| PMMA bone cement is a high molecular polymer, which is generated by polymerization reaction of poly methyl methacrylate (PMMA) and methyl methacrylate (MMA). PMMA bone cement can be firmly fixed with artificial grafts, and has good operability, so the PMMA bone cement is seen as the "gold standard" for replacement of hip joint, knee joint replacement and dentaloperation, etc. However, the tensile strength of PMMA bone cement (24-50MPa) is much lower than its compressive strength (73-120MPa), which leads to brittle fracture of bone cement when subjected to heavy loads. Under cyclic loading, the interface between PMMA bone cement shell and host bone, or bone cement shell and the interface of the implant, easy to produce fatigue crack, cause fatigue fracture. At the same time, the polymeriz-ation reaction of PMMA bone cement is a highly exothermic reaction, with an average of about 554 joule per gram of methyl methacrylate (MMA), so the Local temperature of 80～120℃,60～40 higher than the normal temperature of the human body, which is easy to cause bone cement in the vicinity of human tissue thermal necrosis.Carbon nanotube (CNT) has excellent physical and mechanical properties and is considered to be the ideal reinforcement of composite materials, which has become the most attractive material for the scientific world. CNT can give a lot of new features, the interfacial mechanical behavior of composite materials is an important factor to affect the macro mechanical properties of composites, which has become the focus of the research of composite materials in recent years. Therefore, CNT can be a good substitute for carbon fiber and other traditional materials. CNT acts as a reinforcing material of bone cement, and develops many functions such as carbon nanotube bone cement (CNT/PMMA) composite with good thermal conductivity and resistance to bending and fatigue. However, the Fan Dehua forces between the original carbon nanotubes are easily to be wrapped around the carbon tube, which is not easy to be uniformly dispersed in the matrix of the bone cement. The carbon nanotubes in the composite process with a large number of agglomeration, which affects the interface with the matrix, and these shortcomings limit the excellent performance of carbon nanotubes. How to disperse the CNT into the matrix of the bone cement and improve the interfacial bonding between CNT and matrix is the key problem to be solved.In this paper, Fenton 3 step method is used to remove impurities such as amorphous carbon and catalyst in the original carbon tube, and then we use 2 different methods to modify the carbon nanotubes:One way is to use the 8mol/l(V suifuric:V Nitrate=3:1) to carry out the oxidation of carbon nanotubes (labeled as f-CNT); the second method is to produce aromatic compounds by using glucose water heat treatment method, and successfully on the surface of carbon nanotubes, a layer of nano scale coating layer, which changes the traditional method of polymer monomer to the carbon nanotubes (g-CNT). After the Raman spectra, the characteristics of the water heat treated carbon nanotubes were characterized by strong peaks at 1580cm-1, which proved that the structure of carbon nanotubes was not destroyed. Characterized by Fourier transform infrared spectroscopy, carboxyl peaks appeared around 1736 cm-1 in IR spectra, and 1601 cm-1 is carbonyl KITT syndrome peak and 1211 cm-1 is hydroxyl surface bending vibration peaks. Origin 9 and XPSPEAK 4.1 software were performed to deal with the C and XPS spectra of the surface of the carbon nanotubes. It can be judged that the surface of the carbon nanotube is divided into five peaks, C1～C5, respectively.286.2eV (C3) is (C-OH), and C4 (287.5eV) is (C=O), and C5 (289.4 eV) is (-COOH). The O1s peak of the carbon nanotube surface is divided into three peaks of 01,02 and 03.01 (531.5 eV) can be attributed to O-C=O (C=O),02 (532.6 eV), and 03 (533.7eV) can be classified as C-0 group in ether or phenol. After glucose hydrothermal treatment, the hydroxyl (-OH), carbonyl (>C=0) and carboxyl (-COOH) functional groups are successfully grafted on the pipe wall. Through TEM transmission electron microscope, the surface of carbon nanotubes can be measured successfully by a layer of 12nm-22nm thick coating layer, which can overcome the Fan Dehua force and greatly increases the solubility of carbon in polar solvent. The experimental results show that compared with the traditional acid oxidation method, hydrothermal method is an effective, mild, green and easy to control method.Using the method of ultrasonic vibration, the functionalized carbon nanotubes and MMA solution were mixed evenly, and the PMMA powder and DMPT and BPO were added to produce the PMMA bone cement. According to the international standard of acrylic bone cement ISO-5833-2002, the thermal performance parameters of Tmax, TNI, t, and thermal conductivity were measured. Analysis of variance of the test data (test hypothesis a= 0.01), the experimental results show that:the thermal properties of bone cement were improved after the incorporation of carbon nanotubes.According to the standard of E399-06 ASTM and F2118-01a ASTM, the compressive strength, bending strength, fracture toughness and fatigue strength of bone cement were tested. Based on the 3 parameter Weibull (Weibull) analysis method, we established the fatigue life prediction model of bone cement. The Paris formula is improved, and the CNT/PMMA composite bone cement with a pre fabricated crack is improved. The C and m values of the fatigue crack growth are obtained, and the fatigue crack propagation law of bone cement with the addition of carbon nanotubes was studied.Through the functionalization of carbon nanotubes, the interface between carbon nanotubes and bone cement was improved. The thermal and mechanical properties of bone cement were optimized, and the composite materials with good mechanical properties were obtained. |
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