Performance of exterior semitransparent PVDF–acrylic coatings

The purpose of this study was to investigate the performance of a semitransparent PVDF–acrylic coating on two wood species: Black spruce and White pine. An accelerated aging test was performed on the PVDF–acrylic coating and the results obtained were compared with those obtained for a water-based acrylic coating. Color changes were found to be more significant for the acrylic coating, especially after 1000 h of exposure, and for the White pine panels. Infrared spectroscopy revealed that the acrylic resin was more affected by the accelerated aging test than the PVDF resin, although X-ray photoelectron spectroscopy revealed that PVDF was slightly affected at the extreme surface (first 10 nm). Star-shaped defects were found at the surface of the White pine panels finished with the PVDF–acrylic coating. Experiments revealed that the PVDF–acrylic coating does not seem to be flexible enough to sustain resin exudation or other stresses.     

Application of Multivariate Analysis in Mid-Infrared Spectroscopy as a Tool for the Evaluation of Waste Frying Oil Blends

Mid-infrared spectroscopy, in association with multivariate chemometric techniques, was employed for pattern recognition and the determination of the composition of waste frying oils (WFO); data are presented in terms of the percentage of soybean oil, palm oil and hydrogenated vegetable fat in frying oil blends. Principal component analysis (PCA) was performed using spectral data (3,000–600 cm⁻¹) to discriminate between the samples containing 100% soybean oil, 100% palm oil, 100% hydrogenated vegetable fat groups and their blends. Additionally, the results indicated that partial least squares (PLS) models based on mid-infrared spectra were suitable as practical analytical methods for predicting the oil contents in WFO blends. PLS models were validated by a representative prediction set, and the root mean square errors of prediction (RMSEP) were 2.8, 4.7 and 5.5% for palm oil, soybean oil and hydrogenated vegetable fat, respectively. The proposed methodology can be very useful for the rapid and low cost determination of waste frying oil composition while also aiding in decisions regarding the management of oil pretreatment and production routes for biodiesel production.     

Isolation and Characterization of Microsatellite Markers for Passiflora contracta

Passiflora contracta Vitta (Passifloraceae) is an endemic species of the Atlantic Rainforest, one of the most species-rich ecoregions in the world, although extremely endangered. We have developed an enriched microsatellite library in order to fine-scale studies of the genetic structure of P. contracta. Twelve pairs of microsatellite primers were designed, and seven loci were successfully amplified and characterized by genotyping two wild populations of P. contracta. All seven loci were polymorphic, with an average number of alleles found being 4.8 and 5 per population. The cross-species transferability was tested using sister species Passiflora ovalis Vell. Ex Roemer. The development of these markers will contribute to the studies of population genetics in P. contracta as well as future studies concerning diversity patterns in the Atlantic Rainforest, and may also help to establish strategies for the conservation of this species.     

Investigation of the properties of niobium pentoxide for use in dye-sensitized solar cells

This work demonstrates the obtention of Nb₂O₅ nanoparticles by the microwave-assisted hydrothermal synthesis method in a fast way and with the use of low temperatures. The heat treatment applied on the samples promotes the phase change in Nb₂O₅ from pseudohexagonal to orthorhombic as the temperature increases, with a particle size between 7.3 and 32.6 nm. The band gap of the samples decreases with increasing temperature, obtaining a minimum value of 3.04 eV at 800°C. Dye-sensitized solar cells (DSSC) were assembled using the Doctor Blade coating technique. The photovoltaic parameters of open-circuit voltage (Voc) and short-circuit current density (Jsc) were evaluated. The cells showed a photovoltaic response, demonstrating that Nb₂O₅ has a semiconductive potential. The DSSC have different characteristics regarding Jsc and Voc, showing that according to the temperature increase in the semiconductor sample, there is a decrease in the photovoltaic parameters of the cells.     

AC corrosion - Part 1: Effects on overpotentials of anodic and cathodic processes

AC-induced corrosion is a controversial subject and many aspects of it need to be clarified, first and foremost, the mechanism and relationship between AC density and corrosion rate. This paper (Part 1) presents and discusses the effects of AC interference on kinetics parameters; the effects on corrosion rate and corrosion mechanism will be discussed in Part 2. Polarisation curves were obtained in different solutions (soil-simulating solution, 35 g L⁻¹ NaCl, 1 M FeSO₄, 1 M CuSO₄ and 1 M ZnSO₄) on different metallic materials (carbon steel, galvanised steel, zinc and copper) in the presence of AC interference (30-1000 A/m²).     

Cathodic protection monitoring of buried carbon steel pipeline: measurement and interpretation of instant-off potential

The criterion used to verify the cathodic protection condition of a structure is based on structure-to-electrolyte potential measurement, which can include an ohmic drop contribution. Among the available techniques, the use of potential probes with internal reference electrode and of corrosion coupons with a so-called soil-access tube represents the most appropriate way to measure the IR-free potential, eliminating the ohmic drop contribution. An alternative is represented by on-off technique if equalising, galvanic or stray currents are not present. Laboratory tests have been carried out in soil-simulating solution on cathodically protected carbon steel in order to evaluate the effectiveness of off-potential for the assessment of cathodic protection. Instant-off potential is not reliable in overprotection condition; moreover, the accuracy of the measurement is strongly influenced by the presence of external current as galvanic or equalising currents. The effect of low-pass filter in the data acquisition system on the potential reading is discussed.     

Imidazolium salts as liquid coupling agents for the preparation of polypropylene‐silica composites

This article describes the application of ionic liquid 1‐decyl‐3‐methylimidazolium tetrafluoroborate in the preparation of polypropylene‐silica composites. The sol‐gel technology was used to prepare xerogel silica‐ionic liquid hybrid S1 , which was obtained as a free flowing powder of aggregated spherical particles. Ionic liquid free silica S2 was obtained by extraction and calcination of S1 . Melt blending of isotactic polypropylene with S1 and S2 afforded the composites C1 (with ionic liquid) and C2 (without ionic liquid), respectively. The presence of ionic liquid on the S1 silica surface promoted significantly improved silica dispersion in the polymer matrix and prevented compression of the silica particles. Furthermore, the crystallization temperature of composite C1 was significantly higher, which indicated that silica‐ionic liquid filler S1 acted as nucleating agent. The resistance to thermal decomposition of both composites was increased, but this was higher in the presence of ionic liquid. These results show that liquid salts can function as coupling agents and compatibalizers for the preparation of polymeric composites with differentiated properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010