Clear Coatings Research Articles

Comparison of two encapsulation systems of UV stabilizers on the UV protection efficiency of wood clear coats

Abstract One of the major issues in the wood industry is the durability of clear coatings. The addition of organic ultraviolet absorbers (UVAs) improves coating resistance by the absorption and conversion of UV radiation into harmless heat. Organic UVAs are, however, easily degraded by free radicals produced by photodegradation inside the polymer matrix and are prone to migration in the coating. In this study, commercial UVAs and hindered amine light stabilizers (HALS) entrapped into poly(methyl methacrylate) (PMMA) microspheres and CaCO3 templates coated with UV-responsive polymers were added into clear acrylic water-based coating formulation. Artificial accelerated weathering experiments were performed on each formulation. Raman spectroscopy mapping was performed to visualize the concentration and distribution of UVAs and HALS. This study also presents a comparison of the mechanical properties of coatings obtained by dynamic mechanical analysis. Results showed that coating mechanical properties were improved when using encapsulated UVAs and HALS inside PMMA microspheres. The color change of the wood and coating system was minimized and the production of photo-oxidation compounds in the binder was also limited.

Photo-Stabilisation and UV Blocking Efficacy of Coated Macro and Nano-Rutile Titanium Dioxide Particles in Paints and Coatings

Surface treated macro and nanoparticle TiO2 samples have been prepared, characterised and their efficiency as UV blockers evaluated in clear coatings and paints. The particle size of the ‘base’ TiO2 has been optimised to block UV radiation and the surface treatment developed to deactivate the photocatalytic activity of the surface of the TiO2 particles. The resultant UV blockers have been evaluated in both solvent and water-based clear coatings. Nanoparticle TiO2 has been prepared from ‘seed’ and the particle size was controlled by calcination. It was found that the choice of particle size is a compromise between UVA absorption, UVB absorption, visible transmission and photoactivity. It has been demonstrated that TiO2 with a crystallite size of 25 nm yields a product with the optimum properties. A range of dispersants was successfully used to disperse and mill the TiO2. Both organic and inorganic dispersants were used; 2-amino-2-methyl-1-propanol and 1-amino-2-propanol (MIPA) and P2O5 and Na2SiO3 respectively. The surface of the nano-TiO2 was coated with mixed oxides of silicon, aluminium, zirconium and phosphorous. Addition of the resultant coated nano-rutiles to an Isocyanate Acrylic clear coating prolonged the lifetime of that coating compared to the blank. Generally, a surface treatment based on SiO2, Al2O3 and P2O5 was more successful than one based on ZrO2, Al2O3 and P2O5. Higher addition levels of the surface treatment were beneficial for protecting the polymeric coating. The UV blocker products were also evaluated in a water-based acrylic, first a water-based dispersion of the UV blocker was prepared before addition to the acrylic. The dispersions and resultant acrylic thin films were evaluated using UV/Vis spectroscopy and durability assessed. The ratio of absorbance at 300:500 nm for the water-based dispersion was shown to be a good predictor of both the transparency of the resultant acrylic thin film and the durability of that film, in terms of weight loss. Macro grade titanium dioxide pigments were also prepared and coated with treatments of silica, alumina and siloxane and their photo-stabilising activity in alkyd paint film assessed and found to be directly related to the electron–hole pair mobility and trapping as determined by micro-wave spectroscopy.

Ferrari, PPG roll out cooler paint system

Following a collaboration, Ferrari and PPG Industries have introduced an auto paint system that cures at 100 °C instead of 150 °C, reducing energy costs. Named LowCure, the two-component paint incorporates a clear coat with a novel hardening agent that provides added chemical and mechanical resistance. The new formula also boosts cross-coat linking, which Ferrari says increases hydrophobicity and reduces water permeability.

Visually Attractive and High-Power-Retention Solar Modules by Coloring with Automotive Paints

The automotive painting technique is highly advantageous for coloring solar modules, because it enables the modules to be visually attractive over a large area, numerous colors can be applied, and they are highly durable. Herein, we present a high-performance solar module colored using an automotive painting technique. We coated a dilute automotive pigment, the high-transmittance mica pigment, with a clear coat material on a crystalline Si solar module to generate blue color. Our measurements show that a pigment weight concentration of around 10% with the mica pigment is suitable for painting the solar modules, because it enables visual attractiveness while retaining over 80% of the output power, compared to the original solar module. We believe that the technique proposed herein can considerably increase the installable area of solar modules on a car body.

Enhancement of bamboo surface photostability by application of clear coatings containing a combination of organic/inorganic UV absorbers

Benzotriazole (BTZ), benzophenone (BP), nano-TiO2 (NTiO2), and nano-ZnO (NZnO) are potential components of UV protection coatings due to being UV light absorbers. Herein, the UV-protective effects of four acrylic coatings containing individual organic and inorganic UV light absorbers and another four coatings containing both types of absorbers were determined by employing accelerated bamboo aging tests. Although organic absorbers decomposed during aging, their degradation rate decreased in the presence of inorganic absorbers. Moreover, individual organic absorbers were better suited for color stabilization than inorganic ones, with the best bamboo surface photostability enhancement achieved by BTZ-containing coatings (BTZ, BTZ-NZnO, and BTZ-NTiO2). Furthermore, strong synergistic effects were detected for BTZ-NZnO and BTZ-NTiO2, whereas an antagonistic effect was observed for BP-NTiO2 and BP-NZnO. Thus, combinations of organic and inorganic UV light absorbers efficiently inhibited the degradation of the former, with the performance of clear coatings determined by the type of the organic absorber.

Effect of Adding UV Absorbers Embedded in Carbonate Calcium Templates Covered with Light Responsive Polymer into a Clear Wood Coating

The limited durability of clear coatings is a major issue for the coating and wood industry. The addition of organic UV absorbers improves coating resistance by the absorption and the conversion of the UV radiation into harmless heat. Organic UVAs are prone to degradation and can migrate in the binder of coatings. In this study, commercial UVAs and HALS have been entrapped into CaCO3 templates coated with stimuli responsive polymers. Microspheres were incorporated into a clear acrylic water-based coating formulation. The formulation was applied on glass and wood panels and was placed into an artificial UV chamber. This study presents a comparison between the aesthetic behavior of coating formulations with free and encapsulated commercial UVAs and HALS during the accelerated ageing test. Encapsulation of UVAs was confirmed by XPS and TGA analysis. Results have shown that the coating’s aesthetic was slightly improved when using the encapsulated products.

Determinants of Airborne Solvent Exposure in the Collision Repair Industry.

To assess the determinants of airborne solvent exposures in contemporary vehicle collision repair workplaces. Personal, full-shift airborne solvent exposures (n = 97) were assessed in 85 vehicle collision repair workers from 18 workshops. Peak exposures were assessed using a small number of video exposure monitoring measurements. Solvent exposures were highest in spray painters (geometric mean = 2.7 ppm) followed by panel beaters (0.5 ppm), but were well below workplace exposure standards. The lowest exposure levels were observed for mixing room extraction located away from the mixing bench [exposure ratio (ER) = 0.51, 95% confidence interval (CI) = 0.30-0.87]. Time spent mixing paint was associated with higher exposures (ER for every 10-min increase = 1.14, 95% CI = 1.05-1.24), as was time spent cleaning equipment with solvents (ER = 1.11, 95% CI = 0.88-1.39), spraying primer (ER = 1.10, 95% CI = 0.96-1.27), and spraying clear coat paint (ER = 1.07, 95% CI = 1.00-1.15). Overall, the combined non-spray painting tasks (mixing paint, degreasing, and cleaning equipment) were more strongly associated with exposure (ER = 1.10, 95% CI = 1.03-1.18) than the combined spray painting tasks (ER = 1.03, 95% CI = 1.00-1.05). Peak exposures ranged from 10 to 1100 ppm with the strongest and most frequent peaks occurring during paint mixing, decanting of solvents, cleaning of equipment, and painting in a cross-draft spray booth. Airborne solvent exposures in the collision repair industry were associated with job title, the design and location of exhaust ventilation and emission sources, and time spent on specific tasks, with the highest average and peak exposures shown for non-spray painting tasks. These findings provide a contemporary basis for intervention programmes to reduce airborne solvent exposures in this industry.

Photooxidative stability provided by condensed tannin additives in acrylic-based surface coatings on exterior exposure

Condensed tannins, also known as proanthocyanidins, have been added as functional additives to acrylic-based clear coatings to promote polymer coating longevity and also stabilize timber color on accelerated and exterior weathering. When added at 20% compared to commercial hindered amine light stabilizers (HALS) and phenolic stabilizers used at comparable coating loadings. Other tannin chemical modifications such as methylcarboxylate groups were also associated with greater coating longevity beyond that achieved with the synthetic UV and antioxidant additives. This study has also revealed that tannin addition to acrylic coatings can act to photostabilize timber coloring on exterior exposure. While tannin use can contribute color to coatings, any color was rapidly bleached on UV exposure with a dependency on tannin content, degree of modification, and coating formulation pH. Moreover, through manipulating tannin addition levels, this tannin decolorization could offset typical wood darkening associated with UV exposure to provide low or no wood color change over longer exposure periods. With the photooxidative stability efficacy of tannins established on exterior exposure, condensed tannins in native and modified form offer potential as sustainable functional additives for the coatings sector.

DART-MS: A New Analytical Technique for Forensic Paint Analysis

Automotive paint evidence is one of the most significant forms of evidence obtained in automotive-related incidents. Therefore, the analysis of automotive paint evidence is imperative in forensic casework. Most analytical schemes for automotive paint characterization involve optical microscopy, followed by infrared spectroscopy and pyrolysis-gas chromatography mass spectrometry ( py-GCMS) if required. The main drawback with py-GCMS, aside from its destructive nature, is that this technique is relatively time intensive in comparison to other techniques. Direct analysis in real-time-time-of-flight mass spectrometry (DART-TOFMS) may provide an alternative to py-GCMS, as the rapidity of analysis and minimal sample preparation affords a significant advantage. In this study, automotive clear coats from four vehicles were characterized by DART-TOFMS and a standard py-GCMS protocol. Principal component analysis was utilized to interpret the resultant data and suggested the two techniques provided analogous sample discrimination. Moreover, in some instances DART-TOFMS was able to identify components not observed by py-GCMS and vice versa, which indicates that the two techniques may provide complementary information. Additionally, a thermal desorption/pyrolysis DART-TOFMS methodology was also evaluated to characterize the intact paint chips from the vehicles to ascertain if the linear temperature gradient provided additional discriminatory information. All the paint samples were able to be discriminated based on the distinctive thermal desorption plots afforded from this technique, which may also be utilized for sample discrimination. On the basis of the results, DART-TOFMS may provide an additional tool to the forensic paint examiner.

Development of Infrared Library Search Prefilters for Automotive Clear Coats from Simulated Attenuated Total Reflection (ATR) Spectra

A previously published study featuring an attenuated total reflection (ATR) simulation algorithm that mitigated distortions in ATR spectra was further investigated to evaluate its efficacy to enhance searching of infrared (IR) transmission libraries. In the present study, search prefilters were developed from transformed ATR spectra to identify the assembly plant of a vehicle from ATR spectra of the clear coat layer. A total of 456 IR transmission spectra from the Paint Data Query (PDQ) database that spanned 22 General Motors assembly plants and served as a training set cohort were transformed into ATR spectra by the simulation algorithm. These search prefilters were formulated using the fingerprint region (1500 cm-1 to 500 cm-1). Both the transformed ATR spectra (training set) and the experimental ATR spectra (validation set) were preprocessed for pattern recognition analysis using the discrete wavelet transform, which increased the signal-to-noise of the ATR spectra by concentrating the signal in specific wavelet coefficients. Attenuated total reflection spectra of 14 clear coat samples (validation set) measured with a Nicolet iS50 Fourier transform IR spectrometer were correctly classified as to assembly plant(s) of the automotive vehicle from which the paint sample originated using search prefilters developed from 456 simulated ATR spectra. The ATR simulation (transformation) algorithm successfully facilitated spectral library matching of ATR spectra against IR transmission spectra of automotive clear coats in the PDQ database.

An Active Corrosion Inhibition Coating of Two Pack Epoxy Polyamide System using Halloysite Nanocontainer

This work deals with encapsulation of corrosion inhibitor in inorganic nanocontainer and the investigation of the corrosion inhibition rate from the nanocontainer. Halloysite nanotubes were used as inorganic nanocontainer for encapsulating the active corrosion inhibitor. These cylindrical shaped halloysite nanotubes are a natural aluminosilicate, which possesses similar chemical composition as that of pure kaolin clay. The structural morphology and functional organic attachments to the halloysite nanocontainers were determined by using TEM and FTIR analysis. It is found that, halloysite nanocontainers are having external and internal lumen is in nanosize (diameter) and length up to several micrometers. A maximum benzotriazole loading up to 10% (by weight) was achieved in inorganic nanotube of 50 nm external diameters and lumen of 15 nm. The release of corrosion inhibitor was carried out for 18 h at different pH ranging from 3 to 10. The weight percent of the benzotriazole encapsulated halloysite nanocontainer was varied from 2 to 10 and then dispersed in 2K clear coat epoxy-polyamide. The self-healing anticorrosion performance of these nanocomposites coating was tested with help of electrochemical impendence spectroscopy (EIS) and Tafel plot. From Tafel plots it is found that the Icorr value decreases to 1.018E–7A/cm2 from 0.018 A/cm2, when coating was applied with 2 wt % nanocontainer.

Library Search Prefilters for Vehicle Manufacturers to Assist in the Forensic Examination of Automotive Paints

Pattern recognition techniques have been applied to the infrared (IR) spectral libraries of the Paint Data Query (PDQ) database to differentiate between nonidentical but similar IR spectra of automotive paints. To tackle the problem of library searching, search prefilters were developed to identify the vehicle make from IR spectra of the clear coat, surfacer-primer, and e-coat layers. To develop these search prefilters with the appropriate degree of accuracy, IR spectra from the PDQ database were preprocessed using the discrete wavelet transform to enhance subtle but significant features in the IR spectral data. Wavelet coefficients characteristic of vehicle make were identified using a genetic algorithm for pattern recognition and feature selection. Search prefilters to identify automotive manufacturer through IR spectra obtained from a paint chip recovered at a crime scene were developed using 1596 original manufacturer's paint systems spanning six makes (General Motors, Chrysler, Ford, Honda, Nissan, and Toyota) within a limited production year range (2000-2006). Search prefilters for vehicle manufacturer that were developed as part of this study were successfully validated using IR spectra obtained directly from the PDQ database. Information obtained from these search prefilters can serve to quantify the discrimination power of original automotive paint encountered in casework and further efforts to succinctly communicate trace evidential significance to the courts.

A study on the depth distribution of melamine in polyester-melamine clear coats

Abstract The depth distribution of melamine in polyester-based coatings was investigated by XPS (X-ray photoelectron spectroscopy) as well as Raman analysis on cryo-ultra-low-angle microtome (cryo-ULAM) prepared coatings on hot dip galvanized (HDG) steel panels. Additionally, free standing films were analyzed on the air/coating and the coating/substrate interfaces: for polyester/melamine ratios ≤20 wt.% the melamine concentration was equal on both sides of free films, which is in accordance with literature. This finding could not be confirmed for the coatings applied on HDG steel panels that revealed a higher amount of melamine in the surface-near region. In addition various types of non-linear melamine concentration gradients have been detected over depth by XPS as well as Raman spectroscopy. This behavior was confirmed for all types of coatings irrespective of binder chemistry and curing temperatures in the range of 220–260°C. Whereas previous studies have mainly focused on higher melamine concentration where gradient properties are more pronounced, this work tries to fills the gap towards lower melamine contents, which are of greater relevance for industrial coatings. According to these results, a qualitative model on the melamine distribution has been established, which explains the observed non-linear gradients on the basis of transport phenomena and crosslinking kinetics within the curing process. This model is also in agreement with experimental findings from previous works.

The Multifactorial Aspect of Wood Weathering: A Review Based on a Holistic Approach of wood Degradation Protected by Clear Coating

Wood is an abundant and renewable natural resource. Its use is promoted as a way to reduce the carbon footprint in building construction. Wood structures are degraded by their environment due to weathering. This review is a meta-analysis of the main factors of degradation that belong to this phenomenon. The impact of irradiation, the role of water, oxygen, temperature, and colonization by fungi are explained. To protect against these factors, the use of coatings is the most common solution. Since currently the trend is to maintain the grain and the natural color of the wood, the use of transparent coatings is favored. This review presents the main technologies used in clear wood coatings. The durability of this protection against weathering is approached. The whole of knowledge gathered has made it possible to begin a discussion on the multifactorial aspect of wood weathering. Schemes were created to synthesize the synergistic and antagonistic effects between the degradation factors.

Study on the synthesis of new blocked polyisocyanates as crosslinking agents for hydrophobic polyurethane powder clear coatings

Abstract Blocked polyisocyanate crosslinkers for powder coatings were synthesized using isophorone diisocyanate (IPDI), formic acid and e-caprolactam. They were modified with fluorinated polyols. Two kinds of catalyst i.e. dibutyltin dilaurate and dibutyl phosphate for the synthesis were employed. The chemical structures of these compounds were confirmed by nuclear magnetic resonance (NMR) spectroscopy. The molecular mass distribution was investigated using gel permeation chromatography (GPC). During the thermal degradation of modified polyisocyanate three main stages of decomposition can be seen. The degradation of modifier occurs in the last decomposition stage at temperature range of 375 – 500 °C, which is confirmed by coupled TG-FTIR technique. Additionally, polyurethane powder coating systems composed of polyester resin and modified blocked polyisocyanate, were examined. The cross-linked polyurethane powder coatings resulted in improved thermal stability and surface properties i.e. lower roughness and surface free energy values as well as higher hydrophobicity, oleophobicity, gloss, scratch and abrasion resistance.

Impact Verification of Aerogel Insulation Paint on Historic Brick Facades

Increasing the sustainability of existing buildings is being motivated by reduction of their energy demands. It is the above all the building envelope and its refurbishment by substitution or addition of new materials that makes the opportunity for reduction of energy consumption. A special type of refurbishment is conservation of historical buildings. Preservation of historic buildings permits also application of innovative methods and materials in addition to the original materials if their effects are known and the gained experience ensures their beneficial effect. On the market, there are new materials with addition of silica aerogel in various forms of products. They are also potentially useful in conservation of monuments. However, the effects of aerogel application in these cases are not known. For refurbishment is commercially available additional transparent insulation paint - Nansulate Clear Coat which is containing aerogel and can be used for structured surfaces such as bricks. A series of experiments examined the thermo-physical manifestation of an ultra-thin insulation coating of Nansulate Clear Coat containing silica aerogel on a brick facade. The experiments of active and passive thermography have observed effects of application on the small-scale samples of the brick façade of a protected historical building. Through a series of experiments were measured thermal insulation effect and influence on the aesthetic characteristics such as change in colour and gloss. The treated samples were compared to a reference. Results have shown no thermal-insulating manifestation of the recommended three layers of insulation paint. The three layers recommended by the manufacturer did not significantly affect the appearance of the brick facade. Color and gloss were not significantly changed. Experiments showed the absence of thermal insulation effect of Nansulate transparent triple coating. The thermal insulation effect could likely be reached by more layers of application, which, on the other hand may be unacceptable on the heritage conservation because of number of applications, time demand and financial costs. The effects of multiple layers on heritage attributes were not researched. Extrapolating the measured results, it can be expected that application of more than three layers of paint can significantly affect the aesthetic characteristics of the monument such as gloss and colours of historic brick facades. Due to specific material consistence of historic architecture and new insulation paint materials on the market, it is recommended to provide independent laboratory testing and on-site tests on facades of historic buildings in cooperation with the Monument Protection Board.

Chapter 13 – Polyurethane Blends for Powder Clear Coatings

Chapter 13 – Polyurethane Blends for Powder Clear Coatings

Effects of nano-layered silicates on mechanical and chemical properties of acrylic-melamine automotive clear coat

PurposeMechanical and chemical properties of acrylic-melamine automotive clear coat in the presence of different percentages of well dispersed nano-layered sodium montmorillonite (Na-MMT) silicate particles were investigated. For this purpose, prepared dry clear coat film samples were subjected to the entire standard test series, usually carried out in automotive coating industry.Design/methodology/approachEffects of adding different percentages of nano-layered silicate on mechanical and chemical properties of acrylic-melamine automotive clear coat were investigated. To increase the compatibility of nanoclays with polymer matrix of clear coat, the surface of nanoclays was modified by benzalkonium chloride as a cationic surfactant. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used for characterization and comparison between clays before and after modification, and also after dispersion in coating. Prepared dry clear coat film samples subjected to the test series are usually carried out in automotive coating industry.FindingsThe results indicated that incorporation of 1 and 2 Wt.% of nano-layered silicate caused desired improvement in chemical and physical properties of the acrylic-melamine clear coat. Increasing the percentage of nanoclay to over 2 Wt.% caused damage in some properties such as hardness, cupping and gloss.Research limitations/implicationsAll materials and methods were used in this research are industrial grade. Therefore, the introduced modified clear coat sample has potential for commercial production as an automotive clear coat.Originality/valueAs far as it was searched in the literature, effects of adding nanoclay particles on mechanical and physical properties of different clear coats, such as epoxy clear coat, have been investigated in a few researches, but in this research, common and special tests which are necessary in automotive coating industry have been ignored. In the present study for the first time, acrylic-melamine clear coat was subjected to modification using nano-clay, and also, the most common industrial test methods were used for investigation of mechanical and chemical properties.

Preparation of photocatalytic TiO 2 -based self-cleaning coatings for painted surface without interlayer

Abstract Photocatalytic TiO 2 provides a promising route to produce self-cleaning coating surfaces, but it often causes decomposition of organic substrates and other coating components. An interlayer is often employed to insulate photocatalytic activity from sensitive substrate layers, complicating the application of these self-cleaning coatings. Herein, photocatalytic TiO 2 -based coatings were prepared based on an aqueous TiO 2 dispersion in a hybrid binder synthesized from tetraethyl orthosilicate and methyl trimethoxy silane via a sol-gel process. Coatings with various levels of nano TiO 2 were prepared and found to be transparent to visible light; i.e., the clear coating could be directly cast on architectural latex coatings without changing its original appearance. The photocatalytic coating system was composed of a TiO 2 -based clear top coat and an opaque latex film underneath. The coatings were evaluated through outdoor exposure studies and accelerated weathering tests. Results of these tests showed that the photocatalytic coatings with a TiO 2 content range of 33–45% exhibited excellent self-cleaning performance, while displaying none of the expected degradation. In fact, this nano TiO 2 -based clear coating actually protected the latex film from UV-induced damage. The increased stability of the organic film may have resulted from reduced UV transmission through the photo-catalyst containing clear coat as well as reduced water permeability. It was demonstrated that the combination of appropriate TiO 2 content and a suitable binder are crucial for the fabrication of robust photocatalytic self-cleaning coatings for painted surfaces without the need for an interlayer.

Modification of Merck's effect pigment yields special automotive clear coat

Modification of Merck's effect pigment yields special automotive clear coat