Search Results (17)

In this study, we developed a cost-effective and rapid method for fabricating force-sensing resistor (FSR) sensors as an alternative to commercial force sensors. Our aim was to achieve performance characteristics comparable to existing commercial products while significantly reducing costs and fabrication time. We analyzed the material composition of two widely used commercial force sensors: Interlink FSR-402 and Flexiforce A201-1. Based on this analysis, we selected 4B and 9B pencils, which contain high concentrations of graphite, and silicone sealant to replicate these material properties. The fabrication process involved creating piezoresistive sheets by shading A4 copy paper with 4B and 9B pencils to form a uniform layer of graphite. Additionally, we prepared a mixture of 9B pencil lead powder and silicone sealant, ensuring a consistent application on the paper substrate. Measurement results indicated that the force sensor fabricated using a mixture of 9B pencil powder and silicone sealant exhibited electrical and mechanical characteristics closely resembling those of commercial sensors. Load tests revealed that the hand-made sensors provided a proportional voltage output in response to increasing and decreasing loads, similar to commercial FSR sensors. These results suggest that our fabrication method can produce reliable and accurate FSR sensors suitable for various applications, including wearable technology, robotics, and force-sensing interfaces. Overall, this study demonstrates the potential for creating cost-effective and high-performance FSR sensors using readily available materials and simple fabrication techniques. Full article

The waterways adjacent to Washington DC, USA have a history of contamination from heavy metals, nutrients, pesticides, and industrial chemicals. Among the chemicals of concern are PAHs, which are a historical contaminant but also have modern pyrogenic and petrogenic sources in the area’s waterways. Another group of contaminants that are of emerging interest are siloxanes (silicones), which are widely used as lubricants, sealants, and cosmetics. Some lower-molecular-weight siloxanes are regulated by the EU in recognition of harm to aquatic life, but there are no restrictions in the United States. In fact, studies examining water pollutants do not typically test for siloxanes. Here, we present the concentrations of specific PAHs and siloxanes from surface sediments in the Potomac and Anacostia Rivers (including the Anacostia’s tributaries) collected between 2018 and 2023. Both D5 (decamethylcyclopentasiloxane) and D6 (dodecamethylcyclohexasiloxane) were found in most locations, with concentrations averaging 0.13 and 0.006 mg/g (dry mass), respectively. Pyrene, fluoranthene, bibenzyl, and phenanthrene were also found in the Anacostia and some of its tributaries, with concentrations increasing downstream. In the Potomac, concentrations were generally lower than those observed in the Anacostia. Based on ratios of pyrene to fluoranthene + pyrene, the likely source of PAHs was petrogenic. Full article

The longevity of polymer-based sealant and jointing products, including elastomers, significantly depends on the level of exposure to sunlight and joint movement. These factors are particularly crucial in the application of polymers in construction due to their susceptibility to degradation under environmental conditions. For instance, diurnal cycles of contraction and dilation, arising from daily temperature fluctuations, impose significant stress on sealants and joints, impacting their durability over time. The elastic nature of polymeric sealants enables them to endure these cyclic mechanical loads. Athough there is considerable information on sealant durability obtained from laboratory accelerated aging, there is limited knowledge about the effect of climatic factors using historical and projected weather data on the durability and expected service life of these products. This study employed the Shephard crack growth model to predict the performance of sealants in a Canadian context; the crack growth and time-to-failure of hypothetical silicone sealants were investigated across 564 locations, for which historical climate data were obtained from 1998 to 2017, including gridded reanalysis data for the period of 1836–2015. The historical climate data were classified into four climate categories, and crack growth was estimated based on historical climatic data within the valid range for the Shephard model, revealing that locations in colder climates with lower levels of precipitation typically exhibit higher cumulative crack growth. The impact of climatic variation and environmental stressors on the longevity of sealants in the context of climate change was also investigated using future projected data. Full article

The evaluation of the shear performance of stone panel–panel joints (SPPJs) in stone cladding has important engineering significance, as it plays a crucial role in stone cladding failure. The purpose of this paper is to analyze and predict the influence of the dimension and the Young’s modulus of sealant on the shear performance of SPPJs. Based on monotonic and cyclic loading tests, the effects of Young’s modulus and the dimension of sealant on the failure characteristics, stress–strain characteristics, stiffness degradation, and energy dissipation capacity of an SPPJs were investigated. According to finite element analysis, the strain distribution of an SPPJ under monotonic loading was analyzed for different sealant widths and number of sealant layers. The results indicate that the failure modes of SPPJs change with the variation of sealant amount. As the Young’s modulus of the sealant increases, the shear failure strength and shear yield strain of SPPJs increase. The increase in sealant thickness reduces the shear failure strength and stiffness of SPPJs. Based on the same shear strain, the increase in the sealant thickness enhances the cumulative energy consumption of SPPJs. The strain concentration zone of the specimens with two sealant layers in unilateral SPPJs becomes larger with the increase in sealant width. Full article

An extensive parametric study of the seismic response of one-storey precast buildings with horizontal cladding panels frequently used in Central Europe was conducted to analyse the panels’ influence on the overall response of buildings and to find out if the panels can be considered non-structural elements when they are attached to the main building with the connections typically used in practice in Central Europe. The studied structural system consisted of reinforced concrete columns and beams connected by dowels. Horizontal cladding panels were attached to columns using one of the most frequently used isostatic fastening systems. The top connections provided out-of-plane stability, and the bottom connections supported the panel in the vertical direction. The parametric study was preceded by extensive experimental research, including cyclic tests on connections and full-scale shaking table tests of whole buildings. The results of experiments were used to reveal the basic response mechanisms of panels and connections and to develop, validate and calibrate numerical models employed in the parametric study presented herein. Fifteen generalised structures with different masses and heights were subjected to 30 accelerograms with two peak ground acceleration (PGA) intensities of 0.3 g and 0.5 g, corresponding to significant damage and near-collapse limit states. The effects of the construction imperfections in connections, the silicon sealant panel-to-panel connections and different types of connections of the bottom panel to the foundation were analysed. The crucial parameter influencing the response was the displacement capacity of the connections, which was considerably affected by the construction imperfections and, consequently, difficult to estimate. It has been observed that in some buildings, particularly in shorter structures with smaller mass, cladding panels can have a somewhat more notable influence on the overall response. However, in general, when the considered types of connections are used, the panels can be considered as non-structural elements, which do not importantly influence the response of the main building. Owing to structural imperfections and relatively short available gaps, the failure of the considered top connections and falling of the panels is very likely in the high seismicity regions. In the most adverse cases, it can occur even in the moderate seismicity regions. Full article

Real-time polymerase chain reaction (real-time PCR) tests were successfully conducted in an aluminum-based microfluidic chip developed in this work. The reaction chamber was coated with silicone-modified epoxy resin to isolate the reaction system from metal surfaces, preventing the metal ions from interfering with the reaction process. The patterned aluminum substrate was bonded with a hydroxylated glass mask using silicone sealant at room temperature. The effect of thermal expansion was counteracted by the elasticity of cured silicone. With the heating process closely monitored, real-time PCR testing in reaction chambers proceeded smoothly, and the results show similar quantification cycle values to those of traditional test sets. Scanning electron microscope (SEM) and atomic force microscopy (AFM) images showed that the surface of the reaction chamber was smoothly coated, illustrating the promising coating and isolating properties. Energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma-optical emission spectrometer (ICP-OES) showed that no metal ions escaped from the metal to the chip surface. Fourier-transform infrared spectroscopy (FTIR) was used to check the surface chemical state before and after tests, and the unchanged infrared absorption peaks indicated the unreacted, antifouling surface. The limit of detection (LOD) of at least two copies can be obtained in this chip. Full article

We propose a complex sealing compound for increasing the efficiency of shutoff operations based on natural materials processing for materials such as sand, peat, rice, and husks. We studied the influence of mechanical activation processes on the mechanical and rheological properties of the developed sealants. Through mechanochemical activation, sand dissolution in a low-concentrated alkali solution was possible, and gelling the resulting sodium silicate while reinforcing it with undissolved sand particles to obtain a sealant composition. We used this approach to produce a hybrid sealing compound based on activated rice husks with up to 20% biogenic silicon dioxide combined with mechanically activated peat: the maximum shear strain of the hybrid sealant was 27.7 ± 1.7 Pa. We produced hydrogels based on sodium silicate, polyacrylamide, and chromium acetate, reinforced with mechanically activated rice husks. We studied the sealants’ rheological and filtration properties and observed the respective viscoplastic and viscoelastic properties. An increase in the dispersion concentration from 0 to 0.5% increased the maximum strain value of undestroyed hydrogel’s structure in the range 50–91 Pa and the maximum shear strain from 104 to 128 Pa. The high residual resistance factor values of the ideal fracture model make the natural and plant-renewable raw materials very promising for repair and sealing work. Full article

This study presents results on the development of strontium oxide (SrO) containing glass sealants used to join Crofer22APU to yttria-stabilized zirconia (3YSZ), in which the main glass components, that is, silicon oxide (SiO₂), strontium oxide (SrO), calcium oxide (CaO) and aluminum oxide (Al₂O₃), have been varied appropriately. Certain properties, such as the crystallization behavior, the coefficient of thermal expansion, adhesion, and reactivity of the sealants in contact with Crofer22APU, have been reviewed and discussed. The optimized glass composition (with CTE in the 9.8–10.3 × 10⁻⁶ K⁻¹ range) results in a good joining behavior by hindering the formation of undesirable strontium chromate (SrCrO₄) on contact with the Crofer22APU steel after 1000 h. at 850 °C. High specific resistivity values of about 10⁶ Ohm.cm have been obtained, thus demonstrating good insulating properties at 850 °C under an applied voltage of 1.6 V. A negligible degradation in the electrical resistivity trend was measured during the test up to 1000 h, thus excluding the presence of detrimental reactions of the glass-ceramic sealant in contact with Crofer22APU under a dual atmosphere, as confirmed using SEM-EDS post-mortem analyses. Full article

Expansion joint failure is one of the main causes that lead to the damages of concrete pavement. The silicon dioxide/shape memory polyurethane (SiO₂/SMPU) is a new kind of sealant which can use its shape memory performance to adapt to the width of the expansion joint with the change of pavement temperature, and it can effectively prolong the service life of the pavement and reduce maintenance costs. In this study, the effects of programming and the addition of SiO₂ particles to the thermodynamic properties of the specimens were detected using differential scanning calorimetry (DSC), the optimal shape memory programming temperature of which is 72.9 °C. Combined with scanning electron microscopy (SEM) and shape memory effect test, the particles are evenly distributed between the two phases, and the shape fixation rate (R_f) of 98.15% and the shape recovery rate (R_r) of 97.31% show that the composite has a good shape memory effect. Fourier transform infrared spectroscopy (FTIR) and dynamic infrared dichroism illustrate the change of the hydrogen bond of soft and hard segments with the SiO₂ particles in the shape memory cycle, revealing the optimal shape memory programming process. This study provides an insight into the reinforcement mechanism of SiO₂ nanoparticles in SMPU matrix and verify whether it can meet the engineering requirements of expansion joints when used as a sealant of concrete pavement. Full article

In this paper, new prefabricated cold-formed light-gauge steel stud wall panels sheathed with fireproof phenolic boards, which are fabricated by connecting the steel studs and the boards by using structural silicone sealant, was proposed. The proposed prefabricated wall has a good fireproof performance and can be manufactured rapidly in a factory. Full-scale tests on the mechanical properties of the prefabricated wall system, consisting of the prefabricated wall and the connection between the wall and the surrounding steel structure under out-of-plane loading, were performed. A total of six specimens were tested considering the effects of the arrangement of the cold-formed light-gauge steel studs, the shape and thickness of the steel connector for jointing the prefabricated wall panel and the surrounding steel structure, and the number of self-tapping screws connecting the surrounding structure. The results show that the out-of-plane stiffness of the prefabricated wall system in the elastic stress state under out-of-plane loading can be increased by increasing the number of self-tapping screws, increasing the thickness of the steel connector, or adopting the symmetrical arrangement of the light-gauge steel studs. The out-of-plane stiffness of the prefabricated wall system and the stiffness contribution of a single special-shaped steel connector can both be increased by increasing the number of special-shaped steel connectors. Furthermore, the special-shaped steel connector is more beneficial to a greater out-of-plane stiffness than the L-shaped steel connector. In addition, the theoretical calculation methods for deflection of the proposed prefabricated wall and flexural stress of the CFS C-channel stud considering the fireproof phenolic board sheathing effect under elastic state were proposed. The predicted results using the proposed method are compared with test results and the predicted results by using other methods. It was found that the predicted results by using the proposed method agreed better with the test results compared with the predicted results using the transformed-section method or the reduced stiffness method, which demonstrates the acceptability and accuracy of the proposed mothed for calculating deflection of the proposed prefabricated wall and flexural stress of the CFS C-channel stud. Full article

High stability and transparent superhydrophobic coating on a glass substrate that can effectively repel the wetting dust as a self-cleaning property are beneficial traits for solving the decrease in optical lens clarity in an unmanned underground mining environment. However, the transparent superhydrophobic coating has still not been applied due to the contradiction between visibility, hydrophobicity and durability. Herein, a sandwich-like superhydrophobic coating was designed and prepared on borosilicate glass, which consisted of a micro/nanostructure body of neutral silicone sealant (primer) and hydrophobic silica nanoparticles (interlayer), as well as a protective layer of ultraviolet (UV) gel. The coated glass exhibited excellent superhydrophobicity towards many aqueous solutions, and had highly visible light transparency of 80% at 4 wt.% primer mass content. Furthermore, significant tests including the droplet impact, hot water boiling, stirring in acetic acid aqueous solution and sandpaper abrasion were performed on our superhydrophobic coating, which indicated that the obtained transparent coating had good stability and excellent mechanical durability. The coated glass also showed a more wonderful self-cleaning property compared with that of the original glass. This superhydrophobic coating on glass substrate, fabricated by a facile and cost-effective layer-by-layer construction approach, has great potential for general and practical application in the unmanned mining environment under multiple dust and atomized water conditions. Full article

In the cyclic racking evaluation of curtain wall systems, physical testing with instrumentation is the standard method for collecting performance data by most design professionals. The resulting testing of full-scale mockups can provide many types of data, including load and displacement values at different stages of loading through failure. While this type of data is valuable for product/system development/fabrication and design, such data can also provide a means for simulation validation of the curtain wall cyclic performance under simulated earthquake loading. Once the simulation study is validated using the test results, then parametric studies by designers can be conducted with greater ease, ideally with commercial software packages, without the need for testing. For the results of this research study, a practical industry formulated finite element modeling (FEM) approach was used to predict the performance of the curtain wall mockups. Here, unitized four-sided structural sealant glazing (4SSG) curtain wall system mockups that incorporate a re-entrant corner were subjected to cyclic racking displacements per the American Architectural Manufacturers Association (AAMA) 501.6 Structural Sealant protocol. System performances, including displacements, were obtained from the FEM study and used to calculate the effective shear strain of the structural silicone and the drift capacity of the system. This paper describes the details of the techniques developed for FEM, the analysis results, and shows an example application of the numerical modeling approach for mockups with racking test results available. The goal of this modeling approach was to create and test methods that practicing consulting engineers can quickly conduct in their offices on common commercially available software often available to them. Full article

Curtain wall glazing systems are a major part of a building due to the multiple roles they have, including occupant protection against environmental effects and the transfer of loads to the structural system. From a structural perspective, limited analytical guidelines and methods exist to aid designers in their determination of the curtain wall performance without extensive simulation or laboratory testing. This study takes experimental data from full-scale, “unitized”, four-sided structural sealant glazing (4SSG) curtain wall system mockups featuring a re-entrant corner subjected to cyclic racking displacements in accordance with the American Architectural Manufacturers Association AAMA 501.6 protocol to derive and establish equations that predict the relative displacements of the glass relative to the glazing frame, based on the amount of inter-story drift. Through derivation and testing, sealant cohesive failure and glass cracking were identified as limit states and corresponding drift levels were determined to control many of the equations. Displacements from the newly derived equations were correlated to the effective shear strain value experienced by the structural silicone in the mockup concurrently with the curtain wall’s drift capacity. This paper provides detailed derivation of the kinematic equations for possible use by glazing design professionals. Such equations can help designers to more easily predict the drifts that cause damage to such systems by manual calculations without the need for expensive mockup testing or time-intensive computer models. Full article

A solid-state Ultraviolet-photoreduction process of silver cations to produce Ag⁰ nanostructures on a mesoporous silica is presented as an innovative method for the preparation of efficient environmental anti-fouling agents. Mesoporous silica powder, contacted with AgNO₃, is irradiated at 366 nm, where silica surface defects absorb. The detailed characterization of the materials enables us to document the silica assisted photo-reduction. The appearance of a Visible (Vis) band centered at 470 nm in the extinction spectra, due to the surface plasmon resonance of Ag⁰ nanostructures, and the morphology changes observed in transmission electron microscopy (TEM) images, associated with the increase of Ag/O ratio in energy dispersive X-ray (EDX) analysis, indicate the photo-induced formation of Ag⁰. The data demonstrate that the photo-induced reduction of silver cation occurs in the solid state and takes place through the activation of silica defects. The activation of the materials after UV-processing is then tested, evaluating their antimicrobial activity using an environmental filamentous fungus, Aspergillus niger. The treatment doubled inhibitory capacity in terms of minimal inhibitory concentration (MIC) and biofilm growth. The antimicrobial properties of silver–silica nanocomposites are investigated when dispersed in a commercial sealant; the nanocomposites show excellent dispersion in the silicon and improve its anti-fouling capacity. Full article

The high crystallization at room temperature and high cost of polyoxytetramethylene glycol (PTMG) have become obstacles to its application. To overcome these problems, a segment of PTMG can be incorporated into a block copolymer. In this work, polypropylene (PPO) glycol-polyoxytetramethylene (PPO-PTMG) multiblock copolymers were designed and synthesized through a chain extension between hydroxyl (OH)-terminated PPO and PTMG oligomers. The chain extenders, feed ratios of the catalyst/chain extender/OH groups, reaction temperature, and time were optimized several times to obtain a PPO-PTMG with low crystallization and high molecular weight. Multiblock copolymers with low crystallization and high average molecular weight (M_n = 1.0–1.4 × 10⁴ Dalton) were harvested using m-phthaloyl chloride as the chain extender. The OH-terminated PPO-PTMG multiblock copolymer with high M_n and a functionality near two was further siliconized by 3-isocyanatopropyltrimethoxysilane to synthesize a novel silyl-terminated polyether. This polyether has an appropriate vulcanizing property and potential applications in sealants/adhesive fields. Full article