Improving hydrophobicity on polyurethane-based synthetic leather through plasma polymerization for easy care effect

This study reports on the deposition of a hydrophobic coating on polyurethane (PU)-based synthetic leather through a plasma polymerization method and investigates the hydrophobic behavior of the plasma-coated substrate. The silicon compound of hexamethyldisiloxane (HMDSO), inactive gas argon (Ar), and toluene were used to impart surface hydrophobicity to a PU-based substrate. Surface hydrophobicity was analyzed by water contact angle measurements. Surface hydrophobicity was increased by deposition of compositions of 100% HMDSO, 3:1 HMDSO/toluene, and 1:1 HMDSO/toluene. Optimum conditions of 40 W, 30 s plasma treatment resulted in essentially the same initial contact angle results of approximately 100° for all three treatment compositions. The initial water contact angle for untreated material was about 73°. A water droplet took 1800 s to spread out on the plasma-treated sample after it had been placed on the sample surface. An increase in plasma power also led to a decrease in contact angle, which may be attributed to oxidization of HMDSO during plasma deposition. XPS analysis showed that plasma polymerization of HMDSO/toluene compositions led to a significant increase in atomic percentage of Si compound responsible for the hydrophobic surface. The easy clean results for the treated and untreated PU-based synthetic leather samples clearly showed that the remaining stain on the plasma-polymerized sample was less than that of untreated sample. The plasma-formed coating was both hydrophobic and formed a physical barrier against water and stain.     

Evaluation of deflection amplification factor in steel moment‐resisting frames

Steel moment‐resisting frames (SMRFs) are the most common type of structural systems used in steel structures. The first step of structural design for SMRFs starts with the selection of the structural sections on the basis of story drift limitation. ASCE 7 (2010) requires that the inelastic story drifts be obtained by multiplying the deflections determined by elastic analysis under design earthquake forces with a deflection amplification factor (C_d). For special moment‐resisting frames, C_d is given as 5.5 in ASCE 7 (2010). Lower C_d values will increase the overall inelastic response of the structure. On the other hand, the inelastic response of the structure is expected to be less severe when designed for higher C_d values. The performance objective is that the structure should sustain the inelastic deformation demand imposed due to design earthquake ground motions. This study aims at investigating the inelastic seismic response that low‐rise, medium‐rise and high‐rise SMRFs can experience under design earthquake ground motions and maximum considered earthquake (MCE) level ground motions and evaluating the deflection amplification factors (C_d) for SMRFs in a rational way. For this purpose, nonlinear dynamic time history and pushover analyses will be carried out on SMRFs with 4, 9 and 20 stories. The results indicate that the current practice for computing the inelastic story drifts for SMRFs is rational and the frames designed complying with the current code requirements can sustain the inelastic deformations imposed during design earthquake ground motions when seismically designed and detailed. Copyright © 2013 John Wiley & Sons, Ltd.     

Influence of different boron precursors on superconducting and mechanical properties of MgB2

The superconducting, structural and mechanical properties of MgB₂ bulk samples have been studied as a function of precursor B powder particle size by means of AC susceptibility, XRD and microhardness measurements, respectively. The in situ processed MgB₂ samples have been prepared by means of conventional solid state reaction method with magnesium powder (99.8 %, 325 mesh) and four different types of boron powders (95.2, >95, 91.9 and 86.7 %) from two sources, Pavezyum and Sigma Aldrich. The XRD measurements showed that the diffraction peaks for our samples belong to the main phase of the MgB₂ diffraction patterns. The highest critical temperature T _c = 37.7 K was achieved for the MgB₂ sample which was fabricated by using >95 % purity amorphous boron. Microhardness measurements were performed to investigate the mechanical properties. Load independent hardness, Vickers microhardness, Young’s modulus, fracture toughness, and yield strength values were calculated separately for all samples. The results were analyzed by using the Meyer’s law, proportional sample resistance model, elastic–plastic deformation model, Hays Kendall approach, and indentation induced cracking (IIC) model. It was found that the IIC model is the most successful model to describe the mechanical properties of our samples.     

An artificial neural network model for virtual Superpave asphalt mixture design

This study presents an artificial neural network (ANN) model to predict the asphalt mixture volumetrics at Superpave gyration levels. The input data-set needed by the algorithm is composed of gradation of the mix, bulk specific gravity of aggregates, low- and high-performance grade of the binder, binder content of the mix and the target number of gyrations (i.e. N_ini, N_des and N_max). The proposed ANN model uses a three-layer scaled conjugate gradient back-propagation (feed-forward) network. The ANN was trained using data obtained from numerous roads with a total of 1817 different mix designs. Results revealed that the ANN was able to predict V_a within V_a (measured) ± 1.0% range 85–93% of the time and within V_a (measured) ± 0.5% range 60–70% of the time. Currently with the developed ANN model, Superpave mix design can take approximately between 1.5 and 4.5 days, which corresponds to 3–6 days of savings.     

Adsorption and surface complexation study of L-DOPA on Rutile (α-TiO₂) in NaCl solutions

Dihydroxyphenylalanine (DOPA) and similar molecules are of considerable interest in studies of bioadhesion to minerals, solar cells involving titanium dioxide, and biomedical imaging. However, the extent and mechanisms of DOPA adsorption on oxides in salt solutions are unknown. We report measurements of DOPA adsorption on well-characterized rutile (α-TiO?) particles over a range of pH, ionic strength, and surface coverage as well as a surface complexation model analysis establishing the stoichiometry, model surface speciation, and thermodynamic equilibrium constants, which permits predictions in more complex systems. DOPA forms two surface species on rutile, the proportions of which vary strongly with pH but weakly with ionic strength and surface loading. At pH < 4.5 a species involving four attachment points ("lying down") is important, whereas at pH > 4.5 a species involving only two attachment points via the phenolic oxygens ("standing up") predominates. Based on evidence of strong attachment of DOPA to titanium dioxide from single molecule AFM (Lee, H. et al., Proc. Natl. Acad. Sci.2006, 103, 12999-12003) and studies of catechol adsorption, one or more of the DOPA attachments for each species is inner-sphere, the others are likely to be H-bonds.     

EFFECT OF FINE SOLID PARTICLES ON GAS-LIQUID MASS TRANSFER RATE IN A SLURRY REACTOR

The influence of suspended fine particles of differing adsorbing capacity (activated carbon, avicell cellulose, SiO₂, and molecular sieves) on the liquid-film mass transfer coefficient κ_L, was examined experimentally in a stirred cell of well-defined gas-liquid interfacial area by chemical methods. The greatest effect on κ_L was observed with the activated carbon (about a threefold increase). An addition of glycerine in excess of 2.5 × 10^-3 k mol/m³, which was adsorbed on the particles preferentially, removed this increase in κ_L totally. Amongst other particles, only avicell cellulose showed measureable effects. The increase in κ_L values was inversely proportional to the temperature and the stirring speed, and the particle loading was found to be immaterial after a certain value. When the reaction rate increased (hence, when the thickness of dissolved gas-rich layer decreased) by gradual addition of a homogeneous catalyst (i.e. Co⁺⁺ for sulphite oxidation), the effect of particles on κ_L decreased and eventually it disappeared.