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Exposure to respirable crystalline silica (RCS) is potentially hazardous to the health of thousands of workers in Great Britain. Both X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy can be used to measure RCS to assess exposures. The current method outlined in the Health and Safety Executive's (HSE) Methods for the Determination of Hazardous Substances (MDHS) guidance series is 'MDHS 101 Crystalline silica in respirable airborne dust - Direct-on-filter analyses by infrared spectroscopy or x-ray'. This describes a procedure for the determination of time-weighted average concentrations of RCS either as quartz or cristobalite in airborne dust. FTIR is more commonly employed because it is less expensive, potentially portable and relatively easy to use. However, the FTIR analysis of RCS is affected by spectral interference from silicates. Chemometric techniques, known as Partial Least Squares Regression (PLSR) and Principal Component Regression (PCR), are two computational processes that have the capability to remove spectral interference from FTIR spectra and correlate spectral features with constituent concentrations. These two common chemometric processes were tested on artificial mixtures of quartz and kaolinite in coal dust using the same commercially available software package. Calibration, validation and prediction samples were prepared by collecting aerosols of these dusts onto polyvinylchloride (PVC) filters using a Safety in Mines Personal Dust Sampler (SIMPEDS) respirable cyclone. PCR and PLSR analyses were compared when processing the same spectra. Good correlations between the target values, measured using XRD, were obtained for both the PCR and PLSR models e.g. 0.98–0.99 (quartz), 0.98–0.98 (kaolinite) and 0.96–0.97 (coal). The level of agreement between PCR and PLSR was within the 95% confidence value for each analyte. Slight differences observed between predicted PCR and PLSR values were due to the number of optimal principal components applied to each chemometric process. The presence of kaolinite in these samples caused an 18% overestimation of quartz, for the FTIR, when following MDHS 101 without a chemometric method. Chemometric methods are a useful approach to obtain interference-free results for the measurement of RCS from some workplace environments and to provide a multicomponent analysis to better characterise exposures of workers. [ABSTRACT FROM AUTHOR]

Hydrothermally synthesised K2ZnSi5O12 has a polymerised framework structure with the same topology as leucite (KAlSi2O6, tetragonal I41/a), which has two tetrahedrally coordinated Al3+ cations replaced by Zn2+ and Si4+. At 293 K it has a cation-ordered framework P21/c monoclinic structure with lattice parameters a = 13.1773(2) Å, b = 13.6106(2) Å, c = 13.0248(2) Å and β = 91.6981(9)°. This structure is isostructural with K2MgSi5O12, the first cation-ordered leucite analogue characterised. With increasing temperature, the P21/c structure transforms reversibly to cation-ordered framework orthorhombic Pbca. This transition takes place over the temperature range 848−863 K where both phases coexist; there is an ~1.2% increase in unit cell volume between 843 K (P21/c) and 868 K (Pbca), characteristic of a first-order, displacive, ferroelastic phase transition. Spontaneous strain analysis defines the symmetry- and non-symmetry related changes and shows that the mechanism is weakly first order; the two-phase region is consistent with the mechanism being a strain-related martensitic transition. [ABSTRACT FROM AUTHOR]

The effects of thermo-mechanical auxetic foam conversion parameters on the Young's modulus and Poisson's ratio of open-cell polyurethane foam are related to changes in chemical bonding and cell structure. Applied volumetric compression, conversion temperature, and duration are reported on foam Young's modulus, Poisson's ratio, and structural stability. Fourier transform infrared spectral analysis on samples converted at and above 160 °C strongly indicates a hydrogen bond interaction increase in urea groups (C¼O---H-N) and an increase in hydrogen bonding population. Spectral changes inferred soft segment degradation following extensive heat exposure (200 °C, 180 min), specifically a shift and intensity change in CH2 and C-O-C polyol bands and a broad baseline increase between 3600 and 2400 cm-1. These changes are linked to (i) resistance to dimensional recovery over time and during re-heating; (ii) Poisson's ratio becoming negative, then zero in tension or marginally positive in compression; (iii) Young's Modulus reducing then increasing; (iv) mass loss, evidenced by thermogravimetric analysis increasing from 150 °C. The minimum mean values of Poisson's ratio of ≈-0.2 (to 10% compression/tension) are comparable to other studies. All samples that retain their imposed compression over time are isotropic, with near constant Young's moduli and Poisson's ratio (to 10% compression/tension). [ABSTRACT FROM AUTHOR]

ABSTRACT Composite films were formed by incorporating three different bentonites into an ethylene modified, water-soluble poly(vinyl alcohol), EPVOH. The interaction of EPVOH with both hydrophilic and hydrophobic bentonites was investigated. EPVOH provided lower water vapor and oxygen transmission rates compared to a conventional PVOH grade when exposed at high relative humidities (70-90% RH). EPVOH films which exhibited oxygen barrier properties comparable to that of a biaxially oriented PET packaging film at 80% RH were produced. High compatibility between EPVOH and hydrophilic bentonites provided an even distribution of clay platelets in the composites. A strong increase in Young's modulus with increased addition of any of the three bentonites was found. At low addition levels the hydrophobic bentonite proved to be effective in terms of maintaining high elongation at break, high transparency and high gloss. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41737. [ABSTRACT FROM AUTHOR]

The competitive adsorption of poly(ethyleneglycol) (PEG) and poly(vinylalcohol) (PVOH) onto Na-bentonite has been assessed quantitatively.Particular emphasis was focused on the amount of organic located withinthe bentonite interlayer and any subsequent effects on the extentof layer expansion. The individual isotherms showed strong adsorptionfor both PVOH and PEG at amounts lower than the quantities requiredto produce a fully loaded bilayer (0.33 g of PVOH/g of clay) and singlelayered structures (0.10 g of PEG/g of clay), respectively. Abovethese concentrations, the incremental amounts adsorbed were smaller,and the concentration of adsorbates in solution gradually increased.Na-bentonite adsorbed more PVOH than PEG at any given concentration.In the competitive study, the amount of PVOH adsorbed was enhancedin the presence of PEG (0.10 and 0.30 g/g of clay), but less PEG wasadsorbed. At low loadings of PVOH (0.02–0.10 g/g of clay),the amount of adsorbed PEG was increased but at higher PVOH levelsPEG adsorption was reduced. The XRD data showed stepped changes inthe d-spacing as the adsorbed amounts of both PEGand PVOH increased. The PEG-bentonite samples did not expand beyonda bilayer structure (18 Å), but the XRD data for PVOH-treatedsamples indicated the formation of multilayer structures (d≥ 44 Å). [ABSTRACT FROM AUTHOR]

Selected instrumental techniques [dilatometry, thermogravimetry - mass spectrometry ( TG- MS), and variable temperature - diffuse reflectance infrared Fourier transform spectroscopy ( VT- DRIFTS)] have been used to investigate the role of moisture in the rehydroxylation reaction which causes expansion and mass gain in fired clay ceramics. The temperature range over which adsorbed water molecules and structural hydroxyl groups are desorbed from fired clay ceramic as it is reheated, and the nature of the structural hydroxyls that are formed as the ceramic is cooled and then held under controlled conditions have been explored. The mass chromatogram for m/ z = 18, supported by VT- DRIFTS, showed that physisorbed water molecules were removed from the ceramic at about 105°C, whereas strongly bound molecules of water and structural hydroxyls were held to ≤500°C. Dilatometry revealed a marked contraction of the ceramic between 200°C and 330°C which corresponded to loss of strongly bound molecules of water. The VT- DRIFTS also showed that the interaction of water molecules with the ceramic body following reheating occurred in two stages and confirmed the kinetic law previously derived from mass gain and moisture expansion in fired clay ceramics. [ABSTRACT FROM AUTHOR]

In this study, both suspensions and thin films of TiO and silver loaded TiO (Ag-TiO) were used in the photocatalytic degradation/disinfection of C. albicans. In the case of thin films coated materials, both microscope slides and steel pieces of similar dimensions were dip coated using sol-gel solutions prepared from titanium isopropoxide. Surface analysis of the materials confirmed that thin film formation had been succesful. After set periods of irradiation in the presence of suspension or thin film coated material, 10 μL aliquots of the solution were withdrawn and directly cultivated on sabouraud dextrose agar for 24 h at 37 °C. The number of living colonies was counted. The results show that both the suspensions and the thin films displayed superior antimicrobial properties towards C. albicans. In particular the Ag-TiO catalyst was extremely active even in the dark, for disinfection of C. albicans. The degradation percentage over TiO and Ag-TiO thin films coated on the steel substrate was higher than those coated on glass achieving 80 and 97.9%, respectively, using the 365 nm, near visible region light source. [ABSTRACT FROM AUTHOR]