Incorporation of multiwalled carbon nanotubes to acrylic based bone cements: Effects on mechanical and thermal properties

Polymethyl methacrylate (PMMA) bone cement–multiwalled carbon nanotube (MWCNT) nanocomposites with a weight loading of 0.1% were prepared using 3 different methods of MWCNT incorporation. The mechanical and thermal properties of the resultant nanocomposite cements were characterised in accordance with the international standard for acrylic resin cements. The mechanical properties of the resultant nanocomposite cements were influenced by the type of MWCNT and method of incorporation used. The exothermic polymerisation reaction for the PMMA bone cement was significantly reduced when thermally conductive functionalised MWCNTs were added. This reduction in exotherm translated in a decrease in thermal necrosis index value of the respective nanocomposite cements, which potentially could reduce the hyperthermia experienced in vivo. The morphology and degree of dispersion of the MWCNTs in the PMMA matrix at different scales were analysed using scanning electron microscopy. Improvements in mechanical properties were attributed to the MWCNTs arresting/retarding crack propagation through the cement by providing a bridging effect into the wake of the crack, normal to the direction of crack growth. MWCNT agglomerations were evident within the cement microstructure, the degree of these agglomerations was dependent on the method used to incorporate the MWCNTs into the cement.

Effect of MWCNT addition on the thermal and rheological properties of polymethyl methacrylate bone cement

Multi-walled carbon nanotube (MWCNT)/polymethyl methacrylate (PMMA) composites with loadings ranging from 0.1 to 1.0 wt.% were prepared for use as bone cement. Unfunctionalised, carboxyl and amine functionalised MWCNT were used. Thermal properties were characterised in accordance with the International Standard for acrylic cements, ISO 5833:2002. The rate of reaction exotherm generated and thermal necrosis index (TNI) values were calculated. Polymerisation kinetics were characterised using parallel plate rheology and the exotherm during polymerisation was reduced by ˜4–34%, as a consequence of the MWCNT thermal conductivity. The rate of reaction was significantly altered, such that the setting times of the cements were extended (˜3–24%). Consequently, significant decreases in TNI values (ranging from 3% to 99%) were recorded, which could reduce the exothermic temperatures experienced in vivo and therefore prevent the likelihood of polymerising PMMA cement causing thermally-induced bone tissue necrosis. Thermal data was supported by the rheological characterisation results. Onset of polymerisation for PMMA cement exhibited a strong linear increase as a function of MWCNT loading, however, polymer gelation was not affected to the same degree. It is proposed that the chemically functionalised MWCNT altered PMMA bone cement polymerisation kinetics, reducing the rate of polymerisation, and hence, the reaction exotherm.

Thermal analysis in the drilling of solid rigid foam materials and ex-vivo bovine bones

Bone is a dynamic, highly vascularized tissue with a unique capacity to heal and regenerate without scarring. However, drilling remains a concern in several clinical procedures due to thermal damage of the bone and surrounding tissue. The success of this surgeries is dependent of many factors and also in temperature generation during the drilling bone. When an excessive heat is produced during the drilling, thermal necrosis can occur and the bone suffers injuries. Studies have shown that the increased temperature is directly related with the drilling parameters, particularly, the drill speed, feed-rate, applied force, the depth of cut, the geometry of the drill bit, the use or not of a cooling system and also the type of bone.

Carboxyl functionalised MWCNT/Polymethyl methacrylate bone cement for orthopaedic applications

The incorporation of carboxyl functionalised multi-walled carbon nanotube (MWCNT-COOH) into a leading proprietary grade orthopaedic bone cement (Simplex PTM) at 0.1 wt% has been investigated. Resultant static and fatigue mechanical properties, in addition to thermal and polymerisation properties, have been determined. Significant improvements (p 0.001) in bending strength (42%), bending modulus (55%) and fracture toughness (22%) were demonstrated. Fatigue properties were improved (p 0.001), with mean number of cycles to failure and fatigue performance index being increased by 64% and 52%, respectively. Thermal necrosis index values at 44C and 55C were significantly reduced (p 0.001) (28% and 27%) versus the control. Furthermore, the onset of polymerisation increased by 58% (p < 0.001), as did the duration of the polymerisation reaction (52%). Peak energy during polymerisation increased by 672% (p < 0.001). Peak area of polymerisation increased by 116% (p < 0.001) indicating that the incorporation of MWCNT-COOH reduced the rate of polymerisation significantly. A non-significant reduction (8%) in percentage monomer conversion was also recorded. Raman spectroscopy clearly showed that the addition of MWCNT-COOH increased the ratio between normalised intensities of the G-Band and D-Band (IG/ID), and also increased the theoretical compressive strain (1.72%) exerted on the MWCNT-COOH by the Simplex PTM cement matrix. Therefore, demonstrating a level of chemical interactivity between the MWCNT-COOH and the Simplex PTM bone cement exists and consequently a more effective mechanism for successful transfer of mechanical load. The extent of homogenous dispersion of the MWCNT-COOH throughout the bone cement was determined using Raman mapping. Ke

Análise microscópica de incisões realizadas com três diferentes pontas do laser Erbio YAG

The study analised microscopic wound healing of incision made with Er:YAg laser with three different tips. In six Rattus norvegicus, incision was made with Laser Er-YAG (KeyLaser) using tips 2051, 2055 and 2056. The animals were killed at 7 e 14 and the sites of incision are photographed in this time. The parts containing the incision area were prepared for microscopic analysis, performing sections of 7µm and staining with haematoxylin and eosin. Zone of tissue ablation, zone of thermal necrosis, the presence and character of inflammatory cell infiltrate and wound healing were measured. The 2051 tip produced faster and defined edges of the wound. To create wound 1.30 mm in depth lasers tips required at last five passes within the same line of incision. Microscopic analysis shows no difference with use of three different laser tips

Raman microscopy of formamide-intercalated kaolinites treated by controlled-rate thermal analysis technology

Raman spectroscopy of formamide-intercalated kaolinites treated using controlled-rate thermal analysis technology (CRTA), allowing the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites, is reported. The Raman spectra of the CRTA-treated formamide-intercalated kaolinites are significantly different from those of the intercalated kaolinites, which display a combination of both intercalated and adsorbed formamide. An intense band is observed at 3629 cm-1, attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm-1, assigned to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl-stretching band of the inner hydroxyl is observed at 3621 cm-1 in the Raman spectra of the CRTA-treated formamide-intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. Significant differences are observed in the CO stretching region between the adsorbed and intercalated formamide.

In Situ Observation of the Thermal Decomposition of Weddelite by Heating Stage Environmental Scanning Electron Microscopy

The morphological and chemical changes occurring during the thermal decomposition of weddelite, CaC2O4·2H2O, have been followed in real time in a heating stage attached to an Environmental Scanning Electron Microscope operating at a pressure of 2 Torr, with a heating rate of 10 °C/min and an equilibration time of approximately 10 min. The dehydration step around 120 °C and the loss of CO around 425 °C do not involve changes in morphology, but changes in the composition were observed. The final reaction of CaCO3 to CaO while evolving CO2 around 600 °C involved the formation of chains of very small oxide particles pseudomorphic to the original oxalate crystals. The change in chemical composition could only be observed after cooling the sample to 350 °C because of the effects of thermal radiation.

Thermal decomposition of the synthetic hydrotalcite iowaite

The thermal stability and thermal decomposition pathways for synthetic iowaite have been determined using thermogravimetry in conjunction with evolved gas mass spectrometry. Chemical analysis showed the formula of the synthesised iowaite to be Mg6.27Fe1.73(Cl)1.07(OH)16(CO3)0.336.1H2O and X-ray diffraction confirms the layered structure. Dehydration of the iowaite occurred at 35 and 79°C. Dehydroxylation occurred at 254 and 291°C. Both steps were associated with the loss of CO2. Hydrogen chloride gas was evolved in two steps at 368 and 434°C. The products of the thermal decomposition were MgO and a spinel MgFe2O4. Experimentally it was found to be difficult to eliminate CO2 from inclusion in the interlayer during the synthesis of the iowaite compound and in this way the synthesised iowaite resembled the natural mineral.

Thermal Treatments of Fe—Mn Alkoxide of Glycerol: Infrared absorption and emission

Synthetic Fe—Mn alkoxide of glycerol samples are submitted to controlled heating conditions and examined by IR absorption spectroscopy. On the other hand, the same sample is studied by infrared emission spectroscopy (IRES), upon heating in situ from 100 to 600°C. The spectral techniques employed in this contribution, especially IRES, show that as a result of the thermal treatments ferromagnetic oxides (manganese ferrite) are formed between 350 and 400°C. Some further spectral changes are seen at higher temperatures.