Dissolution rate measurements of sea water soluble pigments for antifouling paints: ZnO

The dissolution of soluble pigments from both tin-based and tin-free chemically active antifouling (AF) paints is a key process influencing their polishing and biocide leaching rates. In this context, a low time- and resources-consuming method capable of screening the pigment behaviour in the search for the most promising materials or mixtures is of great interest. A preliminary attempt to develop such a method is presented in this paper based on the widely used ZnO pigments.

While highly pure, nano-polished, monocrystalline ZnO substrates yielded very low dissolution rates in the order of 17.3 ± 3.7 μg Zn²⁺ cm⁻² day⁻¹, pellets prepared by compacting and sintering technical grade ZnO pigments dissolved about three times faster according to inductively-coupled plasma mass spectrometry (ICP-MS) measurements. The rougher and more porous surface exposed, together with the larger number of defects in the lattice structure, are hypothesised to be responsible for the faster sea water attack of the pellets compared to the ZnO crystals. In any case, the ZnO dissolution rates reported in this paper are markedly lower than those associated with the sea water dissolution of cuprous oxide (Cu₂O) particles which are also used in AF paints. Experimental performance testing of model antifouling paints formulated with ZnO and/or Cu₂O demonstrates that the binder/pigment interaction should not be disregarded if the leaching of sea water soluble pigments from paint systems is to be determined.     

Theoretical development of a graphical analysis technique to optimize the particle size distribution of pigments in paints and coatings

The new analytical expression introduced in this study shows that a plot of the accumulated volume fraction of pigment particles vs. the square root of particle size should be a straight line for the theoretically preferred particle size distribution. This linear theoretical model was also found to be consistent with the experimentally developed linear model proposed by Kaeuffer. However, Kaeuffer proposed that his straight line went through the origin, but the analytical model developed in this paper has shown that this intercept is not zero. Thus, Kaeuffer’s experimental model is only partially correct. Starting with this new linear model for the theoretically preferred particle size distribution, another simplified analytical expression was also derived to calculate the xth moment average particle size, . The desired xth moment average particle size was found to depend primarily on the physical property to be predicted. Finally, the simplified calculation of the various particle size averages for this same square root particle size distribution should be useful in predicting the maximum packing fraction, maximum impact, and/or the minimum viscosity for pigments in most paint and coating applications. 102 Rue Le Bois, Lafayette, LA 70508.     

A study of the leaching of cuprous oxide from vinyl antifouling paints

The sea water leaching rate of cuprous oxide used as a toxicant in vinyl antifouling paints was studied in this work. Three paints were formulated: one of the soluble matrix type and the other two with an insoluble matrix. Two different toxicant levels were employed, and the paints were tested on a raft in Mar del Plata's Harbour, Argentina.

Cuprous oxide lixiviation was studied over 15 months by determining weight changes and by means of microscopical examination (optical and SEM) of specially prepared cross-sections. A complementary analysis by EDAX electron dispersive analysis of the leached matrix and of the paint film/sea water interface was made.

It was determined that the leaching line is parallel to the film surface. Experimental values demonstrated the different dissolution rates of paints with soluble and insoluble matrices and the lineal relationship existing between leaching rate and immersion time. Marson's formula for the determination of leaching rate at the laboratory (using the sodium glycinate method) was correlated with values obtained in sea water immersion, introducing a constant for each type of paint.     

An integrated approach to evaluate the leaching behaviour of silver from sulfide concentrates

The leaching rates of two different mineral concentrates with the same silver content were investigated by cyanide leaching with silver phases identified by scanning electron microscopy (SEM) and electrochemical analysis. The mineralogical characterization (SEM) of the concentrates showed that each contained the silver in different phases. After leaching, the disappearance of only one of the phases in each concentrate was detected. The remaining silver was contained in phases that are refractory to cyanidation. Simultaneously, an electrochemical method for the detection of the different leachable and refractory silver phases in concentrates and leach residues was developed. Cyclic voltammetry was employed with the concentrate-carbon paste electrodes (concentrate-CPE) in order to detect the oxidation of the different phases of silver contained in the mineral concentrates. The extreme sensitivity of this method allowed the rapid and reliable detection of small quantities of silver, as well as the evaluation of its refractory nature.     

Radiometric studies of mercury loss from fungicidal paints III. Loss from three paints with various mercury contents

Losses of mercury have been measured over a period of 220 days from paint films prepared from polyvinyl acetate emulsion (PVA), styrene/acrylic emulsion or alkyd gloss paints containing concentrations of mercury as phenyl mercuric acetate (PMA) from 0.005 to 0.16%. At all concentrations, simple PVA films lose mercury at lower rates than do comparable films prepared from PVA containing coalescing agent, or from styrene/acrylic emulsion. Mercury losses from alkyd gloss films are lower than those from other films at the lower mercury concentrations studied, but percentage loss rates for alkyd films increase somewhat with increasing mercury concentration. A simple explanation for this difference is offered in terms of physical structures of the paint films.     

The pigments of crude cottonseed oils. II. Nitrogen-containing pigments derived from Gossypol

Summary Dark, crude cottonseed oil has been shown to contain a mixture of ninhydrin-sensitive substances combined with gossypol. Phenylalanine, aspartic acid, and glycine have been obtained by acid hydrolysis of the addition compound, followed by paper chromatography of the hydrolysate. The presence of other amino acids was indicated, but their identification could not be established with certainty; proline and hydroxyproline were apparently absent. The possibility that part of the color of dark, crude oils arises from gossypol-α-amino acid interaction is discussed. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Transport and related properties of paint films. I. Composition and structure

This is the first of a series of articles on ionic and molecular transport processes and related properties of paint films. The intention is to correlate adhesion and initiation of corrosion to these relevant physical and chemical properties. Chemical formulas and structure of three vinyl–three epoxy– and one polyurethane–paint system are given in this article. Each paint has been formulated to meet appropriate military specifications. Subsequent articles will deal with dynamic mechanical properties, small angle x-ray scattering measurements of porosity, and transport properties.     

Carbonization and liquid-crystal (mesophase) development. 16. Carbonizations of soluble and insoluble fractions of coal-extract solution

A coal-extract solution prepared by extraction of a coking coal (CRC 301a) with anthracene oil by the National Coal Board is separated into fractions using solvents of increasing solvent power. These fractions are carbonized to 823 K and the optical textures of resultant cokes are assessed. The objective of the study is to examine the role of the molecular components of the coal-extract solution including the residual anthracene oil in mechanisms of formation of the optical texture of the anisotropic coke. Generally, the low-molecular-weight fractions of the coal-extract solution produce cokes with larger sized optical textures than the coke from the parent coal-extract solution. The higher-molecular-weight fractions produce cokes with smaller sized optical textures. Isotropic coke is produced from material which is not soluble in benzene and tetrahydrofuran. Within this parent-coal-extract solution it would appear that the dominant partner effect is influential over the size of the optical texture of coke from the coal-extraction solution, that is the minor component of smaller molecules controls the necessary growth of liquid crystals. Also, the presence of anthracene oil augments the size of optical texture of resultant cokes by providing the necessary physical fluidity of the system and possibly some chemical stability.     

Anolyte cells of electrocoating paint. I: Anodes,impurities and dissolution

The occasionally occurring sudden destruction of the used stainless steel anodes during the electrocoating process and the regular consumption of their thickness are due respectively to local and non-local anodic dissolutions. The aim of this paper is to identify the operating conditions that protect the anode from the sudden destruction of local dissolution, and also to assess the non-local dissolution rate in order to predict the mean life of these anodes. Both types of dissolution are known in the field of corrosion, but this field concerns passivation and trans-passivation potential and not higher range, i.e. oxygen evolution reaction potential. Specific tests are performed with stainless steels that contain different concentrations of molybdenum and typical weak acids of anolyte solution that normally also contain traces of chloride, sulphate phosphate and nitrate as impurities. The results of these tests show that the anodes operate in non-safeguard conditions with respect local dissolution when: (i) traces of nitrates are absent from the anolyte solution and (ii) low molybdenum concentration stainless steels are used as anodes. When the safeguard conditions are ensured, the rate of non-local dissolution is easily detected and the results obtained show that its value increases with (i) the increase in molybdenum in the stainless steel, (ii) the decrease the pH value of the anolyte solution (iii) the increase in the temperature and (iv) the decrease in anolyte recycling in the cell. The results obtained show that sudden destruction and the mean life of anodes are the result of added chemicals in the paint bath and from the pre-treatments adopted. In other words, the interactions between pre-treatments, electrocoating and accessories (anodes), is required when the optimization of the electrocoating process is proposed.     

Long-term behavior of oil-based varnishes and paints I. Spectroscopic analysis of curing drying oils

The curing of drying oils at 60°C has been investigated by Fourier transform infrared spectroscopy and Fourier transform Raman analysis of linseed oil and poppyseed oil. In the first step, hydroperoxides are formed (broad vibration band centered around 3425 cm⁻¹) with concomitant conjugation and cis-trans isomerization of the double bonds (disappearance of cis bands at 3011 and 716 cm⁻¹, appearance of trans conjugated and trans nonconjugated bands at 987 and 970 cm⁻¹). The subsequent decomposition of hydroperoxides in the presence of oxygen leads to the formation of alcohols (nitrite band at 779 cm⁻¹ after nitrogen monoxide treatment), aldehydes (bands at 2810 and 2717 cm⁻¹ in gas phase), ketones (saturated and unsaturated at 1720 and 1698 cm⁻¹, respectively), carboxylic acids (saturated and unsaturated acid fluorides identified at 1843 and 1810 cm⁻¹ after SF₄ treatment), and peresters or γ-lactones (near 1770 cm⁻¹). A rapid decrease in the double-bond concentration is recorded when curing continues, and the formation of epoxides, characterized by a vibration band at 885 cm⁻¹, is observed. Thermolysis experiments have suggested the proposal of a reaction of addition of peroxyl radicals on the conjugated double bonds as a probable mechanism. This mechanism explains both the rapid disappearance of conjugated double bonds and the formation of epoxides as intermediate products observed in the initial step of curing.     

Stepwise decreasing current modes. I. Electrodeposition of metals from a bath with insoluble anode and limited volume of solution

A model of the stepwise decreasing current mode of electrodeposition of metals has been developed and checked with experiments. The electrodeposition of copper has been used for this purpose. It has been shown that the deposition time in the stepwise decreasing current mode, for sufficiently high step number, becomes close to that potentiotiostatic deposition.Nomenclature C concentration - C ₀ initial concentration - D diffusion coefficient - F Faraday constant - i integer - I current - I ₀ initial limiting diffusion current - k integer - m number - n number - Q quantity of electricity - S electrode surface area - t time - t _k ^* deposition time fork current steps - t ^* lim_k t _k ^* - t _m deposition time required to decrease concentration from (m + 0.1)C ₀ tomC ₀ byI=mI ₀ - t _n deposition time required to decrease concentration fromC ₀ tonC ₀ byI =nI ₀ - U cell voltage - V volume of solution - z number of electrons - thickness of the diffusion layer - defined by Equation 3     

One‐step facile process to obtain insoluble polysaccharides fibrous mats from electrospinning of water‐soluble PMDA/cyclodextrin polymer

Herein, we used an electrospinning process to develop nanofibers based on poly‐cyclodextrin. This article describes a simple and effective method to produce fibers of a water‐soluble hyperbranched polymer based on β‐CD and pyromellitic dianhydride via electrospinning. The obtained fibers were made insoluble in water with a simple thermal crosslinking without the use of further reactive or solvent. After 24 h of dipping in distilled water or phosphate buffer solution morphology and size of fibers remain unaltered as observed in scanning electron microscopy. The crosslinking mechanism was studied with thermogravimetric analysis, attenuated total reflectance–Fourier infrared spectroscopy, and elemental analysis and a reaction mechanism is proposed. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46490.     

Optimal design and planning of heap leaching process. Application to copper oxide leaching

Although the process of heap leaching is an established technology for treating minerals, such as copper, gold, silver, uranium and saltpeter, as well as remediating soil, no studies to date have investigated process optimization. This work presents a methodology for the design and planning of heap leaching systems to optimize the process. This methodology consists of the creation of a superstructure that represents a set of alternatives to search for the optimal solution; from this superstructure, a mixed integer nonlinear programming (MINLP) model was generated, and a BARON-GAMS solver was used to find the optimal solution. This method was applied to the extraction of copper from systems with one, two and three heaps, and the effects of copper price, ore grade and other variables were analyzed for each system. From the results, it can be concluded that this methodology can be used to optimize heap leaching processes, including planning and design issues.     

Radiometric studies of mercury loss from fungicidal paints. 1. Loss of phenyl mercuric acetate

Exposure tests have been made on paint films prepared from an emulsion paint containing phenyl mercuric acetate (PMA) labelled with ²⁰³Hg. Loss of mercury from the films has been followed radiometrically. Films exposed indoors in a confined space (no air circulation) showed little, if any, mercury loss for up to 8 months. Films exposed in the open laboratory lost from 20 to more than 60% of mercury after 250 days. This agrees qualitatively with the results of other workers on similar paints. At 50°, films lost mercury at rates about 10 times greater than those at ambient temperature. Films exposed out-of-doors lost the majority of their mercury after a few days of rain. Pre-treatment of films, e.g. by u.v. radiation, had no effect on their subsequent outdoor behaviour. Even well-dried films lost mercury at the same rate as newly applied films. Films with a low PMA content (0·02% Hg) lost mercury at a higher percentage rate than films with a high one (0·2% Hg). Thick films (0·002 in.) lost mercury at a lower rate than thin ones (0·001 in.). A mercury-free top coat also reduced loss rate. All loss rates decreased with increasing time. These trends applied to all the exposure conditions studied. Mercury loss appears to be due to both volatilisation and dissolution of PMA and not to decomposition. The results indicate a non-homogeneous distribution of PMA throughout the paint film, and a diffusion-controlled process.     

A modeling approach to thermoplastic pultrusion. I: Formulation of models

A fundamental understanding of the effects of processing parameters and die geometry in a pultrusion process requires a mathematical model in order to minimize the number of necessary experiments. Previous investigators have suggested a variety of models for thermoset pultrusion, while comparatively little effort has been spent modeling its less well understood thermoplastic counterpart. Herein, models to describe temperature and pressure distributions within a thermoplastic composite as it travels through the pultrusion line are presented. The temperature model considers heat transfer in an infinite slab with either prescribed boundary temperature, or prescribed heat flux from the surfaces. The pressure model is based upon matrix flow relative to the fibers and incorporates a non-Newtonian matrix viscous, compaction, and friction resistance, is also presented. The models are evaluated studying and ideal pultrusion process for manufacturing of unidirectional carbon-fiber-reinforced polyether ehterketone composites.     

Semiconductor-electrochemical aspects of bacterial leaching. I. Oxidation of metal sulphides with large energy gaps

Thiobacillus ferrooxidans has been cultivated successfully on synthetic metal sulphides with large energy gaps (CdS, ZnS) as the only energy source for many culture generations during a period of 4 years. The results obtained, which were quantitatively evaluated by calculations of electron transfer probabilities, show that a direct electron transfer from the metal sulphide valence band to the bacterial metabolic system (hole injection into the valence band of the sulphide) has to be excluded as the cause for the enhanced oxidative dissolution for energetic reasons. A detailed analysis of the dynamics of the metal sulphide aqueous electrolyte interface reveals that protons are involved in the mechanism on which bacterial activity is based. By reacting chemically with the metal sulphide surface they break chemical bonds and shift electronic states energetically into the forbidden energy gap to produce surface states which can be chemically described as ?SH? groups. These control the rate of dissolution of the metal sulphide and are removed by bacterial activity. In this way the proton is recycled and its action can be considered catalytic. For sulphides in which the valence band of the semiconductor is derived from metal orbitals instead of from sulphur orbitals, this mechanism is bound to fail. MoS₂ and WS₂ are discussed as examples of such metal sulphides which are not a suitable energy source for bacteria. Some kinetic aspects of the bacterial surface reaction are discussed.     

Water‐soluble/dispersible cationic pressure‐sensitive adhesives. I. Adhesives from solution polymerization

Pressure‐sensitive adhesives (PSAs) have long been a problem as sticky contaminants for paper recycling mills. The main problem associated with such stickies is that the PSAs in the waste papers deposit on the felts, press rolls, and drying cylinders of paper machines, and this creates problems with paper formation, reducing the paper quality and paper machine runnability. The annual cost of stickies to the U.S. paper industry is estimated to be about $600,000,000–650,000,000. To solve this problem, a series of cationic water‐soluble/dispersible PSAs have been synthesized by the free‐radical solution polymerization of butyl acrylate and [3‐(methacryloylamino)propyl]trimethylammonium chloride in ethanol. The PSA end‐use properties, repulpability in paper recycling, and the effects on the properties of recycled paper products have been studied. The cationic PSAs can be dissolved or dispersed in water if the cationic charge density in the PSA backbone is controlled, and so they do not deposit as stickies during recycling and papermaking processes. Because the PSAs are cationically charged, they can easily be removed from the papermaking system by adsorption onto the negatively charged fibers and fine surfaces. Furthermore, the adsorbed colloidal or dissolved PSAs have little effect on the final paper properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 1624–1630, 2003     

Radiometric studies of mercury loss from fungicidal paints. II. Comparison of three phenyl mercury compounds

The fungicides, phenyl mercuric dodecyl succinate (PMS) and phenyl mercuric dimethyldithiocarbamate (PMDDC), have been prepared labelled with ²⁰³Hg. Comparative exposure tests have been carried out on emulsion paints each containing one of the labelled compounds phenyl mercuric acetate (PMA), PMS, or PMDDC. After 236 days of indoor exposure, approximate losses from films are 60 (PMA), 50 (PMS), and 20% (PMDDC). Relative losses from films of low-Hg content (0·02%) are a few per cent higher than those from comparable films of high-Hg content (0·2%). After 56 days of outdoor exposure, approximate losses are 95 (PMA), 90 (PMS), and 40% (PMDDC). PMS and PMDCC films of high-Hg content show relative losses slightly higher than those of low-Hg content; a behaviour opposite to that of PMA films. This may be due to the distribution of PMS or PMDDC through a paint film being less uniform than that of PMA. A correlation between mercury loss and rainfall is observed for all three fungicides. The loss rates from all films decrease with time during indoor exposure. Out-of-doors, this decrease becomes well defined only when a substantial portion of the fungicide has been removed by rain. The results indicate that in emulsion paint films, under the exposure conditions used in this work, PMS is retained slightly better than PMA, but that PMDDC is retained much better than either. The high retention of PMDDC is probably due to its low saturation vapour pressure and to its low solubility in water. The solubility of PMDDC in water at 20° has been determined radiometrically as 5·7 ppm.     

Expression and enzymatic characterization of the soluble recombinant plasmepsin I from Plasmodium falciparum

The plasmepsins are involved in the degradation of host cell hemoglobin during malaria infection. Plasmepsin I (PM I) initiates the degradative process, and has been suggested as an attractive target for the treatment of malaria. The production of active recombinant PM I, however, has been challenging. We report for the first time, the expression and partial characterization of soluble recombinant PM I from Plasmodium falciparum in which a truncated form of PM I (Lys77P-Leu329) (P indicates a propart residues) was fused to thioredoxin in the pET32b(+) vector, Trx-tPM I and expressed in Escherichia coli Rosetta-gami B (DE3)pLysS. The soluble fusion protein was purified from cell culture using a combination of Ni(2+) affinity and gel filtration chromatography and was capable of autocatalytic activation at pH 4.0-5.5, which occurred at Leu116P-Ser117P, seven residues upstream of the native cleavage site (Gly123P-Asn1). The mature tPM I (mtPM I) was capable of hydrolyzing both human hemoglobin with a pH optimum of pH 2.8-4.0 and the synthetic fluorogenic peptide EDANS-CO-CH(2)-CH(2)-CO-ALERMFLSFP-Dap(DABCYL)-OH with a dual pH optima of pH 2.5-3.0 and pH 4.5-5.5. Using the synthetic substrate, mtPM I exhibited kinetic parameters comparable to native PM I.