Paint Dispersions Research Articles

Disentangling biological effects of primary nanoplastics from dispersion paints’ additional compounds

Microplastic particles (MP) and nanoplastic particles (NP) as persistent anthropogenic pollutants may impact environmental and human health. A relevant potential source of primary MP and NP is water-based dispersion paint which are commonly used in any household. Given the worldwide high application volume of dispersion paint and their diverse material composition MP and NP may enter the environment with unforeseeable consequences. In order to understand the relevance of these MP and NP from paint dispersion we investigated the components of two representative wall paints and analyzed their composition in detail. The different paint components were then investigated for their impact on the model organism Daphnia magna and on a murine cell line. Plastic NP, dissolved polymers, titanium dioxide NPs, and calcium carbonate MPs demonstrated adverse effects in both biological test systems, indicating detrimental consequences of several typical components of wall paints upon release into the environment. The outcome of this study may form the basis for the evaluation of impact on other organisms, environmental transport and impact, other related technical materials and for the development of strategies for the prevention of potential detrimental effects on organisms.

Modeling of laser speckles of heterogeneous dynamics in drying and aging paint dispersions using a view-based temporal template method

Assessments of the microscopic mechanism underlying the phenomenon of drying and aging of various paint dispersions are important for the requirements of sustainable and high-quality paints. The present work demonstrates the application of the motion history image (MHI) algorithm to visualize the microscopic mechanisms during drying and aging of different paints dispersions. We assessed the micromechanical dynamics of the drying process on laser speckle imaging data after generating the MHI maps. The processes such as cracking and delamination of paint on a glass substrate and the flow of an imbibition front on a porous substrate were analyzed using the MHI analysis, which identifies the locations where the phenomenon evolves with time.

Quantitative imaging of heterogeneous dynamics in drying and aging paints.

Drying and aging paint dispersions display a wealth of complex phenomena that make their study fascinating yet challenging. To meet the growing demand for sustainable, high-quality paints, it is essential to unravel the microscopic mechanisms underlying these phenomena. Visualising the governing dynamics is, however, intrinsically difficult because the dynamics are typically heterogeneous and span a wide range of time scales. Moreover, the high turbidity of paints precludes conventional imaging techniques from reaching deep inside the paint. To address these challenges, we apply a scattering technique, Laser Speckle Imaging, as a versatile and quantitative tool to elucidate the internal dynamics, with microscopic resolution and spanning seven decades of time. We present a toolbox of data analysis and image processing methods that allows a tailored investigation of virtually any turbid dispersion, regardless of the geometry and substrate. Using these tools we watch a variety of paints dry and age with unprecedented detail.

Bactericidal Activity of Aqueous Acrylic Paint Dispersion for Wooden Substrates Based on TiO₂ Nanoparticles Activated by Fluorescent Light.

The photocatalytic effect of TiO2 has great potential for the disinfection of surfaces. Most studies reported in the literature use UV activation of TiO2, while visible light has been used only in a few applications. In these studies, high concentrations of TiO2, which can compromise surface properties, have been used. In this work, we have developed an acrylic-water paint dispersion containing low TiO2 content (2 vol %) for the inactivation of microorganisms involved in hospital-acquired infections. The nanoparticles and the coating have been characterized using spectroscopic techniques and transmission electron microscopy, showing their homogenous dispersion in the acrylic urethane coating. A common fluorescent light source was used to activate the photocatalytic activity of TiO2. The paint dispersion showed antimicrobial activity against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. The coating containing the TiO2 nanoparticles maintained good UV stability, strong adhesion to the substrate and high hardness. Therefore, the approach used is feasible for paint formulation aimed at disinfection of healthcare surfaces.

The effect of polyhedral oligomeric silsesquioxane dispersant and low surface energy additives on spectrally selective paint coatings with self-cleaning properties

Thickness-Insensitive Spectrally Selective (TISS) paint coatings were made of fluoropolymer resin binder (Lumiflon (LF), Asahi Glass Co., Ltd., Japan) and their water- and oil-repellent properties were obtained (contact angle: θ water~150°, θ n−hexadecane~55°) by the addition of Polyhedral Oligomeric Silsesquioxane (POSS) characterized by amino (AP), isooctyl (IO) and perfluoro (PF) groups (i.e. AP 2IO 4PF 2) attached on the silsesquioxane cube (–SiO 3/2) 8. Paint dispersions were made by modifying of black spinel pigment with trisilanol isobutyl (IB 7T 7(OH) 3) POSS dispersant and with a single-capped silane isobutyltrimethoxysilane (IBTMS). Infrared and 29Si NMR spectra measurements were used for the identification of the structural characteristic of the corresponding POSS compounds. Surface free energy values of the pure cross-linked (no pigment added) LF binder which was determined from the measured contact angles for water, diiodomethane and formamide revealed the γ tot value of the LF unpigmented resin with added AP 2IO 4PF 2 T 8 POSS was about 16.4 mN/m, which led to the θ water~110°, indicating enhancement of the hydrophobicity of the pure LF resin binder ( θ water~89°). SEM micrographs, which were used for the assessment of the TISS paint coating surface morphology confirmed the beneficial dispersive effect of IB 7 T 7(OH) 3 dispersant as compared to the IBTMS silane. The presence of large Aluminium flake pigment and finely ground black pigment led to the formation of TISS paint coating surface, which exhibited bi-hierarchical roughness, resulting in water sliding angles of less than 10°, indicating the possible self-cleaning effect ( θ water>150° and θ n−hexadecane~55°). The use of POSS dispersant and POSS low surface energy additive also enhanced spectral selectivity, which became the highest known so far for the black TISS paint coatings ( e T~0.24 and a s~0.93). The use of simple silane IBTMS dispersant even in the presence of the AP 2IO 4PF 2 T 8 POSS did not lead to the oil-repellent effect confirmed by spreading of n-hexadecane on the surface of the corresponding TISS paint coating.

Electric conductivity measurements in water dispersion paints for mechanistic studies of reflection properties formation during surface painting and paint film drying

Electric conductivity measurements of water dispersion paints were carried out in order to understand the mechanism of film formation and drying and the formation of painted surface reflection properties. The classical model of electric conductivity in viscous media based on a comparison of the Coulomb and Stokes formulas was used to determine the effective mechanism of the paint properties. This model was verified by measurements in the paint bulk. The classical concept of the electric conductivity of viscous liquids was found to be applicable to the conductivity analysis of the studied water dispersion paint specimens. The electric conductivity of the studied paints was found to be determined by the existing admixtures being soluble in water and/or dispersion organic particles. The formulated method for dynamic conductivity measurements of paint film thickness assumed a constant temperature and viscosity. Strong electrostatic phenomena were detected at the initial stage of paint aerosol deposition, while a compact film has not been formed yet. The film conductivity measuring experiments found that the film drying process consists of two stages. At the first stage, conductivity is sharply decreasing and the paint film reflectivity is sharply increasing. At the second stage, evaporation is delayed. It is limited by the diffusion transfer of volatile components from the film bulk and from the paint dispersion particles. Here, a slow growth of the reflectivity and a decelerating decrease in the conductivity is observed. A qualitative mathematical dynamic model was developed for the paint film reflectivity due to the orientation of pigment particles, and the calculations showed that the first stage of drying is the most important for the orientation.

Selective paint coatings for coloured solar absorbers: Polyurethane thickness insensitive spectrally selective (TISS) paints (Part II)

Red, green and blue paints were prepared for use as thickness insensitive spectrally selective (TISS) paint coatings for solar façade absorbers. The paints were composed of a polyurethane resin binder in which various pigments were incorporated in such a way that they formed stable paint dispersions, satisfying stability criteria for façade coatings. A low emittance of the paints was achieved by using low-emittance aluminium flake pigments combined with iron oxide (red coloured paints). Black pigment was added to adjust solar absorptance. Blue and green paints were made by the addition of coloured aluminium flake pigment and the solar absorptance was also adjusted by the addition of black pigment. Efficiency for photo-thermal conversion of solar radiation was assessed by evaluation of the corresponding performance criteria, which enabled the selection of paints whose performance criteria values were higher than 0 (spectrally non-selective black coating). The results confirmed that blue and green paints and to minor extent red ones, combined selectivity with colour. The morphology of the paints was assessed, revealing that the colours originated from the deposition of finely dispersed colour and/or black pigment on the surface of the aluminium flakes during paint preparation.

Reaction rate estimation of controlled-release antifouling paint binders: Rosin-based systems

Biofouling on ship hulls is prevented by the use of antifouling (A/F) paints. Typically, sea water soluble rosin or rosin-derivatives are used as the primary means of adjusting the polishing rate of the current chemically active self-polishing paint systems to a suitable value. Previous studies have shown that mathematical coating models based on a fundamental knowledge of the underlying mechanisms of A/F paints is a promising tool for accelerated product testing at different operational conditions of a sailing ship or a paint rotor. Such models can also be used for generation of ideas aiming at product optimisation and innovation (e.g. incorporation of natural active agents). This study seeks to attain scientifically founded knowledge of the reaction mechanisms and the rate of reaction with sea water of a Zn-carboxylate of a synthetic rosin compound. The kinetic expression attained can be used as input to mathematical models describing the behaviour of rosin-containing tin-free A/F paints. The experimental procedures developed can be easily implemented by marine paint companies for the screening of novel controlled-release binder materials for A/F paints. As a first step, it is demonstrated that the degradation of this Zn-containing rosin-derivative by sea water plays a key role in the polishing mechanism of paints formulated with such a resin. Then, the relevant literature available on the sea water behaviour of rosin and rosin-based binders is reviewed. Subsequently, two experimental procedures for the reaction rate estimation of the selected rosin-derived resin are presented; one is based on a gravimetric approach while the other uses flame atomic absorption spectroscopy (FAAS) to determine the total Zn 2+ released by the resin. Both methods yield well-defined reaction conditions and sufficiently high accuracies. The latter is important because very low steady state reaction rates (about 0.70 ± 0.26 μg Zn 2+ cm −2 day −1 at 25 °C and pH 8.2) are measured. Steady state reaction rates of Cu 2+- and Mg 2+-derivatives are also determined and discussed. The experimental procedures developed are used to investigate the influence of NaCl concentration (12–52 g/l), pH (7.8–8.5) and sea water temperature (10–35 °C) on the rate of reaction of the Zn-carboxylate. Within that range of sea water conditions, the following kinetic expression is found to describe the steady state Zn 2+ release rate resulting from the reaction of the Zn-carboxylate with sea water: ( − r ZnR ) = k 1 C O H − a − k − 1 C R − b C Z n 2 + c μ g Z n 2 + ( c m 2 film ) day k 1 = A e ( − E a / R T ) μ g Z n 2 + ( c m 2 film ) day 1 mol a k − 1 = k 1 C O H − a L ZnR 2 b − 2 ( C Z n 2 + ) eq b + c − 3 μ g Z n 2 + ( c m 2 film ) day 1 mol b + c where the natural logarithm of the pre-exponential factor, ln ( A), is 18.0 ± 2.5 (the unit of A being the same as k 1), the activation energy, E a, is 18.5 ± 6.0 kJ/mol and the reaction order with respect to the hydroxide ion concentration, a, is 0.86 ± 0.42. L ZnR is the estimated solubility product of the ZnR resin which has a value of 3.1 × 10 −12 (mol/l) −3 (about 6 mg Zn 2+/l in equilibrium). The low value of the activation energy is believed to result from the complex reaction mechanisms hypothesised rather than pointing at a certain diffusion control in the reaction rate experiments. The reverse reaction is found not to affect the hydrolysis rate within the pores of antifouling paints significantly. It is concluded, from the reaction mechanism proposed, that the observed partial exchange of Zn 2+ for Cu 2+ in the resin structure during paint dispersion and immersion results in a lower reaction rate compared to the pure ZnR. Cu-carboxylate has a reaction rate of about 5.8 ± 1.0 μg CuR cm −2 day −1 at 25 °C and pH 8.2. The presence of Mg and Na compounds (probably Mg- and Na-resinate) in the solid paint film has also been detected, and will influence the reaction rate by modifying the ZnR exposed surface area.

The influence of paint dispersion parameters on the spectral selectivity of black-pigmented coatings

Abstract The optical properties of variously prepared black-pigmented solar absorbing paints were calculated in terms of their effective absorption and scattering abilities. The phenomenological two-parameter Kubelka–Munk effective medium theory was applied. Paints with the same composition were prepared for different degrees of pigment dispersion and characterized by the average size of pigment agglomerates present in the pigment/vehicle system. Prepared paints were applied to aluminum foil in two ways, by coil coating and by spraying. The size of coarse pigment particles and the paint application technique influence the spectral selectivity and thus determine the final performance of spectrally selective surfaces.

Polydispersity and Functional Group Distribution of Dispersant Polymer: Adsorption Properties and Magnetic Paint Dispersion

The quantitative analysis examining the functional group distribution of a dispersant polymer for magnetic paints is conducted by statistical estimation and adsorption experiments. The dispersant polymer contains averagely one or two functional groups on the chain, and has generally large polydispersity. By the calculation based on the random distribution of the functional group and the molecular weight, a typical design of the dispersant polymer is found to contain a significant amount of nonfunctionalized chains and highly functionalized ones. In adsorption experiments, the adsorbed amount of the polymer mass and the functional group are separately measured to determine the functional group distribution. The distribution is also evaluated by a sequential adsorption experiment, in which the chains are fractionated by the adsorption strength. Obtained experimental results agree with the calculated results. A practical method for increasing the effective chains in the paint is to make use of a preferential adsorption of the functionalized chain.

Application of multi‐flux theory based on Mie scattering to the problem of modeling the optical characteristics of colored pigmented paint films

AbstractMulti‐flux theory for multiple scattering calculations in pigmented/protective coating is described. Performance evaluation of the theory is made by comparing theoretically computed reflectance with experimentally measured ones for selected wavelengths for three different paint samples. Diffuse reflectance spectra for hypothetical particulate systems in visible spectral range are generated through computer calculations. Effect of variation in average pigment size and pigment size distribution on reflectance spectra is studied. Overall thrust of morphological characteristics of pigments on the color exhibited by paint dispersion is studied by calculating CIE color and color‐difference parameters of particulate systems. Results show that a very complex relationship exists between the morphological characteristics of pigments and color exhibited by the system. The outcome of the study is important for applications in paint, coating, and plastic industries. © 2001 John Wiley & Sons, Inc. Col Res Appl, 26, 234–245, 2001

Radiative cooling efficiency of white pigmented paints

Nocturnal temperature measurements of various infrared selective radiators performing radiative cooling have been carried out. Measured temperature differences between the radiators and ambient temperature were about 10°C. Radiating surfaces have been prepared by applying different kinds of paints on aluminium substrates. It was shown that the addition of a BaSO 4 extender in the paint dispersion increased the cooling performance of the paint radiators. Comparisons between predicted cooling performances by calculations and measured ones are discussed in detail.

Characterization of TSSS paint coatings for solar collectors by FTIR spectroscopy

The background to the spectral selectivity of thickness sensitive spectrally selective (TSSS) paint coatings is discussed from the chemical point of view. This means considering the solar absorptance ( a s) and thermal emittance ( e T) of the TSSS paint coatings as a function of paint film thicknesses in terms of the degree of flocculation of the pigment dispersion and from the viewpoint of the relevant intermolecular interactions which influence the ability of the pigment particles to become distributed uniformly in the paint, thus increasing its colour strength. We investigated eight TSSS paint coatings based on the standard formulation of Solariselect ® paint [Sol. Energy Mater. 18 (1989) 97], which is currently used for solar collector panels. The influence of carbon soot (C - Degussa FW2), inorganic pigment (F - Ferro 6331) and fumed silica thixotropic agent (Aerosil - Degussa) in TSSS paint coatings on the degree of their flocculation was determined from the infrared hemispherical reflectivity R ( d) λ = 2.5 which was measured from the paint film thickness. The absorption coefficient for diffuse radiation ( K) and the scattering coefficient ( S) were determined by fitting the experimentally determined R ( d) λ = 2.5 curves to a modified Kubelka-Munk function derived by Körte and Otto [Appl. Spectrosc. 43 (1988) 38]. Correlations between the type of black pigment (F and C) and elementary particle size and surface activity of fumed silica (Aerosil 380, 200 and 972) were established and compared with the experimentally determined solar absorptance values ( a s) of the corresponding TSSS paint coatings. Since fumed silica in spite of its small content (<1% by weight) in the paint dispersion, decreases the gloss of the paint, the correlation between the RMS heights of irregularities (σ) and RMS slopes ( m) of irregularities derived from the infrared reflectivity measurements according to the procedure by Bennett and Porteus [J. Opt. Soc. Am. 51 (1961) 123] were determined. This revealed that the σ values are inversely proportional to the elementary particle size of the fumed silica used (Aerosil 380, 200, 972) in the TSSS paint coatings. FTIR spectra of Solariselect ® paints, the corresponding TSSS paint coatings and model dispersions prepared from the resin binder (phenoxy resin) and various types of Aerosils were measured, and the influence of the composition of the paint dispersions on the frequency shifts of -OH vibrations and intensity changes of skeletal modes of the resin binder were established. The changes of infrared bands observed revealed that resin binder molecules become more strongly bonded when fumed silica is present in dispersions. The correlation among the strength of the interactions in a dispersion, the degree of flocculation and σ values are given and discussed.