Centro de Investigaciones en Tecnologia de Pinturas

Thymol is a natural volatile monoterpenoid phenol that is the main active ingredient of oil extracted from species Thymus vulgaris L., commonly known as thyme, and other plants such as Ocimum gratissimum L., Origanum L., Carum copticum L., different species of the genus Satureja L., Oliveria decumbens Vent, and many others. It is a versatile molecule with a wide variety of practical applications such as medical, dentistry, veterinary, food, and agrochemicals, among others. Its pharmacological applications have been the most investigated and reported, focusing on its prominent antimicrobial, antioxidant, anti-inflammatory, cicatrizing activities. Furthermore, it is noteworthy that the research on its agricultural applications has increased, highlighting its uses as a natural agrochemical and preservative to safeguard foods from pathogenic microorganisms both in sowing and storage, which could have a beneficial effect on human health and the environment. Research has also been reported on its activity as an insecticide, acaricide, and animal repellent. This review summarizes important aspects of thymol such as its bioavailability, synthesis, and biological activities, with special interest in practical applications.

The cobalt hexacyanoferrate system, Mh [FeB(CN)6]l, (where M is an alkali metal cation, and the subscripts h, k, and l are stoichiometric coefficients, and A and B are the formal oxidation states of the Co and Fe metal sites in the structure) was shown to contain a rich series of compounds that are inter-linked through various redox processes (involving both electron and cation transfer) either in the dark or under the near-infrared (IR) activation. These processes were studied by a combined use of cyclic voltammetry, in situ IR spectroelectrochemistry (using both intensity or potential modulation), and ex situ X-ray photoelectron spectroscopy.

The most common anticorrosive pigments contain lead (Pb) or hexavalent chromium (Cr) compounds. These pigments are particularly hazardous and contribute to contamination of the environment. The use of zinc phosphate (ZP) has been recommended often for the formulation of environmentally compatible anticorrosive priming compositions. Ferrites and barrier pigments of lamellar structure also have been proposed. The protective action of ZP results from phosphatization of the metal substrate and the formation of complex substances with binder components to improve adhesion. However, experimental results have been contradictory. The mechanism of the anticorrosive action of ZP was studied using electrochemical tests (corrosion potential-vs-time curves, polarization curves, and corrosion rate measurements) performed in pigment suspensions and by scanning electron microscopy (SEM) analysis of steel surfaces subjected to the action of a ZP suspension or painted with an anticorrosive paint pigmented with ZP. ZP was shown to react with iron (Fe) to generate a protective oxide layer with a certain degree of crystallinity.

Electrochemical impedance spectroscopy (EIS) was applied over a wide frequency range to characterize the corrosion protection behavior by two types of zinc-rich paints (ZRP) (zinc-rich epoxy polyamide and zinc-rich ethyl silicate) on steels. Information concerning the properties of ZRP coatings has been evaluated from the changes of open-circuit potential and impedance spectrum with exposure time in ASTM artificial seawater. The influence of pigment volume concentration (PVC) and coating thickness was studied in order to determine the appropriate values that enable beneficial effects for improving corrosion protection. Characteristic coating parameters obtained from nonlinear fit routines of experimental impedance spectra at different exposure times, according to a circuit model consisting of a series combination of the uncompensated RΩ and a parallel Rt-CPE element, correlate well with the gradual coating deterioration as the barrier-like properties of ZRP are diminished progressively. Results can be interpreted in terms of corrosion processes going on extensively through pores and cracks in the ZRP coatings.

Honeys from different regions of the province of Buenos Aires were stored at −20°C, and factors that affect crystallization were analyzed. Crystals were observed by light microscopy. Firmness, adhesivity and viscosity of the samples were measured. Honey was characterized by determining the water activity, turbidity, moisture, fructose, and glucose contents. Results show that the viscous characteristics of the samples depend on the number, size, and disposition of crystals. Various honey samples exhibited Newtonian, pseudoplastic, and thixotropic behaviors. Crystallization was favored at higher moisture contents, suggesting that the parameters that affect honey crystallization at room temperature have a different effect at freezing temperatures. Honey that presented higher values of firmness had a moisture content lower than 17%, and a linear inverse relationship was observed between the adhesivity and firmness of honey samples.

Three azulenoid sesquiterpenes ( 1 – 3 ) were isolated from the Antarctic gorgonian Acanthogorgia laxa collected by bottom trawls at −343 m. Besides linderazulene ( 1 ), and the known ketolactone 2 , a new brominated C 16 linderazulene derivative ( 3 ) was also identified. This compound has an extra carbon atom at C(7) of the linderazulene framework. The antifouling activity of compounds 1 and 2 was assayed in the laboratory with Artemia salina larvae, and also in field tests, by incorporation in soluble‐matrix experimental antifouling paints. The results obtained after a 45 days field trial of the paints, showed that compounds 1 and 2 displayed good antifouling potencies against a wide array of organisms. Compound 3 , a benzylic bromide, was unstable and for this reason was not submitted to bioassays. Two known cembranolides: pukalide and epoxypukalide, were also identified as minor components of the extract.

Abstract Substitution of zinc chromate or zinc yellow, traditionally used as anticorrosive pigment, for other phosphate‐based pigments that are not hazardous to health and have the same anticorrosive behaviour or even better, is studied in this paper. Four alkyd paints were specially prepared; two of them contained calcium acid phosphate or micronised zinc phosphate as anticorrosive pigments respectively. A paint containing zinc chromate was used as reference and a paint without anticorrosive pigments was used as a blank, in which the other ingredients were increased proportionally to attain the desired PVC relationship. The corrosion behaviour of low carbon steel panels coated with these paints in a 3 per cent NaCl solution was assessed by electrochemical impedance spectroscopy (EIS). In addition, other painted panels were evaluated by salt spray and humidity chamber tests. Results of all tests showed that the paint with calcium acid phosphate and especially that with micronised zinc phosphate exhibited better behaviour than paint with zinc chromate. Analysis of impedance parameters (ionic resistance and capacitance of the paint film) against immersion time allowed the paints to be ranked in the same order as that obtained with salt spray and humidity chamber tests.

During the past decade, the necessity of new ecofriendly antifouling pigments was established. Among these new pigments, special attention should be paid to tannin and its derivatives. Tannins are synthesized by plants as part of their defense mechanism against the attack of pathogens. The objective of this work was to study the antifouling efficiency of paints containing zinc “tannate” in artificial seawater. The zinc “tannate” was precipitated at pH 4 and pH 8. Insoluble and soluble matrix antifouling paints, with different plasticizers, were formulated and tannins leached from the paints immersed in artificial seawater were determined by the Folin−Denis assay for polyphenols. The antifouling action of paints was assessed in a natural seawater environment. The results showed that the leaching rate of tannin from insoluble matrix paint decreases, reaching a constant value after 25 days of immersion. In the case of the soluble matrix paints, a lesser amount of tannin was leached, depending on the tannin and the plasticizer employed. The results in a natural sea environment are dependent on the matrix and the plasticizer employed.

The efficiency of two anticorrosive pigments containing aluminium polyphosphate was studied. Pigments were analysed by current analytical techniques and characterised by FT‐IR spectrometry. The anticorrosive properties of the selected pigments were evaluated following the electrochemical behaviour of a steel electrode in pigments suspensions. In a second stage, solvent‐borne paints with 30 and 10% v/v of the pigment and PVC/CPVC (pigment volume concentration/critical pigment volume concentration) ratio 0.8 were formulated. Three resins were chosen as film forming materials: an alkyd, an epoxy and a vinyl. The performance of the resulting anticorrosive paints was assessed by accelerated (salt spray cabinet and humidity chamber) and electrochemical tests (corrosion potential, ionic resistance and polarisation resistance). The anticorrosive performance of the tested paints was closely related with pigment composition. The nature of the resin was also of importance; in this sense, epoxy paints showed the best anticorrosive performance. Good correlation has been obtained between accelerated and electrochemical tests.

Health and safety legislation has forced changes in the type of anticorrosive pigments used in paint formulations, mainly focused on their substitution with different phosphates. The zinc phosphate pigment used with different types of binders has provided contradictory experimental results. In this paper, waterborne anticorrosive paints pigmented with zinc phosphates were studied. The main variables considered were PVC and the anticorrosive pigment content. Accelerated tests (salt spray, humidity chamber, and electrochemical tests) were performed to evaluate the paints’ anticorrosive performance. Good correlation was found using salt spray and impedance tests. From analysis of the time dependence of all the experimental results it was concluded that an efficient steel protection could be obtained using a waterborne epoxy primer pigmented with zinc phosphate. Such protection is attained through the barrier effect afforded by the paint film as well as the precipitation of a pretty stable ferric phosphate layer under the intact and damaged coating areas.

Abstract Combined treatment with Beauveria bassiana, and diatomaceous earth (DE) was evaluated against the bean weevil Acanthoscelides obtectus and rice weevil Sitophilus oryzae. DE from Argentina was screened both alone or in combination with water or dry fungal formulations. DE killed 100% of A. obtectus and 68% of S. oryzae showing a significantly higher insecticidal effect than the fungal dust. For A. obtectus, median lethal time (MLT) with the DE–dry fungus was significantly lower than with a fungal aqueous-suspension. In S. oryzae, powder formulations with either of B. bassiana or DE showed a MLT significantly higher than the wet treatments.

The objective of this work was to study the anticorrosive behaviour of three commercial pigments containing micronized zinc phosphate. The chemical analyses of the pigments were carried out in the laboratory to characterise them with respect to their composition and soluble matter. It was proposed to check pigments’ efficiency in solvent‐borne paints with 30 per cent v/v of the pigment by volume and a pigment volume concentration/critical pigment volume concentration ratio (PVC/CPVC) equal to 0.8. The behaviour of paints formulated with two binders (alkyd and epoxy) was assessed by accelerated (salt spray cabinet, humidity chamber and accelerated weathering) and electrochemical (corrosion potential, ionic resistance and polarisation resistance) tests. It was demonstrated that pigment performance is highly influenced by their solubility which, in turn, could influence the formation of the protective layer on the metal substrate. Good correlation was obtained between salt spray and electrochemical tests.

Current antifouling coatings are based on toxic compounds that can be harmful to the natural environment. A promising alternative to these compounds is the use of natural products that are non-toxic, but have antifouling properties. Tannins are natural, water-soluble, complex polyphenolic substances, which precipitate proteins and have anticorrosive and antimicrobial properties. In this study, the effect of quebracho tannin as a probable antifouling pigment in both laboratory and field trials is evaluated. As tannins have high solubility in aqueous media and consequently would leach rapidly, they were precipitated as aluminium tannate, which has an adequate solubility for use as a component in marine paints. In vitro exposure of Balanus amphitrite and Polydora ligni larvae to low concentrations of both quebracho tannin and saturated aluminium tannate solutions produced complete appendage immobilisation. In 28-d field trials of test gels, a significant decrease in micro- and macrofouling density and diversity in relation to the control gel was detected (p < 0.05). This study suggests that natural tannins could be employed as bioactive pigment for new antifouling technologies.

Lamellar micaceous iron oxide paints are successfully employed to provide longlife corrosion protection for metallic structures when exposed to highly aggressive environments. The aim of this work was to formulate and manufacture lamellar micaceous iron oxide paints, able to be used on the protection of steel structures exposed to water. Several formulation and manufacture variables were taken into account. Many paint films fail when they are saturated with moisture and blistering is a common failure because primers usually are not designed to allow the liquid to dissipate back out through the film. Consequently the film can not resist the formation of projections which result in local adhesion loss. For maximum durability, primers must be properly formulated and manufactured. Film permeability, which depends on paint composition (pigment volume concentration) and micaceous iron oxide dispersion time, seems to be the key characteristic controlling subsequent coating performance. Laboratory results indicated that lamellar micaceous iron oxide is a pigment which provides an anticorrosive action by providing a barrier effect. Film permeability must be compatible so as to attain a satisfactory rusting and blistering resistance.

Fungi grow especially in dark and moist areas, deteriorating the indoor environment and causing infections that particularly affect immunosuppressed individuals. Antimicrobial coatings have as principal objective to prevent biofilm formation and infections by incorporation of bioactive additives. In this sense, metallic nanoparticles, such as silver, have proven to be active against different microorganisms specially bacteria. Biosynthesized method is a promising environmentally friendly option to obtain nanoparticles. The aim of this research was assess the employment of plants extracts of Aloysia triphylla (cedrón), Laurelia sempervirens (laurel) and Ruta chalepensis (ruda) to obtain silver nanoparticles to be used as an antimicrobial additive to a waterborne coating formulation. The products obtained were assessed against fungal isolates from biodeteriorated indoor coatings. The fungi were identified by conventional and molecular techniques as Chaetomium globosum and Alternaria alternate. The results revealed that the coating with silver nanoparticles obtained with L. sempervirens extract at 60°C with a size of 9.8 nm was the most efficient against fungal biofilm development.

Abstract The objective of this paper is to know the fire performance of wooden panels ( Pinus radiata ) impregnated with silica nanoparticles added to silica/alkali colloidal solutions. Two series of impregnated panels were prepared with diverse penetrations and retentions (a) after drying/curing the impregnants at laboratory conditions until reaching constant weight and (b) after finishing this stage with prior distiller water immersion for seven days and a later air exposition for attaining moisture balance. Panels were tested in a limiting oxygen chamber and in a two‐foot tunnel. Some results displayed a high fire‐retardant efficiency. Copyright © 2009 John Wiley &amp; Sons, Ltd.

Zirconia is a widely used multifunctional material. Its interesting properties, such as high chemical resistance, thermal stability and high mechanical toughness, have turned this material into object of study within fields such as optics, electronics, and magnetism, among others. In recent years, the chemical properties of zirconium oxide have been used, mixed with silicon, in order to obtain more stable and robust mixed oxides, with the final application of toughening ceramics. These properties are related to the degree of mixing of the components at molecular level, therefore, the linking between Si-O-Zr. Considering the effective antimicrobial capacity of silver nanoparticles, their incorporation into different materials is very interesting, acting as biocides. The objective of this work is to obtain zirconium oxides by the sol-gel technique, using zirconium n-propoxide as precursor, and also to study the effect of different solvents (water, ethanol) and the use of various acid catalysts in the synthesis [acetic acid and a heteropolyacid (HPA), as the phosphomolybdic acid (H3PMo12O40)] on the physicochemical properties of the obtained solids. Finally, the addition of a silver salt was carried out into the sample with acetic acid and heteropolyacid as catalyst, in order to incorporate it as antimicrobial filler in paints. The obtained materials were characterized by SEM, XRD, FT-IR, textural properties through the absorption of N2 (SBET) and potentiometric titration with n-butylamine. Homogeneous solids were obtained in all the synthesis with acetic acid as catalysts. In addition, x-ray diffraction diagrams of amorphous solids were observed. The values obtained of surface areas are influenced by the variables of synthesis. The characteristic bands of zirconia were observed by FTIR in the solids synthesized. The results show that the solids environmentally synthesized are promising additives for use in paints.

The use of classic anticorrosive pigments is becoming more and more restricted by increasing environmental concerns; they are gradually being replaced by zinc phosphate and related compounds. Other anticorrosive pigments such as surface-exchanged silicas were also proposed. The object of this research is to study the anticorrosive properties of calcium acid phosphate as an inhibitive pigment, introducing a careful selection of complementary pigments in order to achieve an efficient anticorrosive protection. Several alkyd paints were prepared and evaluated through accelerated and electrochemical tests. The nature of the passive film formed was also studied. Paint containing zinc oxide and calcium carbonate (50/50) as complementary pigments showed the best performance in the salt spray test. Zinc oxide and calcium carbonate decreased film permeability and improved steel passivation. The passive film was composed of ferric oxyhydroxide, the pores of which became plugged by ferric phosphate.

The objective of this research was to study the efficiency of calcium tripolyphosphate and zinc tripolyphosphate as anticorrosive pigments for paints in aggressive environments. Alkyd and epoxy paints, of the solvent-borne type, containing 30% by volume (v/v) of the pigment, were formulated. The pigment volume concentration/critical pigment volume concentration (PVC/CPVC) ratio was fixed at 0.8. In a second stage, water-borne paints containing 30% v/v of both tripolyphosphates and different PVC values (20 and 25%) were also formulated. Finally, standardized accelerated (salt spray and humidity chamber exposure) and electrochemical impedance spectroscopy (EIS) tests were used to assess the protective performance of the coatings. Analysis and interpretation of the experimental data show that both, calcium and zinc tripolyphosphates, inhibit corrosion of painted steel panels exposed to aggressive environments.

Over the past two decades, polyoxometalates (POM) have received considerable attention as solid catalysts, due to their unique physicochemical characteristics, since, first, they have very strong Bronsted acidity, approaching the region of a superacid, and second, they are efficient oxidizers that exhibit rapid redox transformations under fairly mild conditions. Their structural mobility is also highlighted, since they are complex molecules that can be modified by changing their structure or the elements that compose them to model their size, charge density, redox potentials, acidity, and solubility. Finally, they can be used in substoichiometric amounts and reused without an appreciable loss of catalytic activity, all of which postulate them as versatile, economic and ecological catalysts. Therefore, in 2009, we wrote a review article highlighting the great variety of organic reactions, mainly in the area of the synthesis of bioactive heterocycles in which they can be used, and this new review completes that article with the contributions made in the same area for the period 2010 to 2020. The synthesized heterocycles to be covered include pyrimidines, pyridines, pyrroles, indoles, chromenes, xanthenes, pyrans, azlactones, azoles, diazines, azepines, flavones, and formylchromones, among others.