Coatings transactions abstracts.

OCCA and FSCT, the publishers of Surface Coatings International and JCT RESEARCH, respectively, share a strategic partnership to promote the transactions of each organization as a service to the international coatings community and, specifically, the readership of each journal.

The following papers were published in Surface Coatings International Part B: Coatings Transactions, Vol. 88, Issue B1, March 2005.

Towards a Theory of Adhesion with Predictive Power -- I.R. Peterson

Currently, there is no satisfactory molecular theory allowing for the prediction of the interaction of two materials across their mutual interface. All existing theories assume there is a part of the molecular interactions involved that obeys the London inverse-sixth power law, as is valid for the separations encountered in gases. It is shown that, just as the London law is no longer valid in the Casimir limit of large separations, so it is also invalid in the limit of close molecular contact encountered in condensed phases. The experimental data on molecular interactions is reviewed. The Szyszkowski formalism is developed, and shown to explain the temperature dependence observed by Vrbanac and Berg. The formula of van Oss, Good and Chaudhury is shown to be valid under certain simplifying assumptions, but in order to develop it into a theory with significant predictive strength, it must be modified in three aspects: by the use of an additional parameter; by non-linearity; and by separate consideration of entropic terms.

Keywords: Adhesion, critical review, Casimir, acid-base, wetting, surface interactions

New Developments in UV Radiation Curing of Protective Coatings -- C. Decker

Recent advances in photoinitiated cross-linking will be presented, in particular regarding the efficiency of novel photoinitiators, monomers and functionalised oligomers, as well as the performance of the polymers obtained by this environmental-friendly technology. Such ultra-fast reactions can be easily followed in real-time and quantitatively by infrared spectroscopy, to assess the influence of chemical and physical parameters on the polymerisation kinetics. Because of their remarkable properties and high resistance, such ultraviolet (UV)-cured coatings proved particularly efficient to protect a large variety of materials (plastics, metals, paper, wood) against chemical attack, corrosion and weathering.

Keywords: UV curing, coatings, acrylate, epoxide 

The Effects of Some Engraving and Film Substrate Parameters on the Solid Density and the Dot Gain in Gravure Printing -- E.N. Gencoglu

The effects of some engraving and film substrate parameters on the solid density and dot gain in gravure printing were studied by using polyester, BOPP plain film and BOPP co-extruded film substrates. Bi-axially oriented polypropylene (BOPP) is a product utilised in numerous industries such as food packaging, printing, laminating and labeling. It was concluded that the solid density of print is affected by the roughness values of the film substrates. Increasing the roughness value increases the print density. The number of cells per cm2 and the depth of the cells also affect the solid density. Deeper and fewer cells per cm2 give a lower solid density value than shallower cells and more cells per cm2.

Engraving parameters have a major effect on the dot gain. The channel between cells has a positive effect on the dot gain. The cell depth and the number of cells per cm2 also affect the dot gain.

The highest dot gain value was measured from the 35% coverage area of all of the scales printed on all the substrates. Also, the highest dot gain values were measured for the prints on polyester the smoothest substrate.

Keywords: Gravure, dot gain, solid density, ink, roughness

Comparison of Textile Print Quality Between Inkjet and Screen Printings -- S. Kiatkamjornwong, P. Putthimai, and H. Noguchi

This research was concerned with an investigation of cotton print qualities that were achieved by inkjet printing and screen printing. The acrylic binder, S-711, with a pigment-to-binder (P/B) ratio of 1:2 (by weight) was used to produce one set of inkjet inks. BR-700 was used in the creation of another set of screen inks. Fume silica was added to the screen ink to increase the viscosity so that the ink would meet the rheology requirements. The viscosity and flow behaviour of both inks were acceptable. Both the ink viscosity and the particle-size distribution were slightly increased during storage at an ambient temperature for two months. The inkjet ink printed fabrics were pretreated with a solution of poly(ethylene oxide) having 2 to 3 million Dalton molecular weight. The printed fabrics from both inks were analysed for colour saturation, colour gamut and their volume, density, tone reproduction, stiffness, air permeability, and crock fastness. The type, concentration and P/B ratio were exactly the same in both inks in the pigment dispersions. Even though the loaded ink volume on fabrics, by inkjet, was tuned to be approximately the same in optical density as that given by the screen ink, by a multi-pass mode printing, both printed fabrics gave different colour saturations, colour gamuts and tone reproductions. The colour gamut volume, stiffness, air permeability and crock fastness of the inkjet inks are superior to those of screen inks. The print quality of the inkjet printing on cotton fabric was, thus, better. However, the inkjet ink printed cotton fabric needed to be printed three times to produce the same colour and tone reproduction as that produced by screen printing.

Keywords: Pigmented inkjet ink, screen ink, print quality, cotton fabric, polyacrylate binder

Antimicrobial Properties of Novel N-halamine Siloxane Coatings -- J.F. Williams, J. Suess, J. Santiago, Y. Chen, J. Wang, R. Wu, and S.D. Worley

Antimicrobial coatings on a wide variety of hard and soft substrates were prepared by exposing surfaces treated with novel N-halamine siloxane precursor monomers and macro-monomers to oxidative halogen solutions. Suspensions of a range of bacterial, viral, fungal and yeast micro-organisms were applied to the halogen-charged coatings for defined intervals, before recovery and quantification of surviving microbes using appropriate neutralisation and culture techniques. The biocidal surfaces exhibited powerful, broad-spectrum antimicrobial properties, inactivating most challenge microbes in contact times measured in minutes to hours, rather than the extended contact incubation periods usually associated with substrate-bound antimicrobial agents. Antimicrobial effects were also demonstrated to prevent odour caused by bacterial generation of ammonia in an experimental simulation of a urine-soaked nappy pad. Contact times for efficacy were related to bound halogen concentrations per unit of surface area. Potential benefits of these novel rechargeable biocidal surfaces cover a range, from limiting contamination of environmental surfaces with disease agents in healthcare or food service facilities, to controlling odour and mildew in bathrooms, and preventing odour formation in incontinence pads. They also confer antimicrobial protective functions on textiles and non-woven filter media for air and water.

Keywords: N-halamines, biocidal coatings, siloxanes, antimicrobial surfaces, chloramines, broad-spectrum, rechargeable

Influence of Biocide Pretreatment of Wood on Performance of Exterior Coatings -- M. Pavlic, B. Kricej, M. Tomazic, and M. Petric

Exterior coatings may not provide sufficient protection of wood against biodeterioration. In order to minimise the decay risk, wood can be impregnated with biocides before finishing. However, pretreatment of wood may have an effect on some important properties of surface coatings. The authors impregnated spruce wood specimens with a new preservative formulation, containing the ester of boric acid with an alkanolamine. The aim of this research was to establish a possible influence of this biocide on the performance of acrylic and alkyd stains on pre-treated wood. They studied the drying characteristics, stackability, adhesion, and permeability of the coatings. A boron-based preservative in a treated spruce wood had a pronounced influence on the drying of coatings and on the permeability of the acrylic stain. However, the influence on adhesion of the coatings was only indicated.

Keywords: Boron, coating properties, stain, wood preservative 

Reloadable Antimicrobial Coatings Based on Amphiphilic Silicone Networks --J.C. Tiller, L. Hartmann, and J. Scherble

Amphiphilic networks composed of polydimethylsiloxane (PDMS), poly(2-hydroxyethylacrylate) (PHEA), and poly(acrylic acid) (PAA) have been prepared as thin covalently surface-attached coatings via a protecting group strategy. Atomic force microscopy (AFM) images revealed that both the hydrophobic PDMS phase as well as the hydrophilic PHEA and PAA phase, respectively, are present at the surface and show nanophase separation. The coatings were loaded with Rhodamine B (RB) as a model compound for release experiments. The dye is quickly released from the pure PHEA-I-PDMS coatings of all the compositions. In contrast, the release of RB from the PAA-I-PDMS is greatly delayed over weeks. First experiments with PHEA-I-PDMS coatings loaded with the disinfectant cetyltrimethylammonium chloride showed that the antimicrobial activity against the bacterium Staphylococcus aureus was retained after washing.

Keywords: Amphiphilic network, poly(acrylic acid), polydimethylsiloxane, antimicrobial, controlled release

Biocidal Nanosol Coatings -- H. Haufe, A. Thron, D. Fiedler, B. Mahltig, and H. Bottcher

This paper was presented at the 2nd Global Congress on Hygienic Coatings and Surfaces in Orlando, FL, USA in January 2004

The inclusion of biocidal compounds into modified silica matrices using the sol-gel technique offers new interesting prospects for antimicrobial coatings with controlled release effects. The coatings are well suited for the functionalisation of flexible supports such as paper, textiles and polymer foils as they exhibit good adhesion and improved mechanical properties. It is possible to combine and coimmobilise different biocidal components to expand the antimicrobial efficiency. In the simplest case, modified silica coatings with immobilised boric acid can be used for the protection of wood against biological degradation. Moreover, silica coatings with embedded nanoparticular silver combined with organic biocidal compounds efficiently decrease the survival rate of different bacteria on textiles and medical catheters. Finally, novel types of antimicrobial nanosol coatings with volatile biocidal compounds (VBCs) are presented.

Keywords: Antimicrobial, biocidal, nanosol, coating

Characterisation of Surface Treatments on Concrete by AC Impedance Spectroscopy -- S. Syropoulou and N.R. Buenfeld

The electrical resistance of a surface-treated layer is generally indicative of its barrier properties, especially its resistance to ion diffusion. AC impedance measurements are rapid and non-destructive, and previous laboratory tests using a simple test cell geometry showed that it may be used to separate the electrical resistance of a surface treatment from that of the underlying concrete without physically separating the two. This suggests that AC impedance measurements might form the basis of an in situ method of characterising surface treatments on concrete.

This paper reports on AC impedance measurements made on surface-treated concrete panels using a test cell geometry that can be used on site. Three different surface treatments were investigated: a silane, a polyurethane coating, and an epoxy resin coating. The ability of the technique to provide separate signals for the substrate and the surface treatments is demonstrated, along with details of the basis of the proposed technique. The effects of surface treatment thickness, test duration and moisture content are also explored.

Keywords: Concrete, in situ measurements, AC impedance spectroscopy

Ultraviolet and Thermostable Non-Isocyanate Polyurethane Coatings -- O. Figovsky, L. Shapovalov, and F. Buslov

Conventional monolithic polyurethanes have good mechanical properties, but they are porous, and possesses poor hydrolytic stability and insufficient permeability. The involvement of toxic components, such as isocyanates, in their production process makes this process extremely toxic and dangerous. Network non-isocyanate polyurethanes (NIPUs) are formed from the reaction between cyclocarbonate oligomers (CCOs) and primary amine oligomers (PAOs). The authors of this paper are studying new types of NIPUs based on acrylic and siloxane CCOs and dendro-polyfunctional siloxane PAOs. These investigations create the possibility to develop high-level UV-stable coatings based on acrylic -dendro-amine systems, which are curable at room temperature, and their most able siloxane-based systems that have good adhesion and mechanical properties. An advanced way of preparing thermo-stable coatings is based on 'blocked' non-isocyanate polyurethane.

Keywords: Non-isocyanate polyurethane, acrylic cyclocarbonate, siloxane oligomers, UV-resistant coatings, thermostability 

Surface Coatings International Part B: Coatings Transactions is available in print (ISSN 1476-4865) and online (ISSN 1742-0261) formats. Individual papers are hosted by INGENTA and may be accessed at http://ingentaselect.com, and down-loaded at $25/paper. Members of FSCT may purchase an annual subscription at a special discount. Email [e-mail] for details. Annual subscriptions are available to corporate organisations. Email [e-mail] for details.