The aim of this study is to investigate the optimum technique to disperse Multi-Walled Carbon Nanotubes (MWCNTs) in SC-1 epoxy uniformly and to evaluate the effect of processing technique on the performance of SC-1 epoxy. To achieve better dispersion, MWCNT was mixed with SC-1 resin directly or premixed with a solvent and then mixed with SC-1 resin after evaporating the solvent using sonication, thinky mixing and three-roll mill methods either in isolation or combination. Flexural tests were performed to evaluate mechanical performances and results exhibit up to 27.13, 13.51, and 21.99% improvement on flexural strength, flexural modulus, and maximum strain, respectively, over neat epoxy with only 0.2 wt % loading. Dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) indicated improvement in storage modulus, T g , inflection temperature, and residue content, respectively over neat SC-1 epoxy. Thermal and mechanical properties at higher loading conditions were seen to either reduce or not significantly improve. This was attributed to high viscosity of nanocomposites as determined by rheological analysis which prevents good dispersion of MWNCTs into epoxy system at 0.4 wt % loading.
Effects of ultraviolet radiation and condensation on the static and dynamic compressive properties of composites with and without nanoclay were investigated. Specimens were exposed to ultraviolet radiation (UV), and alternate ultraviolet radiation and condensation (UC) conditions for 5, 10, and 15 days, respectively. Compression test results showed an increase in strength and modulus with increase in strain rate and nanoclay weight percent loading. However, properties degraded upon conditioning with nanoclay infused systems showing less degradation. Scanning electron micrographs of fractured samples show better interfacial bonding in nanoclay infused composites in 2 wt. % system showing best properties.
Calcium polyphosphate (CPP) hydrogel is used to load erythromycin (EM) and vancomycin (VCM) by means of two loading methods: they are either added directly to the formed CPP hydrogel (Gel Mixture method) or mixed with CPP powders, followed by the formation of CPP‐antibiotic hydrogel (Powder Mixture method). The release of loaded antibiotics from CPP hydrogel is measured up to 48 hr. Compared to Powder Mixture method, Gel Mixture method significantly reduced the burst release of embedded antibiotics. A significant change in CPP hydrogel Raman characteristic peaks is observed only in Gel Mixture method, indicating a close interaction between embedded antibiotics with CPP hydrogel matrix. In contrast, a similarity between characteristic peaks of CPP hydrogel and Powder Mixture method shows that antibiotic incorporation does not interfere with CPP gel formation, resulting in no ionic interaction between antibiotic and polyphosphate chains. Rheometer analysis further confirms that the hydrophobic nature of EM impacts the viscoelastic properties of CPP hydrogel, whereas the hydrophilic VCM exhibits a higher loading efficiency. The potential application of CPP hydrogel as a ceramic matrix for sustained drug release warrants further investigation.
The implementation of biodegradable stents has the potential to revolutionize obstructive coronary artery disease treatment. Limitations still currently exist, however, that prevent biodegradable stents from replacing permanent metallic stents in the global market. The ideal combination of stent properties, including sufficient mechanical strength, controlled degradation, and biocompatibility, has yet to be realized. A novel manufacturing process is proposed that utilizes cold gas-dynamic spraying to fabricate a metal structure with significantly reduced grain size. Iron and stainless steel 316L are combined to form a novel amalgamate with enhanced mechanical strength and a controllable degradation rate, due to the resulting microgalvanic reaction. Flat specimens composed of iron and 316L are fabricated in various compositions, and mechanical and degradation tests were conducted. Femto laser techniques are utilized to produce stents composed of 80% Fe and 20% stainless steel 316L. The in vitro degradation behaviour of the stent is investigated using static and dynamic corrosion tests. It is shown that the corrosion rate can be adjusted to desired values, by varying the weight percentage of iron and stainless steel 316L within the amalgamate.
The aim of this study is to investigate the optimum technique to disperse vapour grown carbon nanofibres (VGCNFs) in SC-1 epoxy uniformly and to evaluate their effect on the performance of SC-1 epoxy. In this study, ultrasonication and Thinky mixing methods were used either in isolation or in combination with 3-roll shear mixing. To achieve better dispersion, VGCNF was tested either by mixing with SC-1 resin directly or premixed with a solvent and then mixed with SC-1 resin after evaporating the solvent. Flexural tests were performed to evaluate mechanical performances, and the results exhibited 25.60% and 8.88% improvement of flexural strength and modulus, respectively over neat epoxy with only 0.2 wt.% loading. Dynamic Mechanical Analysis (DMA), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) indicated improvement in storage modulus, Tg, inflection temperature and residue content respectively over neat SC-1 epoxy. The high viscosity found by rheological analysis prevents their ubiquitous use in fibre reinforced composites. Thermal and mechanical properties at higher loading conditions were seen either to reduce or not significantly improve. These results indicate that the methods used for dispersion are suitable for low weight percent loading only.
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