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The aim of this study was to compare the effect of monomers, prepolymers, and nanosilica on the scratch and abrasion resistance of nanocomposite coatings. Ultraviolet (UV) and electron beam (EB) curing were used to cure the nanocomposite coatings. The effect of monomers, prepolymers and nanosilica particles on the viscosity, pendulum hardness, gel...
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In this study silicon dioxide - tin dioxide nanomaterials modified by fullerenol were obtained through sol-gel technology. The porousity changes caused by the fullerenols addition are discussed.
Current - voltage characteristics of samples containing silicon nanodots embedded in an amorphous silicon dioxide matrix were investigated. A percolation mechanism was evidenced by the dependence on the concentration of the initial differential conductance and by the appearance of several thresholds in the l- Vcharacteristics.
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... However, understanding how coating composition influences the surface damages from different sources of mechanical aggressions remains considerably unknown, although crosslinking density plays a key role from storing and releasing part of the mechanical energy transferred to the coating [13,14]. Therefore, increasing crosslinking density by UV cured systems produces harder clear organic coatings and enhances scratch and abrasion resistance compared to conventional thermal curing systems [15][16][17][18]. Other approach is based on combining silane chemistry with the performance of organic clear coats [19]. ...
Mar and scratch resistance are a major concern for automotive and other industrial sectors from causing inconvenient aesthetic changes on clear coats. Then, a series of two-component solvent-borne polyurethane coatings were formulated with branched polycaprolactone (PCL) oligomers. The effect of the partial substitution of acrylic polyols by tri- and tetra-functional PCL polyols on adhesion, chemical resistance, thermo-mechanical properties and aesthetic response was analysed. The PCL polyols drove to plasticised networks with lower glass transition temperature (Tg) and promoted rubbery state at room temperature. The associated growth in chain mobility did not appreciably affect the key performance of the coatings, apart from the chemical resistance of formulations with PCL triols. Furthermore, remarkable improvement of wear resistance from promoted recovery response was demonstrated. The clear coats with moderated content of PCL polyols yielded a reduced loss of specular gloss with time after repeated scrubbing operations by an abrasive paper. The proposed approach, thus, is presented as a versatile strategy to tailor the mechanical surface properties of clear coats.
... Several strategies were developed over the years to improve UV-curable coatings performance. The addition of inorganic particles increasing mechanical and thermal resistance [3][4][5][6][7][8] and the synthesis and application of hyper-branched polymers to improve mechanical performances [9][10][11][12] are some notable examples. However, one of the most challenging drawback of this chemistry remains the inhibition of free-radical polymerization by atmospheric oxygen. ...
The multiple advantages of UV-curable coatings, such as high curing speeds and cross-linking densities, low VOC and energy consumption led to a widespread interest for a wide range of applications. Free-radical photopolymerization constitutes one of the most used methods of polymerization. However, oxygen present in the atmosphere is able to inhibit radical formation and propagation, which is considered a major drawback. Among all the strategies developed for reducing the oxygen inhibition, the addition of reactive additives is often preferred. This method does not require major changes in the production lines of the industries or in the formulations compositions. The efficiency of reactive additives against oxygen inhibition has been investigated in multiple studies, but in different experimental conditions. The addition of the reactive additives can also influence coatings hardness and abrasion resistance which are considered important mechanical properties. The aim of this study is to evaluate additives overall performances. Eleven of the chosen additives were previously described in the literature. The four remaining are commercial products never used for that application, like a polyhedral oligomeric silsesquioxane bearing a thiol function, which later showed the best results. Reduction of oxygen inhibition was analyzed by photo differential scanning calorimetry (Photo-DSC) and Confocal Raman Micro-spectroscopy (CRM). Pendulum hardness and abrasion resistance measurements were used to determine the influence of the additives on the mechanical properties of the coatings. The results obtained show that most of the additives tested had reducing effect on the pendulum hardness, but helped in improving the abrasion resistance.
... The main properties investigated include mechanical reinforcement of polymeric films, improvement in scratch and abrasion resistance, enhancement of thermal and insulation properties, as well as increasing the resistance against UV radiation [16]. Salleh et al. [17] demonstrated that increasing in silica content in a UV cured coatings increase hardness and improve scratch resistance. The hardness increased because of increase in modulus as well as the presence of the hard silica nanoparticles. ...
... And yet everyone knows that during its life, an automotive headlight is strongly subjected to scratches, impacts, abrasion… That is why the use of a protective coating is required. To go further into a sustainable development approach, such coatings can be photo-cured [1][2][3][4][5][6][7][8][9]. Indeed, photopolymerization is an environmentally-friendly technique, since it allows to work with mixtures containing no solvents, curing them at a very high rate, and it is an energetically economic process. ...
... In the literature, many authors assess the efficiency of their coatings by hardness measurements [7][8][9][10][11], abrasion [1][2][3]7,10], indentation [8][9] or scratch tests [6,[10][11][12][13][14], amongst other experiments evaluating the damage resistance [8][9]11]. However, all these techniques are closely related. ...
... In the literature, many authors assess the efficiency of their coatings by hardness measurements [7][8][9][10][11], abrasion [1][2][3]7,10], indentation [8][9] or scratch tests [6,[10][11][12][13][14], amongst other experiments evaluating the damage resistance [8][9]11]. However, all these techniques are closely related. ...
The relationships between the composition and the scratch resistance of clear photo-polymerized protective coatings for thermoplastic substrates were studied in relation with their thermomechanical properties. For this purpose, dynamic mechanical analyses of free-standing films were compared to micro-scratch tests of thick or thin coatings deposited on polycarbonate. In these experiments, the depth indented by the tip, the elastic recovery of the material, the residual depth of the scratch, and the load at which the first crack appears, were analyzed. Different coatings close in formulation were studied. First, the proportion of a specific difunctional monomer featuring a hard structure was varied in order to change the crosslinking density of the polymer network. The thermomechanical properties were consequently modified at high temperature, but remained similar at 23 °C, whereas at this temperature, the scratch properties of the coating evolved with its composition. The addition of 5 wt% alumina or silica nanoparticles did not modify the thermomechanical properties or the scratch resistance of the coatings, even if a more concentrated filler layer was observed near the surface of the coating. Nevertheless, the consequent incorporation of a new diacrylate monomer in the polymer matrix delayed the ductile-brittle transition. Finally the substitution of petro-based monomers by slightly different bio-based compounds led to a change of the scratch behavior of the thickest coatings (150 μm-thick), and increased the critical load for the thinnest coatings (15 μm-thick). It comes out that micro-scratch tests allow a finer comparison of the samples.
... Certains auteurs suggèrent l'existence d'une concentration optimale en photoamorceur. [ALI94,SAL09] Il est aussi possible d'introduire plusieurs types de photoamorceurs dans une même formulation [CAS07,END06] : ...
... De nombreux auteurs qui étudient des revêtements s'intéressent à la dureté de ces derniers ; il est notamment fréquent de les voir faire le lien entre celle-ci et la résistance à l'indentation, à la rayure et à l'abrasion. [SAL09,SAN05,SCH97,YAH13] Nous allons nous intéresser dans un premier temps aux techniques de mesure de la dureté. Puis, nous présenterons deux techniques de détermination de la résistance aux endommagements, plus précisément à la rayure et à l'indentation. ...
... Ainsi, bien que la photo-polymérisation conduise à des revêtements ayant une résistance à la rayure et à l'abrasion élevée [SAL09] , les performances atteintes sont limitées et souvent insatisfaisantes. C'est pourquoi les nano-composites organiques/inorganiques sont de plus en plus étudiés et développés. ...
The aim of this work was to develop 100% solids photo-polymerizable acrylate coatings, intended to protect thermoplastic pieces made of polycarbonate against mechanical damage, in particular scratches. The relationships between the composition, the structure and the properties of these coatings were examined. For this purpose the morphology, the thermomechanical properties and the scratch resistance of the materials, assessed by micro-scratch tests, were studied. The kinetics of the polymer network formation was also studied by photo-DSC experiments. All the materials feature a high elastic modulus and a broad mechanical relaxation in dynamic thermomechanical analysis. A 100% solids petro-based coating (standard) constituted the starting point of this work. First it was compared to a commercial photo-polymerizable coating containing solvents, specially designed to protect thermoplastic pieces. This commercial coating turned out to be more efficient against scratches. In a second time was studied the influence of the percentage of a multicyclic monomer, taking part in the composition of the standard petro-based coating, on the properties of the latter. The modification of its proportion does not bring any advantage concerning the scratch resistance. Silica, alumina and zirconia nanoparticles, dispersed in an acrylate monomer, were then incorporated in the standard petro-based coating. A particular organization of the silica or alumina nanoparticles in the materials could be observed by transmission electron microscopy. A high filler content is required to observe an increase in the elastic modulus and an enhancement of the scratch resistance of the coating (≥15% by weight for the nano-silica). Moreover, no change of the photo-polymerization kinetics was noticed through the addition of 5% by weight of nano-silica in the coating. Finally, some of the petro-based acrylate compounds of the standard coating were substituted by commercially available bio-based acrylate monomers. Both types of coatings feature similar polymerization kinetics. The conclusions concerning the comparison of the scratch resistance of the bio-based and standard petro-based coatings depend on their thickness. The incorporation of a bio-based monoacrylate compound in low thickness coatings tends to improve the elastic recovery. Isobornyl acrylate is particularly interesting since it also tends to delay the apparition of cracks along the scratch.
MXene-reinforced composite coatings have recently shown promise for metal anticorrosion due to their large aspect ratio and antipermeability; however, the challenges of the poor dispersion, oxidation, and sedimentation of MXene nanofillers in a resin matrix that are often encountered in the existing curing methods have greatly limited practical applications. Herein, we reported an efficient, ambient, and solvent-free electron beam (EB) curing technology to fabricate PDMS@MXene filled acrylate-polyurethane (APU) coatings for anticorrosion of 2024 Al alloy, a common aerospace structural material. We showed that the dispersion of MXene nanoflakes modified by PDMS-OH was dramatically improved in EB-cured resin and enhanced the water resistance through the additional water-repellent groups of PDMS-OH. Moreover, the controllable irradiation-induced polymerization enabled a unique high-density cross-linked network, presenting a large physical barrier against corrosive media. The newly developed APU-PDMS@MX1 coatings achieved excellent corrosion-resistance with the highest protection efficiency of 99.9957%. The coating filled with uniformly distributed PDMS@MXene promoted the corrosion potential, corrosion current density, and corrosion rate to be -0.14 V, 1.49 × 10-9 A/cm2, and 0.0004 mm/year, respectively, and the impedance modulus was increased by 1-2 orders of magnitude compared to that of APU-PDMS coating. This work combining 2D material with EB curing technology broadens the avenue for designing and fabricating composite coatings for metal corrosion protection.
In electron-beam (EB) polymerizations, altering the dose rate can cause property changes in the cured polymer, such as conversion, glass transition temperature (Tg), and physical or mechanical properties. These dose rate effects (DREs) complicate scale-up of EB polymerizations in industrial processes. A predictive relationship between DRE and changes in Tg was used to determine that DREs correlate to the number and lability of available bonds, not monomer size. Furthermore, the relationship between the primary radicals produced during EB irradiation and dose rate was explored via measurement of primary radical radiation chemical yield, G(R•). Namely, G(R•) is independent of dose rate, and instantaneous primary radical concentration is directly proportional to dose rate. Moreover, it was shown that non-reciprocity between dose rate and the rate of polymerization results in DREs. Future developments in radiation chemical yield measurements will aid in determining whether this disproportionality is due to the impact of dose rate on the concentration of propagating radicals or on the kinetic mechanism itself.
Graphene oxide (GO) reinforcement to enhance the property of epoxy has been reported many times; with most of the papers focusing on how to modify GO with different functional groups to achieve better dispersion. Here, the importance of the preparation route on the coating systems performance was investigated. It was found that a mixed polar/nonpolar solvent BuOH/xylene (3/1 vol/vol) was the best choice for forming the epoxy/GO coatings. Furthermore, it was found that when the freeze‐dried GO sonicated with the curing agent trimethylhexamethylene diamine in the mix solvent, the as‐prepared coating exhibited best performance, including better GO dispersion and hydrophobicity, higher adhesion, and anti‐corrosion property. Without any additional chemical to modify the GO, this optimized preparation route for epoxy/GO coatings will provide a guide for future similar research works, especially for the GO dispersion in nonaqueous systems.
