Liquid Coatings Research Articles

PPG to Display its Range of Liquid and Powder Coatings at CONSTRUCT 2016

PPG to Display its Range of Liquid and Powder Coatings at CONSTRUCT 2016

Graphitic Carbon Films Across Systems

When metal surfaces come into contact, lubricants are used to overcome friction. Various forms of hydrocarbons play a central role in lubrication, through both liquid lubricants and surface coatings. Solid lubricants like graphite and complex surface coatings such as diamond-like carbon have led to great advancements in friction mitigation. In addition to these designed carbon films, unintentional carbon films can also spontaneously form during metal–metal sliding. Here, we analyze various systems that produce carbon films, focusing on systems with cyclical metal sliding, hydrocarbon lubricants, and catalytic activity. The systems we analyze include friction polymers, diamond-like carbon coatings, varnish from industrial machines, metal-on-metal hip implants, microelectromechanical systems, and catalysis coke. These films, analyzed at the nanoscale, are primarily graphitic carbon with local regions of sp2 bonding. The graphitic carbon can act as a lubricant in some systems and not in others. Through comparing these various fields, we seek to better understand the formation, evolution, and friction properties of carbon films. Through design and control of carbon films formation, we can control triboactivity to improve system performance.

Free-standing thin film interactions with small particles

In order to investigate foam stability and coating ability via interactions with particles a free-standing film of initial thickness 150 μm to 350 μm was created within a metallic ring of 16 mm diameter. The weight change of the film is monitored and attributed to water loss with time. The effects of film drying are investigated with respect to the film′s interaction with a solid, spherical, 3 mm diameter glass bead. This particle was dropped onto the film and high-speed camera imaging was used to examine the moment it interacts with the film. In addition to the water content of the film, the relative humidity of the environment, the initial film thickness of the film and the moment the bead interacts with the film are all factors that influence the quality of the film and hence how it interacts with the glass bead. The bead would cause defect points in the film to turn into tears. Films with a higher final water content presented with less tears and gave the particle a more homogeneous coating. Thin films are often used in experimental and theoretical studies as a basis to investigate foam behavior (Bergeron & Radke, 1992; Myers, 1998, Stubenrauch and Von Klitzing, 2003, Weaire and Kermode, 1983). The importance of foam interaction with small solids spans a wide range of industrial and scientific fields such as agriculture, food science, pharmaceuticals, drilling fluids, household & personal care products (Dickinson, 2010, Eisner et al., 2007, Hunter et al., 2008, Mason et al., 2006, Murray, 2007, Quebaud et al., 1998). Liquid coatings are often used within the food industry, most notably for snack foods and animal feeds (Baldwin et al., 2011, Beckett, 2008, Rockey et al., 2010). What is under investigation here is how a foam, represented via a liquid thin film, can be used to coat a small spherical particle. In addition the drying of the thin, surfactant-based films is taken under consideration with respect to the interaction of such films with solid particles.

Curable Imidazolium Poly(ionic liquid)/Ionic Liquid Coating for Containment and Decontamination of Toxic Industrial Chemical-Contacted Substrates

A curable, imidazolium-based room-temperature ionic liquid (RTIL) coating system has been developed for the containment and decontamination of toxic industrial chemical-contacted surfaces. The curing times and mechanical properties of this poly(RTIL)/RTIL platform, which is based on alcohol–isocyanate step-growth polymerization chemistry, can be tuned by modifying the structures of the step-growth monomers, the stoichiometric ratio of linear (diol, A2) to cross-linking (triol, A3) RTIL monomers used, and the amount of free RTIL in the formulation. When applied to painted steel and rubber test substrates contacted with o-dichlorobenzene (o-DCB) (a polychlorinated biphenyl simulant), a 50:50 (A2:A3) step-growth alcohol-RTIL monomer mixture cross-linked with a stoichiometric amount of a commercial di-isocyanate monomer (B2) and containing 43 wt % free RTIL in the coating, reduced the o-DCB vapor amount by 96–99% compared to the uncoated, o-DCB-contacted control samples. This peelable, flexible, solid coating also removed by sorption up to >99% of the o-DCB liquid applied to the substrates after 24 h of contact.

Novel thermal and photo curable anti-reflective coatings using fluoroelastomer nanocomposites and self-assembly of nanoparticles

We describe novel optical coatings which require either thermal or photocuring to render them mechanically robust and abrasion resistant. These new coatings are low refractive index fluoroelastomer-nanoparticle composites that form a unique nanostructure during drying of the liquid coating. During drying, the nanoparticles in these liquid coatings migrate towards the substrate. The final, 100-nm-thick anti-reflective coatings are novel and exhibit a unique bilayer structure in which the nanoparticles are ordered and segregated towards the substrate. The coatings are rapidly cured using a new process and exhibit surprising “scratch durability” as measured by aggressively testing with steel wool. Sol gel chemistry is used which involves the reaction of the nanoparticles with an acrylic oxysilane to form nanoparticles which are functionalized with sol gel derived oligomers. The functionalized nanoparticles are combined with a fluoroelastomer containing a free radical initiator and multiolefinic crosslinker, and the composite film is rapidly cured by a thermal or UV process at low temperatures. The final product is a mechanically robust, low refractive index anti-reflective film which is useful for displays and photovoltaic devices. These are unique fluoropolymer nanocomposites which utilize nanoparticle self-assembly to enhance important properties.

Valspar Exhibits its Powder and Liquid Coatings Range at Architect@Work London

Valspar Exhibits its Powder and Liquid Coatings Range at Architect@Work London

The empirical evaluation of thermal conduction coefficient of some liquid composite heat insulating materials

We experimentally determined the coefficients of thermal conductivity of some ultra thin liquid composite heat insulating coatings, for sample #1 λ = 0.086 W/(m·°C), for sample #2 λ = 0.091 W/(m·°C). We performed the measurement error calculation. The actual thermal conduction coefficient of the studied samples was higher than the declared one. The manufactures of liquid coatings might have used some "ideal" conditions when defining heat conductivity in the laboratory or the coefficient was obtained by means of theoretical solution of heat conduction problem in liquid composite insulating media. However, liquid insulating coatings are of great interest to builders, because they allow to warm objects of complex geometric shapes (valve chambers, complex assemblies, etc.), which makes them virtually irreplaceable. The proper accounting of heating qualities of paints will allow to avoid heat loss increase above the specified limits in insulated pipes with heat transfer materials or building structures, as well as protect them from possible thawing in the period of subzero weather.

Evaluation of mammalian and bacterial cell activity on titanium surface coated with dicationic imidazolium-based ionic liquids

This work presents a new strategy to protect titanium surfaces against bacterial colonization and biofilm formation using dicationic imidazolium-based ionic liquid coatings.

Ionic Liquid Coatings for Titanium Surfaces: Effect of IL Structure on Coating Profile.

Dicationic imidazolium-based ionic liquids (ILs) having bis(trifluoromethylsulfonyl)imide (NTf2) and amino acid-based (methionine and phenylalanine) anionic moieties were synthesized and used to coat titanium surfaces using a dip-coating technique. Dicationic moieties with varying alkyl chains (8 and 10 carbons) and anions with distinct characteristics were selected to understand the influence of IL structural features on deposition profile. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used in this study to help elucidate intermolecular interactions within ILs as well as between ILs and TiO2 surfaces and to investigate IL coating morphology. Charge concentration on IL moieties, as well as the presence of functional groups that can interact via hydrogen bond, such as carboxylate and amino groups, were observed to influence the deposition profile. ILs containing amino acids as the anionic moiety were observed to interact strongly with TiO2, which resulted in more pronounced changes in Ti 2p binding energy. The higher hydrophobicity of the IL having NTf2 as the anionic moiety resulted in higher adhesion strength between the IL coating and TiO2.

PPG Launches Liquid and Powder Coatings Platforms for the Automotive Industry

PPG Launches Liquid and Powder Coatings Platforms for the Automotive Industry

Bulk processing of ZnO nanostructures via microwave assisted oxidation of mechanically seeded Zn dust for functional paints and coatings

Micron sized metallic zinc dust (99.9%, Davg=40μm) was mechanically milled to have zinc oxide seed nuclei on its surface, eventually transforming it into ZnO nanostructures by microwave irradiation for 15min. Effect of milling on the growth of seed layer, oxidation kinetics, particle size distribution, nano ZnO morphologies, phase purity, dispersion and UV absorption properties were studied and reported. ZnO rods with length 5–6μm and diameter of nearly 200nm were successfully synthesized in bulk through this facile route. The products were systematically characterized and studied with the motive to design multifunctional nano-products. A paint formulation was made by blending the as-synthesized nano ZnO with a natural organic resin; cashew nut shell liquid (CNSL) and surface coatings were developed over glass and metal substrates. ZnO–CNSL paint coatings were further studied for NIR reflectance, optical transparency and hydrophobic surface property. Its effective corrosion resistance has been validated with highly corrosive Mg-alloy substrates, an upcoming key material for automobiles. The ZnO–CNSL paint developed showed about 33% enhancement in NIR shielding and about 156% improvement in corrosion resistance when compared to their uncoated counterparts. The study strongly recommends microwave accelerated oxidation as a technologically competent process for the bulk preparation of multifunctional nano ZnO.

Headspace versus direct immersion solid phase microextraction in complex matrixes: investigation of analyte behavior in multicomponent mixtures.

This work aims to investigate the behavior of analytes in complex mixtures and matrixes with the use of solid-phase microextraction (SPME). Various factors that influence analyte uptake such as coating chemistry, extraction mode, the physicochemical properties of analytes, and matrix complexity were considered. At first, an aqueous system containing analytes bearing different hydrophobicities, molecular weights, and chemical functionalities was investigated by using commercially available liquid and solid porous coatings. The differences in the mass transfer mechanisms resulted in a more pronounced occurrence of coating saturation in headspace mode. Contrariwise, direct immersion extraction minimizes the occurrence of artifacts related to coating saturation and provides enhanced extraction of polar compounds. In addition, matrix-compatible PDMS-modified solid coatings, characterized by a new morphology that avoids coating fouling, were compared to their nonmodified analogues. The obtained results indicate that PDMS-modified coatings reduce artifacts associated with coating saturation, even in headspace mode. This factor, coupled to their matrix compatibility, make the use of direct SPME very practical as a quantification approach and the best choice for metabolomics studies where wide coverage is intended. To further understand the influence on analyte uptake on a system where additional interactions occur due to matrix components, ex vivo and in vivo sampling conditions were simulated using a starch matrix model, with the aim of mimicking plant-derived materials. Our results corroborate the fact that matrix handling can affect analyte/matrix equilibria, with consequent release of high concentrations of previously bound hydrophobic compounds, potentially leading to coating saturation. Direct immersion SPME limited the occurrence of the artifacts, which confirms the suitability of SPME for in vivo applications. These findings shed light into the implementation of in vivo SPME strategies in quantitative metabolomics studies of complex plant-based systems.

Laboratory Tests with Liquid Nano-ceramic Thermal Insulation Coating

Liquid nano-ceramic thermal insulation coatings appeared in the last decades on the market of thermal insulation materials. This paint-on insulation contains microscopic cellular ceramic microspheres. These vacuum-hollow balls were made of on high temperature melted ceramic. Its binding material is a mixture of synthetic rubber and other polymers. After mixing with the raw material with its binder, using brush or vacuum vaporizer can be taken on the surface to be insulated.The special literature of liquid nano-ceramic thermal insulation coatings gives different and contradictory thermodynamic details about this material. According to some sources its thermal conductivity is around 0,001-0,003W/mK, but other papers publish much higher thermal conductivity values (from 0,01W/mK to 0,14W/mK).In the Laboratory of Building Materials and Building Physics at Szechenyi Istvan University (Gyor, Hungary) several thermodynamic test were made with liquid nano-ceramic thermal insulation coatings. On basis of European Standards (EN) the thermal conductivity and water absorption of this material was determined. The relationship between thermal conductivity and water content was analyzed. Experiments were performed with conventional thermal insulation materials with additional ceramic coating on one side, two sides and beside two plates. Results were analyzed in order to prove the low thermal conductivity and heat mirror effect of this material.

The Effect of Treatment Temperature on Corrosion Resistance and Hydrophilicity of an Ionic Liquid Coating for Mg-Based Stents

Mg alloys are attractive candidate materials for biodegradable stents. However, there are few commercially available Mg-based stents in clinical use because Mg alloys generally undergo rapid localized corrosion in the body. In this study, we report a new surface coating for Mg alloy AZ31 based on a low-toxicity ionic liquid (IL), tributyl(methyl)phosphonium diphenyl phosphate (P1,4,4,4 dpp), to control its corrosion rate. Emphasis is placed on the effect of treatment temperature. We showed that enhancing the treatment temperature provided remarkable improvements in the performances of both corrosion resistance and biocompatibility. Increasing treatment temperature resulted in a thicker (although still nanometer scale) and more homogeneous IL film on the surface. Scanning electron microscopy and optical profilometry observations showed that there were many large, deep pits formed on the surface of bare AZ31 after 2 h of immersion in simulated body fluid (SBF). The IL coating (particularly when formed at 100 °C for 1 h) significantly suppressed the formation of these pits on the surface, making corrosion occur more uniformly. The P1,4,4,4 dpp IL film formed at 100 °C was more hydrophilic than the bare AZ31 surface, which was believed to be beneficial for avoiding the deposition of the proteins and cells on the surface and therefore improving the biocompatibility of AZ31 in blood. The interaction mechanism between this IL and AZ31 was also investigated using ATR-FTIR, which showed that both anion and cation of this IL were present in the film, and there was a chemical interaction between dpp(-) anion and the surface of AZ31 during the film formation.

Improvement of thermo-mechanical properties of basalt fiber using heat resistant polymeric coatings

Heat resistant coatings of textile materials are required so that they can fulfill the high security demand in the case of resistance to fire and improve thermo-mechanical properties. These coatings also enhance the interface properties of textiles in the composites. Liquid phase coatings, based on polysilazane and polysiloxane polymers were deposited onto the basalt fiber (BF) yarn using impregnation coating method. Tensile testing under thermal stress was conducted to examine the thermo-mechanical properties of both coated and uncoated yarns. The thermo-mechanical study indicated that the heat resistant coatings enhanced 40–70 % tensile strength and 25–40 % stiffness of original BF yarns up to 400 °C. BF yarn retained 65–90 % of its tensile strength at 500 °C due to coatings, whereas the uncoated BF yarn lost 85 % strength at this temperature. Thermo gravimetric analysis (TGA) showed that the coatings have good thermal stability. In addition, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, optical microscopy and fourier transform infrared (FTIR) spectroscopy analyses were executed in order to evaluate the surface microstructure as well as surface chemical compositions of the BF yarns.

Polymeric ionic liquid coatings versus commercial solid-phase microextraction coatings for the determination of volatile compounds in cheeses

The extraction performance of four polymeric ionic liquid (PIL)-based solid-phase microextraction (SPME) coatings has been studied and compared to that of commercial SPME coatings for the extraction of 16 volatile compounds in cheeses. The analytes include 2 free fatty acids, 2 aldehydes, 2 ketones and 10 phenols and were determined by headspace (HS)-SPME coupled to gas chromatography (GC) with flame-ionization detection (FID). The PIL-based coatings produced by UV co-polymerization were more efficient than PIL-based coatings produced by thermal AIBN polymerization. Partition coefficients of analytes between the sample and the coating (Kfs) were estimated for all PIL-based coatings and the commercial SPME fiber showing the best performance among the commercial fibers tested: carboxen-polydimethylsyloxane (CAR-PDMS). For the PIL-based fibers, the highest K(fs) value (1.96 ± 0.03) was obtained for eugenol. The normalized calibration slope, which takes into account the SPME coating thickness, was also used as a simpler approximate tool to compare the nature of the coating within the determinations, with results entirely comparable to those obtained with estimated K(fs) values. The PIL-based materials obtained by UV co-polymerization containing the 1-vinyl-3-hexylimidazolium chloride IL monomer and 1,12-di(3-vinylimiazolium)dodecane dibromide IL crosslinker exhibited the best performance in the extraction of the select analytes from cheeses. Despite a coating thickness of only 7 µm, this copolymeric sorbent coating was capable of quantitating analytes in HS-SPME in a 30 to 2000 µg L(-1) concentration range, with correlation coefficient (R) values higher than 0.9938, inter-day precision values (as relative standard deviation in %) varying from 6.1 to 20%, and detection limits down to 1.6 µg L(-1).

Influences of added sand-dust particles on the tribological performance of graphite-like coating under solid–liquid lubrication

Graphite-like carbon (GLC) coatings were fabricated by unbalanced magnetron sputtering technique. Raman spectroscopy and XPS analysis confirmed the nanostructured GLC coatings have high concentration of sp2-hybridized carbon. HRTEM analysis demonstrated that the microstructure of GLC coatings was composed of nanocrystalline graphite, fcc-center cubic (fcc) diamond and amorphous carbon. The tribological performance of GLC coatings combined with five types of liquid lubricants (PFPE, PAO, SO, IL and MAC) has been investigated under the conditions without and with sand-dust particles. Experimental results showed that the obtained excellent low friction and wear-resistance was attributed to the synergistic effect of liquid lubricants and GLC coatings.

Electrochemical Preparation of Polypyrrole-Ionic Liquid Coating for Solid Phase Microextraction and Its Application in Gas Chromatographic Determination of Benzene Derivatives

Electrochemical Preparation of Polypyrrole-Ionic Liquid Coating for Solid Phase Microextraction and Its Application in Gas Chromatographic Determination of Benzene Derivatives

Heterogeneous ice nucleation on phase-separated organic-sulfate particles: effect of liquid vs. glassy coatings

Abstract. Atmospheric ice nucleation on aerosol particles relevant to cirrus clouds remains one of the least understood processes in the atmosphere. Upper tropospheric aerosols as well as sub-visible cirrus residues are known to be enhanced in both sulfates and organics. The hygroscopic phase transitions of organic-sulfate particles can have an impact on both the cirrus cloud formation mechanism and resulting cloud microphysical properties. In addition to deliquescence and efflorescence, organic-sulfate particles are known to undergo another phase transition known as liquid–liquid phase separation. The ice nucleation properties of particles that have undergone liquid–liquid phase separation are unknown. Here, Raman microscopy coupled with an environmental cell was used to study the low temperature deliquescence, efflorescence, and liquid–liquid phase separation behavior of 2 : 1 mixtures of organic polyols (1,2,6-hexanetriol and 1 : 1 1,2,6-hexanetriol + 2,2,6,6-tetrakis(hydroxymethyl)cyclohexanol) and ammonium sulfate from 240–265 K. Further, the ice nucleation efficiency of these organic-sulfate systems after liquid–liquid phase separation and efflorescence was investigated from 210–235 K. Raman mapping and volume-geometry analysis indicate that these particles contain solid ammonium sulfate cores fully engulfed in organic shells. For the ice nucleation experiments, we find that if the organic coatings are liquid, water vapor diffuses through the shell and ice nucleates on the ammonium sulfate core. In this case, the coatings minimally affect the ice nucleation efficiency of ammonium sulfate. In contrast, if the coatings become semi-solid or glassy, ice instead nucleates on the organic shell. Consistent with recent findings that glasses can be efficient ice nuclei, the phase-separated particles are nearly as efficient at ice nucleation as pure crystalline ammonium sulfate.

Fluid drag reduction and efficient self-cleaning with rice leaf and butterfly wing bioinspired surfaces

Researchers are continually inspired by living nature to solve complex challenges. For example, unique surface characteristics of rice leaves and butterfly wings combine the shark skin (anisotropic flow leading to low drag) and lotus leaf (superhydrophobic and self-cleaning) effects, producing the so-called rice and butterfly wing effect. In this paper, we present an overview of rice leaf and butterfly wing fluid drag and self-cleaning studies. In addition, we examine two other promising aquatic surfaces in nature known for such properties, including fish scales and shark skin. Morphology, drag, self-cleaning, contact angle, and contact angle hysteresis data are presented to understand the role of wettability, viscosity, and velocity. Liquid repellent coatings are utilized to recreate or combine various effects. Discussion is provided along with conceptual models describing the role of surface structures related to low drag, self-cleaning, and antifouling properties. Modeling provides design guidance when developing novel low drag and self-cleaning surfaces for applications in the medical, marine, and industrial fields.