Recent Highlights

Section 53 Weathering, Corrosion, Etc

BALIJPALLI S, NANJUNDIAH K, LI Y & BARSACCHI M Self-healing coatings: new technology developments. Proc. European Coatings Conf, Nurnberg 2009, Paper, 10 pp.

An overview of self-healing coating technologies is presented. Details of self-healing mechanisms discussed are dispersion of microcapsules filled with a monomer, phase-separated systems, cross-linked networks, human skin mimics utilising capillary networks, reversible chemical cross-links, self-replenishing coatings, and self-healing in thermoplastic elastomers. Design requirements for coatings are discussed in the context of hydrophobic proprietary natural oil polyols for self-healing, two-part polyurethane systems. The coatings designed from these systems show good acid-etch resistance and also multiple healing cycles. This is due to a self-levelling mechanism attributable to the hydrophobicity of polyols used to make the coatings. 23 refs. (WSCA Item Number 09/02593)

Section 55 Fouling and Microbiological Attack

CHUNG C-J & OTHERS Inactivation of Staphylococcus aureus and Escherichia coli under various light sources on photocatalytic titanium dioxide thin film. Surface & Coatings Tech. 2009, Vol 203 No 8, 1081-5.

The mechanism by which photocatalytic titanium dioxide thin film inactivates Staphylococcus aureus and Escherichia coli under various light sources was elucidated using a bacterial cell culture and the microscopic observation of bacterial cells. The experimental results indicated that antimicrobial behaviour may only be activated when the light source emits with a threshold energy that exceeds the band gap energy of anatase titanium dioxide. The black light source with a stronger UV emission than the fluorescent lamp is associated with an earlier bacterial growth inhibition phase. The bacterial inactivation mechanism of Staphylococcus aureus differs from that of Escherichia coli. The former suffers the detachment of the cell wall from the cell membrane and the later undergoes a nucleoid pattern change from features of relaxation toward features of condensation. 29 refs. (WSCA Item Number 09/02624)

Books

Reviews of the following books also appeared in the May 2009 issue of WSCA:

ARAI T, HARINO H, OHJI M & LANGSTON W J (EDITORS) Ecotoxicologyof Antifouling Biocides. Springer Japan, Tokyo 2009, 437pp. (ISBN 978-4-431-85708-2 (Print) 978-4-431-85709-9 (Online)). Price £171.00 (Individual chapters available on-line fromwww.springerlink.com). (WSCA Item Number 09/02853)

MITTAL K L (EDITOR) Silanes and Other Coupling Agents. Volume5. VSP BV, Leiden & Boston, 2009, 348 pp. (ISBN978-90-04-16591-5). Price 147.00 euros, $198.00. (WSCA Item Number 09/02854)

MITTAL K L (EDITOR) Polymer Surface Modification: Relevance toAdhesion, Volume 5. VSP BV, Leiden & Boston, 2009, 394 pp.(ISBN 978-90-04-16590-8). Price 159.00 euros, $248.00. (WSCA Item Number 09/02855)

TIPPING J (EDITOR) Flooring Yearbook 2009. MPP Ltd,London 2009, 106 pp. Price £9.95.  (WSCA Item Number 09/02856)

Section 11 Synthetic Resins (General)

SOOD A Modelling of the particle size distribution in emulsion polymerisation. J. Appl. Polym. Sci. 2008, Vol 109 No 3, 1403-19.

A mathematical model to predict the evolution of the latex particle size distribution in an emulsion polymerisation reactor was developed. The mathematical framework is based on the population balance approach. The general framework is readily expandable to incorporate the physiochemical phenomena of the reacting system of interest. The model includes such mechanistic details as particle generation from radicals entering micelles, particle size dependence of the radical entry mechanism, coupling of the radical concentration in the aqueous phase and the particle phase, determination of the particle phase radical concentration by radical entry into, exit from, and termination inside the particle, and thermodynamic equilibrium between the monomer concentration in the aqueous phase and the particle phase. The model was solved efficiently with orthogonal collocation. Dynamic simulations were compared with experimental data taken from the literature for the emulsion polymerisation of styrene (monomer), potassium persulphate (initiator), and sodium dodecyl sulphate (emulsifier). The variables considered were the total number of particles formed, duration of the nucleation period, conversion at the end of the nucleation period, variation of the monomer volume fraction in the particles with time, and conversion/time curves for different monomer, initiator, and emulsifier concentrations. Close agreement was found between the simulations and the experimental data. 99 refs. (WSCA Item Number 09/01926)

Section 53 Weathering, Corrosion, Etc

PICKETT J E & SARGENT J R Sample temperatures during outdoor and laboratory weathering exposures. Polym. Deg. & Stabil. 2009, Vol 94 No 2, 189-95.

Effective exposure temperatures in Arizona were calculated from hourly or 10 minute parsed irradiation data along with ambient, black panel, and sample temperatures. The effective exposure temperature represents a constant temperature that creates the same amount of photodegradation as the naturally varying temperature and provides a benchmark temperature for making lifetime predictions from accelerated laboratory exposures. The annual ambient and black panel effective exposure temperature at a Wittmann, Arizona, site were 30 deg. C and 42 deg. C, respectively, assuming that the photodegradation has an activation energy of 21 kilojoule per mole. Effective exposure temperature was only weakly dependent on the activation energy over the range of 10-40 kilojoule per mole. Samples exposed as van sunroofs were found to have effective exposure temperature that were offset from the black panel temperatures by a constant amount for the entire year. Thus, measurements of sample and black panel need to be made for only a few weeks to determine the offset and provide the annual sample effective exposure temperature if the annual black panel effective exposure temperature is known. Light-coloured samples are probably better compared with the ambient temperatures. Sample temperatures in xenon arc exposures usually are higher than the outdoor effective exposure temperature, so Arrhenius temperature corrections need to be carried out to relate accelerated to outdoor exposures. Temperatures in xenon arc exposure tests often correspond more closely to maximum temperatures that samples might encounter for only a few hours per year. (WSCA Item Number 09/02104)

Section 63 Paints, Etc for Other Specific Uses

WOUTERS M & OTHERS Preparation and properties of a novel remendable coating concept. Progr. Org. Coat. 2009, Vol 64 Nos 2/3, 156‑62.

Molecular design in combination with different synthetic routes was used. A series of new building blocks was prepared that render conventional coating types thermally remendable. Damage may be repaired through thermally reversible cross‑linking of the coating through reversible bond scission within these specially designed building blocks. At room temperature, a fully cross‑linked network is present, whereas at elevated temperatures the cross‑link density becomes much lower and the system becomes mouldable or low viscous. This self‑healing concept was proven by various techniques. Both the thermal reversibility window and the final coating properties may be tuned by careful design of the system. It was shown that the furan/maleimide Diels‑Alder system is an interesting candidate to introduce new functionalities. 29 refs. (WSCA Item Number 09/02176)

Section 71 Other Properties and Testing Methods

SCHROEDER W F & OTHERS Early stages of coalescence and polymer diffusion in latex films. ACS, Div. of PMSE, Papers 2008, Vol 99, 146.

Polymer diffusion was investigated in latex films at very early stages of coalescence. Fluorescence resonance energy transfer (FRET) measurements were used to monitor the rate and extent of polymer diffusion at various distances from the drying front, the acrylic latices being labelled, one by phenanthrylmethyl methacrylate and the other by dimethylaminobenzophenone. Results showed that coalescence does not necessarily occur with the passing of the drying front. Evidently there is a humidity dependent barrier to the onset of polymer diffusion. It is considered that after the drying front has passed, there still remains a thin film of water between the packed latex particles that blocks polymer diffusion. The water evaporation rate, which decreases at higher humidity levels, affects the rate of breakup of this water film. Particle coalescence and polymer interdiffsion are able to occur only after this water barrier has been largely removed. (WSCA Item Number 09/02259)

Section 83 Markets, Marketing and Management

WRIGHT T Interior decorative coatings. Coatings World 2009, Vol 14 No 1, 34‑5.

The flooding of mature interior decorative markets with green products to try and keep sales buoyant during tough economic times is described. The US decorative coatings market is compared with Europe and with the rest of the world. Green coatings technology is one area that is growing exponentially, due to increased volatile organic compound (VOC) legislation at the government level and the trend toward healthier living and environmental awareness in popular culture. Some proprietary products are discussed. (WSCA Item Number 09/02327)

Section 08 Patents: Driers and Minor Additives

BASF CORP Dispersant for use in a fluorocarbon coating composition. United States Patent Application 20090012235, 9 pp.

A fluorocarbon coating composition is disclosed which comprises a fluorocarbon resin, a dispersant, and a cross‑linking agent reactive with the dispersant. The dispersant comprises a reaction product of a non‑functional acrylic monomer, an amino‑functional vinyl monomer, and a hydroxy‑functional acrylic monomer. The dispersant has amine functionality from the amino‑functional vinyl monomer to aid in dispersion of the fluorocarbon resin in the fluorocarbon coating compsn. and has hydroxyl functionality from the hydroxy‑functional acrylic monomer to enhance cross‑linking with the cross‑linking agent in the fluorocarbon coating compsn. A fluorocarbon coating system comprising a substrate and the fluorocarbon coating compsn. disposed on the substrate is also claimed. (WSCA Item Number 09/01316)

Section 55 Fouling and Microbiological Attack

TODOROVA V & RAYMOND M Surface treatments and cathodic electrocoating bath. Galvano‑Organo 2008, No 777, 43‑5.

Methods for determining microbiological contamination in cathodic electrocoating baths are discussed. A new method is described which has been implemented at two French companies. The method involves quantification of the adenosine triphosphate molecule in the bath water. A typical water sample contains adenosine triphosphate in three forms, these being intra‑cellular adenosine triphosphate in healthy biomass (which indicates the amount of living biomass in the sample), intra‑cellular adenosine triphosphate in unhealthy biomass, and extracellular adenosine triphosphate (which is liberated on the death of the organism). Examples of measurements using the instrument are presented. (In French) (WSCA Item Number 09/01584)

Section 63 Paints, Etc for Other Specific Uses

CARLSON B, BULLOCK J P, HANCE T M & PHELAN G D Barometric sensitive coatings based on osmium complexes dissolved in a fluoroacrylic polymer. Anal. Chem. 2009, Vol 81 No 1, 262‑7.

Osmium complexes (heptafluorobutyrate salts of complexes of 1,10‑phenanthroline ligand(s) and ligand(s) that are a diphosphine or diarsine) were dissolved in 1,1,1,3,3,3‑hexafluoroisopropyl methacrylate/perfluoropropylmethyl methacrylate copolymer. The luminescence of the coatings was tested for pressure sensitivity, temperature dependence, and photodegradation. The paints featured strong pressure response, and the temperature dependence of the luminescence was measured as low as ‑0.11%/deg. C. Several of the complexes exhibited little photodegradation upon exposure to 400 nm light. (WSCA Item Number 09/01605)

Section 69 Analytical Methods

ERICH S J F & OTHERS Influence of the pigment volume concentration on the curing of alkyd coatings: a one‑dimensional magnetic resonance imaging depth profiling study. Progr. Org. Coat. 2008, Vol 63 No 4, 399‑404

A one‑dimensional high spatial resolution magnetic resonance imaging (MRI) technique was applied to monitor the curing of alkyd coatings with different degrees of pigmentations as a function of depth. The MRI depth profiles clearly showed a change in curing behaviour around the critical pigment volume concentration (CPVC). Below the CPVC a macroscopic reaction front is observed, of which the speed does not depend on the degree of pigmentation and moves with the square root of time. Such fronts are considered to develop because the cross‑linking process is limited by oxygen diffusion towards the reaction front. Above the CPVC a coating appears to cure homogeneously. This sudden change in curing behaviour is attributed to the existence of coating spanning the pore networks above the CPVC. Therefore, oxygen easily penetrates the complete coating. Scanning electron microscopy images confirm the existence of porosity at high degrees of pigmentation. 24 refs. (WSCA Item Number 09/01689)

Books

A review of the following book also appeared in the March 2009 issue of WSCA: 

GOMATAM R & MITTAL K L (EDITORS) Electrically Conductive Adhesives. VSP BV, Leiden & Boston 2008, 425 pp. (ISBN 978‑90‑04‑16592‑2). Price 159.00 euro, $248.00. (WSCA Item Number 09/01838)

Section 01 Pigments, Extenders, Dyestuffs and Phosphors

ANON Functionalising microspheres with coating technology. JCT CoatingsTech 2008, Vol 5 No 10, 22-3.

The opportunities afforded by adding a coating to hollow microspheres, which increases their functionality and broadens their use potential, are presented. The coating technology is described and applications in water treatment, flow visualisation, and electronics are cited. They may also be used in paints, and hollow glass microspheres with an electrically conducting silver coating are considered ideal for use in paints, adhesives, and composites where they may also provide shielding against electromagnetic interference. Microspheres may be coated by pigments. (WSCA Item Number 09/00627)

Section 02 Patents: Pigments, Extenders, Dyestuffs and Phosphors

SHERWIN-WILLIAMS CO Pigment and coating composition capable of inhibiting corrosion of substrates. United States Patent 7462233: Off. Gaz. 2008, Vol 1337 No 2.

A pigment is disclosed comprising the reaction product of a filler compound, a calcium reagent, a borate compound, a molybdate compound, and a phosphate compound. Further claims specify that the filler compound and the calcium reagent are calcium carbonate, that the borate compound is boric acid, that the molybdate compound is molybdenum trioxide, and that the phosphate compound is phosphoric acid. In one embodiment, the pigment comprises a filler having calcium borate, calcium molybdate and calcium phosphate deposited on the surface. (WSCA Item Number 09/00674)

Section 55 Fouling and Microbiological Attack

DAMM C & MUNSTEDT H Properties of silver-filled acrylate photopolymer layers prepared by a heterogeneous photocatalytic polymerisation reaction. Surface & Coatings Tech. 2008, Vol 202 No 21, 5122-6.

Cross-linked, silver-filled acrylate photopolymer coatings on polyether ketone films were prepared without the aid of molecular photoinitiators by exploiting the photocatalytic activity of a silver-coated titanium dioxide pigment for the initiation of the polymerisation reaction. Because of the strong hydrophilic properties of the photopolymer the layers exhibit an efficient release of silver ions into water. The kinetics of the silver ion release from the coatings is governed by diffusion. The diffusion coefficient of silver ions in the acrylate photopolymer layer was estimated to be eight orders of magnitude lower than the diffusion coefficient of silver ions in water. As expected from the results of the silver ion release tests the acrylate photopolymer layers exhibit an antimicrobial activity. 5 micrometres thick photopolymer films containing between 2.5 and 7.5 wt. % of the silver-coated titanium dioxide pigment (which corresponds to a silver content between 0.03 and 0.1 wt. %) eliminate more than 90% of Escherichia coli within 5 hours. Within 24 hours the bacteria are killed completely. Under the test conditions used only the release of silver ions and not the activity of the titanium dioxide is responsible for the antimicrobial efficacy of the photopolymer layers. 21 refs. (WSCA Item Number 09/00964)

Section 71 Other Properties and Testing Methods

SUDDUTH R D Modelling cluster voids and pigment distribution to predict properties and critical pigment volume concentration in coatings. I. Dry coating analysis. Pig. Resin Tech. 2008, Vol 37 No 6, 375-88

A pigment clustering model with an analytical solution was developed in order to show how pigment cluster voids and pigment distribution will influence the critical pigment volume concentration (CPVC) and consequently the properties of the dry coating. It was found that the largest deviation from 100% pigment dispersion with no pigment clusters occurred just before and just after the ultimate CPVC (UCPVC). A theoretical relationship was also found between the pigment cluster dispersion coefficient and CPVC. The density ratio of overall coating to the pigment density was found to go through a maximum at a global volume fraction of pigment that was slightly greater than the UCPVC. It was also identified that mechanical failure of most coating formulations should be apparent at either the 'lower zero limit' or the 'upper zero limit' global volume fraction pigment, as defined in the study. 17 refs. (WSCA Item Number 09/01116)

Section 73 Industrial and Other Hazards

OSTROWSKI A D & OTHERS Nanotoxicology: characterising the scientific literature, 2000-2007. J. Nanoparticle Research 2009, Vol 11 No 2, 251-7.

Bibliometric techniques were used to characterise the prevalence and distribution of the current scientific literature on nanotechnology. It was found that the nano-toxicological literature is dispersed across a range of disciplines and sub-fields, focused on in vitro testing, often does not specify an exposure pathway, and tends to emphasise acute toxicity and mortality rather than chronic exposure and morbidity. Finally, there is very little research on consumer products, particularly on their environmental fate, and most research is on the toxicity of basic nanomaterials. The implications for toxicologists, regulators and social scientists studying nanotechnology and society are discussed. (WSCA Item Number 09/01131)

Books

A review of the following book also appeared in the February 2009 issue of WSCA.

HEILIG M Deutsches Taschenbuch fur Maler und Lackierer 2009 (German Handbook for Painters 2009). 2 volumes. Verlag Georg D W Callwey, Munchen 2008, 272, 136 pp. (ISBN 978-3-7667-1800-6). Price 15 euros. (WSCA Item Number 09/01232)

Section 53 Weathering, Corrosion, Etc

ANDREEVA D V & SHCHUKIN D G Smart self-repairing coatings. Materials Today 2008, Vol 11 No 10, 24-30.

A review and report of investigations is presented. It is concluded that manocontainers possessing the ability to release encapsulated active materials in a controlled manner may be employed to develop a new family of self-healing anticorrosive coatings. Several approaches to fabricate such self-healing coatings by the impregnation of sol/gel films with inhibitor-loaded polyelectrolyte multilayers, silica and titanium dioxide containers, and halloysites (aluminosilicate clay) have been demonstrated. Inorganic containers may be modified with a polyelectrolyte or polyelectrolyte/nanoparticle shell in order to provide them with permeability properties controlled by the changes in pH caused by corrosion or by external electromagnetic irradiation, whereas polyelectrolyte multilayers may be employed as an inhibitor storage nano-network without further modification. The release of the anticorrosive materials occurs only when triggered by corrosion processes or focussed light, which prevents leakage of the active component out of the coating. Reference is included to benzotriazole corrosion inhibitor loaded into titanium dioxide, polyelectrolyte shells blocking leakage and ultraviolet-induced shell oxidation and release of inhibitor. 47 refs. (WSCA Item Number 09/00285)

Section 55 Fouling and Microbiological Attack

HEMAIDA H A E, EL-DISSOUKY ALI A & SADEK S M M Potential antifouling agents: metal complexes of 3-(2-furylidene)hydrazino-5,6-diphenyl-1,2,4-triazine. Pig. Resin Tech. 2008, Vol 37 No 4, 243-9.

Seven copper(II) and cobalt complexes of 3-(2-furylidene)hydrazino-5,6-diphenyl-1,2,4-triazine were prepared by interacting 3-(2-furylidene)hydrazino-5,6-diphenyl-1,2,4-triazine with cobalt(II) and copper salts. The structures of the prepared complexes were confirmed by elemental analyses, infrared and nujol mull electronic spectra, as well as magnetic susceptibility measurements. The antifouling activity was measured on barnacle larvae. The results indicated that the toxicity of the ligand increased upon complexation and that copper complexes are the most active ones. It is considered that the successful development of some new copper(II) and cobalt complexes of 1,2,4-triazine that have in vitro antifouling activity against barnacle larvae and might provide new antifouling agents that are friendlier to the marine environment. 20 refs. (WSCA Item Number 09/00322)

Section 73 Industrial and Other Hazards

LARESE F F & OTHERS Human skin penetration of silver nanoparticles through intact and damaged skin. Toxicology 2009, Vol 255 No 1, 33-7.

In vitro skin penetration of silver nanoparticles was evaluated. Experiments were performed using the Franz diffusion cell method with intact and damaged human skin. Physiological solution was used as receiving phase and silver nanoparticles coated with polyvinylpyrrolidone dispersed in synthetic sweat were applied as donor phase to the outer surface of the skin for 24 hours. The receptor fluid measurements were performed by electrothermal atomic absorption spectroscopy. Human skin penetration was also determined by using transmission electron microscopy to verify the location of silver nanoparticles in exposed membranes. It was demonstrated that silver applied as nanoparticles coated with polyvinylpyrrolidone is able to permeate the damaged skin in an in vitro diffusion cell system. 36 refs. (WSCA Item Number 09/00504)

Section 76 Patents: Pollution and Utilisation of Wastes

MILLENNIUM INORGANIC CHEMICALS INC Depolluting coating composition. World (PCT) Patent Application 2008/048765, 15 pp. (Also US Patent Application 20080097018).

A coating composition is disclosed which comprises photocatalytic titanium dioxide particles, an opacifying agent, a silicone compound, particles which are able to remove nitric acid (especially calcium carbonate particles), styrene resin hollow microspheres, and a solvent. The combination of a silicone compound and styrene resin hollow microspheres in a depolluting coating compsn. results in improved opacity and durability compared to conventional coatings. The coatings may further comprise an organic polymer. (WSCA Item Number 09/00517)

Books

Reviews of the following books also appeared in the January 2009 issue of WSCA:

BRUNE B (EDITOR) European Coatings Directory 2009. Special Issue: Powder Coatings. Vincentz Network, Hannover 2009, 90 pp.
(WSCA Item Number 09/00622)

GLOCKNER P, JUNG T, STRUCK S & STUDER K Radiation Curing. Vincentz Network, Hannover 2008, 172 pp. (ISBN 978-3-86630-907-4). Price 129.00 euros.
(WSCA Item Number 09/00623)

TYLER S (EDITOR) Polymers Paint Colour Journal (PPCJ) Yearbook 2009. DMG World Media (UK) Ltd, Redhill (Surrey) 2008, 248 pp. (ISBN 1-84313-056-4). Price £160.00 (UK), £168.00 (elsewhere).
(WSCA Item Number 09/00624)