Anti-graffiti Properties Research Articles

Removal of graffiti paint from construction materials coated with TiO2-based photocatalysts.

Graffiti on construction materials has significant social and economic impacts, especially on artistic and historical artefacts. Anti-graffiti protective coatings are used to generate low surface energies that limit graffiti adhesion to the surface, thereby reducing surface damage and facilitating removal. The anti-graffiti properties of three commercial TiO2-based coatings were tested under outdoor exposure conditions using four colours of graffiti paint (red, blue, black, and white). Chemical removers were used to clean the stained surfaces to understand the impact of the photocatalytic coatings during the conventional cleaning procedure. The effectiveness of cleaning was assessed by visual observations, colour measurements, and the percentage of residual stain. The anti-graffiti efficacy was strongly dependent on the colour of the graffiti and characteristics of the TiO2 coating. The cleaning performance of TiO2-treated samples was likely related to the photocatalytic redox reactions that decompose the graffiti. Additionally, their hydrophilicity may also prevent the adhesion and/or penetration of graffiti paint on the surface and/or pore matrix.

Solvent-free polyurethane coatings based on an in-situ curing strategy at room temperature with self-cleaning, anti-corrosion and anti-graffiti properties

Anti-smudge coatings have attracted extensive attention in recent years owing to their hydrophobic, self-cleaning, anti-graffiti properties and so on. However, most of the anti-smudge coatings are solvent-based and cured at high temperature or using special curing equipment, which negatively impacts the environment and limits their large-scale application in daily life. Herein, we report a solvent-free anti-smudge coating with potential for large-scale and green manufacturing. In detail, polydimethylsiloxane (PDMS) was used as the hydrophobic component, (3-aminopropyl)triethoxysilane (APTES) and 3-glycidoxypropyltrimethoxysilane (GPTMS) were used as the cross-linking agent, and a solvent-free polyurethane (SFPU) anti-smudge coating was in-situ constructed at room temperature for 24 h without any curing equipment. Due to the enrichment of PDMS chains on the surface and the dense cross-linked network of the coating, the as-prepared coating not only exhibited a high contact angle for water (99.3 ± 1.5°) and diiodomethane (69.5 ± 0.9°), but also excellent anti-smudge to contaminants, with both water and oily liquids were easy to slide off the surface of the coating without leaving any traces. Even after writing with an oil-based marker, the ink on the coated surface could be easily wiped off. Further study reveals that the coating surface maintained its original liquid repellency and stain resistance even after 10 d immersion in a 10 wt% NaCl solution, showing durable anti-corrosion properties. In addition, pigments did not affect the anti-graffiti performance of the coating, providing a multi-color scheme for practical application. This convenient, low-energy, environmentally friendly anti-smudge coating has great potential for widespread application in industry and daily life.

Fabrication of UV-curable waterborne polyurethane coatings with self-cleaning, anti-graffiti performance, and corrosion resistance

A novel UV-curable anti-smudge coating based on waterborne polyurethane (WPU) was constructed by using polydimethylsiloxane (PDMS) as hydrophobic material and pentaerythritol triacrylate (PETA) as UV-curable cross-linking agent. At the same time, the effect of PDMS loading and the cross-linking density on the transparency, hydrophobicity, as well as graffiti resistance of the coating, were investigated. Due to the high cross-linking density, the obtained coating possessed desirable optical transparency. The synergistic effect of hydrophobic side chains and dense cross-linking imparts the coating favorable repellency to pollutant liquids such as water, coffee, muddy water, ink, hexadecane, ethanol, fingerprint liquid and others. The coating showed good anti-graffiti properties on a variety of substrates, including glass, tinplate, ceramics, wood, and paper sheet. In addition, aside from protecting the substrate against strong acid, alkali, and salt solutions, the coatings remained stain resistant despite being folded and curled. This study provides a new strategy for the design of WPU UV-curable anti-smudge coatings.

Robust and Highly Transparent Photocurable Fluorinated Polyurethane Coating Prepared via Thiol-Click Reactions and What Essentially Influences Omniphobic Coating’s Anti-Graffiti Properties

Without a fragile micro/nanostructure, omniphobic coatings have a natural advantage over superomniphobic coatings in mechanical durability, especially when confronted with finger wipes and squeezes in practical use. Many reported omniphobic coatings with lower liquid sliding angles showed better ink trace resistance. However, according to our results, these two properties are not positively related. The respective critical factors for lowering the liquid sliding angle and resisting tiny contaminants, such as ink stroke and fingerprint, remain elusive. Through three steps of the thiol-click reaction, a surface-dried, highly transparent, mechanically and chemically robust, fluorinated polyurethane coating was photocured efficiently. Surfaces that exhibited better sliding performance but worse resistance to ink stroke and fingerprint were reported. Our results indicate that a heavy cross-linked structure was beneficial for the resistance to tiny contaminants, while the liquid sliding performance only depended on the surface fluorine content, especially the surface enrichment of flexible low-surface-tension chains. Interestingly, an unexpected transformation from a turbid dispersion to a transparent solution during the preparation was observed. The efficient thiol-click reaction induces a micelle-like structure to open and imparts high transparency to the final coatings. Therefore, this work provides useful information to facilitate the study of omniphobic coatings, as well as a good candidate in anti-graffiti applications.

Influence of Laboratory Ageing on the Preservation of Anti-graffiti Properties for Paint Systems Used in Rolling Stock

The article describes and presents the influence of selected ageing mechanisms of paint systems currently used in railways in Poland in the context of maintaining their original protective properties against graffiti. Six paint systems with different types of finish, which had anti-graffiti properties, were tested, and the characteristics of the surface of the paint system, such as gloss and colour, were determined after a series of painting and cleaning of graffiti (markers and sprays). The tested objects were subjected to artificial simulated ageing using laboratory solar radiation in a synergistic combination of temperature and humidity in accordance with PN-EN ISO 16474-2 and in accordance with the proprietary methodology described in DN 001/08/A2/16 section 4.1.8 using the UV-C radiation source (discrete spectrum). The tested samples were also subjected to a different type of ageing mechanism under strong corrosive conditions in the form of neutral salt spray according to the methodology described in PN-EN ISO 9227. Keywords: ageing tests, xenon-arc radiation, UV-C radiation, neutral salt spray, paint systems, xenotest, gloss, colour, anti-graffiti protection, rolling stock

Improving the property of castor oil-based waterborne polyurethane by polyhydroxy sapium sebiferum oil as crosslinking agent

In this paper, the sapium sebiferum oil-based polyols (SOP) were prepared by thiol-ene photo-click reaction with mercaptoethanol and inedible sapium sebiferum oil with high iodine value. The molecular structure and hydroxyl values of the SOPs were determined. Then, modified castor oil based waterborne polyurethane was prepared by using SOP, castor oil and isocyanate as raw materials. The particle size and the chemical structure of the emulsions were characterized. Anti-graffiti properties, water contact angle, mechanical properties and thermal properties of the films were tested. When the mass ratio of the SOP to castor oil increased, the water contact angle of the modified film increased by nearly 20°, and it showed good anti-graffiti performance, which can be erased by dry bumf without leaving trace after being written by marker. In addition, the temperature of 50% weight loss of modified film increased by 12 °C and the tensile strength and elongation at break can be improved 2.2 and 2.8 times than before, respectively, which may be related to the addition of crosslinking in the polyurethane by polyhydroxy SOP.

Liquid-like transparent and flexible coatings for anti-graffiti applications

Transparent, durable and smooth coatings with anti-fouling properties are highly desirable for many applications e.g. windows and touch screens. However, most of smooth anti-fouling coatings are limited by complicated preparation and application conditions such as synthesis at high temperatures or curing under ultraviolet irradiation. In this paper, two kinds of siloxane were cross-linked to form a highly transparent anti-fouling coating, which can be rapidly applied on different substrates by a facile brushing process (~3 min for curing) at room temperature. This coating has excellent anti-graffiti properties for liquids with complex components such as water-based and oil-based inks, furthermore, it also exhibits good flexibility, anti-reflection and anti-corrosion properties. The durability test shows that the performance of the coating remains unchanged under various harsh environments. This work would provide a pathway for developing solid and smooth anti-fouling coating, which is expected to be quickly applied in practice due to its simple principle and rapid preparation.

Polysilazane-based coatings: corrosion protection and anti-graffiti properties

ABSTRACTPolyorganosilazanes (PSZs) are innovative materials which can be used to develop thin coatings of potential interest where corrosion protection, anti-graffiti and ease to clean properties are requested. In this work, the properties of polysilazane coatings deposited on AA1050 have been studied. A trialkoxysilylane substituted polymethyl-(hydro)/polymethylsilazane was employed to obtain 400–500 nm thick transparent coatings. The effect of four different curing temperatures (80–230°C) and four different curing times (30–180 min) on the final properties of the coatings has been evaluated. Electrochemical impedance spectroscopy measurements have been carried out in order to assess the corrosion protection properties of the deposited films. The temperature has been proved to have a greater influence on corrosion protection performance compared to the curing time. Contact angle measurements and marking/cleaning tests have been carried out to highlight the anti-graffiti properties.

Surfaces Bearing Fluorinated Nucleoperfluorolipids for Potential Anti-Graffiti Surface Properties

Graffiti can sometimes be a problem when put in an inappropriate place. We looked at a means to prevent such inconvenience. In this work, we explore the possibility of developing surfaces with controlled wettability. If the paint does not spread, the graffiti does not stay. Here, the synthesis and electrodeposition of original 3,4-ethylenedioxythiophene (EDOT) with perfluorinated nucleolipids (ante approach) is reported. The elaboration of similar surfaces using post functionalization is also described. All the prepared surfaces were then investigated for their roughness, wettability, and morphology. Highly hydrophobic features are reported (θ = 137°) and oleophobic properties are also reported (θ = 110°) showing real potential for the control of surface wettability and for potential anti-graffiti applications, consequently. The surfaces obtained with the ante approach are rougher and more hydrophobic.

Anti-Graffiti Properties of Polyurethane Powder Coatings

Abstract Graffiti in street furniture and architectural facades is an increasingly important issue. For metallic structures, anti-graffiti coatings have to guarantee excellent corrosion protection, as well as have an easy-to-remove capability. In addition, color and gloss should not be changed because of natural weathering. In this work, two anti-graffiti polyurethane powder coatings applied were studied. In particular, these layers were deposited on aluminum substrate used in architectural application. Two different surface finishes, smooth and wrinkled, were considered. The efficiency of four different removers was investigated. For this purpose graffiti were drawn on the coatings by means of blue felt-tip marker and a red acrylic spray paint. Gloss and color changes were collected. Methyl–ethyl–ketone and a remover, based on aliphatic and aromatic compounds, resulted in the most effective means, producing a limited change in the appearance. On the contrary, the wrinkled surface result was less resistant. To simulate the weathering effect, UV-B cyclic tests and the Taber abrasion test were carried out.

Characterization of the Anti-Graffiti Properties of Powder Organic Coatings Applied in Train Field

The widespread prevalence of the phenomenon of graffiti and the growth of the removal cost—in particular in public transport systems—has pushed the research for technical solutions to this problem. Suitable solutions to address graffiti-related concerns are needed in order to reduce the cleaning costs as well as the downtime of trains. Graffiti are a big problem for painted metal, because the protective coatings and graffiti have the same chemical nature (polymeric matter). A permanent coating is expected to be able to resist the highest possible number of cleanings of the graffiti without modifying its aesthetic and corrosion protection properties. The purpose of this study is to develop a methodological approach for the characterization of graffiti-resistant organic coatings. For this purpose, a critical review of the existing standards is carried out. The anti-graffiti properties of a polyurethane organic coating were investigated before and after accelerated weathering. In order to understand the behavior of the coatings during cleaning, the aging of the coating in contact with the remover was carried out. The effect on the corrosion protection properties was assessed during the accelerated aging. The resistance of the coating was proved to be strongly affected by the surface finishing. UV exposure modified surface properties and graffiti removal efficiency.

A sprayable protective coating for marble with water-repellent and anti-graffiti properties

Abstract A pore-lining coating method for marble stone surfaces based on the fluorosurfactant Capstone FS-63 has been optimized for application through spray coating by tuning the solvent composition. The optimized application conditions showed an effective penetration depth of the hydrophobic properties down to at least 0.5 mm, ensuring a long-term protection against water uptake. Mechanistic studies of the functionalization process revealed that the solution mixtures containing ethylene glycol provide the best pore-lining functionalization, due to the prolonged functionalization time as a consequence of the slow evaporation rate of the solvent combined with the beneficial shift in the surfactant-vesicle equilibrium towards free surfactants. The coatings also display anti-graffiti properties, allowing for graffiti paint to easily be washed away with a standard pressure washer repeatedly 3–4 times. For optimal re-usability of the anti-graffiti coatings, a new coating can be applied when the first coating loses its effectiveness.

Behaviour of different removers on permanent anti-graffiti organic coatings

Abstract: Graffiti removal presents high costs in street furniture, transport and architectural facades. Considering painted metallic surfaces, the removal has to be easy and not modify the protective and the aesthetic properties. The study of the interaction between paint and remover and the effects on the anti-graffiti properties is the aim of this paper. Two kinds of polyurethane organic coatings, indicated for metallic substrates, and two different surface finishing were considered. This kind of organic coatings shows a very good corrosion properties connected with the low water uptake together a very interesting aesthetical aspect. The behaviour of methylethylketone, xylene and an aliphatic and aromatic solvent mixture, before and after accelerated weathering, was evaluated. MEK was proven to be particularly aggressive. The wrinkled finishing shows strong criticality.

Enhanced anti-graffiti or adhesion properties of polymers using versatile combination of fluorination and polymer grafting

Commonly used polymers and polymer articles have some advantages, e.g. low. But very often they have not very good adhesion, barrier properties, low conductivity, etc. Specialty polymers possessing necessary properties, e.g. fluoropolymers, can be used to fabricate polymer articles. However, practical use of specially synthesized polymers is restricted due to their high cost and complexity of synthesis. It is possible to coat a polymer with another polymer layer with necessary properties but this co-extrusion method is difficult to apply due to a complexity of applied equipment. Also the problems of adhesion between two polymers and polymers compatibility are to be solved. Very often application properties of polymer goods (adhesion, barrier properties, conductivity, etc.) are defined mainly by their surface properties. Hence, it is not necessary to fabricate articles from specialty polymers but simpler, cheaper, and more convenient to apply a surface treatment of articles made from commonly used relatively cheap polymers. In this case, only thin surface layer several nm to several μm in thickness is to be modified and direct fluorination (treatment with mixture of F2 and other gases) can be effectively used. For our research we have chosen common widely used polymers. We targeted to improve hydrophobicity/hydrophylicity, adhesion properties and surface conductivity of polymers. For the first time modification of the surface of high density (HDPE), low density (LDPE) and ultrahigh molecular weight polyethylene (UHMWPE), polypropylene (PP), polyethylene terephthalate (PET) and polyvinylchloride (PVC) was performed by direct fluorination followed by a grafting of acrylic acid, styrene, acrylonitrile, vinylidene chloride, aniline and thiophene from the gas phase. Aniline grafting was studied to improve surface conductivity of polymers. Grafting of polymers was confirmed by ATR and MATR FTIR spectroscopy and energy-dispersive X-ray microprobe spectroscopy (cartography). AFM was used to study polymers surface. Influence of the nature of grafted monomers on the surface energy was studied. It was shown that depending on the nature of a grafted monomer hydrophobicity or hydrophilicity can be markedly improved. The hydrophobicity of modified polymers is not changed and is even improved with time contrary to virgin polymers. For the case of PP and UHMWPE grafting of styrene and acrylonitrile improved anti-graffiti properties (graffiti and pollutions from the polymer surface can be easier removed). For the case of HDPE and LDPE grafting of styrene and acrylonitrile improved printability. Grafting of aniline did not improved electrical conductivity. The uniformity of grafted polymers distribution was investigated by energy-dispersive X-ray microprobe spectroscopy (cartography) for the first time.

Preparation and characterization of polyurethane clearcoats and investigation into their antigraffiti property

A type of antigraffiti polyurethane clearcoat was prepared and characterized. Polymethylsiloxane grafted by fluorocarbon side chains (PSF) was first synthesized through hydrosilylation of polymethylhydrosiloxane with dodecafluoroheptyl acrylate. Hydroxyl fluoroacrylate resins with different hydroxyl contents were synthesized via free radical-initiated solution polymerization and further applied to prepare polyurethane clearcoats. The synthesized polymers were structurally characterized by using Fourier transform infrared and 1H nuclear magnetic resonance. The prepared polyurethane clearcoats underwent contact angle measurement, dynamic thermal mechanical analysis, nanoscratch experiments, and atomic force microscopy. The results reveal that low surface energy, high crosslink density, low coefficient of friction, and low roughness were jointly beneficial to antigraffiti properties. Antigraffiti testing was carried out on the clearcoat with 8.0 wt% PSF and 2.0 wt% active silicone fluid, and this clearcoat showed high resistance to acrylic spray paint, permanent markers, and other graffiti materials.

Investigating the antigraffiti properties of a polyurethane clearcoat containing a silicone polyacrylate additive

In this study, a polyurethane clearcoat was modified using a silicone polyacrylate antigraffiti additive and its surface free energy and mechanical properties were evaluated by various analytical techniques. The results showed that surface free energy decreased by replacing the polyol resin with the additive up to 10 mol%. Dynamic mechanical thermal analysis (DMTA) showed that the presence of the additive increased the storage modulus of the samples at ambient temperature. Evaluation of stainability of the coatings containing the additive revealed that a spray paint would be repelled from the surface showing a proper antigraffiti behavior. The additive did not affect the surface roughness of the films, indicating that the antigraffiti properties resulted from changes in surface chemistry due to migration of the additive to the surface.

Novel, water-based fluorinated polymers with excellent antigraffiti properties

In this article we describe novel, water-based, crosslinkable fluorinated polymers that form coatings with excellent antigraffiti properties. The synthesis of the binders and the surface and bulk properties of their coatings are discussed. The surface properties of these coatings are characterized in terms of their surface-free energy, as calculated from static contact angle measurements. The distribution of the fluorine atoms throughout the coating is measured by X-ray photoelectron spectroscopy (XPS). The bulk properties are studied by determining the crosslink density through dynamic mechanical thermal analysis (DMTA), and the effect of the crosslinking conditions on the crosslink density and the antigraffiti properties is discussed. The results indicate that a combined action of surface and bulk properties gives these coatings their excellent antigraffiti properties. The applicability of these polymers as protective coatings for metal and concrete surfaces are demonstrated.