups in its slice layer surface and the edge including the hydroxyl (C-OH), carbonyl (C=O) and carboxyl-(-COOH) group. This makes GO as a reinforcing filler showing a excellent mechanical performance in composite materials, for example, the low friction characteristic and good biocompatibility.Therefore, the UHMWPE and PMMA were used as the main research object in this work. The physical properties and the tribological characteristics of these composites were investigated in this work. The main researches and results are as follows:1. The GO was prepared using a modified Hummers’method, the morphology and the structural of GO were characterized by the Optical microscope (OM), Scanning electron microscope (SEM) and Atomic-force microscope (AFM). The results showed that the GO exhibits a typically wrinkled and layered structure with the width in micrometer range and its thickness within nanometer range. The GO is very easily dispersed into the matrix of composite materials due to some functional groups, such as the carboxyl, hydroxyl, epoxy and other oxygen, Therefore, we can predict that the GO may have a very important value in the medical application field.2. The GO/UHMWPE composites were successfully fabricated through the synthesis route step of liquid-phase ultrasonic dispersion, high-speed ball mill mixing and hot pressing molding technology. The section morphology, the micro-hardness and the tribological performance of GO/UHMWPE composite materials under different lubricating mediums were studied by the SEM, Vicker microhardness meter and UHM-3MT wear testing. The results demonstrated that the fracture surface of pure UHMWPE presents a typical brittle characteristics with smoothing, the smooth section becomes coarse more and more with the increasing of GO in GO/UHMWPE composite materials. The micro-hardness of the composites was improved significantly and the wear resistance was increased varying degrees under different lubrication mediums.3. GO/PMMA composite materials were mixed successfully by the step of liquid-phase ultrasonication dispersion, high-speed ball mill mixing, and finally processed according to dental conventional method. The micro-hardness, the surface hydrophilicity and the tribological performance of these composite materials in artificial saliva were studied by a Contact angle meter, Vicker microhardness meter and UHM-3MT wear testing. The micro-hardness of these composite materials shows slowing down gradually after the first rapid increase trend. The static contact angle become a decreasing trend with the increasing of GO amought. The GO/PMMA composite material exhibits the best wear resistance in artificial saliva lubricating medium, when the GO addition is up to O.lwt.%.