Liquid Coatings Research Articles

Effects of Elevated CO2, Liquid Coating, and Ethylene Inhibitors on Postharvest Storage and Quality of Mango

Mango fruits (Mangifera indica L. cv. Tommy Atkins) were harvested at early physiological maturity to study the effects of postharvest treatments on storage and fruit shelf-life. The fruits were subjected to control atmosphere (20 CO2 +3% O2, and 30% CO2 + 3% O2), liquid coating (NatureSeal and Polyamine), and ethanol vapor. The fruits were kept for 4 weeks at 50 + 3°F then removed from the cold storage and maintained at room temperature. Mango fruits stored at high level of CO2 or dipped in NatureSeal had better shelf-life than fruits stored at a low level of CO2 or with ethanol vapor.

Differential laser absorption and thermal emission for remote identification of opaque surface coatings

We experimentally and theoretically studied the phenomenon of thermal emission from nonvolatile liquid surface coatings following heating with a pulsed CO(2) laser. The effects of thermal diffusion across the liquid-air and liquid-substrate interfaces as well as the full absorption spectrum of the liquid are addressed theoretically. The differential temporal and intensity characteristics of the thermal emission signal from the heated surface coating, resulting from the differential heat deposition profile for on- and off-resonance excitation, are shown to be useful for the purposes of identifying different surface contaminants. The application of this technique to standoff thermal imaging of contaminated surfaces is discussed.

Self-stratifying coatings — an overview of a European Community Research Project

The objective of the project, which was funded by the European Commission and Europwan coatings and resins manufacturers, was the formulation of liquid self-stratifying coatings which after application as thin films spontaneously form two coherent layers, thus providing an undercoat and finishing coat in one operation. As a first step a database was compiled of the relevant physical properties of polymers used in surface coatings. This necessitated extensive new measurements of solubility, surface energies, phase equilibria and other parameters. A theory of stratification was developed for films comprising binary mixtures of polymers in solution and tested for a wide range of polymer mixtures. Group-contribution (UNIFAC) theory was employed to predict phase-separation and surface properties. A preliminary study was also made of the principles of formulating waterborne stratifying coatings from aqueous polymer dispersions. Solution coatings were successfully formulated for steel, plastic and wood substrates. Their performance was then evaluated under industrial spray application conditions. The mechanism of formation of stratified films in the experimental compositions could be described in terms of the solubility relationships of the polymer mixtures, the surface tensions of the separate phases and the kinetic aspects of solvent evaporation from paint films. Principal component and discriminant analysis of the experimental data generated quantitative equations for calculating the probability of stratification from the physical properties of polymers. For medium to high solids application, the coatings were liquid in liquid emulsions rather than homogeneous solutions. The problem of reproducibly locating pigments in the two layers was not fully resolved and would require further study to achieve commercially viable coatings. A fuller description of the research including experimental details is to be found in the accompanying papers from the participating research institutes.

Self-stratifying coatings for plastic substrates (BRITE EURAM PROJECT RI 1B 0246 C(H))

The objective of the project was the investigation of liquid coatings which, after application, will stratify spontaneously during film formation into two well separated functional layers. Seven European laboratories participated in the project: PRA (UK) prime partner, CERIPEC (F), CoRI (B), DTI (DK), EnPro (DK), EOLAS (IRL), FPL (D) and TNO (NL). The task assigned to CoRI was to investigate the feasibility of such systems for painting plastic substrates. This paper is restricted to the essential points of the work undertaken. It reports the main experimental results and the main conclusions derived therefrom and commented through theoretical considerations. A guideline for the formulation of a self-stratifying coating is finally proposed.

An Analysis of the Effect of Surfactant on the Leveling Behavior of a Thin Liquid Coating Layer

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn Analysis of the Effect of Surfactant on the Leveling Behavior of a Thin Liquid Coating LayerL. W. Schwartz, D. E. Weidner, and R. R. EleyCite this: Langmuir 1995, 11, 10, 3690–3693Publication Date (Print):October 1, 1995Publication History Published online1 May 2002Published inissue 1 October 1995https://doi.org/10.1021/la00010a017RIGHTS & PERMISSIONSArticle Views331Altmetric-Citations39LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (412 KB) Get e-Alerts Get e-Alerts

Instability of liquid coatings on cylindrical surfaces

Capillary instability of long annular viscous liquid layers coating the surface of a cylindrical wire is studied. Effects of Reynolds number, Re, initial disturbance wave numbers, k, and wire radii, s on the growth rate of the instability are considered. The initial disturbance amplitude is chosen as 5% of the initial unperturbed liquid thickness. It is found that the growth rate of the disturbance amplitude is composed of a linear portion, which is well predicted by the linear theory, and a relatively flat portion, which is not predicted by the linear theory and is strongly dependent on the Re, k, and s. A unique feature of this instability is a double pinch-off process (in certain parameter range) which results in the formation of secondary satellite drops.

Vibrating piezoelectric sensors

Abstract This paper presents the original results obtained in the development of the vibrating piezoelectric sensors loaded with any medium, either solid, liquid or gas. The common feature of such a loading is its ability to vibrate synchronously with the piezoelectric resonator as a compound resonator. The paper introduces a new concept in vibrating sensors, where the vibrational characteristics of a piezoelectric resonator, namely, the nominal frequency and vibrational amplitude, are correlated with the physical characteristics of a medium vibrating synchronously with a piezoelectric resonator as a compound resonator. The energy transfer model is introduced in order to explain the microweighing capability of the quartz resonators. The general equation derived from this model is proved to be valid for both solid and liquid coatings. Further, it is proved that microweighing is a common feature of all quartz resonators, whatever their vibrational mode. It is also proved that other piezoelectric resonators exhibit the same capability. Damping of the quartz resonator vibrations at certain temperatures during a temperature sweep is correlated with the morphology of the deposited film. This property might be developed in thin-film vibrational spectroscope. Resonance of a gas within a cavity is used for the development of tunable gas sensors. Examples are given for hydrogen and methane detection in air without using a catalyst. Another application is moisture sensing down to the ppb concentration range.

Mini articles

Finishing Today's Bicycles The name Raleigh is undoubtedly one of the best known in cycling throughout the world and Kemira Coatings are proud to be their leading supplier of liquid surface coatings.

Dynamic Considerations in the Closing and Opening of Holes in Thin Liquid Films

Whether holes in thin films close or open is an important issue in the design of liquid coatings. Previous analyses, for example the work of Taylor and Michael (J. Fluid Mech. 58, 625 (1973)) predict a static criterion for hole closure based on a balance between capillary and gravitational forces. In the present work we develop a numerical model which follows the evolution of holes to determine whether they close or open. The model is based on the lubrication approximations and requires input of the advancing and receding contact angles. Because viscous forces are also included in the present model, the static criteria can be reevaluated using the more complete theory. We find that holes which the static criteria predict will close can actually open, and vice versa.

Polymer company bets on powder coatings growth

Ruco Polymer Corp. of Hicksville, N.Y., may be in the right place at the right time. As a supplier of polyester powder to powder coatings producers, the small firm could benefit if a recently announced Detroit-based research consortium, USCAR—composed of General Motors, Ford, and Chrysler—makes headway in identifying polyester powder coatings for use in automotive assembly plants. Dieter Jungclaus, vice president and general manager of Morton International powder coatings division, the largest U.S. powder coatings producer, notes that automakers already use the heat-fusible powder coatings to decorate and protect such automotive parts as engine blocks and wheel covers. The market could grow much larger if the big three automakers, in their USCAR consortium, decide to coat their car and truck bodies with powder formulations, rather than the currently used solvent-borne liquid coatings, which contribute to atmospheric smog. Ruco is already a significant supplier of polyester powders to such major powder coa...

Above ground protection using petrolatum tapes

Maintenance of protective coatings on metal structures presents problems of surface preparation, accessibility and the limitations of various coating systems. Traditional liquid coatings generally require a high standard of surface preparation and are often not applied with due regard to the manufacturer's instructions. Hence, breakdown and subsequent corrosion are inevitable. Re-coating leads to further problems with surface preparation and compatibility. Petrolatum tapes require minimal surface preparation and they provide a thick coating and instant preparation. Nowadays petrolatum tapes may be successfully applied to surfaces that have been manually cleaned and the exterior surface of the tape can be coloured and toughened to suit site requirements. Hence, in many environments petrolatum tapes now offer a viable alternative to liquid coatings.

Liquid crystal coatings for surface shear-stress visualization in hypersonic flows

Experiments were conducted to test the surface-shear-stress visualization capabilities of shear-stress-sensitive/temperature- insensitive liquid crystal compounds in hypersonic flow. Liquid crystal coatings were applied to the surface of a conical model, which was then exposed to a high-unit-Reynolds-number (2.3 {times} 10{sup 7}/m) Mach 5 flow. The coating was illuminated by white light, and its response to the various flow situations was monitored and recorded with standard video and high-speed movie cameras. Boundary layer transition to turbulence was clearly demarcated by the technique. The dynamic location of the transition front as a function of model angle of attack (for sharp and blunt cones, with and without boundary-layer trips) was recorded, and observations were found to be consistent with established (published) trends for hypersonic flows over conical bodies. Normal shock passage over the model during tunnel shutdown was recorded (at 400 frames/second), and the liquid crystal coating was observed to respond to this event in a time interval less than or equal to the time between sequential movie frame exposures ({le} 0.0025 seconds). The liquid crystal technique has thus been demonstrated as a viable diagnostic tool for use in transient/compressible flows. 18 refs., 3 figs.

Noncontacting low-cost instrument for film thickness measurement

A low-cost, noncontacting, nondestructive technique is presented for measuring the thickness of thin liquid or solid films and coatings in real time by utilizing the resonance properties of microstrip structures. A new measurement system in which all the microwave components are internal to the instrument, thereby eliminating the need for microwave test equipment, is described. Only a low-voltage DC source, such as a battery, is required to power the unit; the output is also a DC voltage or current. Using a linear model, sample coefficients of determination, r/sup 2/, greater than 0.98 have been obtained for film thickness measurements of water, enamel paint, and silicon rubber up to 0.8-1.5- and 2-mm thick, respectively. Copper sheet metal up to 0.9-mm thick has been measured with an r/sup 2/ greater than 0.99. The measurement range can be extended or improved even further if nonlinear circuit behavior is accounted for.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

New developments in weather resistant powder coatings

A disadvantage found when conventional weather resistant powder coatings are compared to liquid coatings is their relatively poor flow properties. The flow of thermoset powder coatings depends on a number of factors, including the selection of suitable pigments and fillers, pigment concentration, additives such as flow agents, bake schedule, reactivity and structure of the resinous components, melt viscosity, and the viscosity profile during crosslinking. This paper reports about recently developed carboxyl terminated triglycidyl isocyanurate (TGIC) cured polyesters which result in powder coatings with remarkably improved flow properties due to the polyester's molecular structure and functionality and the viscosity profile during the curing process. These improvements have been reached without any prolongation of the gel time and without compromising the weathering resistance of the film. Such new powder coatings completely crosslink at 160°C within 15 minutes yielding films with excellent mechanical properties.

An Analysis of Jet Stripping of Liquid Coatings

This paper presents a new analysis of the jet stripping process, as used to control coating thicknesses in the paper, photographic and galvanizing industries, and demonstrates that the inclusion of a surface shear stress term, acting in conjunction with the pressure gradient on the coating, gives theoretical predictions of coating behavior quite different from those based on stripping which allows only for pressure gradient effect. An illustration is given of how jets operating close to, and further from, the strip during hot dip galvanizing have different effects on the molten coating even though the final coating mass might be the same. Measurements of coating mass, taken from galvanizing line trials, have shown good agreement with the revised theory.

Liquid and Powder coatings for architectural purposes

Three standards relating to the quality of coatings applied to aluminium alloys (BS 4842, BS 6496) and galvanized steels (BS 6497) used externally in inaccessible positions; have just been published by the British Standards Institution. All three will be found relevant to the construction industry and of significance to architects, designers and the paint industry as well as to window manufacturers at whose request the new standards were formulated.

Reduction of harmful discharges on contact shielding of liquid media with liquid coatings

A formula is given for evaluating the efficiency of using the method of shielding technological solutions. A satisfactory correlation has been found between the calculated and experimental data. Shielding technological solutions makes it possible to reduce losses of toxic and valuable substances in the manufacture of man-made fibres from polymer solutions and in other branches of industry.

Influence of solid and liquid metallic coatings on the microprocesses in the surface layers of solids

Influence of solid and liquid metallic coatings on the microprocesses in the surface layers of solids

Equipment

Robnorganic Systems Ltd., of Highworth Road, South Marston, Swindon, Wiltshire, have introduced a new dipping unit capable of applying one‐part liquid protective coatings. Applications include adding an overall coating of varnish to loaded printed circuit boards, protecting them from vibrational stress and adverse humidity.

Peak reflectance and color gamut of superimposed left- and right-handed cholesteric liquid crystals

Coatings of cholesteric liquid crystals (CLCs) have properties of narrowband optical filters. It has been proposed and tested experimentally that superimposed coatings of left- and right-handed CLCs double the peak reflectance from 0.5 to 1.0. In an alternate method a halfwave plate inserted between two coatings of leftor right-handed CLCs accomplishes the same result. As the spectra of such superimposed coatings resemble those of optimum colors, the color gamut obtained with such liquid crystal coatings approaches that of optimum colors.