Paint Curing Research Articles

Comprehensive Characterization of Drying Oil Oxidation and Polymerization Using Time-Resolved Infrared Spectroscopy.

Drying oils like linseed oil are composed of multifunctional triglyceride molecules that can cure through three-dimensional free-radical polymerization into complex polymer networks. In the context of oil paint conservation, it is important to understand how factors like paint composition and curing conditions affect the chemistry and network structure of the oil polymer network and subsequently the links between the structure and long-term paint stability. Here, we employed time-resolved ATR-FTIR spectroscopy and comprehensive data analysis to study the curing behavior of five types of drying oil and the effects of curing temperature as well as the presence of a curing catalyst (PbO). Extracted concentration curves of key reactive functional groups point to a phase transition similar to a gel point that is especially pronounced in the presence of PbO, after which curing reactivity slows down dramatically. Analysis of kinetic parameters suggests that PbO induces a network structure with a more heterogeneous cross-link density, and the ATR-FTIR spectra indicate lower levels of oxidation in those cases. Finally, lower temperatures appear to favor the formation of carboxylic acid groups in oil mixtures with PbO.

Revisit of bake hardening mechanism: Influence of baking on tensile properties of press hardening steels

Paint baking is a process in automotive industries to accelerate the curing of paint and increase yield strength of steel panel for improving the dent resistance due to the formation of well-known Cottrell's atmosphere. However, our careful study on bake hardening mechanism of three press hardening steels (PHS) indicates a different explanation. We developed two novel Nb/Si alloyed steels with superior tensile properties when compared with the commercial grade of 22MnB5. It was found that the paint baking at 170 °C led to the significant increase of yield strength but the decreases of both uniform and total elongation for all the three PHSs. According to the neutron diffraction results, both the baking and the tensile straining until the elastic-plastic transition strain (εep) led to the decrease of full width at half maximum (FWHM), indicating that both should release the residual stress (RS) that was generated during martensite transformation; whilst the internal friction examinations reveal no presence of Snoke peak and no influence of the baking on Snoek-Kê-Köster peak. Based on these results, the kinetics simulation on forming Cottrell's atmosphere and the relevant microstructural characterization results, we can safely conclude that the strengthening caused by the baking is not ascribed to the change of Cottrell atmosphere, carbide precipitates or retained austenite (RA) grains during the baking although commonly believed, but just due to the release of RS. Moreover, the relaxation of compressive RS in martensite and the transformation of RA grains to martensite are the main contributor to the strain hardening of invented PHSs before εep. Therefore, the baking treatment decreases both strain hardening capability and ductility of studied PHSs due to the release of the RS.

Methods for Optimizing the Content of VOCs to Create Environmentally Friendly Materials for Protective Coatings

In order to successfully reduce the emission of toxic organic solvents harmful to human health and the environment during the application and curing of paints and varnishes (VPM), ways to create environmentally friendly organically soluble VPM "SB" and water-dispersed VPM "WB" are proposed. The influence of the values of dry residues in solutions of organic oligomers and the density of the components of pigmented materials on the values of the content of volatile organic compounds (VOC) for different types of materials has been studied. Mathematical analysis of situations with the addition and reduction of the amount of solvents allowed to set the limit values of the amount of solvents in varnishes for "SB" materials with different densities and VOC = 300 g/l. The influence of volumetric concentration of pigments, dry residue of varnishes and density of pigments and fillers on the VOC content in materials has been studied. The ratios of VPM components have been optimized and formulations of environmentally friendly materials have been developed.

Thermal/Blue Light Induced Cross-Linking of Acrylic Coatings with Diazo Compounds.

The thermal curing of industrial coatings (e.g., car painting and metal coil coatings) is accompanied by a substantial energy consumption due to the intrinsically high temperatures required during the curing process. Therefore, the development of new photochemical curing processes-preferably using visible light-is in high demand. This workdescribes new diazo-based cross-linkers that can be used to photocure acrylic coatings using blue light.This workdemonstrates that the structure of the tethered diazo compounds influences the cross-linking efficiency, finding that side reactions are suppressed upon engineering greater molecular flexibility. Importantly,this work shows that these diazo compounds can be employed as either thermal or photochemical cross-linkers, exhibiting identical crosslinking performances. The performance of diazo-cross-linked coatingsis evaluated to reveal excellent water resistance and demonstrably similar material properties to UV-cured acrylates. These studies pave the way for further usage of diazo-functionalized cross-linkers in the curing of paints and coatings.

Embrittlement mechanism of ferrite-martensite dual-phase steel during strain-baking

Press forming and paint curing are necessary in automobile production. However, strain and baking effects induced by these processes cannot be ignored in steel plates. Previously researchers have focused on the baking hardening effect but neglected the embrittlement issue. Baking embrittlement occurs when the elongation of ferrite-martensite dual-phase (DP) steel decreases significantly after strain-baking. In this work, the baking embrittlement value (ΔE) was defined for the first time as an evaluation index, and the baking embrittlement mechanism of DP steels was clarified. The baking embrittlement process of DP steels was divided into two stages. The first stage consisted of dislocations pinned by C clusters or low-temperature carbide, while the second stage was the tempering effect of martensite. Furthermore, the volume contraction of martensite led to the release of internal stress, resulting in an increase in the critical stress for dislocation movement. Both processes reduced dislocation mobility. In addition, by calculating the geometrically necessary dislocation (GND) densities before and after strain-baking, we found that the multiplication ability of dislocations was weakened.

A parametric study on energy, exergy and exergoeconomic analysis of a paint curing oven

This study examines a drying process for paint-drying ovens with actual operating data. This process is one of the most energy consuming processes in the manufacturing process of a company that produces propeller shafts in Manisa. This paper aims to determine the energy and exergy belts on a sectoral basis in light of the examined company and make an efficiency analysis. As a result of the analysis, the exergoeconomic values are calculated as the energy loss/cost ratio in current fresh air temperature is Ren: 7.368 W/$, exergy losses/cost Rex: 0.318 W/$, and the total energy need is reduced by 13.25%.

A parametric study on energy, exergy and exergoeconomic analysis of a paint curing oven

A parametric study on energy, exergy and exergoeconomic analysis of a paint curing oven

Oil crystallization properties as an index for monitoring early stage curing of oil-based paints: DSC analysis on linseed oil systems

In this work, we propose to follow the crystallization capability of oils in oil-based paints, during curing, as an indirect index of the matrix status in the early stages of paint film formation that usually are indicative and crucial to understand the process evolution. To proof the concept, the oil crystallization properties were investigated through DSC measurements on samples of both unpigmented linseed oil and two model paints, composed by lead white + linseed oil (LWLO) and ultramarine blue + linseed oil (UBLO), at different ageing time at room and oxygen-limiting conditions. The results indicate that the curing process strongly affects the oil’s ability of forming crystals in the paint layers, and the proposed experimental approach is rather suitable and sensitive enough to discriminate differences between the action of pigments and environmental conditions. On the other hand, despite the simplicity and the potentiality, this approach is limited at the early stages of paint curing offering an index of the overall matrix status and therefore must be intended as a complementary method that has to be integrated with other approaches if the aim is to explore in detail the chemical and physical aspects of the curing process.

Photoactive Fe Catalyst for Light-Triggered Alkyd Paint Curing.

Herein, we show that the photoactive complexes [(Cp)Fe(arene)]+ (Cp = cyclopentadienyl; arene = C6H6, C6H5Me) act as latent catalysts that allow for photochemical control over the onset of alkyd paint curing, without the need for antiskinning agents such as the volatile 2-butanone oxime normally used to prevent curing during paint storage. The highly soluble neutral complexes [(Cp)Fe(Ch)] and [(Cp)Fe(Ch′)] (Ch = cyclohexadienyl, Ch′ = methylcyclohexadienyl) readily convert to the photoactive complexes [(Cp)Fe(arene)]+ upon oxidation in alkyd, allowing the latter to be dosed in a wide range of concentrations. Infrared and Raman studies show similar spectral changes of the alkyd paint matrix as have been observed in alkyd curing mediated by well-known, industrially applied cobalt- and manganese-based catalyst Co(neodecanoate)2 and [(Me3TACN)2Mn2(μ-OOCR)3](OOCR). The [(Cp)Fe(Ch)]/[(Cp)Fe(arene)]+ system performs equally well as these cobalt- and manganese-based catalysts in terms of drying time and outperform the manganese catalyst by showing a hardness development (increase) similar to that of the cobalt-based catalyst. Based on electron paramagnetic resonance and light–activity studies, we propose that photolysis of [(Cp)Fe(arene)]+ generates short-lived active FeII species, explaining the desired latency. The [(Cp)Fe(Ch)]/[(Cp)Fe(arene)]+ alkyd curing systems presented herein are unique examples of intrinsically latent paint curing catalysts that (1) are based on an abundant and harmless transition metal (Fe), (2) do not require any antiskinning agents, and (3) show favorable performance in terms of drying times and hardness development.

New insights to the interactions between amorphous georgite pigment and linseed oil binder that lead to a drastic color change

Understanding pigment-binder interactions is very important to predict final paint colors and paint stabilities, which is vital for art-making and art conservation. However, previous effort has been focused on long-term chemical stabilities following exposure to the elements, while initial interactions between the pigment and the binder are less understood. Here, we report an investigation into two polymorph basic copper carbonate pigments, georgite and malachite synthesized by varying reaction time and their interactions with linseed oil directly following the paint curing process. Despite the drastic differences in color of these two pigments, incorporation of them into linseed oil binders, resulted in a surprising color change for the georgite based paints from blue to green. FTIR showed a new peak ∼1575 cm−1 in both paint samples, which was assigned to a Cu2+-carboxylate vibration. Furthermore, EPR spectra of the paints exhibited anisotropic Cu2+ signal, indicating a square-planar Cu2+ molecular complex. These results indicated that carboxylic acid biproducts of the linseed oil autooxidation process were able to efficiently extract Cu2+ from the georgite structure to form new and well-distributed Cu2+ molecular complexes throughout the paint, leading to a color change which resulted in similar final paint color compared to the malachite pigment-based paint. This work has demonstrated the structure-property relationship of two polymorph pigment materials, provided new insights to the interactions between amorphous georgite pigment and linseed oil binder that lead to a drastic color change, and revealed the importance of understanding pigment-binder interactions which can be used to predict final paint colors and enhance pigment stabilities.

Oxidation and Cross-Linking in the Curing of Air-Drying Artists’ Oil Paints

In this study, the chemistry of air-drying artist’s oil paint curing and aging up to 24 months was studied. The objective is to improve our molecular understating of the processes that lead to the ...

Investigation of the paint curing mechanism

Each modern vehicle shall be painted in order to protect the metal surfaces of the body and some closures and get an appearance that meets current requirements. Paint coatings of special-purpose machinery are subject to increased wear as a result of more intensive use and/or various environmental conditions, frequent and sharp changes in temperature, etc. All this negatively affects the properties of paint coating and may cause premature destruction of the protective layer. Studies of the coating curing mechanism will allow for a more detailed analysis of various processes that occur during drying. The data obtained as a result of the study will make it possible to provide synthesized paints with properties that have a positive effect on the operation of such special-purpose machinery.

Conservation Issues of Modern Oil Paintings: A Molecular Model on Paint Curing.

The 20th and 21st century oil paintings are presenting a range of challenging conservation problems that can be distinctly different from those noted in paintings from previous centuries. These include the formation of vulnerable surface "skins" of medium and exudates on paint surfaces, efflorescence, unpredictable water and solvent sensitivity, and incidence of paint dripping which can occur within a few years after the paintings were completed. Physicochemical studies of modern oil paints and paintings in recent years have identified a range of possible causal factors for the noted sensitivity of painting surfaces to water and protic solvents, including the formation of water-soluble inorganic salts and/or the accumulation of diacids at the paint surface, which are oxidation products of the oil binder. Other studies have investigated the relationship between water sensitivity and the degree of hydrolysis of the binder, the proportions of free fatty and dicarboxylic acids formed, as well as the relative content of free metal soaps. Thus far, data indicate that the qualitative and quantitative composition of the nonpolymerized fractions of the oil binder cannot be solely or directly related to the solvent sensitivity of the paint film. Conclusions therefore indicate that the polymeric network, formed upon the curing of the oil, plays a fundamental role, suggesting that water sensitivity, at least in some cases, may be related to the poor development and/or polar nature of the formed polymeric network rather than the composition of the nonpolymerized fractions. Poorly developed polymeric networks, in combination with the migration of polar fractions, i.e., dicarboxylic and hydroxylated fatty acids toward the paint surface, can be related to other degradation phenomena, including the separation and migration of the paint binder which can lead to the presence of observable skins of medium as well as the more alarming phenomenon of liquefying or dripping oil paints. It is thus crucial to understand the molecular composition of these paints and their physicochemical behavior to aid the further development of appropriate conservation and preservation strategies, as the risks currently associated with surface cleaning treatments and other conservation procedures can be unacceptably high. This Account reviews the relationships between the degradation phenomena associated with modern oil paintings and the chemical composition of the oil binder and proposes a molecular model for the development of water sensitivity and other noted degradation phenomena. It is suggested that water sensitivity (and possibly other degradation phenomena) is a consequence of processes that take place upon curing, and in particular to the rate of formation and decomposition of alkoxyl and peroxyl radicals. These reactions are strongly dependent on the type of oil present, the ambient environmental conditions, and the chemical and physical nature of the pigments and additives present in the paint formulation. When the curing environment is oxidizing, the chemistry of peroxyl radicals dominates the reaction pathways, and oxidative decomposition of the paint film overwhelms cross-linking reactions.

Curing of Air-Drying Paints: A Critical Review

This review provides an overview of air-drying binders and chemical processes responsible for their solidification and hardening. It is focused not only on binders derived from plant oils but also ...

К ВОПРОСУ ОБ ОТВЕРЖДЕНИИ ВОДНО-ДИСПЕРСИОННЫХ ЛАКОКРАСОЧНЫХ МАТЕРИАЛОВ

К ВОПРОСУ ОБ ОТВЕРЖДЕНИИ ВОДНО-ДИСПЕРСИОННЫХ ЛАКОКРАСОЧНЫХ МАТЕРИАЛОВ

Effects of Austenite Stability on Forming and Work Hardening Behavior of 1.2 GPa Gen3 AHSS

For this study, three 1.2GPa Gen3 AHSS grades with different steel designs were selected for an industrial stamping trial of a B Pillar part. Formability analyses were performed using an Argus system, the material work hardening was evaluated using sub-size tensile specimens sampled from different locations of the formed part and the TRIP effect was quantified using X-Ray diffraction. It was found that the strain distribution and strain localization are strongly related with the microstructural phase composition of the steel and with the mechanical stability of the retained austenite. The increase of the mechanical properties of the formed part represents a combined effect of strain hardening and transformation strengthening. The paint baking contribution to the increase of the yield strength of the formed panels decreases above certain percentage of induced effective strains. The remaining austenite after forming shows high thermal stability at the paint curing temperature.

Impact of spatially correlated pore‐scale heterogeneity on drying porous media

AbstractWe study the effect of spatially‐correlated heterogeneity on isothermal drying of porous media. We combine a minimal pore‐scale model with microfluidic experiments with the same pore geometry. Our simulated drying behavior compares favorably with experiments, considering the large sensitivity of the emergent behavior to the uncertainty associated with even small manufacturing errors. We show that increasing the correlation length in particle sizes promotes preferential drying of clusters of large pores, prolonging liquid connectivity and surface wetness and thus higher drying rates for longer periods. Our findings improve our quantitative understanding of how pore‐scale heterogeneity impacts drying, which plays a role in a wide range of processes ranging from fuel cells to curing of paints and cements to global budgets of energy, water and solutes in soils.

Influence of copper additions on materials properties and corrosion behaviour of Al–Mg alloy sheet

Abstract Additions of a few tenths of a percent of Cu to Al–Mg alloys give rise to a noticeable age-hardening effect. This can be utilized to overcome the softening during paint curing of conventional Cu-free Al–Mg alloys of the AA 5xxx series for car body applications. In the present study we explore this effect in sheet material of the Al–Mg–Cu alloy AA 5023. Mechanical properties and formability of AA 5023 sheet were determined and compared with results obtained in the Cu-free alloys AA 5019 and AA 5182. The resistance to corrosion, viz. general pitting behaviour, filiform corrosion and, most notably, intergranular corrosion was probed. As to the latter, TEM analysis was performed to assess type, composition and spatial arrangement of grain boundary phases causing intergranular corrosion in AA 5xxx series alloys. The results are discussed as a function of alloy composition, recrystallized grain size as well as final heat treatment, i.e. batch annealing vs. continuous solution heat treatment.

Microkinetic modeling of the autoxidative curing of an alkyd and oil-based paint model system

Elucidating the curing and aging mechanisms of alkyd and other oil-based paints is valuable for the fields of conservation and bio-based coatings. Recent research has demonstrated the limitations of artificial aging in predicting the actual properties of paints that are hundreds of years old. Kinetic modeling offers pathways to develop a realistic and dynamic description of the composition of these oil-based paint coatings and facilitates the exploration of the effects of various environmental conditions on their long-term chemical stability. This work presents the construction of a kinetic Monte Carlo framework from elementary steps for the cobalt-catalyzed autoxidative curing of an ethyl linoleate model system up to the formation of single cross-links. Kinetic correlations for reaction families of similar chemistry are employed to reduce the number of parameters required to calculate rate constants in Arrhenius form. The model, developed from mechanisms proposed in the literature, shows good agreement with experiment for the formation of primary products in the early stages of curing. The model has also revealed that the mechanisms proposed in the literature for the formation of secondary products, such as volatile aldehydes, are still not well established, and alternative routes are under evaluation.

Enhancement of energy efficiency in a paint curing oven via CFD approach: Case study in an air-conditioning plant

An oven has been commonly employed to cure powder painted on metal parts for an air-conditioning production. There are many options to improve efficiency in fuel use for the paint curing oven; however some options need deep understanding to prove the possibility of thermal performance. In this work, computational fluid dynamic (CFD) modeling and simulation have been applied to study the temperature distribution and the flow pattern in the paint curing oven on a large scale. The CFD model has been validated against real data. The validated CFD model is used to investigate the temperature distribution and the flow pattern for two proposed options: eliminating stored heat and rearranging airflow. Results demonstrate that both cases provide temperature increase of 1.9 and 1.3°C for air compared to the present paint curing oven. It can be concluded that the two proposed options are applicable for further implementation to the present paint curing oven.