Influence of surface roughness on the diffuse to near‐normal viewing reflectance factor of coatings and its consequences on color measurements

In this work, we discuss the effect of surface roughness on the measurement of the diffuse to near‐normal viewing reflectance factor of coatings and evaluate its impact on the corresponding color coordinates. We compare specular component included (SCI) and excluded measurements. We introduce a gloss‐factor to account for surface roughness in specular component excluded measurements. We present experimental results on samples with different degrees of surface roughness. Samples in this study were chosen to expose the contribution of the surface in the reflectance factor. For slightly rough surfaces, the influence on the measured reflectance factor depends on whether the specular‐component is included or excluded. As the surface roughness increases, the specular‐excluded reflectance factor increases approaching its value with the SCI further roughness lead to similar measurement results in both configurations. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 177–187, 2013.     

Performance of organic nanoparticle coatings for hydrophobization of hardwood surfaces

The protection of wood surfaces against water is a primary requirement to enhance their life-time and durability. In this article, a hydrophobic surface modification of selected hardwood surfaces (including high-density (HD) and low-density (LD) samples) is presented, by coating them with waterborne imidized nanoparticles under pure conditions or with vegetable oil. The performance of both nanoparticle coatings relative to noncoated and oil-coated samples was evaluated by water contact angles, microscopy, and optical profilometry. The pure nanoparticle coatings often increase the hydrophobicity, but they do not yet form a fully protective layer due to their porous structure after drying. The nanoparticle coatings with vegetable oil form a continuous layer with a maximum contact angle of 118°. The coating formation highly depends on the wood density (and resulting surface porosity), resulting in spreading of the aqueous dispersion on HD wood and penetration on LD wood. A thin continuous nanoparticle coating with incorporated vegetable oil provides highest contact angles, as the roughness of the original wood fibers remains visible in the surface profile.     

Angle‐resolved light scattering from textured injection‐molded plastics

With regard to surface appearance, the angle‐resolved light scattering from textured polymeric surfaces was evaluated to link the reflectance properties to measured gloss as well as visually perceived gloss. Bidirectional reflectance distributions were determined by means of a scatterometer and the specimens involved were textured injection‐molded plaques manufactured from three different polymers; an acrylonitrile‐butadiene‐styrene (ABS) copolymer, a polypropylene (PP), and a polycarbonate and ABS copolymer blend (PC/ABS). The influence of color, surface roughness, and angle of incidence on the scattering characteristics was evaluated. An off‐specular reflectance peak was observed for the textured specimens the magnitude of which was clearly determined by the surface roughness and the angle of incidence. The color of the specimens mainly influenced the diffuse reflectance. The results provide a measure of perceived gloss and supported previously reported findings regarding the relevance of the concept of contrast gloss for the gloss characterization of textured polymeric surfaces. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Specular reflection,gloss, roughness and surface heterogeneity of biopolymer coatings

The gloss values of biopolymer coatings were predicted by the Fresnel model from solid film refractive index measurements. Measured gloss properties of transparent coatings fit the model better than did those of wax‐ or lipid‐dispersion coatings. Lipid content and particle size of dispersion coatings had a large influence on coating gloss. The effect of surface roughness on gloss was small compared with that of surface heterogeneity. Whey protein isolate and shellac coatings had higher gloss than hydroxypropyl methylcellulose coatings. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2221–2229, 2001     

Transparent UV-cured clay/UV-based nanocomposite coatings on wood substrates: surface roughness and effect of relative humidity on optical properties

The esthetic durability of coatings on wood surfaces of components constituting wood furniture used in bathrooms is generally affected by high humidity. In this study, surfaces of yellow birch wood (Betula alleghaniensis Britton) were protected with three different types of transparent UV-cured multilayer coatings (MCs), namely MC1, MC2, and MC3. Each MC consisted of three layers: primer, sealer, and topcoat. MC1, MC2, and MC3 contained, respectively, 0, 1, and 3 wt% of nanoclay (NC) in the topcoat, while no nanoparticle was added in the primer and sealer. The surface roughness of coated wood surfaces was measured before accelerated aging and optical properties (color and gloss) were investigated before, during, and after accelerated aging. Statistical results have shown that: (1) all coated wood samples have a similar surface roughness and (2) NC in the topcoat does not have a significant effect on initial color, whereas its effect on initial gloss is significant. There is a significant effect on relative humidity (RH) on color changes, but not between the different types of MCs. With respect to gloss, a lowering of gloss retention with the increase in aging time and RH has been observed for all coatings on wood surfaces. Significant differences appear only at high RH between: MC1 vs MC3 and MC2 vs MC3.     

Visual perception and measurements of texture and gloss of injection‐molded plastics

The effect of an imposed texture on the gloss of injection‐molded polymeric surfaces was evaluated as well as the way in which these properties are visually perceived. Specimens having small differences in surface topography were produced using two mold cavities with slight differences in texture and three different polymers. The texture and gloss were characterized using laser profilometry, gloss measurements, and by means of psychometric evaluations. The measured surface topography parameters and gloss were determined mainly by the texture of the mold surface and the gloss also by the processing conditions. Variations in surface topography due to differences in the rheological properties of the polymer melts were, in most cases, too small to be reflected in the measurements. The visual assessments of the texture and the gloss of specimens from the same cavity were in fair agreement with the measurements, although the observers could discern differences between some specimens not revealed by the measurements. When the specimens molded in the two cavities differing significantly both in gloss and texture were compared, the agreement between the measured topography parameters and the perceived roughness was poorer. It is suggested that higher gloss of a textured surface enhances the perception of a higher roughness. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers     

Improving the cleanability of melamine‐formaldehyde‐based decorative laminates

Decorative laminates based on melamine formaldehyde (MF) resin impregnated papers are used at great extent for surface finishing of engineered wood that is used for furniture, kitchen, and working surfaces, flooring and exterior cladding. In all these applications, optically flawless appearance is a major issue. The work described here is focused on enhancing the cleanability and antifingerprint properties of smooth, matt surface‐finished melamine‐coated particleboards for furniture fronts, without at the same time changing or deteriorating other important surface parameters such as hardness, roughness or gloss. In order to adjust the surface polarity of a low pressure melamine film, novel interface‐active macromolecular compounds were prepared and tested for their suitability as an antifingerprint additive. Two hydroxy‐functional surfactants (polydimethysiloxane, PDMS‐OH and perfluoroether, PF‐OH) were oxidized under mild conditions to the corresponding aldehydes (PDMS‐CHO and PF‐CHO) using a pyridinium chlorochromate catalyst. With the most promising oxidized polymeric additive, PDMS‐CHO, the contact angles against water, n‐hexadecane, and squalene increased from 79.8°, 26.3° and 31.4° for the pure MF surface to 108.5°, 54.8°, and 59.3°, respectively, for the modified MF surfaces. While for the laminated MF surface based on the oxidized fluoroether the gloss values were much higher than required, for the surfaces based on oxidized polydimethylsiloxane the technological values as well as the lower gloss values were in agreement with the requirements and showed much improved surface cleanability, as was also confirmed by colorimetric measurements. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40964.     

Pool boiling fouling and corrosion properties on liquid‐phase‐deposition TiO2 coatings with copper substrate

Fouling on the heat transfer surfaces of industrial heat exchangers is an intractable problem, and several techniques have been suggested to inhibit fouling. Surface coatings are of such techniques by which the adhesion force between fouling and heat transfer surface can be reduced with low surface free energy thin films. In this article, liquid phase deposition was applied to coat titanium dioxide thin films on the red copper substrates with film thickness in micro‐ or nano‐meter scale. Coating thickness, contact angle, roughness, surface topography, and components were measured with X‐ray diffraction, contact angle analyzer, stylus roughmeter, scanning electron microscopy, and energy dispersive X‐ray spectroscopy, respectively. Surface free energy of coating layers was calculated based on the contact angle. Heat transfer and fouling characteristics in pool boiling of distilled water and calcium carbonate solution on coated surfaces were investigated. Heat transfer enhancement was observed on coated surfaces compared with untreated or polished surfaces due to the micro‐ and nano‐structured surfaces which may increase the number of nucleation sites. The nonfouling time on the coated surfaces is extended than that on the untreated or polished surfaces due to the reducing of the surface free energy of coated surfaces. Corrosion behavior of coated surfaces soaked in the corrosive media of hydrochloric acid, sodium hydroxide alkali, and sodium chloride salt solutions with high concentration at room temperature a few hours was also explored qualitatively. Anticorrosion results of the coated surfaces were obtained. The coatings resisted alkali corrosion within 7.2 × 10⁵ s, acidic corrosion within 3.6 × 10⁵ s and salt corrosion within 2.16 × 10⁶ s. The present work may open a new coating route to avoid fouling deposition and corrosion on the heat transfer surfaces of industry evaporators, which is very important for energy saving in the related industries. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

The effect of plasma‐polymerised silicon hydride‐rich polyhydrogenmethylsiloxane on the adhesion of silicone elastomers

BACKGROUND: Silicone elastomers have outstanding material properties including good thermal stability, low electrical conductivity, biocompatibility and resilient physical and chemical properties. These elastomers, however, exhibit relatively poor adhesion to stainless steel, and the use of a nanometre thick plasma‐polymerised primer layer as a means of enhancing this adhesion was investigated in this study. The primer coatings studied consisted of polyhydrogenmethylsiloxane (PHMS), tetraethyl orthosilicate (TEOS) and mixtures of these two liquid precursors. RESULTS: The plasma‐polymerised primer coatings were deposited onto stainless steel substrates using a PlasmaStream^? atmospheric pressure plasma jet system. Deposited coatings were examined using ellipsometry, contact angle measurements, optical profilometry, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy. The adhesion of silicone elastomers bonded to the primed and bare stainless steel surfaces was assessed using 45° adhesion strength measurements. Elastomer adhesion was correlated with surface energy, thickness and roughness. CONCLUSION: An up to 15‐fold increase in adhesive fracture energy was observed for silicone elastomers bonded to the primed versus untreated stainless steel. The highest adhesion was observed for a coating deposited from a PHMS‐to‐TEOS precursor molar ratio of 3 to 1. Copyright © 2009 Society of Chemical Industry     

Optical and surface properties of whey protein isolate coatings on plastic films as influenced by substrate,protein concentration,and plasticizer type

Composite film structures of common plastic polymers including polypropylene (PP) or poly(vinyl chloride) (PVC) with whey protein isolate (WPI) coatings may be obtained by a casting method. Optical and surface properties of the resulting WPI‐coated plastic films, as affected by protein concentration and plasticizer type, were investigated to examine the biopolymer coating effects on surface modification with polymeric substrates of opposite polarity. The measured properties involved specular gloss, color, contact angle, and critical surface energy. Regardless of the substrates, WPI‐coated films possessed excellent gloss and no color, as well as good adhesion between the coating and the substrate when an appropriate plasticizer was added to the coating formulations. The protein concentration did not significantly affect gloss of WPI‐coated plastic films. Among five plasticizers applied, sucrose conferred the most highly reflective and homogeneous surfaces to the coated films. The WPI coatings were very transparent and the coated films with various protein concentrations and plasticizers showed no noticeable changes in color. Experimental results suggest that WPI coatings formulated with a proper plasticizer can improve the visual characteristics of the polymeric substrate and enhance water wettability of the coated plastic films. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 335–343, 2004     

Synthesis and surface analysis of self-matt coating based on waterborne polyurethane resin and study on the matt mechanism

Self-matt coating of waterborne polyurethane (WBPU) was synthesized by combining prepolymer and self-emulsification methods. The emulsion was fabricated from both hydroxy carboxylic acid and aminosulfonic acid types of hydrophilic chain-extending agents, in which the 2-[(2-aminoethyl) amino] ethane sulphonate sodium (AAS salt) was produced in laboratory. This emulsion demonstrated an excellent matt performance without the addition of extra matting agents after filming. Four different kinds of surface properties were measured on the film: the specular gloss (60° gloss meter), the contact angle (CA), the surface roughness degree (3D Surface Profilometer), and the topography of the coatings surface (SEM). The results showed that tons of spherical particles with diameter in a few micrometers were aggregated on the film surface. The effect of the roughness parameters (R _a and R _q ) and the average particle size of the emulsions on the specular gloss degree were probed. The research indicated that the emulsion with average particle size in the range of 2.5–3.0 µm and, meanwhile, the film with roughness parameters R _a and R _q both greater than 1 µm could attain the best matt effect. The WBPU emulsions showed good physical and mechanical properties, and were introduced into wood varnish for matting purpose.     

Studies on urethane‐modified alumina‐filled polyesteramide anticorrosive coatings cured at ambient temperature

Coatings prepared from polyesteramide resin synthesized from linseed oil, a renewable resource, have been found to show improved physicomechanical and anticorrosive characteristics. These properties are further improved when aluminum is incorporated in the polyesteramide resin. The coatings of this resin are generally obtained by baking at elevated temperatures. With a view toward the use of linseed oil, as a precursor for the synthesis of polyesteramide resins and to cure their coatings at ambient temperature, toluylene diisocyanate (TDI) was incorporated into polyesteramide and alumina‐filled polyesteramide in varying proportions to obtain urethane‐modified resins. The latter resins were found to cure at room temperature. The broad structural features of the urethane‐modified polyesteramide and alumina‐filled polyesteramide were confirmed by FTIR and ¹H–NMR spectroscopies. Scratch hardness; impact resistance; bending resistance; specular gloss; and resistance to acid, alkali, and organic solvents of the coatings of these resins were determined by standard methods. Physicomechanical and anticorrosive properties, specular gloss, and thermal stability of the urethane‐modified alumina‐filled polyesteramide coatings were found to be at higher levels among these resins. It was found that TDI could be incorporated in polyesteramide up to only 6 wt %, such that above this loading its properties started to deteriorate, whereas alumina‐filled polyesteramide could take up to 10 wt % TDI. Explanation is provided for the increase in scratch hardness and impact resistance above 6 and 10 wt % addition of TDI in polyesteramide and alumina‐filled polyesteramide, respectively, as well as for the decrease in flexibility and resistance to solvents, acid, and alkali of coatings of these resins above these limits of TDI addition. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1855–1865, 2001     

Modifications of paper and paperboard surfaces with a nanostructured polymer coating

Organic nanoparticles synthesized by imidization of styrene-maleic anhydride copolymers are deposited as a top-coating onto paper and paperboard substrates from a stable aqueous dispersion with maximum solid content of 35 wt.%. The morphology, physical characteristics and chemical surface properties of the coatings are discussed in this paper, using scanning electron microscopy, atomic force microscopy, contact angle measurements and Raman spectroscopy. Due to the high glass transition temperature of the polymer nanoparticles, a unique micro- to nanoscale structured coating is formed that favourably improves the gloss, printing properties (ink-jet printing test and off-set printing test), surface hydrophobicity (maximum water contact angle 140°) and water repellence (reduction of Cobb-values). The interaction of the nanoparticle coatings with the cellulosic paper web results in improvement of the mechanical paper strength and is attributed to hydrogen-bonding between the nanoparticles and the cellulosic fibers.     

Towards a practical metric of surface gloss for metallic coatings from automotive industry

The specular gloss of metallic coatings from the automotive industry can be well measured by current glossmeters when the geometry is appropriately chosen from 20°, 60°, and 85° based on the gloss levels observed. However, the measurements are discontinuous and even nonmonotonic at the breakpoints dividing samples into different gloss levels in the whole range, which causes confusion and inconvenience for industry applications. In this study, attempts were made to link the measurements at the three geometries to be continuous monotonically and in the meanwhile to improve the accuracy of estimating visual gloss. A psychophysical experiment based on a magnitude method was carried out to assess the gloss of metallic coatings with different colors and textures. The visually scaled gloss data were compared with spectrophotometric measurements and instrumental specular gloss values under different geometries. With different weighing coefficients for measurements at individual geometries depending on the gloss levels, a model was proposed to describe the visual surface gloss of metallic coatings comprehensively via a practical metric based on the geometry-dependent measurements. In this way, each sample would have a unique overall gloss value highly correlated with its perceptual evaluation over the entire gloss range.     

Influence of surface characteristics on insect residue adhesion to aircraft leading edge surfaces

Leading edge contamination caused by insects is problematic for modern aircraft utilizing laminar flow aerofoils. The residue of crushed insect bodies adhering to aircraft leading edge surfaces can cause transition of the boundary layer, from laminar to turbulent, resulting in a significant increase in drag and therefore causing an increase in fuel consumption. Consequently, current research is focused on the evaluation of novel low surface energy coatings that will reduce or prevent insect adhesion. Insect residue adhesion tests were conducted on a range of surfaces, from superhydrophobic to hydrophilic. Surface free energy of the investigated substrates was obtained from measured dynamic contact angle values and surface roughness was measured using profilometry. Live insect testing with Drosophila melanogaster and Drosophila hydei was conducted using an insect delivery device inserted into a medium-speed wind tunnel. Tests were conducted at speeds ranging from 90 to 100 m/s (speeds representative of those on take-off and landing of a commercial passenger aircraft). Topography of insect residues was characterized using scanning electron microscopy and confocal laser scanning microscopy. Results obtained indicate that coatings with high surface roughness values and low wettability exhibit good anti-contamination properties.     

Relationship between brightness and roughness of polypropylene abraded surfaces

This article proposes to analyze the relation between gloss and roughness of surfaces of polypropylene samples abraded at different magnitudes. Experiments consist of mechanical polishing at different grades, roughness profiles measurement, and specular light reflectometry with three incidence angles of resulting surfaces. About 100 roughness parameters were considered in this investigation and an original statistical methodology combining the conventional one‐way ANOVA to the recent and powerful Computer Based Bootstrap Method (CBBM) is presented to select which of them is the most relevant, first, to characterize the polypropylene surfaces abraded at different magnitude and, second, to model the physical interaction of these abraded surfaces with a white light beam. The statistical treatment of the experimental results of this investigation shows that the fractal dimension is the most relevant roughness parameter in the two cases. As far as the optical properties are concerned, it is shown that the fractal dimension of an abraded surface is closely related to the local curvature radii of peaks which are known to play a major role in physical interactions with a white light beam. POLYM. ENG. SCI., 56:103–117, 2016. © 2015 Society of Plastics Engineers     

Relating gloss loss to topographical features of a PVDF coating

Semi-gloss commerical poly(vinylidene fluoride) (PVDF) coatings typically have 60° gloss values between 20 and 50. Gloss is affected by PVDF crystallite structures and by the pigmentation. In this article, we have demonstrated that for some pigmented PVDF coatings, after 10 years of Florida exposure, the principal proximal cause of gloss changes is the formation of micron-scale pits, rather than the emergence of pigment particles at the coating surface. We have used laser scanning confocal microscopy (LSCM) and light scattering to characterize the surface topography and near-surface structure of weathered and unweathered PVDF coatings. Florida-weathered PVDF coatings show only a modest increase in the root mean square (RMS) roughness of the surface, even when oticeable gloss loss has occurred. Changes in gloss can be correlated with surface roughness and other topographical, features, including the formation of pits and the emergence of pigments. Presented at the 82nd Annual Meeting of the Federation of Societies for Coatings Technology, October 25–27, 2004, in Chicago, IL.     

Preparation and performance on polycarbonate of B/F/Si‐containing hybrid coatings

A series of UV‐curable B/F/Si‐containing hybrid coatings was prepared by the anhydrous sol‐gel technique. The chemical structure of the coatings was characterized by FTIR, RTIR, and ¹HNMR techniques. The UV‐curable coatings were applied to polycarbonate substrates. The physical and mechanical properties of the UV‐cured coatings, such as pendulum hardness, pencil hardness, contact angle, gel content, MEK rubbing test values, tensile strength, abrasion resistance, and gloss, were examined. Thermal gravimetric analysis (TGA) was done. The relative flammability of the hybrid coatings was tested by the limiting oxygen index (LOI) method. Results of all analyses conducted on the free films and coatings are discussed. J. VINYL ADDIT. TECHNOL., 19:39–46, 2013. © 2013 Society of Plastics Engineers     

Multiscale physical characterization of an outdoor-exposed polymeric coating system

Surface topography and gloss are two related properties affecting the appearance of a polymeric coating system. Upon exposure to ultraviolet (UV) radiation, the surface topography of a coating becomes more pronounced and, correspondingly, its gloss generally decreases. However, the surface factors affecting gloss and appearance are difficult to ascertain. In this article, atomic force microscopy (AFM) and laser scanning confocal microscopy (LSCM) measurements have been performed on an amine-cured epoxy coating system exposed to outdoor environments in Gaithersburg, Maryland. The formation of the protuberances is observed at the early degradation stages, followed by the appearance of circular pits as exposure continues. At long exposure times, the circular features enlarge and deepen, resulting in a rough surface topography and crack formation. Fourier Transform Infrared Spectroscopy (FTIR) study indicates that the oxidation and chain scission reactions are likely the origins of the surface morphological changes. The relationship between changes in surface roughness and gloss has been analyzed. The root mean square (RMS) roughness of the coating is related to nanoscale and microscale morphological changes in the surface of the coating as well as to the gloss retention. A near-linear dependence of RMS roughness with the measurement length scale (L) is found on a double logarithmic scale, i.e., RMS ∼ L ^f. The scaling factor, f, decreases with exposure time. The relationship between surface topography, on nano- to microscales, and the macroscale optical properties such as gloss retention is discussed. Moreover, a recent development in using an angle-resolved light scattering technique for the measurement of the specular and off-specular reflectance of the UV-exposed specimens is also demonstrated, and the optical scattering data are compared to the gloss and the roughness results.

Surface properties of polyurethane powder lacquers modified with polysiloxane‐methacrylic core‐shell nanoparticles

Non‐ and core‐shell nanoparticles‐containing polyurethane‐based powder coating systems, crosslinked with allophanate bonds containing polyisocyanates were examined. The surface structure of the powder coatings were investigated with a confocal microscopy and polarized optical microscopy (POM) using reflected light. The three‐dimensional surface topography and the values of surface roughness were determined. The surface structure was correlated with the chemical structure of the coatings and macroscopic surface behavior: surface free energy and gloss. These experimental results led to a better understanding of the development of surface topography and morphology and provide valuable information for the development of new polyurethane powder coating systems. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011