Summary: The use of PMMA as dental and osseous cement and also in the fabrication of intraocular lenses has been widely reported. The combination of its excellent properties with those of hydroxyapatite (HA) to form a composite material, can result in very interesting properties as a biomaterial. The key is to obtain a good filler dispersion and interface bonding. Ultrasonic radiation seems to be a very versatile method for the synthesis of these materials, since the use of conventional initiators can be avoided, the filler dispersion improved and the interface interaction can be promoted. In the present work PMMA/HA composite materials were prepared by three different synthesis routes using ultrasonic radiation, in order to study the effect of the synthesis method on the final microstructure. Method I : in situ synthesis of PMMA and HA, under ultrasonic radiation by emulsion polymerization of MMA and HA precursors. Method II : in situ synthesis of HA, (from its precursors) by high frequency ultrasound in commercial PMMA solution Method III : in situ polymerization of MMA under high frequency ultrasonic radiation and adding HA to the solution and Method IV Mixing of hydroxyapatite nanocrystals, in different proportions, in a solution of commercial PMMA, by different periods from 10 min to 7 h, under low frequency (conventional) ultrasonic radiation, to compare the effect of high frequency and conventional ultrasound radiation. The different materials were characterized by FTIR, SEM, TEM, DRX, 1H NMR and TGA. The results showed that, all the composites prepared by in situ synthesis showed an interaction between HA and PMMA, manifested by a bonding of the phosphate groups with the polar groups of the polymer matrix observed by FTIR. On the other hand, when the synthesis was carried out simultaneously adding HA and PMMA precursors a inhibition of the polymerization reaction of MMA was observed. 相似文献
Novel apatite/silica composite materials were synthesized by modifying the surface of silica gel beads or plates with apatite. An alternate soaking process, which involves alternate soaking in a CaCl2/tris-HCl aqueous solution (pH 7.4) and a Na2HPO4 aqueous solution, was utilized to prepare a composite of silica gel and apatite. The characteristics of apatite formed on the surface of silica gel have been studied using X-ray diffraction, Fourier-transform infrared spectrophotometry (FT-IR) and scanning electron microscopy (SEM). Data clearly showed surface modification of silica with the crystalline apatite. Pore volume and specific total surface area, which were measured using nitrogen gas adsorption apparatus, were decreased after apatite deposition on the surface of silica gel beads, whereas the external surface area was increased drastically. The alternate soaking process made it possible to prepare apatite/silica gel composites in a remarkably short period of time, i.e. several hours. 相似文献
Membranes of chitosan (CTS) and composite membranes of CTS with bioglass are prepared by solvent casting. The composite membranes are shown to induce the precipitation of apatite upon immersion in SBF. The biomineralization process is followed by measuring the variation of the viscoelastic properties of the membranes immersed in SBF, both online and offline. Non‐conventional DMA is used to measure the change in the storage modulus, E′, and the loss factor, tan δ, as a function of the immersion in SBF. A simple model is used to estimate the E′ of the apatite layer formed in vitro that is about 130 MPa. This work shows that innovate mechanical tests can be useful to characterize the mechanical performance of composites under physiological conditions.
In this study we investigated the interdiffusion between PVDF and PMMA below the melting temperature of PVDF by ATR-FTIR spectroscopy. The influence of the stereoregularity of different PMMA samples was studied. The PMMA tacticity showed a significant influence on the kinetics of the diffusion. Syndiotactic PMMA diffuses faster than isotactic and atactic PMMA which can be explained from the difference of chains stiffness between the two stereoisomers. 相似文献
HA/TiO2 composite coating were fabricated via adding TiO2 powder in the electrolyte by electrodeposition. The influence of current density and deposition time on the content of TiO2 in the coating, the influence of the content of TiO2 in the coating on the bonding strength of coating and the influence of sintering temperature on the structure and the bonding strength of coating were investigated. The experiment results show that the content of TiO2 in the coating increase with reducing the current density and prolonging the deposition time, the bonding strength improve with increasing the content of TiO2 in the coating, which can obtain 18.7 MPa when the weight percent TiO2 in the coating attain 72.2 %. The addition of TiO2 in the coating reduces the thermal expansion coefficient of the coating, improves the bonding strength of coating and changes the fracture mechanism of the coating from adhesion failure to cohesive failure. HA in the composite coatings is decomposed by the catalysis reaction of TiO2 at the temperature of sinter 850 ℃. Differential scanning calorimetry and X-ray diffractometry analyses showed that the chemical reaction between HA and TiO2 lead to the product are α-TCP and CaTiO3 at the temperature of sinter 1200 ℃. In order to prevent the coating from decomposing and attain hign bonding strength, the sintering temperature should be less than 820 ℃. 相似文献
Summary: Dispersing surface‐modified zinc oxide nanoparticles (ZnO) in methyl methacrylate (MMA) improves the free radical bulk polymerization process as well as the thermal stability of the formed polymer. Hydroxy groups available on the ZnO surface may induce a degenerative transfer. This suppresses the gel effect, which leads to a better control of the heat evolution during the late stages of polymerization. The formation of chains having vinylidene end groups and head‐to‐head links is suppressed, which shifts the onset of thermal decomposition to the regime where decomposition occurs by random chain scission.
Thermal degradation profiles of PMMA and its composite with ZnO at 11 wt.‐%. 相似文献
